static inline void process_channel(const fix15_t Cs, fix15_t &Cb)
{
if (Cs > 0) {
const fix15_t tmp = fix15_div(fix15_one - Cb, Cs);
if (tmp < fix15_one) {
Cb = fix15_one - tmp;
return;
}
}
Cb = 0;
}
inline void operator() (const fix15_short_t * const src,
fix15_short_t * const dst,
const fix15_short_t src_opacity) const
{
#ifndef HEAVY_DEBUG
// Skip tile if it can't affect the backdrop
const bool skip_empty_src = ! compositefunc.zero_alpha_has_effect;
if (skip_empty_src && src_opacity == 0) {
return;
}
#endif
// Pixel loop
fix15_t Rs,Gs,Bs,as, Rb,Gb,Bb,ab, one_minus_ab;
#pragma omp parallel for private(Rs,Gs,Bs,as, Rb,Gb,Bb,ab, one_minus_ab)
for (unsigned int i = 0; i < BUFSIZE; i += 4)
{
// Calculate unpremultiplied source RGB values
as = src[i+3];
if (as == 0) {
#ifndef HEAVY_DEBUG
// Skip pixel if it can't affect the backdrop pixel
if (skip_empty_src) {
continue;
}
#endif
// Otherwise just avoid the divide-by-zero by assuming the
// value before premultiplication was also zero.
Rs = Gs = Bs = 0;
}
else {
Rs = fix15_short_clamp(fix15_div(src[i+0], as));
Gs = fix15_short_clamp(fix15_div(src[i+1], as));
Bs = fix15_short_clamp(fix15_div(src[i+2], as));
}
#ifdef HEAVY_DEBUG
assert(Rs <= fix15_one); assert(Rs >= 0);
assert(Gs <= fix15_one); assert(Gs >= 0);
assert(Bs <= fix15_one); assert(Bs >= 0);
#endif
// Calculate unpremultiplied backdrop RGB values
if (DSTALPHA) {
ab = dst[i+3];
if (ab == 0) {
Rb = Gb = Bb = 0;
}
else {
Rb = fix15_short_clamp(fix15_div(dst[i+0], ab));
Gb = fix15_short_clamp(fix15_div(dst[i+1], ab));
Bb = fix15_short_clamp(fix15_div(dst[i+2], ab));
}
}
else {
ab = fix15_one;
Rb = dst[i+0];
Gb = dst[i+1];
Bb = dst[i+2];
}
#ifdef HEAVY_DEBUG
assert(Rb <= fix15_one); assert(Rb >= 0);
assert(Gb <= fix15_one); assert(Gb >= 0);
assert(Bb <= fix15_one); assert(Bb >= 0);
#endif
// Apply the colour blend functor
blendfunc(Rs, Gs, Bs, Rb, Gb, Bb);
// Apply results of the blend in place
if (DSTALPHA) {
one_minus_ab = fix15_one - ab;
Rb = fix15_sumprods(one_minus_ab, Rs, ab, Rb);
Gb = fix15_sumprods(one_minus_ab, Gs, ab, Gb);
Bb = fix15_sumprods(one_minus_ab, Bs, ab, Bb);
}
#ifdef HEAVY_DEBUG
assert(Rb <= fix15_one); assert(Rb >= 0);
assert(Gb <= fix15_one); assert(Gb >= 0);
assert(Bb <= fix15_one); assert(Bb >= 0);
#endif
// Use the blend result as a source, and composite directly into
// the destination buffer as premultiplied RGB.
compositefunc(Rb, Gb, Bb, fix15_mul(as, src_opacity),
dst[i+0], dst[i+1], dst[i+2], dst[i+3]);
}
}
