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fix excessive rounding error in mySDL_BlitTransform (completely opaque

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surfaces would be set to an alpha value of 0xFB); fix latent alpha channel
bug
This commit is contained in:
Glenn Maynard
2004-05-02 03:49:22 +00:00
parent ac81016af4
commit fa83dfc552
1 changed files with 10 additions and 6 deletions
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stepmania/src/SDL_utils.cpp
+10 -6
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@@ -747,14 +747,18 @@ void mySDL_BlitTransform( const SDL_Surface *src, SDL_Surface *dst,
Uint8 out[4] = { 0,0,0,0 }; Uint8 out[4] = { 0,0,0,0 };
for(int i = 0; i < 4; ++i) for(int i = 0; i < 4; ++i)
{ {
Uint32 sum = 0; float sum = 0;
sum += Uint8(v[0][i] * (1-weight_x) * (1-weight_y)); sum += v[0][i] * (1-weight_x) * (1-weight_y);
sum += Uint8(v[1][i] * (1-weight_x) * (weight_y)); sum += v[1][i] * (1-weight_x) * (weight_y);
sum += Uint8(v[2][i] * (weight_x) * (1-weight_y)); sum += v[2][i] * (weight_x) * (1-weight_y);
sum += Uint8(v[3][i] * (weight_x) * (weight_y)); sum += v[3][i] * (weight_x) * (weight_y);
out[i] = (Uint8) clamp(sum, 0u, 255u); out[i] = (Uint8) clamp( lrintf(sum), 0, 255 );
} }
/* If the source has no alpha, set the destination to opaque. */
if( src->format->Amask == 0 )
out[3] = Uint8( dst->format->Amask >> dst->format->Ashift );
mySDL_SetRawRGBAV(dstpx, dst, out); mySDL_SetRawRGBAV(dstpx, dst, out);
dstpx += dst->format->BytesPerPixel; dstpx += dst->format->BytesPerPixel;