###### (This is the legacy documentation for stable SDL2, the current stable version; [SDL3](https://wiki.libsdl.org/SDL3/) is the current development version.)
# SDL_SetColorKey

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

## Header File

Defined in [SDL_surface.h](https://github.com/libsdl-org/SDL/blob/SDL2/include/SDL_surface.h), but apps should _only_ `#include "SDL.h"`!

## Syntax

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

```

## Function Parameters

|                 |                                                                                       |
| --------------- | ------------------------------------------------------------------------------------- |
| **surface**     | the [SDL_Surface](SDL_Surface) structure to update                                    |
| **flag**        | [SDL_TRUE](SDL_TRUE) to enable color key, [SDL_FALSE](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](SDL_GetError)() for more information.

## Remarks

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](SDL_MapRGB)().

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

## Version

This function is available since SDL 2.0.0.

## See Also

* [SDL_BlitSurface](SDL_BlitSurface)
* [SDL_GetColorKey](SDL_GetColorKey)

----
[CategoryAPI](CategoryAPI), [CategoryAPIFunction](CategoryAPIFunction)