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SDL alpha ...

Started by artois Oct 28, 2004 at 10:39 AM 2 replies 1.5k views

Original Post

Oct 28, 2004 at 10:39 AM

Hello, i'm new to SDL development, i'm trying to do transparency, but it dont work. Here is the code :


 SDL_Surface *mySurface  = SDL_CreateRGBSurface(SDL_SRCALPHA | SDL_SWSURFACE |SDL_SRCCOLORKEY,256,256,32, rmask, gmask, bmask, amask);
 
 SDL_Rect myRect= {0,0,mySurface->w,mySurface->h};
 SDL_Rect half = {0,0,mySurface->w/2,mySurface->h/2};
 
 result= SDL_FillRect(mySurface,&myRect,SDL_MapRGB(mySurface->format,0,255,255));

 result=SDL_FillRect(mySurface,½,SDL_MapRGB(mySurface->format,0,255,0));

 result=SDL_SetColorKey(mySurface,SDL_SRCCOLORKEY, SDL_MapRGB(mySurface->format,0,255,0));

 result= SDL_BlitSurface(mySurface,&myRect,screen,&myRect);

I'm trying to make the small rectangle transparent, (half). I can do transpanrency with surface loaded from bmp file but not directly created like this one.. Can someone help me please

Gaiiden

589

Gaiiden

Oct 28, 2004 at 8:37 PM

see if calling SDL_DisplayFormat() after you set the colorkey does the trick.

artois

Author

artois

Oct 29, 2004 at 8:49 AM

Cheer ! it worked !

Thanks !

Gaiiden

589

Gaiiden

Oct 30, 2004 at 4:38 AM

Nice. As a further note, you should use this function everytime you load in an image, since blitting an surface of a different format to the main surface (i.e. - loading a 16bit image when you have a 32bit main surface) can be very slow if SDL has to convert the surface every blit rather than just once.

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