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/* Reference implementation using divisions. Since the slow path is
* so very slow this version specialises runs of constant or solid
* pixels. */
#include <stddef.h>
#include <stdint.h>
/* Pixel format config for a 32 bit pixel with 8 bit components. Only
* the location of alpha matters. */
#ifndef ASHIFT
# define ASHIFT 24
#endif
#define RSHIFT ((24 + ASHIFT) % 32)
#define GSHIFT ((16 + ASHIFT) % 32)
#define BSHIFT (( 8 + ASHIFT) % 32)
#define AMASK (255 << ASHIFT)
#define RMASK (255 << RSHIFT)
#define GMASK (255 << GSHIFT)
#define BMASK (255 << BSHIFT)
void
unpremultiply_with_div(
uint32_t * restrict dst,
uint32_t const * restrict src,
size_t n)
{
size_t i;
for (i=0; i<n; i++) {
uint32_t rgba = src[i];
if (rgba & AMASK) {
uint32_t a = (rgba >> ASHIFT) & 0xFF;
uint32_t r = (rgba >> RSHIFT) & 0xFF;
uint32_t g = (rgba >> GSHIFT) & 0xFF;
uint32_t b = (rgba >> BSHIFT) & 0xFF;
r = r*255 / a;
g = g*255 / a;
b = b*255 / a;
dst[i] = (r<<RSHIFT) | (g<<GSHIFT) | (b<<BSHIFT) | (a << ASHIFT);
} else {
dst[i] = 0;
}
}
}
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