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Improved color accuracy blitting floating point surfaces to 8-bit indexed surfaces

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This commit is contained in:
Sam Lantinga
2024-08-12 11:00:42 -07:00
parent e87647c351
commit 375f303d97
1 changed files with 24 additions and 12 deletions
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36
src/video/SDL_blit_slow.c
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@@ -281,7 +281,7 @@ void SDL_Blit_Slow(SDL_BlitInfo *info)
switch (dst_access) {
case SlowBlitPixelAccess_Index8:
dstpixel = (dstR << 24 | dstG << 16 | dstB << 8 | dstA);
dstpixel = ((dstR << 24) | (dstG << 16) | (dstB << 8) | dstA);
if (dstpixel != last_pixel) {
last_pixel = dstpixel;
last_index = SDL_LookupRGBAColor(palette_map, dstpixel, dst_pal);
@@ -583,7 +583,7 @@ static void ReadFloatPixel(Uint8 *pixels, SlowBlitPixelAccess access, const SDL_
*outA = fA;
}
static void WriteFloatPixel(Uint8 *pixels, SlowBlitPixelAccess access, const SDL_PixelFormatDetails *fmt, Uint8 *table, SDL_Colorspace colorspace, float SDR_white_point,
static void WriteFloatPixel(Uint8 *pixels, SlowBlitPixelAccess access, const SDL_PixelFormatDetails *fmt, SDL_Colorspace colorspace, float SDR_white_point,
float fR, float fG, float fB, float fA)
{
Uint32 R, G, B, A;
@@ -614,15 +614,8 @@ static void WriteFloatPixel(Uint8 *pixels, SlowBlitPixelAccess access, const SDL
switch (access) {
case SlowBlitPixelAccess_Index8:
R = (Uint8)SDL_roundf(SDL_clamp(fR, 0.0f, 1.0f) * 7.0f);
G = (Uint8)SDL_roundf(SDL_clamp(fG, 0.0f, 1.0f) * 7.0f);
B = (Uint8)SDL_roundf(SDL_clamp(fB, 0.0f, 1.0f) * 3.0f);
pixel = (R << 5) | (G << 2) | B;
if (table) {
*pixels = table[pixel];
} else {
*pixels = pixel;
}
// This should never happen, checked before this call
SDL_assert(0);
break;
case SlowBlitPixelAccess_RGB:
R = (Uint8)SDL_roundf(SDL_clamp(fR, 0.0f, 1.0f) * 255.0f);
@@ -828,6 +821,7 @@ void SDL_Blit_Slow_Float(SDL_BlitInfo *info)
const SDL_Palette *src_pal = info->src_pal;
const SDL_PixelFormatDetails *dst_fmt = info->dst_fmt;
const SDL_Palette *dst_pal = info->dst_pal;
SDL_HashTable *palette_map = info->palette_map;
int srcbpp = src_fmt->bytes_per_pixel;
int dstbpp = dst_fmt->bytes_per_pixel;
SlowBlitPixelAccess src_access;
@@ -842,6 +836,8 @@ void SDL_Blit_Slow_Float(SDL_BlitInfo *info)
float dst_headroom;
float src_headroom;
SDL_TonemapContext tonemap;
Uint32 last_pixel = 0;
Uint8 last_index = 0;
src_colorspace = info->src_surface->internal->colorspace;
dst_colorspace = info->dst_surface->internal->colorspace;
@@ -892,6 +888,9 @@ void SDL_Blit_Slow_Float(SDL_BlitInfo *info)
src_access = GetPixelAccessMethod(src_fmt->format);
dst_access = GetPixelAccessMethod(dst_fmt->format);
if (dst_access == SlowBlitPixelAccess_Index8) {
last_index = SDL_LookupRGBAColor(palette_map, last_pixel, dst_pal);
}
incy = ((Uint64)info->src_h << 16) / info->dst_h;
incx = ((Uint64)info->src_w << 16) / info->dst_w;
@@ -972,7 +971,20 @@ void SDL_Blit_Slow_Float(SDL_BlitInfo *info)
break;
}
WriteFloatPixel(dst, dst_access, dst_fmt, info->table, dst_colorspace, dst_white_point, dstR, dstG, dstB, dstA);
if (dst_access == SlowBlitPixelAccess_Index8) {
Uint32 R = (Uint8)SDL_roundf(SDL_clamp(SDL_sRGBfromLinear(dstR), 0.0f, 1.0f) * 255.0f);
Uint32 G = (Uint8)SDL_roundf(SDL_clamp(SDL_sRGBfromLinear(dstG), 0.0f, 1.0f) * 255.0f);
Uint32 B = (Uint8)SDL_roundf(SDL_clamp(SDL_sRGBfromLinear(dstB), 0.0f, 1.0f) * 255.0f);
Uint32 A = (Uint8)SDL_roundf(SDL_clamp(dstA, 0.0f, 1.0f) * 255.0f);
Uint32 dstpixel = ((R << 24) | (G << 16) | (B << 8) | A);
if (dstpixel != last_pixel) {
last_pixel = dstpixel;
last_index = SDL_LookupRGBAColor(palette_map, dstpixel, dst_pal);
}
*dst = last_index;
} else {
WriteFloatPixel(dst, dst_access, dst_fmt, dst_colorspace, dst_white_point, dstR, dstG, dstB, dstA);
}
posx += incx;
dst += dstbpp;