Image *image_sub(const Image *a, const Image *b, Image *out) {
int wi, hi;
for (hi = 0; hi < a->height; ++hi)
for (wi = 0; wi < a->width; ++wi)
color_sub(a->channels, sample(a,wi,hi), sample(b,wi,hi),
sample(out,wi,hi));
return out;
}
pixel_t truecolor_match_color(const rgba_t *color, rgba_t *error)
{
rgba_t approx;
u32 r, g, b, a;
r = COMPRESS_FROM_16BIT(color->r, red_len-1);
g = COMPRESS_FROM_16BIT(color->g, green_len-1);
b = COMPRESS_FROM_16BIT(color->b, blue_len-1);
a = COMPRESS_FROM_16BIT(color->a, alpha_len-1);
if (error) {
approx.r = EXPAND_TO_16BIT(r, red_len-1);
approx.g = EXPAND_TO_16BIT(g, green_len-1);
approx.b = EXPAND_TO_16BIT(b, blue_len-1);
approx.a = EXPAND_TO_16BIT(a, alpha_len-1);
color_sub(error, color, &approx);
}
return rgba_pixel(r, g, b, a);
}
