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begin work on arbitrary alpha values in paletted textures

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This commit is contained in:
Glenn Maynard
2004-05-16 05:51:25 +00:00
parent 3e91007367
commit 04a74a4455
3 changed files with 29 additions and 11 deletions
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stepmania/src/SDL_utils.cpp
+24 -10
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@@ -430,6 +430,18 @@ int FindSurfaceTraits( const SDL_Surface *img )
const int NEEDS_NO_ALPHA=0, NEEDS_BOOL_ALPHA=1, NEEDS_FULL_ALPHA=2;
int alpha_type = NEEDS_NO_ALPHA;
/* If 8bpp and neither SDL_SRCCOLORKEY nor ALPHA_PALETTE, there is no transparency
* to search for. */
if( img->format->BitsPerPixel == 8 &&
!(img->flags & SDL_SRCCOLORKEY) && !(img->unused1 & ALPHA_PALETTE) )
return TRAIT_NO_TRANSPARENCY;
Uint32 max_alpha;
if( img->format->BitsPerPixel == 8 )
max_alpha = 0xFF;
else
max_alpha = img->format->Amask;
for(int y = 0; y < img->h; ++y)
{
Uint8 *row = (Uint8 *)img->pixels + img->pitch*y;
@@ -438,16 +450,18 @@ int FindSurfaceTraits( const SDL_Surface *img )
{
Uint32 val = decodepixel(row, img->format->BytesPerPixel);
if( img->format->BitsPerPixel == 8 ) {
if(img->flags & SDL_SRCCOLORKEY && val == img->format->colorkey )
alpha_type = max( alpha_type, NEEDS_BOOL_ALPHA );
} else if(img->format->Amask) {
Uint32 masked_alpha = val & img->format->Amask;
if(masked_alpha == 0)
alpha_type = max( alpha_type, NEEDS_BOOL_ALPHA );
else if(masked_alpha != img->format->Amask)
alpha_type = max( alpha_type, NEEDS_FULL_ALPHA );
}
Uint32 alpha;
if( img->flags & SDL_SRCCOLORKEY )
alpha = (val == img->format->colorkey)? 0x00:0xFF;
if( img->unused1 & ALPHA_PALETTE )
alpha = img->format->palette->colors[val].unused;
else
alpha = (val & img->format->Amask);
if( alpha == 0 )
alpha_type = max( alpha_type, NEEDS_BOOL_ALPHA );
else if( alpha != max_alpha )
alpha_type = max( alpha_type, NEEDS_FULL_ALPHA );
row += img->format->BytesPerPixel;
}