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

SDL_SetSurfaceAlphaMod

Set an additional alpha value used in blit operations.

Header File

Defined in SDL_surface.h

Syntax

int SDL_SetSurfaceAlphaMod(SDL_Surface * surface,
                           Uint8 alpha);

Function Parameters

SDL_Surface *	surface	the SDL_Surface structure to update.
Uint8	alpha	the alpha value multiplied into blit operations.

Return Value

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

Remarks

When this surface is blitted, during the blit operation the source alpha value is modulated by this alpha value according to the following formula:

srcA = srcA * (alpha / 255)

Version

This function is available since SDL 2.0.0.

See Also

• SDL_GetSurfaceAlphaMod
• SDL_SetSurfaceColorMod

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CategoryAPI, CategoryAPIFunction, CategorySurface

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