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Updated readme with per-pixel alpha surface example

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pelya
2010-11-01 17:56:39 +02:00
parent 47c05904ed
commit 66f0e9126e
1 changed files with 19 additions and 6 deletions
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25
readme.txt
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@@ -62,14 +62,27 @@ Basically your code should be like:
// Init HW-accelerated video
SDL_SetVideoMode( 640, 480, 16, SDL_DOUBLEBUF | SDL_HWSURFACE );
// Load graphics
SDL_Surface *sprite = IMG_Load( "sprite.png" );
// Set pink color as transparent
SDL_SetColorKey( sprite, SDL_SRCCOLORKEY, SDL_MapRGB(sprite->format, 255, 0, 255) );
// Create HW-accelerated surface
SDL_Surface * hwSprite = SDL_DisplayFormat(sprite);
// Set per-surface alpha, if necessary
SDL_SetAlpha( hwSprite, SDL_SRCALPHA, 128 );
SDL_Surface * hwSprite;
if( sprite->format->Amask )
{
// Surface contains per-pixel alpha, convert it to HW-accelerated format
hwSprite = SDL_DisplayFormatAlpha(sprite);
}
else
{
// Set pink color as transparent
SDL_SetColorKey( sprite, SDL_SRCCOLORKEY, SDL_MapRGB(sprite->format, 255, 0, 255) );
// Create HW-accelerated surface
hwSprite = SDL_DisplayFormat(sprite);
// Set per-surface alpha, if necessary
SDL_SetAlpha( hwSprite, SDL_SRCALPHA, 128 );
}
SDL_FreeSurface(sprite);
// Blit it in HW-accelerated way
SDL_BlitSurface(hwSprite, sourceRect, SDL_GetVideoSurface(), &targetRect);