sdl_setcolorkey(3) [redhat man page]

SDL_SetColorKey(3)						 SDL API Reference						SDL_SetColorKey(3)

NAME

       SDL_SetColorKey- Sets the color key (transparent pixel) in a blittable surface and RLE acceleration.

SYNOPSIS

       #include "SDL.h"

       int SDL_SetColorKey(SDL_Surface *surface, Uint32 flag, Uint32 key);

DESCRIPTION

	Sets the color key (transparent pixel) in a blittable surface and enables or disables RLE blit acceleration.

       RLE  acceleration  can  substantially speed up blitting of images with large horizontal runs of transparent pixels (i.e., pixels that match
       the key value). The key must be of the same pixel format as the surface, SDL_MapRGB is often useful for obtaining an acceptable value.

       If flag is SDL_SRCCOLORKEY then key is the transparent pixel value in the source image of a blit.

       If flag is OR'd with SDL_RLEACCEL then the surface will be draw using RLE acceleration when drawn with SDL_BlitSurface.	The  surface  will
       actually be encoded for RLE acceleration the first time SDL_BlitSurface or SDL_DisplayFormat is called on the surface.

       If flag is 0, this function clears any current color key.

RETURN VALUE

       This function returns 0, or -1 if there was an error.

SEE ALSO

       SDL_BlitSurface, SDL_DisplayFormat, SDL_MapRGB, SDL_SetAlpha

SDL
							      Tue 11 Sep 2001, 23:01						SDL_SetColorKey(3)

SDL_BlitSurface(3)						 SDL API Reference						SDL_BlitSurface(3)

NAME

       SDL_BlitSurface - This performs a fast blit from the source surface to the destination surface.

SYNOPSIS

       #include "SDL.h"

       int SDL_BlitSurface(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);

DESCRIPTION

       This performs a fast blit from the source surface to the destination surface.

       Only the position is used in the dstrect (the width and height are ignored).

       If either srcrect or dstrect are NULL, the entire surface (src or dst) is copied.

       The final blit rectangle is saved in dstrect after all clipping is performed (srcrect is not modified).

       The blit function should not be called on a locked surface.

       The  results  of  blitting operations vary greatly depending on whether SDL_SRCAPLHA is set or not. See SDL_SetAlpha for an explaination of
       how this affects your results. Colorkeying and alpha attributes also interact with surface blitting, as the  following  pseudo-code  should
       hopefully explain.

       if (source surface has SDL_SRCALPHA set) {
	   if (source surface has alpha channel (that is, format->Amask != 0))
	       blit using per-pixel alpha, ignoring any colour key
	   else {
	       if (source surface has SDL_SRCCOLORKEY set)
		   blit using the colour key AND the per-surface alpha value
	       else
		   blit using the per-surface alpha value
	   }
       } else {
	   if (source surface has SDL_SRCCOLORKEY set)
	       blit using the colour key
	   else
	       ordinary opaque rectangular blit
       }

RETURN VALUE

       If the blit is successful, it returns 0, otherwise it returns -1.

       If  either  of the surfaces were in video memory, and the blit returns -2, the video memory was lost, so it should be reloaded with artwork
       and re-blitted:

	       while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {
		       while ( SDL_LockSurface(image)) < 0 )
			       Sleep(10);
		       -- Write image pixels to image->pixels --
		       SDL_UnlockSurface(image);
	       }

	This happens under DirectX 5.0 when the system switches away from your fullscreen application. Locking the surface will  also  fail  until
       you have access to the video memory again.

SEE ALSO

       SDL_LockSurface, SDL_FillRect, SDL_Surface, SDL_Rect

SDL
							      Tue 11 Sep 2001, 23:01						SDL_BlitSurface(3)