Commit d024c724d10c2e77d08fe473260bf38759ed1cf8
2017-01-05T08:16:39
Fixed signedness issue when blitting on a big endian platform, as reported by capehill For example, if sR is 0 and dR is 255, we will get -255*sA casted to an unsigned value. Basically results are quite large numbers instead of the expected 0-255 range.
diff --git a/src/video/SDL_blit.h b/src/video/SDL_blit.h
index a4c0f4b..ad705d1 100644
--- a/src/video/SDL_blit.h
+++ b/src/video/SDL_blit.h
@@ -443,19 +443,19 @@ do { \
/* Blend the RGB values of two pixels with an alpha value */
#define ALPHA_BLEND_RGB(sR, sG, sB, A, dR, dG, dB) \
do { \
- dR = ((((unsigned)(sR-dR)*(unsigned)A)/255)+dR); \
- dG = ((((unsigned)(sG-dG)*(unsigned)A)/255)+dG); \
- dB = ((((unsigned)(sB-dB)*(unsigned)A)/255)+dB); \
+ dR = (Uint8)((((int)(sR-dR)*A)/255)+dR); \
+ dG = (Uint8)((((int)(sG-dG)*A)/255)+dG); \
+ dB = (Uint8)((((int)(sB-dB)*A)/255)+dB); \
} while(0)
/* Blend the RGBA values of two pixels */
#define ALPHA_BLEND_RGBA(sR, sG, sB, sA, dR, dG, dB, dA) \
do { \
- dR = ((((unsigned)(sR-dR)*(unsigned)sA)/255)+dR); \
- dG = ((((unsigned)(sG-dG)*(unsigned)sA)/255)+dG); \
- dB = ((((unsigned)(sB-dB)*(unsigned)sA)/255)+dB); \
- dA = ((unsigned)sA+(unsigned)dA-((unsigned)sA*dA)/255); \
+ dR = (Uint8)((((int)(sR-dR)*sA)/255)+dR); \
+ dG = (Uint8)((((int)(sG-dG)*sA)/255)+dG); \
+ dB = (Uint8)((((int)(sB-dB)*sA)/255)+dB); \
+ dA = (Uint8)((int)sA+dA-((int)sA*dA)/255); \
} while(0)