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Improved performance scaling 8-bit surfaces

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This commit is contained in:
Sam Lantinga
2025-11-08 10:22:15 -08:00
parent 01d359c1df
commit d145e78cd6
3 changed files with 26 additions and 12 deletions
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29
src/video/SDL_pixels.c
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@@ -1441,24 +1441,31 @@ void SDL_GetRGBA(Uint32 pixelvalue, const SDL_PixelFormatDetails *format, const
}
}
bool SDL_IsSamePalette(const SDL_Palette *src, const SDL_Palette *dst)
{
if (src->ncolors <= dst->ncolors) {
// If an identical palette, no need to map
if (src == dst ||
(SDL_memcmp(src->colors, dst->colors,
src->ncolors * sizeof(SDL_Color)) == 0)) {
return true;
}
}
return false;
}
// Map from Palette to Palette
static Uint8 *Map1to1(const SDL_Palette *src, const SDL_Palette *dst, int *identical)
{
Uint8 *map;
int i;
if (identical) {
if (src->ncolors <= dst->ncolors) {
// If an identical palette, no need to map
if (src == dst ||
(SDL_memcmp(src->colors, dst->colors,
src->ncolors * sizeof(SDL_Color)) == 0)) {
*identical = 1;
return NULL;
}
}
*identical = 0;
if (SDL_IsSamePalette(src, dst)) {
*identical = 1;
return NULL;
}
*identical = 0;
map = (Uint8 *)SDL_calloc(256, sizeof(Uint8));
if (!map) {
return NULL;

1
src/video/SDL_pixels_c.h
View File

@@ -48,6 +48,7 @@ extern void SDL_InvalidateMap(SDL_BlitMap *map);
extern bool SDL_MapSurface(SDL_Surface *src, SDL_Surface *dst);
// Miscellaneous functions
extern bool SDL_IsSamePalette(const SDL_Palette *src, const SDL_Palette *dst);
extern void SDL_DitherPalette(SDL_Palette *palette);
extern Uint8 SDL_FindColor(const SDL_Palette *pal, Uint8 r, Uint8 g, Uint8 b, Uint8 a);
extern Uint8 SDL_LookupRGBAColor(SDL_HashTable *palette_map, Uint32 pixelvalue, const SDL_Palette *pal);

8
src/video/SDL_surface.c
View File

@@ -1252,7 +1252,8 @@ bool SDL_BlitSurfaceUncheckedScaled(SDL_Surface *src, const SDL_Rect *srcrect, S
if (scaleMode == SDL_SCALEMODE_NEAREST || scaleMode == SDL_SCALEMODE_PIXELART) {
if (!(src->map.info.flags & complex_copy_flags) &&
src->format == dst->format &&
!SDL_ISPIXELFORMAT_INDEXED(src->format) &&
(!SDL_ISPIXELFORMAT_INDEXED(src->format) ||
(SDL_BITSPERPIXEL(src->format) == 8 && SDL_IsSamePalette(src->palette, dst->palette))) &&
SDL_BYTESPERPIXEL(src->format) <= 4) {
return SDL_StretchSurface(src, srcrect, dst, dstrect, SDL_SCALEMODE_NEAREST);
} else if (SDL_BITSPERPIXEL(src->format) < 8) {
@@ -2244,6 +2245,11 @@ SDL_Surface *SDL_ScaleSurface(SDL_Surface *surface, int width, int height, SDL_S
return result;
}
if (SDL_ISPIXELFORMAT_INDEXED(surface->format)) {
// Linear scaling requires conversion to RGBA and then slow pixel color lookup
scaleMode = SDL_SCALEMODE_NEAREST;
}
// Create a new surface with the desired size
if (surface->pixels || SDL_MUSTLOCK(surface)) {
convert = SDL_CreateSurface(width, height, surface->format);