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SDLTest_CompareSurfaces: Decode pixels correctly on big-endian platforms #8317

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merged 1 commit into from
Sep 29, 2023
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SDLTest_CompareSurfaces: Decode pixels correctly on big-endian platforms #8317

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26 changes: 24 additions & 2 deletions src/test/SDL_test_compare.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,25 @@
/* Counter for _CompareSurface calls; used for filename creation when comparisons fail */
static int _CompareSurfaceCount = 0;

static Uint32
GetPixel(Uint8 *p, size_t bytes_per_pixel)
{
Uint32 ret = 0;

SDL_assert(bytes_per_pixel <= sizeof(ret));

/* Fill the appropriate number of least-significant bytes of ret,
* leaving the most-significant bytes set to zero, so that ret can
* be decoded with SDL_GetRGBA afterwards. */
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
SDL_memcpy(((Uint8 *) &ret) + (sizeof(ret) - bytes_per_pixel), p, bytes_per_pixel);
#else
SDL_memcpy(&ret, p, bytes_per_pixel);
#endif

return ret;
}

/* Compare surfaces */
int SDLTest_CompareSurfaces(SDL_Surface *surface, SDL_Surface *referenceSurface, int allowable_error)
{
Expand Down Expand Up @@ -71,11 +90,14 @@ int SDLTest_CompareSurfaces(SDL_Surface *surface, SDL_Surface *referenceSurface,
/* Compare image - should be same format. */
for (j = 0; j < surface->h; j++) {
for (i = 0; i < surface->w; i++) {
Uint32 pixel;
p = (Uint8 *)surface->pixels + j * surface->pitch + i * bpp;
p_reference = (Uint8 *)referenceSurface->pixels + j * referenceSurface->pitch + i * bpp_reference;

SDL_GetRGBA(*(Uint32 *)p, surface->format, &R, &G, &B, &A);
SDL_GetRGBA(*(Uint32 *)p_reference, referenceSurface->format, &Rd, &Gd, &Bd, &Ad);
pixel = GetPixel(p, bpp);
SDL_GetRGBA(pixel, surface->format, &R, &G, &B, &A);
pixel = GetPixel(p_reference, bpp_reference);
SDL_GetRGBA(pixel, referenceSurface->format, &Rd, &Gd, &Bd, &Ad);

dist = 0;
dist += (R - Rd) * (R - Rd);
Expand Down