Merge pull request #747 from julienmalik/update_libpng

update libpng to from 1.6.17 to 1.6.21
2016-04-22 10:48:40 +02:00 · 2016-04-22 10:48:40 +02:00 · f5446fdcfb
parent e1a93d9e59 8611d127db
commit f5446fdcfb
23 changed files with 1294 additions and 2000 deletions
--- a/thirdparty/libpng/LICENSE
+++ b/thirdparty/libpng/LICENSE
@ -10,21 +10,18 @@ this sentence.
 This code is released under the libpng license.
-libpng versions 1.2.6, August 15, 2004, through 1.6.17, March 26, 2015, are
+libpng versions 1.0.7, July 1, 2000, through 1.6.21, January 15, 2016, are
-Copyright (c) 2004, 2006-2015 Glenn Randers-Pehrson, and are
+Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
-distributed according to the same disclaimer and license as libpng-1.2.5
+derived from libpng-1.0.6, and are distributed according to the same
-with the following individual added to the list of Contributing Authors
+disclaimer and license as libpng-1.0.6 with the following individuals
-
+added to the list of Contributing Authors:
   Cosmin Truta
 libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are
 Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.0.6
 with the following individuals added to the list of Contributing Authors
   Simon-Pierre Cadieux
   Eric S. Raymond
   Mans Rullgard
   Cosmin Truta
   Gilles Vollant
   James Yu
 and with the following additions to the disclaimer:
@ -36,18 +33,20 @@ and with the following additions to the disclaimer:
   the user.
 libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
-Copyright (c) 1998, 1999 Glenn Randers-Pehrson, and are
+Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
-distributed according to the same disclaimer and license as libpng-0.96,
+libpng-0.96, and are distributed according to the same disclaimer and
-with the following individuals added to the list of Contributing Authors:
+license as libpng-0.96, with the following individuals added to the list
 of Contributing Authors:
   Tom Lane
   Glenn Randers-Pehrson
   Willem van Schaik
 libpng versions 0.89, June 1996, through 0.96, May 1997, are
-Copyright (c) 1996, 1997 Andreas Dilger
+Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
-Distributed according to the same disclaimer and license as libpng-0.88,
+and are distributed according to the same disclaimer and license as
-with the following individuals added to the list of Contributing Authors:
+libpng-0.88, with the following individuals added to the list of
 Contributing Authors:
   John Bowler
   Kevin Bracey
@ -57,7 +56,7 @@ with the following individuals added to the list of Contributing Authors:
   Tom Tanner
 libpng versions 0.5, May 1995, through 0.88, January 1996, are
-Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
+Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 For the purposes of this copyright and license, "Contributing Authors"
 is defined as the following set of individuals:
@ -80,13 +79,13 @@ Permission is hereby granted to use, copy, modify, and distribute this
 source code, or portions hereof, for any purpose, without fee, subject
 to the following restrictions:
-1. The origin of this source code must not be misrepresented.
+  1. The origin of this source code must not be misrepresented.
-2. Altered versions must be plainly marked as such and must not
+  2. Altered versions must be plainly marked as such and must not
-   be misrepresented as being the original source.
+     be misrepresented as being the original source.
-3. This Copyright notice may not be removed or altered from any
+  3. This Copyright notice may not be removed or altered from any
-   source or altered source distribution.
+     source or altered source distribution.
 The Contributing Authors and Group 42, Inc. specifically permit, without
 fee, and encourage the use of this source code as a component to
@ -94,18 +93,20 @@ supporting the PNG file format in commercial products.  If you use this
 source code in a product, acknowledgment is not required but would be
 appreciated.
 END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
 A "png_get_copyright" function is available, for convenient use in "about"
 boxes and the like:
-   printf("%s",png_get_copyright(NULL));
+   printf("%s", png_get_copyright(NULL));
 Also, the PNG logo (in PNG format, of course) is supplied in the
 files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
-Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is a
+Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
-certification mark of the Open Source Initiative.
+a certification mark of the Open Source Initiative. OSI has not addressed
 the additional disclaimers inserted at version 1.0.7.
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-March 26, 2015
+January 15, 2016
--- a/thirdparty/libpng/png.c
+++ b/thirdparty/libpng/png.c
@ -1,8 +1,8 @@
 /* png.c - location for general purpose libpng functions
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.19 [November 12, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -14,7 +14,7 @@
 #include "pngpriv.h"
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_17 Your_png_h_is_not_version_1_6_17;
+typedef png_libpng_version_1_6_21 Your_png_h_is_not_version_1_6_21;
 /* Tells libpng that we have already handled the first "num_bytes" bytes
 * of the PNG file signature.  If the PNG data is embedded into another
@ -26,15 +26,20 @@ typedef png_libpng_version_1_6_17 Your_png_h_is_not_version_1_6_17;
 void PNGAPI
 png_set_sig_bytes(png_structrp png_ptr, int num_bytes)
 {
   unsigned int nb = (unsigned int)num_bytes;
   png_debug(1, "in png_set_sig_bytes");
   if (png_ptr == NULL)
      return;
-   if (num_bytes > 8)
+   if (num_bytes < 0)
      nb = 0;
   if (nb > 8)
      png_error(png_ptr, "Too many bytes for PNG signature");
-   png_ptr->sig_bytes = (png_byte)((num_bytes < 0 ? 0 : num_bytes) & 0xff);
+   png_ptr->sig_bytes = (png_byte)nb;
 }
 /* Checks whether the supplied bytes match the PNG signature.  We allow
@ -101,7 +106,7 @@ png_zfree(voidpf png_ptr, voidpf ptr)
 void /* PRIVATE */
 png_reset_crc(png_structrp png_ptr)
 {
-   /* The cast is safe because the crc is a 32 bit value. */
+   /* The cast is safe because the crc is a 32-bit value. */
   png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);
 }
@ -129,7 +134,7 @@ png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)
   }
   /* 'uLong' is defined in zlib.h as unsigned long; this means that on some
-    * systems it is a 64 bit value.  crc32, however, returns 32 bits so the
+    * systems it is a 64-bit value.  crc32, however, returns 32 bits so the
    * following cast is safe.  'uInt' may be no more than 16 bits, so it is
    * necessary to perform a loop here.
    */
@ -243,15 +248,15 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
      create_struct.user_height_max = PNG_USER_HEIGHT_MAX;
 #     ifdef PNG_USER_CHUNK_CACHE_MAX
-         /* Added at libpng-1.2.43 and 1.4.0 */
+      /* Added at libpng-1.2.43 and 1.4.0 */
-         create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
+      create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
 #     endif
 #     ifdef PNG_USER_CHUNK_MALLOC_MAX
-         /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
+      /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
-          * in png_struct regardless.
+       * in png_struct regardless.
-          */
+       */
-         create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
+      create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
 #     endif
 #  endif
@ -275,7 +280,9 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
 #  ifdef PNG_SETJMP_SUPPORTED
      if (!setjmp(create_jmp_buf))
 #  endif
      {
 #  ifdef PNG_SETJMP_SUPPORTED
         /* Temporarily fake out the longjmp information until we have
          * successfully completed this function.  This only works if we have
          * setjmp() support compiled in, but it is safe - this stuff should
@ -284,8 +291,6 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
         create_struct.jmp_buf_ptr = &create_jmp_buf;
         create_struct.jmp_buf_size = 0; /*stack allocation*/
         create_struct.longjmp_fn = longjmp;
 #  else
      {
 #  endif
         /* Call the general version checker (shared with read and write code):
          */
@ -304,10 +309,10 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
               create_struct.zstream.opaque = png_ptr;
 #              ifdef PNG_SETJMP_SUPPORTED
-                  /* Eliminate the local error handling: */
+               /* Eliminate the local error handling: */
-                  create_struct.jmp_buf_ptr = NULL;
+               create_struct.jmp_buf_ptr = NULL;
-                  create_struct.jmp_buf_size = 0;
+               create_struct.jmp_buf_size = 0;
-                  create_struct.longjmp_fn = 0;
+               create_struct.longjmp_fn = 0;
 #              endif
               *png_ptr = create_struct;
@ -413,6 +418,8 @@ png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),
      free(info_ptr);
      info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
         (sizeof *info_ptr)));
      if (info_ptr == NULL)
         return;
      *ptr_ptr = info_ptr;
   }
@ -664,19 +671,20 @@ png_init_io(png_structrp png_ptr, png_FILE_p fp)
 #  endif
 #  ifdef PNG_SAVE_INT_32_SUPPORTED
-/* The png_save_int_32 function assumes integers are stored in two's
+/* PNG signed integers are saved in 32-bit 2's complement format.  ANSI C-90
- * complement format.  If this isn't the case, then this routine needs to
+ * defines a cast of a signed integer to an unsigned integer either to preserve
- * be modified to write data in two's complement format.  Note that,
+ * the value, if it is positive, or to calculate:
- * the following works correctly even if png_int_32 has more than 32 bits
+ *
- * (compare the more complex code required on read for sign extension.)
+ *     (UNSIGNED_MAX+1) + integer
 *
 * Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
 * negative integral value is added the result will be an unsigned value
 * correspnding to the 2's complement representation.
 */
 void PNGAPI
 png_save_int_32(png_bytep buf, png_int_32 i)
 {
-   buf[0] = (png_byte)((i >> 24) & 0xff);
+   png_save_uint_32(buf, i);
   buf[1] = (png_byte)((i >> 16) & 0xff);
   buf[2] = (png_byte)((i >> 8) & 0xff);
   buf[3] = (png_byte)(i & 0xff);
 }
 #  endif
@ -722,6 +730,7 @@ png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
      APPEND(':');
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);
      APPEND_STRING(" +0000"); /* This reliably terminates the buffer */
      PNG_UNUSED (pos)
 #     undef APPEND
 #     undef APPEND_NUMBER
@ -766,14 +775,15 @@ png_get_copyright(png_const_structrp png_ptr)
 #else
 #  ifdef __STDC__
   return PNG_STRING_NEWLINE \
-     "libpng version 1.6.17 - March 26, 2015" PNG_STRING_NEWLINE \
+      "libpng version 1.6.21 - January 15, 2016" PNG_STRING_NEWLINE \
-     "Copyright (c) 1998-2015 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
+      "Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson" \
-     "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
+      PNG_STRING_NEWLINE \
-     "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
+      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
-     PNG_STRING_NEWLINE;
+      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
 #  else
-      return "libpng version 1.6.17 - March 26, 2015\
+   return "libpng version 1.6.21 - January 15, 2016\
-      Copyright (c) 1998-2015 Glenn Randers-Pehrson\
+      Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson\
      Copyright (c) 1996-1997 Andreas Dilger\
      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
 #  endif
@ -811,9 +821,9 @@ png_get_header_version(png_const_structrp png_ptr)
 #ifdef __STDC__
   return PNG_HEADER_VERSION_STRING
 #  ifndef PNG_READ_SUPPORTED
-   "     (NO READ SUPPORT)"
+      " (NO READ SUPPORT)"
 #  endif
-   PNG_STRING_NEWLINE;
+      PNG_STRING_NEWLINE;
 #else
   return PNG_HEADER_VERSION_STRING;
 #endif
@ -1086,10 +1096,10 @@ png_colorspace_set_gamma(png_const_structrp png_ptr,
      errmsg = "gamma value out of range";
 #  ifdef PNG_READ_gAMA_SUPPORTED
-      /* Allow the application to set the gamma value more than once */
+   /* Allow the application to set the gamma value more than once */
-      else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
+   else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
-         (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
+      (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
-         errmsg = "duplicate";
+      errmsg = "duplicate";
 #  endif
   /* Do nothing if the colorspace is already invalid */
@ -1130,31 +1140,31 @@ png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)
         PNG_INFO_iCCP);
 #     ifdef PNG_COLORSPACE_SUPPORTED
-         /* Clean up the iCCP profile now if it won't be used. */
+      /* Clean up the iCCP profile now if it won't be used. */
-         png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
+      png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
 #     else
-         PNG_UNUSED(png_ptr)
+      PNG_UNUSED(png_ptr)
 #     endif
   }
   else
   {
 #     ifdef PNG_COLORSPACE_SUPPORTED
-         /* Leave the INFO_iCCP flag set if the pngset.c code has already set
+      /* Leave the INFO_iCCP flag set if the pngset.c code has already set
-          * it; this allows a PNG to contain a profile which matches sRGB and
+       * it; this allows a PNG to contain a profile which matches sRGB and
-          * yet still have that profile retrievable by the application.
+       * yet still have that profile retrievable by the application.
-          */
+       */
-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0)
+      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0)
-            info_ptr->valid |= PNG_INFO_sRGB;
+         info_ptr->valid |= PNG_INFO_sRGB;
-         else
+      else
-            info_ptr->valid &= ~PNG_INFO_sRGB;
+         info_ptr->valid &= ~PNG_INFO_sRGB;
-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
+      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
-            info_ptr->valid |= PNG_INFO_cHRM;
+         info_ptr->valid |= PNG_INFO_cHRM;
-         else
+      else
-            info_ptr->valid &= ~PNG_INFO_cHRM;
+         info_ptr->valid &= ~PNG_INFO_cHRM;
 #     endif
      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0)
@ -1235,16 +1245,17 @@ png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)
   /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically
    * have end points with 0 tristimulus values (these are impossible end
-    * points, but they are used to cover the possible colors.)
+    * points, but they are used to cover the possible colors).  We check
    * xy->whitey against 5, not 0, to avoid a possible integer overflow.
    */
-   if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1;
+   if (xy->redx   < 0 || xy->redx > PNG_FP_1) return 1;
-   if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
+   if (xy->redy   < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
   if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;
   if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;
-   if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1;
+   if (xy->bluex  < 0 || xy->bluex > PNG_FP_1) return 1;
-   if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
+   if (xy->bluey  < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
   if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;
-   if (xy->whitey < 0 || xy->whitey > PNG_FP_1-xy->whitex) return 1;
+   if (xy->whitey < 5 || xy->whitey > PNG_FP_1-xy->whitex) return 1;
   /* The reverse calculation is more difficult because the original tristimulus
    * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
@ -1702,7 +1713,6 @@ png_colorspace_set_chromaticities(png_const_structrp png_ptr,
          */
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_error(png_ptr, "internal error checking chromaticities");
         break;
   }
   return 0; /* failed */
@ -1730,7 +1740,6 @@ png_colorspace_set_endpoints(png_const_structrp png_ptr,
      default:
         colorspace->flags |= PNG_COLORSPACE_INVALID;
         png_error(png_ptr, "internal error checking chromaticities");
         break;
   }
   return 0; /* failed */
@ -2056,8 +2065,8 @@ png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
   temp = png_get_uint_32(profile+12); /* profile/device class */
   switch (temp)
   {
-      case 0x73636E72: /* 'scnr' */
+      case 0x73636e72: /* 'scnr' */
-      case 0x6D6E7472: /* 'mntr' */
+      case 0x6d6e7472: /* 'mntr' */
      case 0x70727472: /* 'prtr' */
      case 0x73706163: /* 'spac' */
         /* All supported */
@ -2068,7 +2077,7 @@ png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
         return png_icc_profile_error(png_ptr, colorspace, name, temp,
            "invalid embedded Abstract ICC profile");
-      case 0x6C696E6B: /* 'link' */
+      case 0x6c696e6b: /* 'link' */
         /* DeviceLink profiles cannot be interpreted in a non-device specific
          * fashion, if an app uses the AToB0Tag in the profile the results are
          * undefined unless the result is sent to the intended device,
@ -2078,7 +2087,7 @@ png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
         return png_icc_profile_error(png_ptr, colorspace, name, temp,
            "unexpected DeviceLink ICC profile class");
-      case 0x6E6D636C: /* 'nmcl' */
+      case 0x6e6d636c: /* 'nmcl' */
         /* A NamedColor profile is also device specific, however it doesn't
          * contain an AToB0 tag that is open to misinterpretation.  Almost
          * certainly it will fail the tests below.
@ -2104,8 +2113,8 @@ png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
   temp = png_get_uint_32(profile+20);
   switch (temp)
   {
-      case 0x58595A20: /* 'XYZ ' */
+      case 0x58595a20: /* 'XYZ ' */
-      case 0x4C616220: /* 'Lab ' */
+      case 0x4c616220: /* 'Lab ' */
         break;
      default:
@ -2275,8 +2284,8 @@ png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
         }
         /* Length *and* intent must match */
-         if (length == png_sRGB_checks[i].length &&
+         if (length == (png_uint_32) png_sRGB_checks[i].length &&
-            intent == png_sRGB_checks[i].intent)
+            intent == (png_uint_32) png_sRGB_checks[i].intent)
         {
            /* Now calculate the adler32 if not done already. */
            if (adler == 0)
@ -2843,7 +2852,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
      if (fp >= DBL_MIN && fp <= DBL_MAX)
      {
-         int exp_b10;       /* A base 10 exponent */
+         int exp_b10;   /* A base 10 exponent */
         double base;   /* 10^exp_b10 */
         /* First extract a base 10 exponent of the number,
@ -2891,7 +2900,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
          */
         {
-            int czero, clead, cdigits;
+            unsigned int czero, clead, cdigits;
            char exponent[10];
            /* Allow up to two leading zeros - this will not lengthen
@ -2921,7 +2930,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
                * of the loop don't break the number into parts so
                * that the final digit is rounded.
                */
-               if (cdigits+czero-clead+1 < (int)precision)
+               if (cdigits+czero+1 < precision+clead)
                  fp = modf(fp, &d);
               else
@ -3027,7 +3036,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
                  *ascii++ = (char)(48 + (int)d), ++cdigits;
               }
            }
-            while (cdigits+czero-clead < (int)precision && fp > DBL_MIN);
+            while (cdigits+czero < precision+clead && fp > DBL_MIN);
            /* The total output count (max) is now 4+precision */
@ -3095,7 +3104,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
            /* Need another size check here for the exponent digits, so
             * this need not be considered above.
             */
-            if ((int)size > cdigits)
+            if (size > cdigits)
            {
               while (cdigits > 0) *ascii++ = exponent[--cdigits];
@ -3143,7 +3152,7 @@ png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
      /* Avoid overflow here on the minimum integer. */
      if (fp < 0)
-         *ascii++ = 45, --size, num = -fp;
+         *ascii++ = 45, num = -fp;
      else
         num = fp;
@ -3674,7 +3683,7 @@ png_exp(png_fixed_point x)
   if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */
   {
      /* Obtain a 4-bit approximation */
-      png_uint_32 e = png_32bit_exp[(x >> 12) & 0xf];
+      png_uint_32 e = png_32bit_exp[(x >> 12) & 0x0f];
      /* Incorporate the low 12 bits - these decrease the returned value by
       * multiplying by a number less than 1 if the bit is set.  The multiplier
@ -4236,7 +4245,7 @@ png_set_option(png_structrp png_ptr, int option, int onoff)
 * contrib/tools/makesRGB.c.  The actual sRGB transfer curve defined in the
 * specification (see the article at http://en.wikipedia.org/wiki/SRGB)
 * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.
- * The sRGB to linear table is exact (to the nearest 16 bit linear fraction).
+ * The sRGB to linear table is exact (to the nearest 16-bit linear fraction).
 * The inverse (linear to sRGB) table has accuracies as follows:
 *
 * For all possible (255*65535+1) input values:
--- a/thirdparty/libpng/png.h
+++ b/thirdparty/libpng/png.h
@ -1,9 +1,9 @@
 /* png.h - header file for PNG reference library
 *
- * libpng version 1.6.17, March 26, 2015
+ * libpng version 1.6.21, January 15, 2016
 *
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -11,17 +11,137 @@
 *
 * Authors and maintainers:
 *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
- *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
+ *   libpng versions 0.89, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.6.17, March 26, 2015: Glenn
+ *   libpng versions 0.97, January 1998, through 1.6.21, January 15, 2016:
 *     Glenn Randers-Pehrson.
 *   See also "Contributing Authors", below.
 */
 /*
 * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
 *
- * Note about libpng version numbers:
+ * If you modify libpng you may insert additional notices immediately following
 * this sentence.
 *
- *   Due to various miscommunications, unforeseen code incompatibilities
+ * This code is released under the libpng license.
- *   and occasional factors outside the authors' control, version numbering
+ *
- *   on the library has not always been consistent and straightforward.
+ * libpng versions 1.0.7, July 1, 2000, through 1.6.21, January 15, 2016, are
- *   The following table summarizes matters since version 0.89c, which was
+ * Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
- *   the first widely used release:
+ * derived from libpng-1.0.6, and are distributed according to the same
 * disclaimer and license as libpng-1.0.6 with the following individuals
 * added to the list of Contributing Authors:
 *
 *    Simon-Pierre Cadieux
 *    Eric S. Raymond
 *    Mans Rullgard
 *    Cosmin Truta
 *    Gilles Vollant
 *    James Yu
 *
 * and with the following additions to the disclaimer:
 *
 *    There is no warranty against interference with your enjoyment of the
 *    library or against infringement.  There is no warranty that our
 *    efforts or the library will fulfill any of your particular purposes
 *    or needs.  This library is provided with all faults, and the entire
 *    risk of satisfactory quality, performance, accuracy, and effort is with
 *    the user.
 *
 * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
 * Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
 * libpng-0.96, and are distributed according to the same disclaimer and
 * license as libpng-0.96, with the following individuals added to the list
 * of Contributing Authors:
 *
 *    Tom Lane
 *    Glenn Randers-Pehrson
 *    Willem van Schaik
 *
 * libpng versions 0.89, June 1996, through 0.96, May 1997, are
 * Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
 * and are distributed according to the same disclaimer and license as
 * libpng-0.88, with the following individuals added to the list of
 * Contributing Authors:
 *
 *    John Bowler
 *    Kevin Bracey
 *    Sam Bushell
 *    Magnus Holmgren
 *    Greg Roelofs
 *    Tom Tanner
 *
 * libpng versions 0.5, May 1995, through 0.88, January 1996, are
 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * For the purposes of this copyright and license, "Contributing Authors"
 * is defined as the following set of individuals:
 *
 *    Andreas Dilger
 *    Dave Martindale
 *    Guy Eric Schalnat
 *    Paul Schmidt
 *    Tim Wegner
 *
 * The PNG Reference Library is supplied "AS IS".  The Contributing Authors
 * and Group 42, Inc. disclaim all warranties, expressed or implied,
 * including, without limitation, the warranties of merchantability and of
 * fitness for any purpose.  The Contributing Authors and Group 42, Inc.
 * assume no liability for direct, indirect, incidental, special, exemplary,
 * or consequential damages, which may result from the use of the PNG
 * Reference Library, even if advised of the possibility of such damage.
 *
 * Permission is hereby granted to use, copy, modify, and distribute this
 * source code, or portions hereof, for any purpose, without fee, subject
 * to the following restrictions:
 *
 *   1. The origin of this source code must not be misrepresented.
 *
 *   2. Altered versions must be plainly marked as such and must not
 *      be misrepresented as being the original source.
 *
 *   3. This Copyright notice may not be removed or altered from any
 *      source or altered source distribution.
 *
 * The Contributing Authors and Group 42, Inc. specifically permit, without
 * fee, and encourage the use of this source code as a component to
 * supporting the PNG file format in commercial products.  If you use this
 * source code in a product, acknowledgment is not required but would be
 * appreciated.
 *
 * END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
 */
 /*
 * A "png_get_copyright" function is available, for convenient use in "about"
 * boxes and the like:
 *
 *    printf("%s", png_get_copyright(NULL));
 *
 * Also, the PNG logo (in PNG format, of course) is supplied in the
 * files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
 */
 /*
 * Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
 * a certification mark of the Open Source Initiative. OSI has not addressed
 * the additional disclaimers inserted at version 1.0.7.
 */
 /*
 * The contributing authors would like to thank all those who helped
 * with testing, bug fixes, and patience.  This wouldn't have been
 * possible without all of you.
 *
 * Thanks to Frank J. T. Wojcik for helping with the documentation.
 */
 /* Note about libpng version numbers:
 *
 *    Due to various miscommunications, unforeseen code incompatibilities
 *    and occasional factors outside the authors' control, version numbering
 *    on the library has not always been consistent and straightforward.
 *    The following table summarizes matters since version 0.89c, which was
 *    the first widely used release:
 *
 *    source                 png.h  png.h  shared-lib
 *    version                string   int  version
@ -59,313 +179,48 @@
 *    1.0.7beta15-18           1    10007  2.1.0.7beta15-18 (binary compatible)
 *    1.0.7rc1-2               1    10007  2.1.0.7rc1-2 (binary compatible)
 *    1.0.7                    1    10007  (still compatible)
- *    1.0.8beta1-4             1    10008  2.1.0.8beta1-4
+ *    ...
- *    1.0.8rc1                 1    10008  2.1.0.8rc1
+ *    1.0.19                  10    10019  10.so.0.19[.0]
- *    1.0.8                    1    10008  2.1.0.8
+ *    ...
- *    1.0.9beta1-6             1    10009  2.1.0.9beta1-6
+ *    1.2.53                  13    10253  12.so.0.53[.0]
- *    1.0.9rc1                 1    10009  2.1.0.9rc1
+ *    ...
- *    1.0.9beta7-10            1    10009  2.1.0.9beta7-10
+ *    1.5.23                  15    10523  15.so.15.23[.0]
- *    1.0.9rc2                 1    10009  2.1.0.9rc2
+ *    ...
- *    1.0.9                    1    10009  2.1.0.9
+ *    1.6.21                  16    10621  16.so.16.21[.0]
 *    1.0.10beta1              1    10010  2.1.0.10beta1
 *    1.0.10rc1                1    10010  2.1.0.10rc1
 *    1.0.10                   1    10010  2.1.0.10
 *    1.0.11beta1-3            1    10011  2.1.0.11beta1-3
 *    1.0.11rc1                1    10011  2.1.0.11rc1
 *    1.0.11                   1    10011  2.1.0.11
 *    1.0.12beta1-2            2    10012  2.1.0.12beta1-2
 *    1.0.12rc1                2    10012  2.1.0.12rc1
 *    1.0.12                   2    10012  2.1.0.12
 *    1.1.0a-f                 -    10100  2.1.1.0a-f (branch abandoned)
 *    1.2.0beta1-2             2    10200  2.1.2.0beta1-2
 *    1.2.0beta3-5             3    10200  3.1.2.0beta3-5
 *    1.2.0rc1                 3    10200  3.1.2.0rc1
 *    1.2.0                    3    10200  3.1.2.0
 *    1.2.1beta1-4             3    10201  3.1.2.1beta1-4
 *    1.2.1rc1-2               3    10201  3.1.2.1rc1-2
 *    1.2.1                    3    10201  3.1.2.1
 *    1.2.2beta1-6            12    10202  12.so.0.1.2.2beta1-6
 *    1.0.13beta1             10    10013  10.so.0.1.0.13beta1
 *    1.0.13rc1               10    10013  10.so.0.1.0.13rc1
 *    1.2.2rc1                12    10202  12.so.0.1.2.2rc1
 *    1.0.13                  10    10013  10.so.0.1.0.13
 *    1.2.2                   12    10202  12.so.0.1.2.2
 *    1.2.3rc1-6              12    10203  12.so.0.1.2.3rc1-6
 *    1.2.3                   12    10203  12.so.0.1.2.3
 *    1.2.4beta1-3            13    10204  12.so.0.1.2.4beta1-3
 *    1.0.14rc1               13    10014  10.so.0.1.0.14rc1
 *    1.2.4rc1                13    10204  12.so.0.1.2.4rc1
 *    1.0.14                  10    10014  10.so.0.1.0.14
 *    1.2.4                   13    10204  12.so.0.1.2.4
 *    1.2.5beta1-2            13    10205  12.so.0.1.2.5beta1-2
 *    1.0.15rc1-3             10    10015  10.so.0.1.0.15rc1-3
 *    1.2.5rc1-3              13    10205  12.so.0.1.2.5rc1-3
 *    1.0.15                  10    10015  10.so.0.1.0.15
 *    1.2.5                   13    10205  12.so.0.1.2.5
 *    1.2.6beta1-4            13    10206  12.so.0.1.2.6beta1-4
 *    1.0.16                  10    10016  10.so.0.1.0.16
 *    1.2.6                   13    10206  12.so.0.1.2.6
 *    1.2.7beta1-2            13    10207  12.so.0.1.2.7beta1-2
 *    1.0.17rc1               10    10017  12.so.0.1.0.17rc1
 *    1.2.7rc1                13    10207  12.so.0.1.2.7rc1
 *    1.0.17                  10    10017  12.so.0.1.0.17
 *    1.2.7                   13    10207  12.so.0.1.2.7
 *    1.2.8beta1-5            13    10208  12.so.0.1.2.8beta1-5
 *    1.0.18rc1-5             10    10018  12.so.0.1.0.18rc1-5
 *    1.2.8rc1-5              13    10208  12.so.0.1.2.8rc1-5
 *    1.0.18                  10    10018  12.so.0.1.0.18
 *    1.2.8                   13    10208  12.so.0.1.2.8
 *    1.2.9beta1-3            13    10209  12.so.0.1.2.9beta1-3
 *    1.2.9beta4-11           13    10209  12.so.0.9[.0]
 *    1.2.9rc1                13    10209  12.so.0.9[.0]
 *    1.2.9                   13    10209  12.so.0.9[.0]
 *    1.2.10beta1-7           13    10210  12.so.0.10[.0]
 *    1.2.10rc1-2             13    10210  12.so.0.10[.0]
 *    1.2.10                  13    10210  12.so.0.10[.0]
 *    1.4.0beta1-5            14    10400  14.so.0.0[.0]
 *    1.2.11beta1-4           13    10211  12.so.0.11[.0]
 *    1.4.0beta7-8            14    10400  14.so.0.0[.0]
 *    1.2.11                  13    10211  12.so.0.11[.0]
 *    1.2.12                  13    10212  12.so.0.12[.0]
 *    1.4.0beta9-14           14    10400  14.so.0.0[.0]
 *    1.2.13                  13    10213  12.so.0.13[.0]
 *    1.4.0beta15-36          14    10400  14.so.0.0[.0]
 *    1.4.0beta37-87          14    10400  14.so.14.0[.0]
 *    1.4.0rc01               14    10400  14.so.14.0[.0]
 *    1.4.0beta88-109         14    10400  14.so.14.0[.0]
 *    1.4.0rc02-08            14    10400  14.so.14.0[.0]
 *    1.4.0                   14    10400  14.so.14.0[.0]
 *    1.4.1beta01-03          14    10401  14.so.14.1[.0]
 *    1.4.1rc01               14    10401  14.so.14.1[.0]
 *    1.4.1beta04-12          14    10401  14.so.14.1[.0]
 *    1.4.1                   14    10401  14.so.14.1[.0]
 *    1.4.2                   14    10402  14.so.14.2[.0]
 *    1.4.3                   14    10403  14.so.14.3[.0]
 *    1.4.4                   14    10404  14.so.14.4[.0]
 *    1.5.0beta01-58          15    10500  15.so.15.0[.0]
 *    1.5.0rc01-07            15    10500  15.so.15.0[.0]
 *    1.5.0                   15    10500  15.so.15.0[.0]
 *    1.5.1beta01-11          15    10501  15.so.15.1[.0]
 *    1.5.1rc01-02            15    10501  15.so.15.1[.0]
 *    1.5.1                   15    10501  15.so.15.1[.0]
 *    1.5.2beta01-03          15    10502  15.so.15.2[.0]
 *    1.5.2rc01-03            15    10502  15.so.15.2[.0]
 *    1.5.2                   15    10502  15.so.15.2[.0]
 *    1.5.3beta01-10          15    10503  15.so.15.3[.0]
 *    1.5.3rc01-02            15    10503  15.so.15.3[.0]
 *    1.5.3beta11             15    10503  15.so.15.3[.0]
 *    1.5.3 [omitted]
 *    1.5.4beta01-08          15    10504  15.so.15.4[.0]
 *    1.5.4rc01               15    10504  15.so.15.4[.0]
 *    1.5.4                   15    10504  15.so.15.4[.0]
 *    1.5.5beta01-08          15    10505  15.so.15.5[.0]
 *    1.5.5rc01               15    10505  15.so.15.5[.0]
 *    1.5.5                   15    10505  15.so.15.5[.0]
 *    1.5.6beta01-07          15    10506  15.so.15.6[.0]
 *    1.5.6rc01-03            15    10506  15.so.15.6[.0]
 *    1.5.6                   15    10506  15.so.15.6[.0]
 *    1.5.7beta01-05          15    10507  15.so.15.7[.0]
 *    1.5.7rc01-03            15    10507  15.so.15.7[.0]
 *    1.5.7                   15    10507  15.so.15.7[.0]
 *    1.6.0beta01-40          16    10600  16.so.16.0[.0]
 *    1.6.0rc01-08            16    10600  16.so.16.0[.0]
 *    1.6.0                   16    10600  16.so.16.0[.0]
 *    1.6.1beta01-09          16    10601  16.so.16.1[.0]
 *    1.6.1rc01               16    10601  16.so.16.1[.0]
 *    1.6.1                   16    10601  16.so.16.1[.0]
 *    1.6.2beta01             16    10602  16.so.16.2[.0]
 *    1.6.2rc01-06            16    10602  16.so.16.2[.0]
 *    1.6.2                   16    10602  16.so.16.2[.0]
 *    1.6.3beta01-11          16    10603  16.so.16.3[.0]
 *    1.6.3rc01               16    10603  16.so.16.3[.0]
 *    1.6.3                   16    10603  16.so.16.3[.0]
 *    1.6.4beta01-02          16    10604  16.so.16.4[.0]
 *    1.6.4rc01               16    10604  16.so.16.4[.0]
 *    1.6.4                   16    10604  16.so.16.4[.0]
 *    1.6.5                   16    10605  16.so.16.5[.0]
 *    1.6.6                   16    10606  16.so.16.6[.0]
 *    1.6.7beta01-04          16    10607  16.so.16.7[.0]
 *    1.6.7rc01-03            16    10607  16.so.16.7[.0]
 *    1.6.7                   16    10607  16.so.16.7[.0]
 *    1.6.8beta01-02          16    10608  16.so.16.8[.0]
 *    1.6.8rc01-02            16    10608  16.so.16.8[.0]
 *    1.6.8                   16    10608  16.so.16.8[.0]
 *    1.6.9beta01-04          16    10609  16.so.16.9[.0]
 *    1.6.9rc01-02            16    10609  16.so.16.9[.0]
 *    1.6.9                   16    10609  16.so.16.9[.0]
 *    1.6.10beta01-03         16    10610  16.so.16.10[.0]
 *    1.6.10rc01-03           16    10610  16.so.16.10[.0]
 *    1.6.10                  16    10610  16.so.16.10[.0]
 *    1.6.11beta01-06         16    10611  16.so.16.11[.0]
 *    1.6.11rc01-02           16    10611  16.so.16.11[.0]
 *    1.6.11                  16    10611  16.so.16.11[.0]
 *    1.6.12rc01-03           16    10612  16.so.16.12[.0]
 *    1.6.12                  16    10612  16.so.16.12[.0]
 *    1.6.13beta01-04         16    10613  16.so.16.13[.0]
 *    1.6.13rc01-02           16    10613  16.so.16.13[.0]
 *    1.6.13                  16    10613  16.so.16.13[.0]
 *    1.6.14beta01-07         16    10614  16.so.16.14[.0]
 *    1.6.14rc01-02           16    10614  16.so.16.14[.0]
 *    1.6.14                  16    10614  16.so.16.14[.0]
 *    1.6.15beta01-08         16    10615  16.so.16.15[.0]
 *    1.6.15rc01-03           16    10615  16.so.16.15[.0]
 *    1.6.15                  16    10615  16.so.16.15[.0]
 *    1.6.16beta01-03         16    10616  16.so.16.16[.0]
 *    1.6.16rc01-02           16    10616  16.so.16.16[.0]
 *    1.6.16                  16    10616  16.so.16.16[.0]
 *    1.6.17beta01-06         16    10617  16.so.16.17[.0]
 *    1.6.17rc01-06           16    10617  16.so.16.17[.0]
 *    1.6.17                  16    10617  16.so.16.17[.0]
 *
- *   Henceforth the source version will match the shared-library major
+ *    Henceforth the source version will match the shared-library major
- *   and minor numbers; the shared-library major version number will be
+ *    and minor numbers; the shared-library major version number will be
- *   used for changes in backward compatibility, as it is intended.  The
+ *    used for changes in backward compatibility, as it is intended.  The
- *   PNG_LIBPNG_VER macro, which is not used within libpng but is available
+ *    PNG_LIBPNG_VER macro, which is not used within libpng but is available
- *   for applications, is an unsigned integer of the form xyyzz corresponding
+ *    for applications, is an unsigned integer of the form xyyzz corresponding
- *   to the source version x.y.z (leading zeros in y and z).  Beta versions
+ *    to the source version x.y.z (leading zeros in y and z).  Beta versions
- *   were given the previous public release number plus a letter, until
+ *    were given the previous public release number plus a letter, until
- *   version 1.0.6j; from then on they were given the upcoming public
+ *    version 1.0.6j; from then on they were given the upcoming public
- *   release number plus "betaNN" or "rcNN".
+ *    release number plus "betaNN" or "rcNN".
 *
- *   Binary incompatibility exists only when applications make direct access
+ *    Binary incompatibility exists only when applications make direct access
- *   to the info_ptr or png_ptr members through png.h, and the compiled
+ *    to the info_ptr or png_ptr members through png.h, and the compiled
- *   application is loaded with a different version of the library.
+ *    application is loaded with a different version of the library.
 *
- *   DLLNUM will change each time there are forward or backward changes
+ *    DLLNUM will change each time there are forward or backward changes
- *   in binary compatibility (e.g., when a new feature is added).
+ *    in binary compatibility (e.g., when a new feature is added).
 *
- * See libpng-manual.txt or libpng.3 for more information.  The PNG
+ * See libpng.txt or libpng.3 for more information.  The PNG specification
- * specification is available as a W3C Recommendation and as an ISO
+ * is available as a W3C Recommendation and as an ISO Specification,
- * Specification, <http://www.w3.org/TR/2003/REC-PNG-20031110/
+ * <http://www.w3.org/TR/2003/REC-PNG-20031110/
 */
 /*
 * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
 *
 * If you modify libpng you may insert additional notices immediately following
 * this sentence.
 *
 * This code is released under the libpng license.
 *
 * libpng versions 1.2.6, August 15, 2004, through 1.6.17, March 26, 2015, are
 * Copyright (c) 2004, 2006-2015 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-1.2.5
 * with the following individual added to the list of Contributing Authors:
 *
 *    Cosmin Truta
 *
 * libpng versions 1.0.7, July 1, 2000, through 1.2.5, October 3, 2002, are
 * Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-1.0.6
 * with the following individuals added to the list of Contributing Authors:
 *
 *    Simon-Pierre Cadieux
 *    Eric S. Raymond
 *    Gilles Vollant
 *
 * and with the following additions to the disclaimer:
 *
 *    There is no warranty against interference with your enjoyment of the
 *    library or against infringement.  There is no warranty that our
 *    efforts or the library will fulfill any of your particular purposes
 *    or needs.  This library is provided with all faults, and the entire
 *    risk of satisfactory quality, performance, accuracy, and effort is with
 *    the user.
 *
 * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
 * Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-0.96,
 * with the following individuals added to the list of Contributing Authors:
 *
 *    Tom Lane
 *    Glenn Randers-Pehrson
 *    Willem van Schaik
 *
 * libpng versions 0.89, June 1996, through 0.96, May 1997, are
 * Copyright (c) 1996, 1997 Andreas Dilger
 * Distributed according to the same disclaimer and license as libpng-0.88,
 * with the following individuals added to the list of Contributing Authors:
 *
 *    John Bowler
 *    Kevin Bracey
 *    Sam Bushell
 *    Magnus Holmgren
 *    Greg Roelofs
 *    Tom Tanner
 *
 * libpng versions 0.5, May 1995, through 0.88, January 1996, are
 * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * For the purposes of this copyright and license, "Contributing Authors"
 * is defined as the following set of individuals:
 *
 *    Andreas Dilger
 *    Dave Martindale
 *    Guy Eric Schalnat
 *    Paul Schmidt
 *    Tim Wegner
 *
 * The PNG Reference Library is supplied "AS IS".  The Contributing Authors
 * and Group 42, Inc. disclaim all warranties, expressed or implied,
 * including, without limitation, the warranties of merchantability and of
 * fitness for any purpose.  The Contributing Authors and Group 42, Inc.
 * assume no liability for direct, indirect, incidental, special, exemplary,
 * or consequential damages, which may result from the use of the PNG
 * Reference Library, even if advised of the possibility of such damage.
 *
 * Permission is hereby granted to use, copy, modify, and distribute this
 * source code, or portions hereof, for any purpose, without fee, subject
 * to the following restrictions:
 *
 *   1. The origin of this source code must not be misrepresented.
 *
 *   2. Altered versions must be plainly marked as such and must not
 *      be misrepresented as being the original source.
 *
 *   3. This Copyright notice may not be removed or altered from
 *      any source or altered source distribution.
 *
 * The Contributing Authors and Group 42, Inc. specifically permit, without
 * fee, and encourage the use of this source code as a component to
 * supporting the PNG file format in commercial products.  If you use this
 * source code in a product, acknowledgment is not required but would be
 * appreciated.
 */
 /*
 * A "png_get_copyright" function is available, for convenient use in "about"
 * boxes and the like:
 *
 *     printf("%s", png_get_copyright(NULL));
 *
 * Also, the PNG logo (in PNG format, of course) is supplied in the
 * files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
 */
 /*
 * Libpng is OSI Certified Open Source Software.  OSI Certified is a
 * certification mark of the Open Source Initiative.
 */
 /*
 * The contributing authors would like to thank all those who helped
 * with testing, bug fixes, and patience.  This wouldn't have been
 * possible without all of you.
 *
 * Thanks to Frank J. T. Wojcik for helping with the documentation.
 */
 /*
 * Y2K compliance in libpng:
 * =========================
 *
- *    March 26, 2015
+ *    January 15, 2016
 *
 *    Since the PNG Development group is an ad-hoc body, we can't make
 *    an official declaration.
 *
 *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.6.17 are Y2K compliant.  It is my belief that
+ *    upward through 1.6.21 are Y2K compliant.  It is my belief that
 *    earlier versions were also Y2K compliant.
 *
 *    Libpng only has two year fields.  One is a 2-byte unsigned integer
@ -427,9 +282,9 @@
 */
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.17"
+#define PNG_LIBPNG_VER_STRING "1.6.21"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.6.17 - March 26, 2015\n"
+     " libpng version 1.6.21 - January 15, 2016\n"
 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@ -437,7 +292,7 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   6
-#define PNG_LIBPNG_VER_RELEASE 17
+#define PNG_LIBPNG_VER_RELEASE 21
 /* This should match the numeric part of the final component of
 * PNG_LIBPNG_VER_STRING, omitting any leading zero:
@ -468,7 +323,7 @@
 * version 1.0.0 was mis-numbered 100 instead of 10000).  From
 * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
 */
-#define PNG_LIBPNG_VER 10617 /* 1.6.17 */
+#define PNG_LIBPNG_VER 10621 /* 1.6.21 */
 /* Library configuration: these options cannot be changed after
 * the library has been built.
@ -525,17 +380,22 @@ extern "C" {
 /* This file is arranged in several sections:
 *
- * 1. Any configuration options that can be specified by for the application
+ * 1. [omitted]
 * 2. Any configuration options that can be specified by for the application
 *    code when it is built.  (Build time configuration is in pnglibconf.h)
- * 2. Type definitions (base types are defined in pngconf.h), structure
+ * 3. Type definitions (base types are defined in pngconf.h), structure
 *    definitions.
- * 3. Exported library functions.
+ * 4. Exported library functions.
- * 4. Simplified API.
+ * 5. Simplified API.
 * 6. Implementation options.
 *
 * The library source code has additional files (principally pngpriv.h) that
 * allow configuration of the library.
 */
-/* Section 1: run time configuration
+
 /* Section 1: [omitted] */
 /* Section 2: run time configuration
 * See pnglibconf.h for build time configuration
 *
 * Run time configuration allows the application to choose between
@ -565,7 +425,7 @@ extern "C" {
 * Otherwise the calls are mapped to png_error.
 */
-/* Section 2: type definitions, including structures and compile time
+/* Section 3: type definitions, including structures and compile time
 * constants.
 * See pngconf.h for base types that vary by machine/system
 */
@ -573,7 +433,7 @@ extern "C" {
 /* This triggers a compiler error in png.c, if png.c and png.h
 * do not agree upon the version number.
 */
-typedef char* png_libpng_version_1_6_17;
+typedef char* png_libpng_version_1_6_21;
 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
 *
@ -889,7 +749,9 @@ typedef png_unknown_chunk * * png_unknown_chunkpp;
 #define PNG_INFO_iCCP 0x1000   /* ESR, 1.0.6 */
 #define PNG_INFO_sPLT 0x2000   /* ESR, 1.0.6 */
 #define PNG_INFO_sCAL 0x4000   /* ESR, 1.0.6 */
 #if INT_MAX >= 0x8000 /* else this might break */
 #define PNG_INFO_IDAT 0x8000   /* ESR, 1.0.6 */
 #endif
 /* This is used for the transformation routines, as some of them
 * change these values for the row.  It also should enable using
@ -993,7 +855,9 @@ PNG_FUNCTION(void, (PNGCAPI *png_longjmp_ptr), PNGARG((jmp_buf, int)), typedef);
 #define PNG_TRANSFORM_GRAY_TO_RGB   0x2000      /* read only */
 /* Added to libpng-1.5.4 */
 #define PNG_TRANSFORM_EXPAND_16     0x4000      /* read only */
 #if INT_MAX >= 0x8000 /* else this might break */
 #define PNG_TRANSFORM_SCALE_16      0x8000      /* read only */
 #endif
 /* Flags for MNG supported features */
 #define PNG_FLAG_MNG_EMPTY_PLTE     0x01
@ -1010,7 +874,7 @@ typedef PNG_CALLBACK(png_voidp, *png_malloc_ptr, (png_structp,
    png_alloc_size_t));
 typedef PNG_CALLBACK(void, *png_free_ptr, (png_structp, png_voidp));
-/* Section 3: exported functions
+/* Section 4: exported functions
 * Here are the function definitions most commonly used.  This is not
 * the place to find out how to use libpng.  See libpng-manual.txt for the
 * full explanation, see example.c for the summary.  This just provides
@ -1383,13 +1247,13 @@ PNG_EXPORT(38, void, png_set_invert_alpha, (png_structrp png_ptr));
 #endif
 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
-/* Add a filler byte to 8-bit Gray or 24-bit RGB images. */
+/* Add a filler byte to 8-bit or 16-bit Gray or 24-bit or 48-bit RGB images. */
 PNG_EXPORT(39, void, png_set_filler, (png_structrp png_ptr, png_uint_32 filler,
    int flags));
 /* The values of the PNG_FILLER_ defines should NOT be changed */
 #  define PNG_FILLER_BEFORE 0
 #  define PNG_FILLER_AFTER 1
-/* Add an alpha byte to 8-bit Gray or 24-bit RGB images. */
+/* Add an alpha byte to 8-bit or 16-bit Gray or 24-bit or 48-bit RGB images. */
 PNG_EXPORT(40, void, png_set_add_alpha, (png_structrp png_ptr,
    png_uint_32 filler, int flags));
 #endif /* READ_FILLER || WRITE_FILLER */
@ -1623,35 +1487,7 @@ PNG_EXPORT(67, void, png_set_filter, (png_structrp png_ptr, int method,
 #define PNG_FILTER_VALUE_LAST  5
 #ifdef PNG_WRITE_SUPPORTED
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* EXPERIMENTAL */
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* DEPRECATED */
 /* The "heuristic_method" is given by one of the PNG_FILTER_HEURISTIC_
 * defines, either the default (minimum-sum-of-absolute-differences), or
 * the experimental method (weighted-minimum-sum-of-absolute-differences).
 *
 * Weights are factors >= 1.0, indicating how important it is to keep the
 * filter type consistent between rows.  Larger numbers mean the current
 * filter is that many times as likely to be the same as the "num_weights"
 * previous filters.  This is cumulative for each previous row with a weight.
 * There needs to be "num_weights" values in "filter_weights", or it can be
 * NULL if the weights aren't being specified.  Weights have no influence on
 * the selection of the first row filter.  Well chosen weights can (in theory)
 * improve the compression for a given image.
 *
 * Costs are factors >= 1.0 indicating the relative decoding costs of a
 * filter type.  Higher costs indicate more decoding expense, and are
 * therefore less likely to be selected over a filter with lower computational
 * costs.  There needs to be a value in "filter_costs" for each valid filter
 * type (given by PNG_FILTER_VALUE_LAST), or it can be NULL if you aren't
 * setting the costs.  Costs try to improve the speed of decompression without
 * unduly increasing the compressed image size.
 *
 * A negative weight or cost indicates the default value is to be used, and
 * values in the range [0.0, 1.0) indicate the value is to remain unchanged.
 * The default values for both weights and costs are currently 1.0, but may
 * change if good general weighting/cost heuristics can be found.  If both
 * the weights and costs are set to 1.0, this degenerates the WEIGHTED method
 * to the UNWEIGHTED method, but with added encoding time/computation.
 */
 PNG_FP_EXPORT(68, void, png_set_filter_heuristics, (png_structrp png_ptr,
    int heuristic_method, int num_weights, png_const_doublep filter_weights,
    png_const_doublep filter_costs))
@ -1661,9 +1497,7 @@ PNG_FIXED_EXPORT(209, void, png_set_filter_heuristics_fixed,
    png_const_fixed_point_p filter_costs))
 #endif /* WRITE_WEIGHTED_FILTER */
-/* Heuristic used for row filter selection.  These defines should NOT be
+/* The following are no longer used and will be removed from libpng-1.7: */
 * changed.
 */
 #define PNG_FILTER_HEURISTIC_DEFAULT    0  /* Currently "UNWEIGHTED" */
 #define PNG_FILTER_HEURISTIC_UNWEIGHTED 1  /* Used by libpng < 0.95 */
 #define PNG_FILTER_HEURISTIC_WEIGHTED   2  /* Experimental feature */
@ -2744,7 +2578,7 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
 #  define PNG_get_int_32(buf) \
     ((png_int_32)((*(buf) & 0x80) \
-      ? -((png_int_32)((png_get_uint_32(buf) ^ 0xffffffffL) + 1)) \
+      ? -((png_int_32)(((png_get_uint_32(buf)^0xffffffffU)+1U)&0x7fffffffU)) \
      : (png_int_32)png_get_uint_32(buf)))
   /* If PNG_PREFIX is defined the same thing as below happens in pnglibconf.h,
@ -2764,10 +2598,17 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
 #  endif
 #endif
-#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) || \
+#ifdef PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED
-    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
+PNG_EXPORT(242, void, png_set_check_for_invalid_index,
    (png_structrp png_ptr, int allowed));
 #  ifdef PNG_GET_PALETTE_MAX_SUPPORTED
 PNG_EXPORT(243, int, png_get_palette_max, (png_const_structp png_ptr,
    png_const_infop info_ptr));
 #  endif
 #endif /* CHECK_FOR_INVALID_INDEX */
 /*******************************************************************************
- *  SIMPLIFIED API
+ * Section 5: SIMPLIFIED API
 *******************************************************************************
 *
 * Please read the documentation in libpng-manual.txt (TODO: write said
@ -2783,8 +2624,9 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
 *
 * To read a PNG file using the simplified API:
 *
- * 1) Declare a 'png_image' structure (see below) on the stack and set the
+ * 1) Declare a 'png_image' structure (see below) on the stack, set the
- *    version field to PNG_IMAGE_VERSION.
+ *    version field to PNG_IMAGE_VERSION and the 'opaque' pointer to NULL
 *    (this is REQUIRED, your program may crash if you don't do it.)
 * 2) Call the appropriate png_image_begin_read... function.
 * 3) Set the png_image 'format' member to the required sample format.
 * 4) Allocate a buffer for the image and, if required, the color-map.
@ -2811,6 +2653,9 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
 * when it is being read or defines the in-memory format of an image that you
 * need to write:
 */
 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) || \
    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
 #define PNG_IMAGE_VERSION 1
 typedef struct png_control *png_controlp;
@ -2910,7 +2755,7 @@ typedef struct
 * called to read or write the color-map and set the format correctly for the
 * image data.  Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly!
 *
- * NOTE: libpng can be built with particular features disabled, if you see
+ * NOTE: libpng can be built with particular features disabled. If you see
 * compiler errors because the definition of one of the following flags has been
 * compiled out it is because libpng does not have the required support.  It is
 * possible, however, for the libpng configuration to enable the format on just
@ -2922,7 +2767,7 @@ typedef struct
 */
 #define PNG_FORMAT_FLAG_ALPHA    0x01U /* format with an alpha channel */
 #define PNG_FORMAT_FLAG_COLOR    0x02U /* color format: otherwise grayscale */
-#define PNG_FORMAT_FLAG_LINEAR   0x04U /* 2 byte channels else 1 byte */
+#define PNG_FORMAT_FLAG_LINEAR   0x04U /* 2-byte channels else 1-byte */
 #define PNG_FORMAT_FLAG_COLORMAP 0x08U /* image data is color-mapped */
 #ifdef PNG_FORMAT_BGR_SUPPORTED
@ -3209,9 +3054,11 @@ PNG_EXPORT(240, int, png_image_write_to_stdio, (png_imagep image, FILE *file,
 *
 * With all APIs row_stride is handled as in the read APIs - it is the spacing
 * from one row to the next in component sized units (1 or 2 bytes) and if
- * negative indicates a bottom-up row layout in the buffer.
+ * negative indicates a bottom-up row layout in the buffer.  If row_stride is zero,
 * libpng will calculate it for you from the image width and number of channels.
 *
- * Note that the write API does not support interlacing or sub-8-bit pixels.
+ * Note that the write API does not support interlacing, sub-8-bit pixels, indexed
 * PNG (color_type 3) or most ancillary chunks.
 */
 #endif /* STDIO */
 #endif /* SIMPLIFIED_WRITE */
@ -3220,17 +3067,8 @@ PNG_EXPORT(240, int, png_image_write_to_stdio, (png_imagep image, FILE *file,
 ******************************************************************************/
 #endif /* SIMPLIFIED_{READ|WRITE} */
 #ifdef PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED
 PNG_EXPORT(242, void, png_set_check_for_invalid_index,
    (png_structrp png_ptr, int allowed));
 #  ifdef PNG_GET_PALETTE_MAX_SUPPORTED
 PNG_EXPORT(243, int, png_get_palette_max, (png_const_structp png_ptr,
    png_const_infop info_ptr));
 #  endif
 #endif /* CHECK_FOR_INVALID_INDEX */
 /*******************************************************************************
- *  IMPLEMENTATION OPTIONS
+ * Section 6: IMPLEMENTATION OPTIONS
 *******************************************************************************
 *
 * Support for arbitrary implementation-specific optimizations.  The API allows
--- a/thirdparty/libpng/pngconf.h
+++ b/thirdparty/libpng/pngconf.h
@ -1,9 +1,9 @@
 /* pngconf.h - machine configurable file for libpng
 *
- * libpng version 1.6.17, March 26, 2015
+ * libpng version 1.6.21, January 15, 2016
 *
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -63,7 +63,7 @@
 */
 #define PNG_CONST const /* backward compatibility only */
-/* This controls optimization of the reading of 16 and 32 bit values
+/* This controls optimization of the reading of 16-bit and 32-bit values
 * from PNG files.  It can be set on a per-app-file basis - it
 * just changes whether a macro is used when the function is called.
 * The library builder sets the default; if read functions are not
@ -295,11 +295,11 @@
    * table entries, so we discard it here.  See the .dfn files in the
    * scripts directory.
    */
 #ifndef PNG_EXPORTA
-#  define PNG_EXPORTA(ordinal, type, name, args, attributes)\
+#ifndef PNG_EXPORTA
-      PNG_FUNCTION(PNG_EXPORT_TYPE(type),(PNGAPI name),PNGARG(args), \
+#  define PNG_EXPORTA(ordinal, type, name, args, attributes) \
-        extern attributes)
+      PNG_FUNCTION(PNG_EXPORT_TYPE(type), (PNGAPI name), PNGARG(args), \
      PNG_LINKAGE_API attributes)
 #endif
 /* ANSI-C (C90) does not permit a macro to be invoked with an empty argument,
@ -307,7 +307,7 @@
 */
 #define PNG_EMPTY /*empty list*/
-#define PNG_EXPORT(ordinal, type, name, args)\
+#define PNG_EXPORT(ordinal, type, name, args) \
   PNG_EXPORTA(ordinal, type, name, args, PNG_EMPTY)
 /* Use PNG_REMOVED to comment out a removed interface. */
@ -480,7 +480,7 @@
 #if CHAR_BIT == 8 && UCHAR_MAX == 255
   typedef unsigned char png_byte;
 #else
-#  error "libpng requires 8 bit bytes"
+#  error "libpng requires 8-bit bytes"
 #endif
 #if INT_MIN == -32768 && INT_MAX == 32767
@ -488,7 +488,7 @@
 #elif SHRT_MIN == -32768 && SHRT_MAX == 32767
   typedef short png_int_16;
 #else
-#  error "libpng requires a signed 16 bit type"
+#  error "libpng requires a signed 16-bit type"
 #endif
 #if UINT_MAX == 65535
@ -496,7 +496,7 @@
 #elif USHRT_MAX == 65535
   typedef unsigned short png_uint_16;
 #else
-#  error "libpng requires an unsigned 16 bit type"
+#  error "libpng requires an unsigned 16-bit type"
 #endif
 #if INT_MIN < -2147483646 && INT_MAX > 2147483646
@ -504,7 +504,7 @@
 #elif LONG_MIN < -2147483646 && LONG_MAX > 2147483646
   typedef long int png_int_32;
 #else
-#  error "libpng requires a signed 32 bit (or more) type"
+#  error "libpng requires a signed 32-bit (or more) type"
 #endif
 #if UINT_MAX > 4294967294
@ -512,7 +512,7 @@
 #elif ULONG_MAX > 4294967294
   typedef unsigned long int png_uint_32;
 #else
-#  error "libpng requires an unsigned 32 bit (or more) type"
+#  error "libpng requires an unsigned 32-bit (or more) type"
 #endif
 /* Prior to 1.6.0 it was possible to disable the use of size_t, 1.6.0, however,
--- a/thirdparty/libpng/pngdebug.h
+++ b/thirdparty/libpng/pngdebug.h
@ -2,7 +2,7 @@
 /* pngdebug.h - Debugging macros for libpng, also used in pngtest.c
 *
 * Last changed in libpng 1.6.8 [December 19, 2013]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2013 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
--- a/thirdparty/libpng/pngerror.c
+++ b/thirdparty/libpng/pngerror.c
@ -2,7 +2,7 @@
 /* pngerror.c - stub functions for i/o and memory allocation
 *
 * Last changed in libpng 1.6.15 [November 20, 2014]
- * Copyright (c) 1998-2014 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2014 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
--- a/thirdparty/libpng/pngget.c
+++ b/thirdparty/libpng/pngget.c
@ -2,7 +2,7 @@
 /* pngget.c - retrieval of values from info struct
 *
 * Last changed in libpng 1.6.17 [March 26, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
--- a/thirdparty/libpng/pnginfo.h
+++ b/thirdparty/libpng/pnginfo.h
@ -2,7 +2,7 @@
 /* pnginfo.h - header file for PNG reference library
 *
 * Last changed in libpng 1.6.1 [March 28, 2013]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2013 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
--- a/thirdparty/libpng/pnglibconf.h
+++ b/thirdparty/libpng/pnglibconf.h
@ -1,10 +1,10 @@
-/* libpng 1.6.17 STANDARD API DEFINITION */
+/* libpng 1.6.21 STANDARD API DEFINITION */
 /* pnglibconf.h - library build configuration */
-/* Libpng version 1.6.17 - March 26, 2015 */
+/* Libpng version 1.6.21 - January 15, 2016 */
-/* Copyright (c) 1998-2014 Glenn Randers-Pehrson */
+/* Copyright (c) 1998-2015 Glenn Randers-Pehrson */
 /* This code is released under the libpng license. */
 /* For conditions of distribution and use, see the disclaimer */
@ -101,8 +101,6 @@
 #define PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SEQUENTIAL_READ_SUPPORTED
 #define PNG_SETJMP_SUPPORTED
 #define PNG_SET_CHUNK_CACHE_LIMIT_SUPPORTED
 #define PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
 #define PNG_SET_OPTION_SUPPORTED
 #define PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SET_USER_LIMITS_SUPPORTED
@ -187,11 +185,14 @@
 /* end of options */
 /* settings */
 #define PNG_API_RULE 0
 #define PNG_COST_SHIFT 3
 #define PNG_DEFAULT_READ_MACROS 1
 #define PNG_GAMMA_THRESHOLD_FIXED 5000
 #define PNG_IDAT_READ_SIZE PNG_ZBUF_SIZE
 #define PNG_INFLATE_BUF_SIZE 1024
 #define PNG_LINKAGE_API extern
 #define PNG_LINKAGE_CALLBACK extern
 #define PNG_LINKAGE_DATA extern
 #define PNG_LINKAGE_FUNCTION extern
 #define PNG_MAX_GAMMA_8 11
 #define PNG_QUANTIZE_BLUE_BITS 5
 #define PNG_QUANTIZE_GREEN_BITS 5
@ -202,7 +203,6 @@
 #define PNG_USER_CHUNK_MALLOC_MAX 8000000
 #define PNG_USER_HEIGHT_MAX 1000000
 #define PNG_USER_WIDTH_MAX 1000000
 #define PNG_WEIGHT_SHIFT 8
 #define PNG_ZBUF_SIZE 8192
 #define PNG_ZLIB_VERNUM 0 /* unknown */
 #define PNG_Z_DEFAULT_COMPRESSION (-1)
--- a/thirdparty/libpng/pngmem.c
+++ b/thirdparty/libpng/pngmem.c
@ -2,7 +2,7 @@
 /* pngmem.c - stub functions for memory allocation
 *
 * Last changed in libpng 1.6.15 [November 20, 2014]
- * Copyright (c) 1998-2014 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2014 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -77,6 +77,9 @@ png_malloc_base,(png_const_structrp png_ptr, png_alloc_size_t size),
   PNG_UNUSED(png_ptr)
 #endif
   /* Some compilers complain that this is always true.  However, it
    * can be false when integer overflow happens.
    */
   if (size > 0 && size <= PNG_SIZE_MAX
 #     ifdef PNG_MAX_MALLOC_64K
         && size <= 65536U
--- a/thirdparty/libpng/pngpread.c
+++ b/thirdparty/libpng/pngpread.c
@ -1,8 +1,8 @@
 /* pngpread.c - read a png file in push mode
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -19,7 +19,6 @@
 #define PNG_READ_SIG_MODE   0
 #define PNG_READ_CHUNK_MODE 1
 #define PNG_READ_IDAT_MODE  2
 #define PNG_SKIP_MODE       3
 #define PNG_READ_tEXt_MODE  4
 #define PNG_READ_zTXt_MODE  5
 #define PNG_READ_DONE_MODE  6
@ -78,32 +77,14 @@ png_process_data_pause(png_structrp png_ptr, int save)
 png_uint_32 PNGAPI
 png_process_data_skip(png_structrp png_ptr)
 {
-   png_uint_32 remaining = 0;
+  /* TODO: Deprecate and remove this API.
-
+   * Somewhere the implementation of this seems to have been lost,
-   if (png_ptr != NULL && png_ptr->process_mode == PNG_SKIP_MODE &&
+   * or abandoned.  It was only to support some internal back-door access
-      png_ptr->skip_length > 0)
+   * to png_struct) in libpng-1.4.x.
-   {
+   */
-      /* At the end of png_process_data the buffer size must be 0 (see the loop
+   png_app_warning(png_ptr,
-       * above) so we can detect a broken call here:
+"png_process_data_skip is not implemented in any current version of libpng");
-       */
+   return 0;
      if (png_ptr->buffer_size != 0)
         png_error(png_ptr,
            "png_process_data_skip called inside png_process_data");
      /* If is impossible for there to be a saved buffer at this point -
       * otherwise we could not be in SKIP mode.  This will also happen if
       * png_process_skip is called inside png_process_data (but only very
       * rarely.)
       */
      if (png_ptr->save_buffer_size != 0)
         png_error(png_ptr, "png_process_data_skip called with saved data");
      remaining = png_ptr->skip_length;
      png_ptr->skip_length = 0;
      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
   }
   return remaining;
 }
 /* What we do with the incoming data depends on what we were previously
@ -135,12 +116,6 @@ png_process_some_data(png_structrp png_ptr, png_inforp info_ptr)
         break;
      }
      case PNG_SKIP_MODE:
      {
         png_push_crc_finish(png_ptr);
         break;
      }
      default:
      {
         png_ptr->buffer_size = 0;
@ -159,7 +134,7 @@ void /* PRIVATE */
 png_push_read_sig(png_structrp png_ptr, png_inforp info_ptr)
 {
   png_size_t num_checked = png_ptr->sig_bytes, /* SAFE, does not exceed 8 */
-             num_to_check = 8 - num_checked;
+       num_to_check = 8 - num_checked;
   if (png_ptr->buffer_size < num_to_check)
   {
@ -439,69 +414,6 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
   png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 }
 void /* PRIVATE */
 png_push_crc_skip(png_structrp png_ptr, png_uint_32 skip)
 {
   png_ptr->process_mode = PNG_SKIP_MODE;
   png_ptr->skip_length = skip;
 }
 void /* PRIVATE */
 png_push_crc_finish(png_structrp png_ptr)
 {
   if (png_ptr->skip_length != 0 && png_ptr->save_buffer_size != 0)
   {
      png_size_t save_size = png_ptr->save_buffer_size;
      png_uint_32 skip_length = png_ptr->skip_length;
      /* We want the smaller of 'skip_length' and 'save_buffer_size', but
       * they are of different types and we don't know which variable has the
       * fewest bits.  Carefully select the smaller and cast it to the type of
       * the larger - this cannot overflow.  Do not cast in the following test
       * - it will break on either 16 or 64 bit platforms.
       */
      if (skip_length < save_size)
         save_size = (png_size_t)skip_length;
      else
         skip_length = (png_uint_32)save_size;
      png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
      png_ptr->skip_length -= skip_length;
      png_ptr->buffer_size -= save_size;
      png_ptr->save_buffer_size -= save_size;
      png_ptr->save_buffer_ptr += save_size;
   }
   if (png_ptr->skip_length != 0 && png_ptr->current_buffer_size != 0)
   {
      png_size_t save_size = png_ptr->current_buffer_size;
      png_uint_32 skip_length = png_ptr->skip_length;
      /* We want the smaller of 'skip_length' and 'current_buffer_size', here,
       * the same problem exists as above and the same solution.
       */
      if (skip_length < save_size)
         save_size = (png_size_t)skip_length;
      else
         skip_length = (png_uint_32)save_size;
      png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
      png_ptr->skip_length -= skip_length;
      png_ptr->buffer_size -= save_size;
      png_ptr->current_buffer_size -= save_size;
      png_ptr->current_buffer_ptr += save_size;
   }
   if (png_ptr->skip_length == 0)
   {
      PNG_PUSH_SAVE_BUFFER_IF_LT(4)
      png_crc_finish(png_ptr, 0);
      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
   }
 }
 void PNGCBAPI
 png_push_fill_buffer(png_structp png_ptr, png_bytep buffer, png_size_t length)
 {
@ -584,13 +496,11 @@ png_push_save_buffer(png_structrp png_ptr)
      if (png_ptr->save_buffer == NULL)
      {
         png_free(png_ptr, old_buffer);
         old_buffer = NULL;
         png_error(png_ptr, "Insufficient memory for save_buffer");
      }
      memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
      png_free(png_ptr, old_buffer);
      old_buffer = NULL;
      png_ptr->save_buffer_max = new_max;
   }
   if (png_ptr->current_buffer_size)
@ -653,7 +563,7 @@ png_push_read_IDAT(png_structrp png_ptr)
       * are of different types and we don't know which variable has the fewest
       * bits.  Carefully select the smaller and cast it to the type of the
       * larger - this cannot overflow.  Do not cast in the following test - it
-       * will break on either 16 or 64 bit platforms.
+       * will break on either 16-bit or 64-bit platforms.
       */
      if (idat_size < save_size)
         save_size = (png_size_t)idat_size;
@ -696,6 +606,7 @@ png_push_read_IDAT(png_structrp png_ptr)
      png_ptr->current_buffer_size -= save_size;
      png_ptr->current_buffer_ptr += save_size;
   }
   if (png_ptr->idat_size == 0)
   {
      PNG_PUSH_SAVE_BUFFER_IF_LT(4)
@ -751,7 +662,7 @@ png_process_IDAT_data(png_structrp png_ptr, png_bytep buffer,
       * change the current behavior (see comments in inflate.c
       * for why this doesn't happen at present with zlib 1.2.5).
       */
-      ret = inflate(&png_ptr->zstream, Z_SYNC_FLUSH);
+      ret = PNG_INFLATE(png_ptr, Z_SYNC_FLUSH);
      /* Check for any failure before proceeding. */
      if (ret != Z_OK && ret != Z_STREAM_END)
--- a/thirdparty/libpng/pngpriv.h
+++ b/thirdparty/libpng/pngpriv.h
@ -1,8 +1,8 @@
 /* pngpriv.h - private declarations for use inside libpng
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.21 [January 15, 2016]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -118,8 +118,12 @@
    * to compile with an appropriate #error if ALIGNED_MEMORY has been turned
    * off.
    *
-    * Note that gcc-4.9 defines __ARM_NEON instead of __ARM_NEON__, so we
+    * Note that gcc-4.9 defines __ARM_NEON instead of the deprecated
-    * check both variants.
+    * __ARM_NEON__, so we check both variants.
    *
    * To disable ARM_NEON optimizations entirely, and skip compiling the
    * associated assembler code, pass --enable-arm-neon=no to configure
    * or put -DPNG_ARM_NEON_OPT=0 in CPPFLAGS.
    */
 #  if (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \
   defined(PNG_ALIGNED_MEMORY_SUPPORTED)
@ -248,17 +252,18 @@
 * always be used to declare an extern data or function object in this file.
 */
 #ifndef PNG_INTERNAL_DATA
-#  define PNG_INTERNAL_DATA(type, name, array) extern type name array
+#  define PNG_INTERNAL_DATA(type, name, array) PNG_LINKAGE_DATA type name array
 #endif
 #ifndef PNG_INTERNAL_FUNCTION
 #  define PNG_INTERNAL_FUNCTION(type, name, args, attributes)\
-      extern PNG_FUNCTION(type, name, args, PNG_EMPTY attributes)
+      PNG_LINKAGE_FUNCTION PNG_FUNCTION(type, name, args, PNG_EMPTY attributes)
 #endif
 #ifndef PNG_INTERNAL_CALLBACK
 #  define PNG_INTERNAL_CALLBACK(type, name, args, attributes)\
-      extern PNG_FUNCTION(type, (PNGCBAPI name), args, PNG_EMPTY attributes)
+      PNG_LINKAGE_CALLBACK PNG_FUNCTION(type, (PNGCBAPI name), args,\
         PNG_EMPTY attributes)
 #endif
 /* If floating or fixed point APIs are disabled they may still be compiled
@ -296,6 +301,22 @@
 #  define PNG_DLL_EXPORT
 #endif
 /* This is a global switch to set the compilation for an installed system
 * (a release build).  It can be set for testing debug builds to ensure that
 * they will compile when the build type is switched to RC or STABLE, the
 * default is just to use PNG_LIBPNG_BUILD_BASE_TYPE.  Set this in CPPFLAGS
 * with either:
 *
 *   -DPNG_RELEASE_BUILD Turns on the release compile path
 *   -DPNG_RELEASE_BUILD=0 Turns it off
 * or in your pngusr.h with
 *   #define PNG_RELEASE_BUILD=1 Turns on the release compile path
 *   #define PNG_RELEASE_BUILD=0 Turns it off
 */
 #ifndef PNG_RELEASE_BUILD
 #  define PNG_RELEASE_BUILD (PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC)
 #endif
 /* SECURITY and SAFETY:
 *
 * libpng is built with support for internal limits on image dimensions and
@ -554,10 +575,6 @@
 #define PNG_STRUCT_PNG   0x0001
 #define PNG_STRUCT_INFO  0x0002
 /* Scaling factor for filter heuristic weighting calculations */
 #define PNG_WEIGHT_FACTOR (1<<(PNG_WEIGHT_SHIFT))
 #define PNG_COST_FACTOR (1<<(PNG_COST_SHIFT))
 /* Flags for the png_ptr->flags rather than declaring a byte for each one */
 #define PNG_FLAG_ZLIB_CUSTOM_STRATEGY     0x0001
 #define PNG_FLAG_ZSTREAM_INITIALIZED      0x0002 /* Added to libpng-1.6.0 */
@ -648,7 +665,7 @@
 /* The fixed point conversion performs range checking and evaluates
 * its argument multiple times, so must be used with care.  The
 * range checking uses the PNG specification values for a signed
- * 32 bit fixed point value except that the values are deliberately
+ * 32-bit fixed point value except that the values are deliberately
 * rounded-to-zero to an integral value - 21474 (21474.83 is roughly
 * (2^31-1) * 100000). 's' is a string that describes the value being
 * converted.
@ -795,7 +812,7 @@
    */
 #endif
-/* This is used for 16 bit gamma tables -- only the top level pointers are
+/* This is used for 16-bit gamma tables -- only the top level pointers are
 * const; this could be changed:
 */
 typedef const png_uint_16p * png_const_uint_16pp;
@ -1198,6 +1215,14 @@ PNG_INTERNAL_FUNCTION(void,png_read_finish_row,(png_structrp png_ptr),
 /* Initialize the row buffers, etc. */
 PNG_INTERNAL_FUNCTION(void,png_read_start_row,(png_structrp png_ptr),PNG_EMPTY);
 #if PNG_ZLIB_VERNUM >= 0x1240
 PNG_INTERNAL_FUNCTION(int,png_zlib_inflate,(png_structrp png_ptr, int flush),
      PNG_EMPTY);
 #  define PNG_INFLATE(pp, flush) png_zlib_inflate(pp, flush)
 #else /* Zlib < 1.2.4 */
 #  define PNG_INFLATE(pp, flush) inflate(&(pp)->zstream, flush)
 #endif /* Zlib < 1.2.4 */
 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
 /* Optional call to update the users info structure */
 PNG_INTERNAL_FUNCTION(void,png_read_transform_info,(png_structrp png_ptr,
@ -1372,10 +1397,6 @@ PNG_INTERNAL_FUNCTION(void,png_push_read_chunk,(png_structrp png_ptr,
 PNG_INTERNAL_FUNCTION(void,png_push_read_sig,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_check_crc,(png_structrp png_ptr),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_crc_skip,(png_structrp png_ptr,
    png_uint_32 length),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_crc_finish,(png_structrp png_ptr),
    PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_save_buffer,(png_structrp png_ptr),
    PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_restore_buffer,(png_structrp png_ptr,
@ -1896,6 +1917,9 @@ PNG_INTERNAL_FUNCTION(void, png_init_filter_functions_neon,
   (png_structp png_ptr, unsigned int bpp), PNG_EMPTY);
 #endif
 PNG_INTERNAL_FUNCTION(png_uint_32, png_check_keyword, (png_structrp png_ptr,
   png_const_charp key, png_bytep new_key), PNG_EMPTY);
 /* Maintainer: Put new private prototypes here ^ */
 #include "pngdebug.h"
--- a/thirdparty/libpng/pngread.c
+++ b/thirdparty/libpng/pngread.c
@ -2,7 +2,7 @@
 /* pngread.c - read a PNG file
 *
 * Last changed in libpng 1.6.17 [March 26, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -63,7 +63,7 @@ png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
         /* In stable builds only warn if an application error can be completely
          * handled.
          */
-#        if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
+#        if PNG_RELEASE_BUILD
            png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
 #        endif
 #     endif
@ -1043,9 +1043,9 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
   /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
    */
   if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
-     /* Added at libpng-1.5.4. "strip_16" produces the same result that it
+      /* Added at libpng-1.5.4. "strip_16" produces the same result that it
-      * did in earlier versions, while "scale_16" is now more accurate.
+       * did in earlier versions, while "scale_16" is now more accurate.
-      */
+       */
 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
      png_set_scale_16(png_ptr);
 #else
@ -1209,7 +1209,7 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
      for (iptr = 0; iptr < info_ptr->height; iptr++)
         info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
-            png_malloc(png_ptr, info_ptr->rowbytes));
+             png_malloc(png_ptr, info_ptr->rowbytes));
   }
   png_read_image(png_ptr, info_ptr->row_pointers);
@ -1683,10 +1683,11 @@ decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
         value *= 257;
         break;
 #ifdef __GNUC__
      default:
         png_error(display->image->opaque->png_ptr,
            "unexpected encoding (internal error)");
-         break;
+#endif
   }
   return value;
@ -2837,7 +2838,6 @@ png_image_read_colormap(png_voidp argument)
      default:
         png_error(png_ptr, "invalid PNG color type");
         /*NOT REACHED*/
         break;
   }
   /* Now deal with the output processing */
@ -2847,10 +2847,6 @@ png_image_read_colormap(png_voidp argument)
   switch (data_encoding)
   {
      default:
         png_error(png_ptr, "bad data option (internal error)");
         break;
      case P_sRGB:
         /* Change to 8-bit sRGB */
         png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
@ -2860,6 +2856,11 @@ png_image_read_colormap(png_voidp argument)
         if (png_ptr->bit_depth > 8)
            png_set_scale_16(png_ptr);
         break;
 #ifdef __GNUC__
      default:
         png_error(png_ptr, "bad data option (internal error)");
 #endif
   }
   if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
@ -3410,10 +3411,6 @@ png_image_read_background(png_voidp argument)
    */
   switch (info_ptr->bit_depth)
   {
      default:
         png_error(png_ptr, "unexpected bit depth");
         break;
      case 8:
         /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
          * to be removed by composing on a background: either the row if
@ -3631,6 +3628,11 @@ png_image_read_background(png_voidp argument)
            }
         }
         break;
 #ifdef __GNUC__
      default:
         png_error(png_ptr, "unexpected bit depth");
 #endif
   }
   return 1;
--- a/thirdparty/libpng/pngrio.c
+++ b/thirdparty/libpng/pngrio.c
@ -2,7 +2,7 @@
 /* pngrio.c - functions for data input
 *
 * Last changed in libpng 1.6.17 [March 26, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -26,7 +26,7 @@
 * reads from a file pointer.  Note that this routine sometimes gets called
 * with very small lengths, so you should implement some kind of simple
 * buffering if you are using unbuffered reads.  This should never be asked
- * to read more than 64K on a 16 bit machine.
+ * to read more than 64K on a 16-bit machine.
 */
 void /* PRIVATE */
 png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
--- a/thirdparty/libpng/pngrtran.c
+++ b/thirdparty/libpng/pngrtran.c
@ -1,8 +1,8 @@
 /* pngrtran.c - transforms the data in a row for PNG readers
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.19 [November 12, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -976,7 +976,6 @@ png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
      default:
         png_error(png_ptr, "invalid error action to rgb_to_gray");
         break;
   }
   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
@ -1997,7 +1996,7 @@ png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
 #     endif
 #  else
-      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
+      /* No 16-bit support: force chopping 16-bit input down to 8, in this case
       * the app program can chose if both APIs are available by setting the
       * correct scaling to use.
       */
@ -2098,10 +2097,10 @@ png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
   if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
   {
-      if (info_ptr->bit_depth < png_ptr->user_transform_depth)
+      if (png_ptr->user_transform_depth != 0)
         info_ptr->bit_depth = png_ptr->user_transform_depth;
-      if (info_ptr->channels < png_ptr->user_transform_channels)
+      if (png_ptr->user_transform_channels != 0)
         info_ptr->channels = png_ptr->user_transform_channels;
   }
 #endif
@ -2382,8 +2381,8 @@ png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
      while (sp < ep)
      {
-         /* The input is an array of 16 bit components, these must be scaled to
+         /* The input is an array of 16-bit components, these must be scaled to
-          * 8 bits each.  For a 16 bit value V the required value (from the PNG
+          * 8 bits each.  For a 16-bit value V the required value (from the PNG
          * specification) is:
          *
          *    (V * 255) / 65535
@ -2404,7 +2403,7 @@ png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
          *
          * The approximate differs from the exact answer only when (vlo-vhi) is
          * 128; it then gives a correction of +1 when the exact correction is
-          * 0.  This gives 128 errors.  The exact answer (correct for all 16 bit
+          * 0.  This gives 128 errors.  The exact answer (correct for all 16-bit
          * input values) is:
          *
          *    error = (vlo-vhi+128)*65535 >> 24;
@ -3148,9 +3147,9 @@ png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
               if (red != green || red != blue)
                  rgb_error |= 1;
-               /* From 1.5.5 in the 16 bit case do the accurate conversion even
+               /* From 1.5.5 in the 16-bit case do the accurate conversion even
                * in the 'fast' case - this is because this is where the code
-                * ends up when handling linear 16 bit data.
+                * ends up when handling linear 16-bit data.
                */
               gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
                  15);
@ -3315,7 +3314,7 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                        if ((png_uint_16)((*sp >> shift) & 0x0f)
                            == png_ptr->trans_color.gray)
                        {
-                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
+                           unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
                           tmp |= png_ptr->background.gray << shift;
                           *sp = (png_byte)(tmp & 0xff);
                        }
@ -3325,7 +3324,7 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                           unsigned int p = (*sp >> shift) & 0x0f;
                           unsigned int g = (gamma_table[p | (p << 4)] >> 4) &
                              0x0f;
-                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
+                           unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
                           tmp |= g << shift;
                           *sp = (png_byte)(tmp & 0xff);
                        }
@ -3351,7 +3350,7 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                        if ((png_uint_16)((*sp >> shift) & 0x0f)
                            == png_ptr->trans_color.gray)
                        {
-                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
+                           unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
                           tmp |= png_ptr->background.gray << shift;
                           *sp = (png_byte)(tmp & 0xff);
                        }
@ -4460,7 +4459,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
               for (i = 0; i < row_width; i++)
               {
-                  if (*sp == gray)
+                  if ((*sp & 0xffU) == gray)
                     *dp-- = 0;
                  else
@ -4478,7 +4477,8 @@ png_do_expand(png_row_infop row_info, png_bytep row,
               dp = row + (row_info->rowbytes << 1) - 1;
               for (i = 0; i < row_width; i++)
               {
-                  if (*(sp - 1) == gray_high && *(sp) == gray_low)
+                  if ((*(sp - 1) & 0xffU) == gray_high &&
                      (*(sp) & 0xffU) == gray_low)
                  {
                     *dp-- = 0;
                     *dp-- = 0;
--- a/thirdparty/libpng/pngrutil.c
+++ b/thirdparty/libpng/pngrutil.c
@ -1,8 +1,8 @@
 /* pngrutil.c - utilities to read a PNG file
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.20 [December 3, 2014]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -89,7 +89,13 @@ png_get_int_32)(png_const_bytep buf)
      return uval;
   uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
-   return -(png_int_32)uval;
+   if ((uval & 0x80000000) == 0) /* no overflow */
       return -(png_int_32)uval;
   /* The following has to be safe; this function only gets called on PNG data
    * and if we get here that data is invalid.  0 is the most safe value and
    * if not then an attacker would surely just generate a PNG with 0 instead.
    */
   return 0;
 }
 /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
@ -98,7 +104,7 @@ png_get_uint_16)(png_const_bytep buf)
 {
   /* ANSI-C requires an int value to accomodate at least 16 bits so this
    * works and allows the compiler not to worry about possible narrowing
-    * on 32 bit systems.  (Pre-ANSI systems did not make integers smaller
+    * on 32-bit systems.  (Pre-ANSI systems did not make integers smaller
    * than 16 bits either.)
    */
   unsigned int val =
@ -341,7 +347,7 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
       * are minimal.
       */
      (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
-#if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
+#if PNG_RELEASE_BUILD
      png_chunk_warning(png_ptr, msg);
      png_ptr->zowner = 0;
 #else
@ -371,10 +377,16 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
      if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
          PNG_OPTION_ON)
      {
         window_bits = 15;
         png_ptr->zstream_start = 0; /* fixed window size */
      }
      else
      {
         window_bits = 0;
         png_ptr->zstream_start = 1;
      }
 # else
 #   define window_bits 0
 # endif
@ -423,6 +435,31 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 #endif
 }
 #if PNG_ZLIB_VERNUM >= 0x1240
 /* Handle the start of the inflate stream if we called inflateInit2(strm,0);
 * in this case some zlib versions skip validation of the CINFO field and, in
 * certain circumstances, libpng may end up displaying an invalid image, in
 * contrast to implementations that call zlib in the normal way (e.g. libpng
 * 1.5).
 */
 int /* PRIVATE */
 png_zlib_inflate(png_structrp png_ptr, int flush)
 {
   if (png_ptr->zstream_start && png_ptr->zstream.avail_in > 0)
   {
      if ((*png_ptr->zstream.next_in >> 4) > 7)
      {
         png_ptr->zstream.msg = "invalid window size (libpng)";
         return Z_DATA_ERROR;
      }
      png_ptr->zstream_start = 0;
   }
   return inflate(&png_ptr->zstream, flush);
 }
 #endif /* Zlib >= 1.2.4 */
 #ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED
 /* png_inflate now returns zlib error codes including Z_OK and Z_STREAM_END to
 * allow the caller to do multiple calls if required.  If the 'finish' flag is
@ -516,7 +553,7 @@ png_inflate(png_structrp png_ptr, png_uint_32 owner, int finish,
          * the previous chunk of input data.  Tell zlib if we have reached the
          * end of the output buffer.
          */
-         ret = inflate(&png_ptr->zstream, avail_out > 0 ? Z_NO_FLUSH :
+         ret = PNG_INFLATE(png_ptr, avail_out > 0 ? Z_NO_FLUSH :
             (finish ? Z_FINISH : Z_SYNC_FLUSH));
      } while (ret == Z_OK);
@ -575,7 +612,7 @@ png_decompress_chunk(png_structrp png_ptr,
    */
   png_alloc_size_t limit = PNG_SIZE_MAX;
-# ifdef PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
+# ifdef PNG_SET_USER_LIMITS_SUPPORTED
   if (png_ptr->user_chunk_malloc_max > 0 &&
       png_ptr->user_chunk_malloc_max < limit)
      limit = png_ptr->user_chunk_malloc_max;
@ -670,7 +707,6 @@ png_decompress_chunk(png_structrp png_ptr,
                   * success)
                   */
                  png_free(png_ptr, text);
                  text = NULL;
                  /* This really is very benign, but it's still an error because
                   * the extra space may otherwise be used as a Trojan Horse.
@ -766,7 +802,7 @@ png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size,
          * the available output is produced; this allows reading of truncated
          * streams.
          */
-         ret = inflate(&png_ptr->zstream,
+         ret = PNG_INFLATE(png_ptr,
            *chunk_bytes > 0 ? Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
      }
      while (ret == Z_OK && (*out_size > 0 || png_ptr->zstream.avail_out > 0));
@ -867,7 +903,7 @@ void /* PRIVATE */
 png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 {
   png_color palette[PNG_MAX_PALETTE_LENGTH];
-   int num, i;
+   int max_palette_length, num, i;
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
   png_colorp pal_ptr;
 #endif
@ -928,6 +964,19 @@ png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   /* The cast is safe because 'length' is less than 3*PNG_MAX_PALETTE_LENGTH */
   num = (int)length / 3;
   /* If the palette has 256 or fewer entries but is too large for the bit
    * depth, we don't issue an error, to preserve the behavior of previous
    * libpng versions. We silently truncate the unused extra palette entries
    * here.
    */
   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      max_palette_length = (1 << png_ptr->bit_depth);
   else
      max_palette_length = PNG_MAX_PALETTE_LENGTH;
   if (num > max_palette_length)
      num = max_palette_length;
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
   for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
   {
@ -960,7 +1009,7 @@ png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
 #endif
   {
-      png_crc_finish(png_ptr, 0);
+      png_crc_finish(png_ptr, (int) length - num * 3);
   }
 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
@ -1147,11 +1196,13 @@ png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
      return;
   for (i=0; i<truelen; ++i)
   {
      if (buf[i] == 0 || buf[i] > sample_depth)
      {
         png_chunk_benign_error(png_ptr, "invalid");
         return;
      }
   }
   if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
   {
@ -1462,10 +1513,10 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
                                    finished = 1;
 #                                   ifdef PNG_sRGB_SUPPORTED
-                                       /* Check for a match against sRGB */
+                                    /* Check for a match against sRGB */
-                                       png_icc_set_sRGB(png_ptr,
+                                    png_icc_set_sRGB(png_ptr,
-                                          &png_ptr->colorspace, profile,
+                                       &png_ptr->colorspace, profile,
-                                          png_ptr->zstream.adler);
+                                       png_ptr->zstream.adler);
 #                                   endif
                                    /* Steal the profile for info_ptr. */
@ -1650,7 +1701,7 @@ png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   ++entry_start;
   /* A sample depth should follow the separator, and we should be on it  */
-   if (entry_start > buffer + length - 2)
+   if (length < 2U || entry_start > buffer + (length - 2U))
   {
      png_warning(png_ptr, "malformed sPLT chunk");
      return;
@ -1675,8 +1726,8 @@ png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   if (dl > max_dl)
   {
-       png_warning(png_ptr, "sPLT chunk too long");
+      png_warning(png_ptr, "sPLT chunk too long");
-       return;
+      return;
   }
   new_palette.nentries = (png_int_32)(data_length / entry_size);
@ -1686,8 +1737,8 @@ png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   if (new_palette.entries == NULL)
   {
-       png_warning(png_ptr, "sPLT chunk requires too much memory");
+      png_warning(png_ptr, "sPLT chunk requires too much memory");
-       return;
+      return;
   }
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
@ -1817,7 +1868,8 @@ png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
         return;
      }
-      if (length > png_ptr->num_palette || length > PNG_MAX_PALETTE_LENGTH ||
+      if (length > (unsigned int) png_ptr->num_palette ||
         length > (unsigned int) PNG_MAX_PALETTE_LENGTH ||
         length == 0)
      {
         png_crc_finish(png_ptr, length);
@ -1980,7 +2032,8 @@ png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   num = length / 2 ;
-   if (num != png_ptr->num_palette || num > PNG_MAX_PALETTE_LENGTH)
+   if (num != (unsigned int) png_ptr->num_palette ||
       num > (unsigned int) PNG_MAX_PALETTE_LENGTH)
   {
      png_crc_finish(png_ptr, length);
      png_chunk_benign_error(png_ptr, "invalid");
@ -2152,7 +2205,7 @@ png_handle_pCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
   /* We need to have at least 12 bytes after the purpose string
    * in order to get the parameter information.
    */
-   if (endptr <= buf + 12)
+   if (endptr - buf <= 12)
   {
      png_chunk_benign_error(png_ptr, "invalid");
      return;
@ -2715,14 +2768,14 @@ png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
      png_ptr->unknown_chunk.data = NULL;
   }
-#  ifdef PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
+#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
-      if (png_ptr->user_chunk_malloc_max > 0 &&
+   if (png_ptr->user_chunk_malloc_max > 0 &&
-          png_ptr->user_chunk_malloc_max < limit)
+       png_ptr->user_chunk_malloc_max < limit)
-         limit = png_ptr->user_chunk_malloc_max;
+      limit = png_ptr->user_chunk_malloc_max;
 #  elif PNG_USER_CHUNK_MALLOC_MAX > 0
-      if (PNG_USER_CHUNK_MALLOC_MAX < limit)
+   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-         limit = PNG_USER_CHUNK_MALLOC_MAX;
+      limit = PNG_USER_CHUNK_MALLOC_MAX;
 #  endif
   if (length <= limit)
@ -2785,7 +2838,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
    */
 #  ifndef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 #     ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-         keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
+   keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
 #     endif
 #  endif
@ -2794,153 +2847,153 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
    * PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
    */
 #  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-      /* The user callback takes precedence over the chunk keep value, but the
+   /* The user callback takes precedence over the chunk keep value, but the
-       * keep value is still required to validate a save of a critical chunk.
+    * keep value is still required to validate a save of a critical chunk.
-       */
+    */
-      if (png_ptr->read_user_chunk_fn != NULL)
+   if (png_ptr->read_user_chunk_fn != NULL)
   {
      if (png_cache_unknown_chunk(png_ptr, length) != 0)
      {
-         if (png_cache_unknown_chunk(png_ptr, length) != 0)
+         /* Callback to user unknown chunk handler */
         int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
            &png_ptr->unknown_chunk);
         /* ret is:
          * negative: An error occurred; png_chunk_error will be called.
          *     zero: The chunk was not handled, the chunk will be discarded
          *           unless png_set_keep_unknown_chunks has been used to set
          *           a 'keep' behavior for this particular chunk, in which
          *           case that will be used.  A critical chunk will cause an
          *           error at this point unless it is to be saved.
          * positive: The chunk was handled, libpng will ignore/discard it.
          */
         if (ret < 0)
            png_chunk_error(png_ptr, "error in user chunk");
         else if (ret == 0)
         {
-            /* Callback to user unknown chunk handler */
+            /* If the keep value is 'default' or 'never' override it, but
-            int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
+             * still error out on critical chunks unless the keep value is
-               &png_ptr->unknown_chunk);
+             * 'always'  While this is weird it is the behavior in 1.4.12.
-
+             * A possible improvement would be to obey the value set for the
-            /* ret is:
+             * chunk, but this would be an API change that would probably
-             * negative: An error occurred; png_chunk_error will be called.
+             * damage some applications.
-             *     zero: The chunk was not handled, the chunk will be discarded
+             *
-             *           unless png_set_keep_unknown_chunks has been used to set
+             * The png_app_warning below catches the case that matters, where
-             *           a 'keep' behavior for this particular chunk, in which
+             * the application has not set specific save or ignore for this
-             *           case that will be used.  A critical chunk will cause an
+             * chunk or global save or ignore.
             *           error at this point unless it is to be saved.
             * positive: The chunk was handled, libpng will ignore/discard it.
             */
-            if (ret < 0)
+            if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
               png_chunk_error(png_ptr, "error in user chunk");
            else if (ret == 0)
            {
-               /* If the keep value is 'default' or 'never' override it, but
+#              ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-                * still error out on critical chunks unless the keep value is
+               if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
                * 'always'  While this is weird it is the behavior in 1.4.12.
                * A possible improvement would be to obey the value set for the
                * chunk, but this would be an API change that would probably
                * damage some applications.
                *
                * The png_app_warning below catches the case that matters, where
                * the application has not set specific save or ignore for this
                * chunk or global save or ignore.
                */
               if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
               {
-#                 ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
+                  png_chunk_warning(png_ptr, "Saving unknown chunk:");
-                     if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
+                  png_app_warning(png_ptr,
-                     {
+                     "forcing save of an unhandled chunk;"
-                        png_chunk_warning(png_ptr, "Saving unknown chunk:");
+                     " please call png_set_keep_unknown_chunks");
-                        png_app_warning(png_ptr,
+                     /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
                           "forcing save of an unhandled chunk;"
                           " please call png_set_keep_unknown_chunks");
                           /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
                     }
 #                 endif
                  keep = PNG_HANDLE_CHUNK_IF_SAFE;
               }
-            }
+#              endif
-
+               keep = PNG_HANDLE_CHUNK_IF_SAFE;
            else /* chunk was handled */
            {
               handled = 1;
               /* Critical chunks can be safely discarded at this point. */
               keep = PNG_HANDLE_CHUNK_NEVER;
            }
         }
-         else
+         else /* chunk was handled */
-            keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
+         {
            handled = 1;
            /* Critical chunks can be safely discarded at this point. */
            keep = PNG_HANDLE_CHUNK_NEVER;
         }
      }
      else
-         /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
+         keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
   }
   else
   /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
 #  endif /* READ_USER_CHUNKS */
 #  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
   {
      /* keep is currently just the per-chunk setting, if there was no
       * setting change it to the global default now (not that this may
       * still be AS_DEFAULT) then obtain the cache of the chunk if required,
       * if not simply skip the chunk.
       */
      if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
         keep = png_ptr->unknown_default;
      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
      {
-         /* keep is currently just the per-chunk setting, if there was no
+         if (png_cache_unknown_chunk(png_ptr, length) == 0)
-          * setting change it to the global default now (not that this may
+            keep = PNG_HANDLE_CHUNK_NEVER;
          * still be AS_DEFAULT) then obtain the cache of the chunk if required,
          * if not simply skip the chunk.
          */
         if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
            keep = png_ptr->unknown_default;
         if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
            (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
             PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
         {
            if (png_cache_unknown_chunk(png_ptr, length) == 0)
               keep = PNG_HANDLE_CHUNK_NEVER;
         }
         else
            png_crc_finish(png_ptr, length);
      }
      else
         png_crc_finish(png_ptr, length);
   }
 #  else
 #     ifndef PNG_READ_USER_CHUNKS_SUPPORTED
 #        error no method to support READ_UNKNOWN_CHUNKS
 #     endif
-      {
+   {
-         /* If here there is no read callback pointer set and no support is
+      /* If here there is no read callback pointer set and no support is
-          * compiled in to just save the unknown chunks, so simply skip this
+       * compiled in to just save the unknown chunks, so simply skip this
-          * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
+       * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
-          * the app has erroneously asked for unknown chunk saving when there
+       * the app has erroneously asked for unknown chunk saving when there
-          * is no support.
+       * is no support.
-          */
+       */
-         if (keep > PNG_HANDLE_CHUNK_NEVER)
+      if (keep > PNG_HANDLE_CHUNK_NEVER)
-            png_app_error(png_ptr, "no unknown chunk support available");
+         png_app_error(png_ptr, "no unknown chunk support available");
-         png_crc_finish(png_ptr, length);
+      png_crc_finish(png_ptr, length);
-      }
+   }
 #  endif
 #  ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
-      /* Now store the chunk in the chunk list if appropriate, and if the limits
+   /* Now store the chunk in the chunk list if appropriate, and if the limits
-       * permit it.
+    * permit it.
-       */
+    */
-      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
+   if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
+      (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
+       PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
   {
 #     ifdef PNG_USER_LIMITS_SUPPORTED
      switch (png_ptr->user_chunk_cache_max)
      {
-#     ifdef PNG_USER_LIMITS_SUPPORTED
+         case 2:
-         switch (png_ptr->user_chunk_cache_max)
+            png_ptr->user_chunk_cache_max = 1;
-         {
+            png_chunk_benign_error(png_ptr, "no space in chunk cache");
-            case 2:
+            /* FALL THROUGH */
-               png_ptr->user_chunk_cache_max = 1;
+         case 1:
-               png_chunk_benign_error(png_ptr, "no space in chunk cache");
+            /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
-               /* FALL THROUGH */
+             * chunk being skipped, now there will be a hard error below.
-            case 1:
+             */
-               /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
+            break;
                * chunk being skipped, now there will be a hard error below.
                */
               break;
-            default: /* not at limit */
+         default: /* not at limit */
-               --(png_ptr->user_chunk_cache_max);
+            --(png_ptr->user_chunk_cache_max);
-               /* FALL THROUGH */
+            /* FALL THROUGH */
-            case 0: /* no limit */
+         case 0: /* no limit */
-#     endif /* USER_LIMITS */
+#  endif /* USER_LIMITS */
-               /* Here when the limit isn't reached or when limits are compiled
+            /* Here when the limit isn't reached or when limits are compiled
-                * out; store the chunk.
+             * out; store the chunk.
-                */
+             */
-               png_set_unknown_chunks(png_ptr, info_ptr,
+            png_set_unknown_chunks(png_ptr, info_ptr,
-                  &png_ptr->unknown_chunk, 1);
+               &png_ptr->unknown_chunk, 1);
-               handled = 1;
+            handled = 1;
-#     ifdef PNG_USER_LIMITS_SUPPORTED
+#  ifdef PNG_USER_LIMITS_SUPPORTED
-               break;
+            break;
         }
 #     endif
      }
 #  endif
   }
 #  else /* no store support: the chunk must be handled by the user callback */
-      PNG_UNUSED(info_ptr)
+   PNG_UNUSED(info_ptr)
 #  endif
   /* Regardless of the error handling below the cached data (if any) can be
@ -3042,13 +3095,13 @@ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
      end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
      end_byte = *end_ptr;
 #     ifdef PNG_READ_PACKSWAP_SUPPORTED
-         if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
+      if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
-            /* little-endian byte */
+         /* little-endian byte */
-            end_mask = 0xff << end_mask;
+         end_mask = 0xff << end_mask;
-         else /* big-endian byte */
+      else /* big-endian byte */
 #     endif
-         end_mask = 0xff >> end_mask;
+      end_mask = 0xff >> end_mask;
      /* end_mask is now the bits to *keep* from the destination row */
   }
@ -3206,12 +3259,12 @@ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
         png_uint_32 mask;
 #        ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
+         if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
-               mask = MASK(pass, pixel_depth, display, 0);
+            mask = MASK(pass, pixel_depth, display, 0);
-            else
+         else
 #        endif
-            mask = MASK(pass, pixel_depth, display, 1);
+         mask = MASK(pass, pixel_depth, display, 1);
         for (;;)
         {
@ -3812,15 +3865,15 @@ png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
      p = b - c;
      pc = a - c;
-#     ifdef PNG_USE_ABS
+#ifdef PNG_USE_ABS
-         pa = abs(p);
+      pa = abs(p);
-         pb = abs(pc);
+      pb = abs(pc);
-         pc = abs(p + pc);
+      pc = abs(p + pc);
-#     else
+#else
-         pa = p < 0 ? -p : p;
+      pa = p < 0 ? -p : p;
-         pb = pc < 0 ? -pc : pc;
+      pb = pc < 0 ? -pc : pc;
-         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#     endif
+#endif
      /* Find the best predictor, the least of pa, pb, pc favoring the earlier
       * ones in the case of a tie.
@ -3867,15 +3920,15 @@ png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
      p = b - c;
      pc = a - c;
-#     ifdef PNG_USE_ABS
+#ifdef PNG_USE_ABS
-         pa = abs(p);
+      pa = abs(p);
-         pb = abs(pc);
+      pb = abs(pc);
-         pc = abs(p + pc);
+      pc = abs(p + pc);
-#     else
+#else
-         pa = p < 0 ? -p : p;
+      pa = p < 0 ? -p : p;
-         pb = pc < 0 ? -pc : pc;
+      pb = pc < 0 ? -pc : pc;
-         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#     endif
+#endif
      if (pb < pa) pa = pb, a = b;
      if (pc < pa) a = c;
@ -4017,7 +4070,7 @@ png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
       *
       * TODO: deal more elegantly with truncated IDAT lists.
       */
-      ret = inflate(&png_ptr->zstream, Z_NO_FLUSH);
+      ret = PNG_INFLATE(png_ptr, Z_NO_FLUSH);
      /* Take the unconsumed output back. */
      if (output != NULL)
@ -4280,18 +4333,18 @@ png_read_start_row(png_structrp png_ptr)
 #ifdef PNG_READ_EXPAND_16_SUPPORTED
   if ((png_ptr->transformations & PNG_EXPAND_16) != 0)
   {
-#     ifdef PNG_READ_EXPAND_SUPPORTED
+#  ifdef PNG_READ_EXPAND_SUPPORTED
-         /* In fact it is an error if it isn't supported, but checking is
+      /* In fact it is an error if it isn't supported, but checking is
-          * the safe way.
+       * the safe way.
-          */
+       */
-         if ((png_ptr->transformations & PNG_EXPAND) != 0)
+      if ((png_ptr->transformations & PNG_EXPAND) != 0)
-         {
+      {
-            if (png_ptr->bit_depth < 16)
+         if (png_ptr->bit_depth < 16)
-               max_pixel_depth *= 2;
+            max_pixel_depth *= 2;
-         }
+      }
-         else
+      else
-#     endif
+#  endif
-         png_ptr->transformations &= ~PNG_EXPAND_16;
+      png_ptr->transformations &= ~PNG_EXPAND_16;
   }
 #endif
--- a/thirdparty/libpng/pngset.c
+++ b/thirdparty/libpng/pngset.c
@ -1,7 +1,7 @@
 /* pngset.c - storage of image information into info struct
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.21 [January 15, 2016]
 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@ -123,12 +123,12 @@ png_set_cHRM_XYZ(png_const_structrp png_ptr, png_inforp info_ptr, double red_X,
      png_fixed(png_ptr, red_X, "cHRM Red X"),
      png_fixed(png_ptr, red_Y, "cHRM Red Y"),
      png_fixed(png_ptr, red_Z, "cHRM Red Z"),
-      png_fixed(png_ptr, green_X, "cHRM Red X"),
+      png_fixed(png_ptr, green_X, "cHRM Green X"),
-      png_fixed(png_ptr, green_Y, "cHRM Red Y"),
+      png_fixed(png_ptr, green_Y, "cHRM Green Y"),
-      png_fixed(png_ptr, green_Z, "cHRM Red Z"),
+      png_fixed(png_ptr, green_Z, "cHRM Green Z"),
-      png_fixed(png_ptr, blue_X, "cHRM Red X"),
+      png_fixed(png_ptr, blue_X, "cHRM Blue X"),
-      png_fixed(png_ptr, blue_Y, "cHRM Red Y"),
+      png_fixed(png_ptr, blue_Y, "cHRM Blue Y"),
-      png_fixed(png_ptr, blue_Z, "cHRM Red Z"));
+      png_fixed(png_ptr, blue_Z, "cHRM Blue Z"));
 }
 #  endif /* FLOATING_POINT */
@ -513,12 +513,17 @@ png_set_PLTE(png_structrp png_ptr, png_inforp info_ptr,
    png_const_colorp palette, int num_palette)
 {
   png_uint_32 max_palette_length;
   png_debug1(1, "in %s storage function", "PLTE");
   if (png_ptr == NULL || info_ptr == NULL)
      return;
-   if (num_palette < 0 || num_palette > PNG_MAX_PALETTE_LENGTH)
+   max_palette_length = (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ?
      (1 << info_ptr->bit_depth) : PNG_MAX_PALETTE_LENGTH;
   if (num_palette < 0 || num_palette > (int) max_palette_length)
   {
      if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
         png_error(png_ptr, "Invalid palette length");
@ -551,8 +556,8 @@ png_set_PLTE(png_structrp png_ptr, png_inforp info_ptr,
   png_free_data(png_ptr, info_ptr, PNG_FREE_PLTE, 0);
   /* Changed in libpng-1.2.1 to allocate PNG_MAX_PALETTE_LENGTH instead
-    * of num_palette entries, in case of an invalid PNG file that has
+    * of num_palette entries, in case of an invalid PNG file or incorrect
-    * too-large sample values.
+    * call to png_set_PLTE() with too-large sample values.
    */
   png_ptr->palette = png_voidcast(png_colorp, png_calloc(png_ptr,
       PNG_MAX_PALETTE_LENGTH * (sizeof (png_color))));
@ -673,7 +678,6 @@ png_set_iCCP(png_const_structrp png_ptr, png_inforp info_ptr,
   if (new_iccp_profile == NULL)
   {
      png_free(png_ptr, new_iccp_name);
      new_iccp_name = NULL;
      png_benign_error(png_ptr,
          "Insufficient memory to process iCCP profile");
@ -710,7 +714,7 @@ png_set_text_2(png_const_structrp png_ptr, png_inforp info_ptr,
 {
   int i;
-   png_debug1(1, "in %lx storage function", png_ptr == NULL ? "unexpected" :
+   png_debug1(1, "in %lx storage function", png_ptr == NULL ? 0xabadca11U :
      (unsigned long)png_ptr->chunk_name);
   if (png_ptr == NULL || info_ptr == NULL || num_text <= 0 || text_ptr == NULL)
@ -1522,6 +1526,9 @@ png_set_compression_buffer_size(png_structrp png_ptr, png_size_t size)
         }
 #ifndef __COVERITY__
         /* Some compilers complain that this is always false.  However, it
          * can be true when integer overflow happens.
          */
         if (size > ZLIB_IO_MAX)
         {
            png_warning(png_ptr,
@ -1566,7 +1573,7 @@ png_set_user_limits (png_structrp png_ptr, png_uint_32 user_width_max,
 {
   /* Images with dimensions larger than these limits will be
    * rejected by png_set_IHDR().  To accept any PNG datastream
-    * regardless of dimensions, set both limits to 0x7ffffffL.
+    * regardless of dimensions, set both limits to 0x7fffffff.
    */
   if (png_ptr == NULL)
      return;
@ -1637,4 +1644,88 @@ png_set_check_for_invalid_index(png_structrp png_ptr, int allowed)
      png_ptr->num_palette_max = -1;
 }
 #endif
 #if defined(PNG_TEXT_SUPPORTED) || defined(PNG_pCAL_SUPPORTED) || \
    defined(PNG_iCCP_SUPPORTED) || defined(PNG_sPLT_SUPPORTED)
 /* Check that the tEXt or zTXt keyword is valid per PNG 1.0 specification,
 * and if invalid, correct the keyword rather than discarding the entire
 * chunk.  The PNG 1.0 specification requires keywords 1-79 characters in
 * length, forbids leading or trailing whitespace, multiple internal spaces,
 * and the non-break space (0x80) from ISO 8859-1.  Returns keyword length.
 *
 * The 'new_key' buffer must be 80 characters in size (for the keyword plus a
 * trailing '\0').  If this routine returns 0 then there was no keyword, or a
 * valid one could not be generated, and the caller must png_error.
 */
 png_uint_32 /* PRIVATE */
 png_check_keyword(png_structrp png_ptr, png_const_charp key, png_bytep new_key)
 {
   png_const_charp orig_key = key;
   png_uint_32 key_len = 0;
   int bad_character = 0;
   int space = 1;
   png_debug(1, "in png_check_keyword");
   if (key == NULL)
   {
      *new_key = 0;
      return 0;
   }
   while (*key && key_len < 79)
   {
      png_byte ch = (png_byte)*key++;
      if ((ch > 32 && ch <= 126) || (ch >= 161 /*&& ch <= 255*/))
         *new_key++ = ch, ++key_len, space = 0;
      else if (space == 0)
      {
         /* A space or an invalid character when one wasn't seen immediately
          * before; output just a space.
          */
         *new_key++ = 32, ++key_len, space = 1;
         /* If the character was not a space then it is invalid. */
         if (ch != 32)
            bad_character = ch;
      }
      else if (bad_character == 0)
         bad_character = ch; /* just skip it, record the first error */
   }
   if (key_len > 0 && space != 0) /* trailing space */
   {
      --key_len, --new_key;
      if (bad_character == 0)
         bad_character = 32;
   }
   /* Terminate the keyword */
   *new_key = 0;
   if (key_len == 0)
      return 0;
 #ifdef PNG_WARNINGS_SUPPORTED
   /* Try to only output one warning per keyword: */
   if (*key != 0) /* keyword too long */
      png_warning(png_ptr, "keyword truncated");
   else if (bad_character != 0)
   {
      PNG_WARNING_PARAMETERS(p)
      png_warning_parameter(p, 1, orig_key);
      png_warning_parameter_signed(p, 2, PNG_NUMBER_FORMAT_02x, bad_character);
      png_formatted_warning(png_ptr, p, "keyword \"@1\": bad character '0x@2'");
   }
 #endif /* WARNINGS */
   return key_len;
 }
 #endif /* TEXT || pCAL || iCCP || sPLT */
 #endif /* READ || WRITE */
--- a/thirdparty/libpng/pngstruct.h
+++ b/thirdparty/libpng/pngstruct.h
@ -1,8 +1,8 @@
 /* pngstruct.h - header file for PNG reference library
 *
- * Last changed in libpng 1.6.1 [March 28, 2013]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -219,16 +219,18 @@ struct png_struct_def
   png_uint_32 row_number;    /* current row in interlace pass */
   png_uint_32 chunk_name;    /* PNG_CHUNK() id of current chunk */
   png_bytep prev_row;        /* buffer to save previous (unfiltered) row.
-                               * This is a pointer into big_prev_row
+                               * While reading this is a pointer into
                               * big_prev_row; while writing it is separately
                               * allocated if needed.
                               */
   png_bytep row_buf;         /* buffer to save current (unfiltered) row.
-                               * This is a pointer into big_row_buf
+                               * While reading, this is a pointer into
                               * big_row_buf; while writing it is separately
                               * allocated.
                               */
-#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_FILTER_SUPPORTED
-   png_bytep sub_row;         /* buffer to save "sub" row when filtering */
+   png_bytep try_row;    /* buffer to save trial row when filtering */
-   png_bytep up_row;          /* buffer to save "up" row when filtering */
+   png_bytep tst_row;    /* buffer to save best trial row when filtering */
   png_bytep avg_row;         /* buffer to save "avg" row when filtering */
   png_bytep paeth_row;       /* buffer to save "Paeth" row when filtering */
 #endif
   png_size_t info_rowbytes;  /* Added in 1.5.4: cache of updated row bytes */
@ -261,6 +263,9 @@ struct png_struct_def
                              /* pixel depth used for the row buffers */
   png_byte transformed_pixel_depth;
                              /* pixel depth after read/write transforms */
 #if PNG_ZLIB_VERNUM >= 0x1240
   png_byte zstream_start;    /* at start of an input zlib stream */
 #endif /* Zlib >= 1.2.4 */
 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
   png_uint_16 filler;           /* filler bytes for pixel expansion */
 #endif
@ -346,17 +351,7 @@ struct png_struct_def
   png_bytep quantize_index; /* index translation for palette files */
 #endif
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+/* Options */
   png_byte heuristic_method;        /* heuristic for row filter selection */
   png_byte num_prev_filters;        /* number of weights for previous rows */
   png_bytep prev_filters;           /* filter type(s) of previous row(s) */
   png_uint_16p filter_weights;      /* weight(s) for previous line(s) */
   png_uint_16p inv_filter_weights;  /* 1/weight(s) for previous line(s) */
   png_uint_16p filter_costs;        /* relative filter calculation cost */
   png_uint_16p inv_filter_costs;    /* 1/relative filter calculation cost */
 #endif
   /* Options */
 #ifdef PNG_SET_OPTION_SUPPORTED
   png_byte options;           /* On/off state (up to 4 options) */
 #endif
--- a/thirdparty/libpng/pngtrans.c
+++ b/thirdparty/libpng/pngtrans.c
@ -1,8 +1,8 @@
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -30,7 +30,7 @@ png_set_bgr(png_structrp png_ptr)
 #endif
 #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
-/* Turn on 16 bit byte swapping */
+/* Turn on 16-bit byte swapping */
 void PNGAPI
 png_set_swap(png_structrp png_ptr)
 {
@ -313,7 +313,7 @@ png_do_invert(png_row_infop row_info, png_bytep row)
 #ifdef PNG_16BIT_SUPPORTED
 #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
-/* Swaps byte order on 16 bit depth images */
+/* Swaps byte order on 16-bit depth images */
 void /* PRIVATE */
 png_do_swap(png_row_infop row_info, png_bytep row)
 {
@ -704,7 +704,7 @@ png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
             */
            for (; rp > png_ptr->row_buf; rp--)
            {
-              if (*rp >> padding != 0)
+              if ((*rp >> padding) != 0)
                 png_ptr->num_palette_max = 1;
              padding = 0;
            }
--- a/thirdparty/libpng/pngwio.c
+++ b/thirdparty/libpng/pngwio.c
@ -2,7 +2,7 @@
 /* pngwio.c - functions for data output
 *
 * Last changed in libpng 1.6.15 [November 20, 2014]
- * Copyright (c) 1998-2014 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2014 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -26,7 +26,7 @@
 * writes to a file pointer.  Note that this routine sometimes gets called
 * with very small lengths, so you should implement some kind of simple
 * buffering if you are using unbuffered writes.  This should never be asked
- * to write more than 64K on a 16 bit machine.
+ * to write more than 64K on a 16-bit machine.
 */
 void /* PRIVATE */
--- a/thirdparty/libpng/pngwrite.c
+++ b/thirdparty/libpng/pngwrite.c
@ -1,8 +1,8 @@
 /* pngwrite.c - general routines to write a PNG file
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.19 [November 12, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -90,43 +90,44 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
   if ((png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE) == 0)
   {
-   /* Write PNG signature */
+      /* Write PNG signature */
-   png_write_sig(png_ptr);
+      png_write_sig(png_ptr);
 #ifdef PNG_MNG_FEATURES_SUPPORTED
-   if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
+      if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
-       png_ptr->mng_features_permitted != 0)
+          png_ptr->mng_features_permitted != 0)
-   {
+      {
-      png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
+         png_warning(png_ptr,
-      png_ptr->mng_features_permitted = 0;
+             "MNG features are not allowed in a PNG datastream");
-   }
+         png_ptr->mng_features_permitted = 0;
      }
 #endif
-   /* Write IHDR information. */
+      /* Write IHDR information. */
-   png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
+      png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
-       info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
+          info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
-       info_ptr->filter_type,
+          info_ptr->filter_type,
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
-       info_ptr->interlace_type
+          info_ptr->interlace_type
 #else
-       0
+          0
 #endif
-      );
+         );
-   /* The rest of these check to see if the valid field has the appropriate
+      /* The rest of these check to see if the valid field has the appropriate
-    * flag set, and if it does, writes the chunk.
+       * flag set, and if it does, writes the chunk.
-    *
+       *
-    * 1.6.0: COLORSPACE support controls the writing of these chunks too, and
+       * 1.6.0: COLORSPACE support controls the writing of these chunks too, and
-    * the chunks will be written if the WRITE routine is there and information
+       * the chunks will be written if the WRITE routine is there and
-    * is available in the COLORSPACE.  (See png_colorspace_sync_info in png.c
+       * information * is available in the COLORSPACE. (See
-    * for where the valid flags get set.)
+       * png_colorspace_sync_info in png.c for where the valid flags get set.)
-    *
+       *
-    * Under certain circumstances the colorspace can be invalidated without
+       * Under certain circumstances the colorspace can be invalidated without
-    * syncing the info_struct 'valid' flags; this happens if libpng detects and
+       * syncing the info_struct 'valid' flags; this happens if libpng detects
-    * error and calls png_error while the color space is being set, yet the
+       * an error and calls png_error while the color space is being set, yet
-    * application continues writing the PNG.  So check the 'invalid' flag here
+       * the application continues writing the PNG.  So check the 'invalid'
-    * too.
+       * flag here too.
-    */
+       */
 #ifdef PNG_GAMMA_SUPPORTED
 #  ifdef PNG_WRITE_gAMA_SUPPORTED
      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
@ -137,50 +138,50 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
 #endif
 #ifdef PNG_COLORSPACE_SUPPORTED
-   /* Write only one of sRGB or an ICC profile.  If a profile was supplied
+      /* Write only one of sRGB or an ICC profile.  If a profile was supplied
-    * and it matches one of the known sRGB ones issue a warning.
+       * and it matches one of the known sRGB ones issue a warning.
-    */
+       */
 #  ifdef PNG_WRITE_iCCP_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
+         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-          (info_ptr->valid & PNG_INFO_iCCP) != 0)
+             (info_ptr->valid & PNG_INFO_iCCP) != 0)
-      {
+         {
-#        ifdef PNG_WRITE_sRGB_SUPPORTED
+#    ifdef PNG_WRITE_sRGB_SUPPORTED
-            if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
+               if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
-               png_app_warning(png_ptr,
+                  png_app_warning(png_ptr,
-                  "profile matches sRGB but writing iCCP instead");
+                     "profile matches sRGB but writing iCCP instead");
-#        endif
+#     endif
-         png_write_iCCP(png_ptr, info_ptr->iccp_name,
+            png_write_iCCP(png_ptr, info_ptr->iccp_name,
-            info_ptr->iccp_profile);
+               info_ptr->iccp_profile);
-      }
+         }
 #     ifdef PNG_WRITE_sRGB_SUPPORTED
         else
 #     endif
 #  endif
 #  ifdef PNG_WRITE_sRGB_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
+         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-          (info_ptr->valid & PNG_INFO_sRGB) != 0)
+             (info_ptr->valid & PNG_INFO_sRGB) != 0)
-         png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
+            png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
 #  endif /* WRITE_sRGB */
 #endif /* COLORSPACE */
 #ifdef PNG_WRITE_sBIT_SUPPORTED
-   if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
+         if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
-      png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
+            png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
 #endif
 #ifdef PNG_COLORSPACE_SUPPORTED
 #  ifdef PNG_WRITE_cHRM_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
+         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-         (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
+             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
-         (info_ptr->valid & PNG_INFO_cHRM) != 0)
+             (info_ptr->valid & PNG_INFO_cHRM) != 0)
-         png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
+            png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
 #  endif
 #endif
 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-      write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
+         write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
 #endif
      png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
@ -205,7 +206,7 @@ png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
      png_write_PLTE(png_ptr, info_ptr->palette,
          (png_uint_32)info_ptr->num_palette);
-   else if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) !=0)
+   else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      png_error(png_ptr, "Valid palette required for paletted images");
 #ifdef PNG_WRITE_tRNS_SUPPORTED
@ -216,8 +217,13 @@ png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
      if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0 &&
          info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
-         int j;
+         int j, jend;
-         for (j = 0; j<(int)info_ptr->num_trans; j++)
+
         jend = info_ptr->num_trans;
         if (jend > PNG_MAX_PALETTE_LENGTH)
            jend = PNG_MAX_PALETTE_LENGTH;
         for (j = 0; j<jend; ++j)
            info_ptr->trans_alpha[j] =
               (png_byte)(255 - info_ptr->trans_alpha[j]);
      }
@ -538,7 +544,7 @@ png_create_write_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
      /* App warnings are warnings in release (or release candidate) builds but
       * are errors during development.
       */
-#if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
+#if PNG_RELEASE_BUILD
      png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
 #endif
@ -849,7 +855,7 @@ png_write_row(png_structrp png_ptr, png_const_bytep row)
    * which is also the output depth.
    */
   if (row_info.pixel_depth != png_ptr->pixel_depth ||
-      row_info.pixel_depth != png_ptr->transformed_pixel_depth)
+       row_info.pixel_depth != png_ptr->transformed_pixel_depth)
      png_error(png_ptr, "internal write transform logic error");
 #ifdef PNG_MNG_FEATURES_SUPPORTED
@ -917,10 +923,6 @@ png_write_flush(png_structrp png_ptr)
 }
 #endif /* WRITE_FLUSH */
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
 static void png_reset_filter_heuristics(png_structrp png_ptr);/* forward decl */
 #endif
 /* Free any memory used in png_ptr struct without freeing the struct itself. */
 static void
 png_write_destroy(png_structrp png_ptr)
@ -937,24 +939,11 @@ png_write_destroy(png_structrp png_ptr)
   png_ptr->row_buf = NULL;
 #ifdef PNG_WRITE_FILTER_SUPPORTED
   png_free(png_ptr, png_ptr->prev_row);
-   png_free(png_ptr, png_ptr->sub_row);
+   png_free(png_ptr, png_ptr->try_row);
-   png_free(png_ptr, png_ptr->up_row);
+   png_free(png_ptr, png_ptr->tst_row);
   png_free(png_ptr, png_ptr->avg_row);
   png_free(png_ptr, png_ptr->paeth_row);
   png_ptr->prev_row = NULL;
-   png_ptr->sub_row = NULL;
+   png_ptr->try_row = NULL;
-   png_ptr->up_row = NULL;
+   png_ptr->tst_row = NULL;
   png_ptr->avg_row = NULL;
   png_ptr->paeth_row = NULL;
 #endif
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
   /* Use this to save a little code space, it doesn't free the filter_costs */
   png_reset_filter_heuristics(png_ptr);
   png_free(png_ptr, png_ptr->filter_costs);
   png_free(png_ptr, png_ptr->inv_filter_costs);
   png_ptr->filter_costs = NULL;
   png_ptr->inv_filter_costs = NULL;
 #endif
 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
@ -1044,6 +1033,7 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
 #endif /* WRITE_FILTER */
      }
 #ifdef PNG_WRITE_FILTER_SUPPORTED
      /* If we have allocated the row_buf, this means we have already started
       * with the image and we should have allocated all of the filter buffers
       * that have been selected.  If prev_row isn't already allocated, then
@ -1052,203 +1042,76 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
       * wants to start and stop using particular filters during compression,
       * it should start out with all of the filters, and then remove them
       * or add them back after the start of compression.
       *
       * NOTE: this is a nasty constraint on the code, because it means that the
       * prev_row buffer must be maintained even if there are currently no
       * 'prev_row' requiring filters active.
       */
      if (png_ptr->row_buf != NULL)
      {
-#ifdef PNG_WRITE_FILTER_SUPPORTED
+         int num_filters;
-         if ((png_ptr->do_filter & PNG_FILTER_SUB) != 0 &&
+         png_alloc_size_t buf_size;
-             png_ptr->sub_row == NULL)
+
         /* Repeat the checks in png_write_start_row; 1 pixel high or wide
          * images cannot benefit from certain filters.  If this isn't done here
          * the check below will fire on 1 pixel high images.
          */
         if (png_ptr->height == 1)
            filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
         if (png_ptr->width == 1)
            filters &= ~(PNG_FILTER_SUB|PNG_FILTER_AVG|PNG_FILTER_PAETH);
         if ((filters & (PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH)) != 0
            && png_ptr->prev_row == NULL)
         {
-            png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
+            /* This is the error case, however it is benign - the previous row
-                (png_ptr->rowbytes + 1));
+             * is not available so the filter can't be used.  Just warn here.
-            png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
+             */
            png_app_warning(png_ptr,
               "png_set_filter: UP/AVG/PAETH cannot be added after start");
            filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
         }
-         if ((png_ptr->do_filter & PNG_FILTER_UP) != 0 &&
+         num_filters = 0;
-              png_ptr->up_row == NULL)
+
         if (filters & PNG_FILTER_SUB)
            num_filters++;
         if (filters & PNG_FILTER_UP)
            num_filters++;
         if (filters & PNG_FILTER_AVG)
            num_filters++;
         if (filters & PNG_FILTER_PAETH)
            num_filters++;
         /* Allocate needed row buffers if they have not already been
          * allocated.
          */
         buf_size = PNG_ROWBYTES(png_ptr->usr_channels * png_ptr->usr_bit_depth,
             png_ptr->width) + 1;
         if (png_ptr->try_row == NULL)
            png_ptr->try_row = png_voidcast(png_bytep,
               png_malloc(png_ptr, buf_size));
         if (num_filters > 1)
         {
-            if (png_ptr->prev_row == NULL)
+            if (png_ptr->tst_row == NULL)
-            {
+               png_ptr->tst_row = png_voidcast(png_bytep,
-               png_warning(png_ptr, "Can't add Up filter after starting");
+                  png_malloc(png_ptr, buf_size));
               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                   ~PNG_FILTER_UP);
            }
            else
            {
               png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
                   (png_ptr->rowbytes + 1));
               png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
            }
         }
         if ((png_ptr->do_filter & PNG_FILTER_AVG) != 0 &&
              png_ptr->avg_row == NULL)
         {
            if (png_ptr->prev_row == NULL)
            {
               png_warning(png_ptr, "Can't add Average filter after starting");
               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                   ~PNG_FILTER_AVG);
            }
            else
            {
               png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
                   (png_ptr->rowbytes + 1));
               png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
            }
         }
         if ((png_ptr->do_filter & PNG_FILTER_PAETH) != 0 &&
             png_ptr->paeth_row == NULL)
         {
            if (png_ptr->prev_row == NULL)
            {
               png_warning(png_ptr, "Can't add Paeth filter after starting");
               png_ptr->do_filter &= (png_byte)(~PNG_FILTER_PAETH);
            }
            else
            {
               png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
                   (png_ptr->rowbytes + 1));
               png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
            }
         }
         if (png_ptr->do_filter == PNG_NO_FILTERS)
 #endif /* WRITE_FILTER */
            png_ptr->do_filter = PNG_FILTER_NONE;
      }
      png_ptr->do_filter = (png_byte)filters;
 #endif
   }
   else
      png_error(png_ptr, "Unknown custom filter method");
 }
-/* This allows us to influence the way in which libpng chooses the "best"
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* DEPRECATED */
 * filter for the current scanline.  While the "minimum-sum-of-absolute-
 * differences metric is relatively fast and effective, there is some
 * question as to whether it can be improved upon by trying to keep the
 * filtered data going to zlib more consistent, hopefully resulting in
 * better compression.
 */
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
 /* Convenience reset API. */
 static void
 png_reset_filter_heuristics(png_structrp png_ptr)
 {
   /* Clear out any old values in the 'weights' - this must be done because if
    * the app calls set_filter_heuristics multiple times with different
    * 'num_weights' values we would otherwise potentially have wrong sized
    * arrays.
    */
   png_ptr->num_prev_filters = 0;
   png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_UNWEIGHTED;
   if (png_ptr->prev_filters != NULL)
   {
      png_bytep old = png_ptr->prev_filters;
      png_ptr->prev_filters = NULL;
      png_free(png_ptr, old);
   }
   if (png_ptr->filter_weights != NULL)
   {
      png_uint_16p old = png_ptr->filter_weights;
      png_ptr->filter_weights = NULL;
      png_free(png_ptr, old);
   }
   if (png_ptr->inv_filter_weights != NULL)
   {
      png_uint_16p old = png_ptr->inv_filter_weights;
      png_ptr->inv_filter_weights = NULL;
      png_free(png_ptr, old);
   }
   /* Leave the filter_costs - this array is fixed size. */
 }
 static int
 png_init_filter_heuristics(png_structrp png_ptr, int heuristic_method,
   int num_weights)
 {
   if (png_ptr == NULL)
      return 0;
   /* Clear out the arrays */
   png_reset_filter_heuristics(png_ptr);
   /* Check arguments; the 'reset' function makes the correct settings for the
    * unweighted case, but we must handle the weight case by initializing the
    * arrays for the caller.
    */
   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
   {
      int i;
      if (num_weights > 0)
      {
         png_ptr->prev_filters = (png_bytep)png_malloc(png_ptr,
             (png_uint_32)((sizeof (png_byte)) * num_weights));
         /* To make sure that the weighting starts out fairly */
         for (i = 0; i < num_weights; i++)
         {
            png_ptr->prev_filters[i] = 255;
         }
         png_ptr->filter_weights = (png_uint_16p)png_malloc(png_ptr,
             (png_uint_32)((sizeof (png_uint_16)) * num_weights));
         png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,
             (png_uint_32)((sizeof (png_uint_16)) * num_weights));
         for (i = 0; i < num_weights; i++)
         {
            png_ptr->inv_filter_weights[i] =
            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
         }
         /* Safe to set this now */
         png_ptr->num_prev_filters = (png_byte)num_weights;
      }
      /* If, in the future, there are other filter methods, this would
       * need to be based on png_ptr->filter.
       */
      if (png_ptr->filter_costs == NULL)
      {
         png_ptr->filter_costs = (png_uint_16p)png_malloc(png_ptr,
             (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
         png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,
             (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
      }
      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
      {
         png_ptr->inv_filter_costs[i] =
         png_ptr->filter_costs[i] = PNG_COST_FACTOR;
      }
      /* All the arrays are inited, safe to set this: */
      png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_WEIGHTED;
      /* Return the 'ok' code. */
      return 1;
   }
   else if (heuristic_method == PNG_FILTER_HEURISTIC_DEFAULT ||
      heuristic_method == PNG_FILTER_HEURISTIC_UNWEIGHTED)
   {
      return 1;
   }
   else
   {
      png_warning(png_ptr, "Unknown filter heuristic method");
      return 0;
   }
 }
 /* Provide floating and fixed point APIs */
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 void PNGAPI
@ -1256,52 +1119,11 @@ png_set_filter_heuristics(png_structrp png_ptr, int heuristic_method,
    int num_weights, png_const_doublep filter_weights,
    png_const_doublep filter_costs)
 {
-   png_debug(1, "in png_set_filter_heuristics");
+   PNG_UNUSED(png_ptr)
-
+   PNG_UNUSED(heuristic_method)
-   /* The internal API allocates all the arrays and ensures that the elements of
+   PNG_UNUSED(num_weights)
-    * those arrays are set to the default value.
+   PNG_UNUSED(filter_weights)
-    */
+   PNG_UNUSED(filter_costs)
   if (png_init_filter_heuristics(png_ptr, heuristic_method, num_weights) == 0)
      return;
   /* If using the weighted method copy in the weights. */
   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
   {
      int i;
      for (i = 0; i < num_weights; i++)
      {
         if (filter_weights[i] <= 0.0)
         {
            png_ptr->inv_filter_weights[i] =
            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
         }
         else
         {
            png_ptr->inv_filter_weights[i] =
                (png_uint_16)(PNG_WEIGHT_FACTOR*filter_weights[i]+.5);
            png_ptr->filter_weights[i] =
                (png_uint_16)(PNG_WEIGHT_FACTOR/filter_weights[i]+.5);
         }
      }
      /* Here is where we set the relative costs of the different filters.  We
       * should take the desired compression level into account when setting
       * the costs, so that Paeth, for instance, has a high relative cost at low
       * compression levels, while it has a lower relative cost at higher
       * compression settings.  The filter types are in order of increasing
       * relative cost, so it would be possible to do this with an algorithm.
       */
      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++) if (filter_costs[i] >= 1.0)
      {
         png_ptr->inv_filter_costs[i] =
             (png_uint_16)(PNG_COST_FACTOR / filter_costs[i] + .5);
         png_ptr->filter_costs[i] =
             (png_uint_16)(PNG_COST_FACTOR * filter_costs[i] + .5);
      }
   }
 }
 #endif /* FLOATING_POINT */
@ -1311,63 +1133,11 @@ png_set_filter_heuristics_fixed(png_structrp png_ptr, int heuristic_method,
    int num_weights, png_const_fixed_point_p filter_weights,
    png_const_fixed_point_p filter_costs)
 {
-   png_debug(1, "in png_set_filter_heuristics_fixed");
+   PNG_UNUSED(png_ptr)
-
+   PNG_UNUSED(heuristic_method)
-   /* The internal API allocates all the arrays and ensures that the elements of
+   PNG_UNUSED(num_weights)
-    * those arrays are set to the default value.
+   PNG_UNUSED(filter_weights)
-    */
+   PNG_UNUSED(filter_costs)
   if (png_init_filter_heuristics(png_ptr, heuristic_method, num_weights) == 0)
      return;
   /* If using the weighted method copy in the weights. */
   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
   {
      int i;
      for (i = 0; i < num_weights; i++)
      {
         if (filter_weights[i] <= 0)
         {
            png_ptr->inv_filter_weights[i] =
            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
         }
         else
         {
            png_ptr->inv_filter_weights[i] = (png_uint_16)
               ((PNG_WEIGHT_FACTOR*filter_weights[i]+PNG_FP_HALF)/PNG_FP_1);
            png_ptr->filter_weights[i] = (png_uint_16)((PNG_WEIGHT_FACTOR*
               PNG_FP_1+(filter_weights[i]/2))/filter_weights[i]);
         }
      }
      /* Here is where we set the relative costs of the different filters.  We
       * should take the desired compression level into account when setting
       * the costs, so that Paeth, for instance, has a high relative cost at low
       * compression levels, while it has a lower relative cost at higher
       * compression settings.  The filter types are in order of increasing
       * relative cost, so it would be possible to do this with an algorithm.
       */
      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
         if (filter_costs[i] >= PNG_FP_1)
      {
         png_uint_32 tmp;
         /* Use a 32 bit unsigned temporary here because otherwise the
          * intermediate value will be a 32 bit *signed* integer (ANSI rules)
          * and this will get the wrong answer on division.
          */
         tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
         tmp /= filter_costs[i];
         png_ptr->inv_filter_costs[i] = (png_uint_16)tmp;
         tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;
         tmp /= PNG_FP_1;
         png_ptr->filter_costs[i] = (png_uint_16)tmp;
      }
   }
 }
 #endif /* FIXED_POINT */
 #endif /* WRITE_WEIGHTED_FILTER */
@ -1616,14 +1386,14 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,
    * alpha channel.
    */
   if ((transforms & (PNG_TRANSFORM_STRIP_FILLER_AFTER|
-      PNG_TRANSFORM_STRIP_FILLER_BEFORE)) != 0)
+       PNG_TRANSFORM_STRIP_FILLER_BEFORE)) != 0)
   {
 #ifdef PNG_WRITE_FILLER_SUPPORTED
      if ((transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER) != 0)
      {
         if ((transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE) != 0)
            png_app_error(png_ptr,
-               "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");
+                "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");
         /* Continue if ignored - this is the pre-1.6.10 behavior */
         png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
@ -1652,7 +1422,7 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,
      png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
 #endif
-   /* Swap bits of 1, 2, 4 bit packed pixel formats */
+   /* Swap bits of 1-bit, 2-bit, 4-bit packed pixel formats */
   if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
      png_set_packswap(png_ptr);
@ -1682,13 +1452,13 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,
 #ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
-#ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */
+# ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */
 /* Initialize the write structure - general purpose utility. */
 static int
 png_image_write_init(png_imagep image)
 {
   png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, image,
-          png_safe_error, png_safe_warning);
+       png_safe_error, png_safe_warning);
   if (png_ptr != NULL)
   {
@ -1697,7 +1467,7 @@ png_image_write_init(png_imagep image)
      if (info_ptr != NULL)
      {
         png_controlp control = png_voidcast(png_controlp,
-            png_malloc_warn(png_ptr, (sizeof *control)));
+             png_malloc_warn(png_ptr, (sizeof *control)));
         if (control != NULL)
         {
@ -1744,12 +1514,12 @@ static int
 png_write_image_16bit(png_voidp argument)
 {
   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
+       argument);
   png_imagep image = display->image;
   png_structrp png_ptr = image->opaque->png_ptr;
   png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
-      display->first_row);
+       display->first_row);
   png_uint_16p output_row = png_voidcast(png_uint_16p, display->local_row);
   png_uint_16p row_end;
   const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
@ -1758,17 +1528,18 @@ png_write_image_16bit(png_voidp argument)
   if ((image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
   {
-#     ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
+#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
-         if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
+      if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
-         {
+      {
-            aindex = -1;
+         aindex = -1;
-            ++input_row; /* To point to the first component */
+         ++input_row; /* To point to the first component */
-            ++output_row;
+         ++output_row;
-         }
+      }
         else
-#     endif
+            aindex = channels;
 #     else
         aindex = channels;
 #     endif
   }
   else
@ -1850,7 +1621,7 @@ png_write_image_16bit(png_voidp argument)
 * calculation can be done to 15 bits of accuracy; however, the output needs to
 * be scaled in the range 0..255*65535, so include that scaling here.
 */
-#define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)
+#   define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)
 static png_byte
 png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
@ -1901,12 +1672,12 @@ static int
 png_write_image_8bit(png_voidp argument)
 {
   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
+       argument);
   png_imagep image = display->image;
   png_structrp png_ptr = image->opaque->png_ptr;
   png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
-      display->first_row);
+       display->first_row);
   png_bytep output_row = png_voidcast(png_bytep, display->local_row);
   png_uint_32 y = image->height;
   const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
@ -1916,17 +1687,17 @@ png_write_image_8bit(png_voidp argument)
      png_bytep row_end;
      int aindex;
-#     ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
+#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
-         if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
+      if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
-         {
+      {
-            aindex = -1;
+         aindex = -1;
-            ++input_row; /* To point to the first component */
+         ++input_row; /* To point to the first component */
-            ++output_row;
+         ++output_row;
-         }
+      }
-         else
+      else
-#     endif
+#   endif
-         aindex = channels;
+      aindex = channels;
      /* Use row_end in place of a loop counter: */
      row_end = output_row + image->width * (channels+1);
@ -1960,7 +1731,7 @@ png_write_image_8bit(png_voidp argument)
         } /* while out_ptr < row_end */
         png_write_row(png_ptr, png_voidcast(png_const_bytep,
-            display->local_row));
+             display->local_row));
         input_row += display->row_bytes/(sizeof (png_uint_16));
      } /* while y */
   }
@ -1999,25 +1770,25 @@ png_image_set_PLTE(png_image_write_control *display)
   const png_imagep image = display->image;
   const void *cmap = display->colormap;
   const int entries = image->colormap_entries > 256 ? 256 :
-      (int)image->colormap_entries;
+       (int)image->colormap_entries;
   /* NOTE: the caller must check for cmap != NULL and entries != 0 */
   const png_uint_32 format = image->format;
   const int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);
-#  if defined(PNG_FORMAT_BGR_SUPPORTED) &&\
+#   if defined(PNG_FORMAT_BGR_SUPPORTED) &&\
      defined(PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED)
      const int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
-         (format & PNG_FORMAT_FLAG_ALPHA) != 0;
+          (format & PNG_FORMAT_FLAG_ALPHA) != 0;
-#  else
+#   else
 #     define afirst 0
-#  endif
+#   endif
-#  ifdef PNG_FORMAT_BGR_SUPPORTED
+#   ifdef PNG_FORMAT_BGR_SUPPORTED
      const int bgr = (format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
-#  else
+#   else
 #     define bgr 0
-#  endif
+#   endif
   int i, num_trans;
   png_color palette[256];
@ -2042,11 +1813,11 @@ png_image_set_PLTE(png_image_write_control *display)
            if (channels >= 3) /* RGB */
            {
               palette[i].blue = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[(2 ^ bgr)]);
+                   entry[(2 ^ bgr)]);
               palette[i].green = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[1]);
+                   entry[1]);
               palette[i].red = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[bgr]);
+                   entry[bgr]);
            }
            else /* Gray */
@ -2122,12 +1893,12 @@ png_image_set_PLTE(png_image_write_control *display)
      }
   }
-#  ifdef afirst
+#   ifdef afirst
 #     undef afirst
-#  endif
+#   endif
-#  ifdef bgr
+#   ifdef bgr
 #     undef bgr
-#  endif
+#   endif
   png_set_PLTE(image->opaque->png_ptr, image->opaque->info_ptr, palette,
      entries);
@ -2155,10 +1926,10 @@ png_image_write_main(png_voidp argument)
   int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA);
   int write_16bit = linear && !colormap && (display->convert_to_8bit == 0);
-#  ifdef PNG_BENIGN_ERRORS_SUPPORTED
+#   ifdef PNG_BENIGN_ERRORS_SUPPORTED
      /* Make sure we error out on any bad situation */
      png_set_benign_errors(png_ptr, 0/*error*/);
-#  endif
+#   endif
   /* Default the 'row_stride' parameter if required. */
   if (display->row_stride == 0)
@ -2227,7 +1998,7 @@ png_image_write_main(png_voidp argument)
   /* Now set up the data transformations (*after* the header is written),
    * remove the handled transformations from the 'format' flags for checking.
    *
-    * First check for a little endian system if writing 16 bit files.
+    * First check for a little endian system if writing 16-bit files.
    */
   if (write_16bit != 0)
   {
@ -2237,23 +2008,23 @@ png_image_write_main(png_voidp argument)
         png_set_swap(png_ptr);
   }
-#  ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
+#   ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
      if ((format & PNG_FORMAT_FLAG_BGR) != 0)
      {
         if (colormap == 0 && (format & PNG_FORMAT_FLAG_COLOR) != 0)
            png_set_bgr(png_ptr);
         format &= ~PNG_FORMAT_FLAG_BGR;
      }
-#  endif
+#   endif
-#  ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
+#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
      if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
      {
         if (colormap == 0 && (format & PNG_FORMAT_FLAG_ALPHA) != 0)
            png_set_swap_alpha(png_ptr);
         format &= ~PNG_FORMAT_FLAG_AFIRST;
      }
-#  endif
+#   endif
   /* If there are 16 or fewer color-map entries we wrote a lower bit depth
    * above, but the application data is still byte packed.
@ -2289,9 +2060,9 @@ png_image_write_main(png_voidp argument)
       * it about 50 times.  The speed-up in pngstest was about 10-20% of the
       * total (user) time on a heavily loaded system.
       */
-#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
+#   ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
      png_set_compression_level(png_ptr, 3);
-#endif
+#   endif
   }
   /* Check for the cases that currently require a pre-transform on the row
@ -2454,6 +2225,6 @@ png_image_write_to_file(png_imagep image, const char *file_name,
   else
      return 0;
 }
-#endif /* STDIO */
+# endif /* STDIO */
 #endif /* SIMPLIFIED_WRITE */
 #endif /* WRITE */
--- a/thirdparty/libpng/pngwtran.c
+++ b/thirdparty/libpng/pngwtran.c
@ -1,8 +1,8 @@
 /* pngwtran.c - transforms the data in a row for PNG writers
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
@ -71,7 +71,8 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
         case 2:
         {
            png_bytep sp, dp;
-            int shift, v;
+            unsigned int shift;
            int v;
            png_uint_32 i;
            png_uint_32 row_width = row_info->width;
@ -110,7 +111,8 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
         case 4:
         {
            png_bytep sp, dp;
-            int shift, v;
+            unsigned int shift;
            int v;
            png_uint_32 i;
            png_uint_32 row_width = row_info->width;
@ -422,7 +424,7 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
               *(dp++) = *(sp++);
               */
               sp+=3; dp = sp;
-               *(dp++) = (png_byte)(255 - *(sp++));
+               *dp = (png_byte)(255 - *(sp++));
            }
         }
@ -446,7 +448,7 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
               */
               sp+=6; dp = sp;
               *(dp++) = (png_byte)(255 - *(sp++));
-               *(dp++) = (png_byte)(255 - *(sp++));
+               *dp     = (png_byte)(255 - *(sp++));
            }
         }
 #endif /* WRITE_16BIT */
@ -484,7 +486,7 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
               */
               sp+=2; dp = sp;
               *(dp++) = (png_byte)(255 - *(sp++));
-               *(dp++) = (png_byte)(255 - *(sp++));
+               *dp     = (png_byte)(255 - *(sp++));
            }
         }
 #endif /* WRITE_16BIT */
--- a/thirdparty/libpng/pngwutil.c
+++ b/thirdparty/libpng/pngwutil.c