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Restore BlitARGB 555 and 565 blending algorithms

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This commit is contained in:
Isaac Aronson
2023-10-10 08:48:14 -05:00
committed by Sam Lantinga
parent 5cec91e27a
commit 8e3afd56f5
1 changed files with 98 additions and 0 deletions
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98
src/video/SDL_blit_A.c
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@@ -952,6 +952,97 @@ static void Blit555to555SurfaceAlpha(SDL_BlitInfo *info)
}
}
/* fast ARGB8888->RGB565 blending with pixel alpha */
static void BlitARGBto565PixelAlpha(SDL_BlitInfo *info)
{
int width = info->dst_w;
int height = info->dst_h;
Uint32 *srcp = (Uint32 *)info->src;
int srcskip = info->src_skip >> 2;
Uint16 *dstp = (Uint16 *)info->dst;
int dstskip = info->dst_skip >> 1;
while (height--) {
/* *INDENT-OFF* */ /* clang-format off */
DUFFS_LOOP4({
Uint32 s = *srcp;
unsigned alpha = s >> 27; /* downscale alpha to 5 bits */
/* FIXME: Here we special-case opaque alpha since the
compositioning used (>>8 instead of /255) doesn't handle
it correctly. Also special-case alpha=0 for speed?
Benchmark this! */
if (alpha) {
if (alpha == (SDL_ALPHA_OPAQUE >> 3)) {
*dstp = (Uint16)((s >> 8 & 0xf800) + (s >> 5 & 0x7e0) + (s >> 3 & 0x1f));
} else {
Uint32 d = *dstp;
/*
* convert source and destination to G0RAB65565
* and blend all components at the same time
*/
s = ((s & 0xfc00) << 11) + (s >> 8 & 0xf800)
+ (s >> 3 & 0x1f);
d = (d | d << 16) & 0x07e0f81f;
d += (s - d) * alpha >> 5;
d &= 0x07e0f81f;
*dstp = (Uint16)(d | d >> 16);
}
}
srcp++;
dstp++;
}, width);
/* *INDENT-ON* */ /* clang-format on */
srcp += srcskip;
dstp += dstskip;
}
}
/* fast ARGB8888->RGB555 blending with pixel alpha */
static void BlitARGBto555PixelAlpha(SDL_BlitInfo *info)
{
int width = info->dst_w;
int height = info->dst_h;
Uint32 *srcp = (Uint32 *)info->src;
int srcskip = info->src_skip >> 2;
Uint16 *dstp = (Uint16 *)info->dst;
int dstskip = info->dst_skip >> 1;
while (height--) {
/* *INDENT-OFF* */ /* clang-format off */
DUFFS_LOOP4({
unsigned alpha;
Uint32 s = *srcp;
alpha = s >> 27; /* downscale alpha to 5 bits */
/* FIXME: Here we special-case opaque alpha since the
compositioning used (>>8 instead of /255) doesn't handle
it correctly. Also special-case alpha=0 for speed?
Benchmark this! */
if (alpha) {
if (alpha == (SDL_ALPHA_OPAQUE >> 3)) {
*dstp = (Uint16)((s >> 9 & 0x7c00) + (s >> 6 & 0x3e0) + (s >> 3 & 0x1f));
} else {
Uint32 d = *dstp;
/*
* convert source and destination to G0RAB65565
* and blend all components at the same time
*/
s = ((s & 0xf800) << 10) + (s >> 9 & 0x7c00)
+ (s >> 3 & 0x1f);
d = (d | d << 16) & 0x03e07c1f;
d += (s - d) * alpha >> 5;
d &= 0x03e07c1f;
*dstp = (Uint16)(d | d >> 16);
}
}
srcp++;
dstp++;
}, width);
/* *INDENT-ON* */ /* clang-format on */
srcp += srcskip;
dstp += dstskip;
}
}
/* General (slow) N->N blending with per-surface alpha */
static void BlitNtoNSurfaceAlpha(SDL_BlitInfo *info)
{
@@ -1127,6 +1218,13 @@ SDL_BlitFunc SDL_CalculateBlitA(SDL_Surface *surface)
}
case 2:
if (sf->BytesPerPixel == 4 && sf->Amask == 0xff000000 && sf->Gmask == 0xff00 && ((sf->Rmask == 0xff && df->Rmask == 0x1f) || (sf->Bmask == 0xff && df->Bmask == 0x1f))) {
if (df->Gmask == 0x7e0) {
return BlitARGBto565PixelAlpha;
} else if (df->Gmask == 0x3e0) {
return BlitARGBto555PixelAlpha;
}
}
return BlitNtoNPixelAlpha;
case 4: