94 lines
2.7 KiB
C++
94 lines
2.7 KiB
C++
#pragma once
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#include <string.h>
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#include "agg_basics.h"
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#include "agg_rendering_buffer.h"
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namespace agg
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{
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// This is a special purpose color type that only has the alpha channel.
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// It can be thought as a gray color but with the intensity always on.
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// It is actually used to store coverage information.
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struct alpha8
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{
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typedef int8u value_type;
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typedef int32u calc_type;
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typedef int32 long_type;
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enum base_scale_e
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{
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base_shift = 8,
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base_scale = 1 << base_shift,
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base_mask = base_scale - 1
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};
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value_type a;
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//--------------------------------------------------------------------
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alpha8(unsigned a_=base_mask) :
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a(int8u(a_)) {}
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};
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// Pixer format to store coverage information.
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class pixfmt_alpha8
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{
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public:
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typedef alpha8 color_type;
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typedef int8u value_type;
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typedef int32u calc_type;
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typedef agg::rendering_buffer::row_data row_data;
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//--------------------------------------------------------------------
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pixfmt_alpha8(rendering_buffer& rb): m_rbuf(&rb)
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{
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}
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//--------------------------------------------------------------------
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unsigned width() const {
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return m_rbuf->width();
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}
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unsigned height() const {
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return m_rbuf->height();
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}
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// This method should never be called when using the scanline_u8.
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// The use of scanline_p8 should be avoided because if does not works
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// properly for rendering fonts because single hspan are split in many
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// hline/hspan elements and pixel whitening happens.
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void blend_hline(int x, int y, unsigned len,
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const color_type& c, int8u cover)
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{ }
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void copy_hline(int x, int y, unsigned len, const color_type& c)
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{
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value_type* p = (value_type*) m_rbuf->row_ptr(y) + x;
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do
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{
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*p = c.a;
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p++;
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}
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while(--len);
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}
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//--------------------------------------------------------------------
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void blend_solid_hspan(int x, int y,
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unsigned len,
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const color_type& c,
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const int8u* covers)
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{
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value_type* p = (value_type*) m_rbuf->row_ptr(y) + x;
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do
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{
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calc_type alpha = (calc_type(c.a) * (calc_type(*covers) + 1)) >> 8;
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*p = alpha;
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p++;
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++covers;
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}
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while(--len);
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}
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private:
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rendering_buffer* m_rbuf;
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};
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}
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