SDL Wiki
(This is the legacy documentation for stable SDL2, the current stable version; SDL3 is the current development version.)


Set the color key (transparent pixel) in a surface.


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

Function Parameters

surface the SDL_Surface structure to update
flag SDL_TRUE to enable color key, SDL_FALSE to disable color key
key the transparent pixel

Return Value

Returns 0 on success or a negative error code on failure; call SDL_GetError() for more information.


The color key defines a pixel value that will be treated as transparent in a blit. For example, one can use this to specify that cyan pixels should be considered transparent, and therefore not rendered.

It is a pixel of the format used by the surface, as generated by SDL_MapRGB().

RLE acceleration can substantially speed up blitting of images with large horizontal runs of transparent pixels. See SDL_SetSurfaceRLE() for details.


This function is available since SDL 2.0.0.


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