pixel.h

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#ifndef PATCHWORK_PIXEL_H
#define PATCHWORK_PIXEL_H 1
 
#include <stdint.h>
 
#if defined(__cplusplus)
extern "C"
{
#endif
 
typedef uint32_t pixel_t;
 
#define PIXEL_ALPHA(pixel) (((pixel) >> 24) & 0xFF)
#define PIXEL_RED(pixel) (((pixel) >> 16) & 0xFF)
#define PIXEL_GREEN(pixel) (((pixel) >> 8) & 0xFF)
#define PIXEL_BLUE(pixel) (((pixel) >> 0) & 0xFF)
 
#define PIXEL_ARGB(a, r, g, b) (((a) << 24) | ((r) << 16) | ((g) << 8) | ((b) << 0))
 
#define PIXEL_BLEND(dest, src) \
    ({ \
        uint8_t aAlpha = PIXEL_ALPHA(*src); \
        uint8_t bAlpha = PIXEL_ALPHA(*dest); \
        uint8_t alpha = aAlpha + ((bAlpha * (0xFF - aAlpha)) / 0xFF); \
        if (alpha != 0) \
        { \
            *dest = PIXEL_ARGB(alpha, \
                (PIXEL_RED(*src) * aAlpha + PIXEL_RED(*dest) * bAlpha * (0xFF - aAlpha) / 0xFF) / alpha, \
                (PIXEL_GREEN(*src) * aAlpha + PIXEL_GREEN(*dest) * bAlpha * (0xFF - aAlpha) / 0xFF) / alpha, \
                (PIXEL_BLUE(*src) * aAlpha + PIXEL_BLUE(*dest) * bAlpha * (0xFF - aAlpha) / 0xFF) / alpha); \
        } \
        else \
        { \
            *dest = 0; \
        } \
    })
 
#if defined(__cplusplus)
}
#endif
 
#endif