SDL Wiki
(This is the documentation for SDL3, which is under heavy development and the API is changing! SDL2 is the current stable version!)


Premultiply the alpha on a block of pixels.


int SDL_PremultiplyAlpha(int width, int height,
                         Uint32 src_format,
                         const void *src, int src_pitch,
                         Uint32 dst_format,
                         void *dst, int dst_pitch);

Function Parameters

width the width of the block to convert, in pixels
height the height of the block to convert, in pixels
src_format an SDL_PixelFormatEnum value of the src pixels format
src a pointer to the source pixels
src_pitch the pitch of the source pixels, in bytes
dst_format an SDL_PixelFormatEnum value of the dst pixels format
dst a pointer to be filled in with premultiplied pixel data
dst_pitch the pitch of the destination pixels, in bytes

Return Value

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


This is safe to use with src == dst, but not for other overlapping areas.

This function is currently only implemented for SDL_PIXELFORMAT_ARGB8888.


This function is available since SDL 3.0.0.


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