(This is the documentation for SDL3, which is the current stable version. SDL2 was the previous version!)

SDL_PremultiplyAlpha

Premultiply the alpha on a block of pixels.

Header File

Defined in <SDL3/SDL_surface.h>

Syntax

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

Function Parameters

int	width	the width of the block to convert, in pixels.
int	height	the height of the block to convert, in pixels.
SDL_PixelFormat	src_format	an SDL_PixelFormat value of the src pixels format.
const void *	src	a pointer to the source pixels.
int	src_pitch	the pitch of the source pixels, in bytes.
SDL_PixelFormat	dst_format	an SDL_PixelFormat value of the dst pixels format.
void *	dst	a pointer to be filled in with premultiplied pixel data.
int	dst_pitch	the pitch of the destination pixels, in bytes.
bool	linear	true to convert from sRGB to linear space for the alpha multiplication, false to do multiplication in sRGB space.

Return Value

(bool) Returns true on success or false on failure; call SDL_GetError() for more information.

Remarks

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

Version

This function is available since SDL 3.1.3.

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CategoryAPI, CategoryAPIFunction, CategorySurface

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