Added OPJ_LIMIT_DECODING enabling us to limit the decoding to main header

ChangeLog

@@ -5,6 +5,9 @@ What's New for OpenJPEG
 ! : changed
 + : added
 
+February 19, 2007
++ [FOD] Added OPJ_LIMIT_DECODING enabling us to limit the decoding to main header (modified openjpeg.c, openjpeg.h, j2k.c and j2k.h)
+
 February 13, 2007
 ! [FOD] David Fries suggestions. In image_to_j2k and j2k_to_image, strncpy() functions: instead of specifying the path size macro, let the compiler read the length out of the array entry.
 ! [FOD] David Fries suggestions. Makefile modified. -fPIC flag used for 64-bit compilation. Move operation (rather than copy) for the dist library creation, and -p flag added.

libopenjpeg/j2k.c

@@ -1522,6 +1522,7 @@ void j2k_setup_decoder(opj_j2k_t *j2k, opj_dparameters_t *parameters) {
 		opj_cp_t *cp = (opj_cp_t*)opj_malloc(sizeof(opj_cp_t));
 		cp->reduce = parameters->cp_reduce;	
 		cp->layer = parameters->cp_layer;
+		cp->limit_decoding = parameters->cp_limit_decoding;
 /* UniPG>> */
 #ifdef USE_JPWL
 		cp->correct = parameters->jpwl_correct;
@@ -1594,11 +1595,18 @@ opj_image_t* j2k_decode(opj_j2k_t *j2k, opj_cio_t *cio) {
 			return 0;
 		}
 		e = j2k_dec_mstab_lookup(id);
+		// Check if the marker is known
 		if (!(j2k->state & e->states)) {
 			opj_image_destroy(image);
 			opj_event_msg(cinfo, EVT_ERROR, "%.8x: unexpected marker %x\n", cio_tell(cio) - 2, id);
 			return 0;
 		}
+		// Check if the decoding is limited to the main header
+		if (e->id == J2K_MS_SOT && j2k->cp->limit_decoding == LIMIT_TO_MAIN_HEADER) {
+			opj_event_msg(cinfo, EVT_INFO, "Main Header decoded.\n");
+			return image;
+		}		
+
 		if (e->handler) {
 			(*e->handler)(j2k);
 		}

libopenjpeg/j2k.h

@@ -197,6 +197,8 @@ typedef struct opj_cp {
 	int reduce;
 	/** if != 0, then only the first "layer" layers are decoded; if == 0 or not used, all the quality layers are decoded */
 	int layer;
+	/** if == NO_LIMITATION, decode entire codestream; if == LIMIT_TO_MAIN_HEADER then only decode the main header */
+	OPJ_LIMIT_DECODING limit_decoding;
 	/** 0 = no index || 1 = index */
 	int index_on;
 	/** XTOsiz */

libopenjpeg/openjpeg.c

@@ -116,6 +116,7 @@ void OPJ_CALLCONV opj_set_default_decoder_parameters(opj_dparameters_t *paramete
 		/* default decoding parameters */
 		parameters->cp_layer = 0;
 		parameters->cp_reduce = 0;
+		parameters->cp_limit_decoding = NO_LIMITATION;
 
 		parameters->decod_format = -1;
 		parameters->cod_format = -1;

libopenjpeg/openjpeg.h

@@ -143,6 +143,14 @@ typedef enum CODEC_FORMAT {
 	CODEC_JP2 = 2		/**< JPEG-2000 file format : read/write */
 } OPJ_CODEC_FORMAT;
 
+/** 
+Limit decoding to certain portions of the codestream. 
+*/
+typedef enum LIMIT_DECODING {
+	NO_LIMITATION = 0,				/**< No limitation for the decoding. The entire codestream will de decoded */
+	LIMIT_TO_MAIN_HEADER = 1	/**< The decoding is limited to the Main Header */
+} OPJ_LIMIT_DECODING;
+
 /* 
 ==========================================================
    event manager typedef definitions
@@ -331,6 +339,14 @@ typedef struct opj_dparameters {
 	*/
 	int cp_layer;
 
+	/** 
+	Specify whether the decoding should be done on the entire codestream, or be limited to the main header
+	Limiting the decoding to the main header makes it possible to extract the characteristics of the codestream
+	if == NO_LIMITATION, the entire codestream is decoded; 
+	if == LIMIT_TO_MAIN_HEADER, only the main header is decoded; 
+	*/
+	OPJ_LIMIT_DECODING cp_limit_decoding;
+
 	/**@name command line encoder parameters (not used inside the library) */
 	/*@{*/
 	/** input file name */