Commit 473051f6bbc89872b1e810baece231ec87bd6220
2016-10-01T13:40:01
Fixed bug 3159 - SDL_blit_slow with BLENDING does not work Fritzor Source Suface is ABGR and Destination Surface is ABGR. We use software blending. In the Switch-Case statement for SDL_COPY_BLEND (Line 126) the alpha-channel is not calculated like in every SDL_blit_auto - function. So if the destination Surface has alpha - channel of zero the resulting surface has zero as well. Add: ?dstA = srcA + ((255 - srcA) * dstA) / 255;? to code and everything is okay.
diff --git a/src/video/SDL_blit_slow.c b/src/video/SDL_blit_slow.c
index 30db4e4..02ab41d 100644
--- a/src/video/SDL_blit_slow.c
+++ b/src/video/SDL_blit_slow.c
@@ -129,6 +129,7 @@ SDL_Blit_Slow(SDL_BlitInfo * info)
dstR = srcR + ((255 - srcA) * dstR) / 255;
dstG = srcG + ((255 - srcA) * dstG) / 255;
dstB = srcB + ((255 - srcA) * dstB) / 255;
+ dstA = srcA + ((255 - srcA) * dstA) / 255;
break;
case SDL_COPY_ADD:
dstR = srcR + dstR;