Compose a custom blend mode for renderers.
SDL_BlendMode SDL_ComposeCustomBlendMode(SDL_BlendFactor srcColorFactor, SDL_BlendFactor dstColorFactor, SDL_BlendOperation colorOperation, SDL_BlendFactor srcAlphaFactor, SDL_BlendFactor dstAlphaFactor, SDL_BlendOperation alphaOperation);
|srcColorFactor||the SDL_BlendFactor applied to the red, green, and blue components of the source pixels|
|dstColorFactor||the SDL_BlendFactor applied to the red, green, and blue components of the destination pixels|
|colorOperation||the SDL_BlendOperation used to combine the red, green, and blue components of the source and destination pixels|
|srcAlphaFactor||the SDL_BlendFactor applied to the alpha component of the source pixels|
|dstAlphaFactor||the SDL_BlendFactor applied to the alpha component of the destination pixels|
|alphaOperation||the SDL_BlendOperation used to combine the alpha component of the source and destination pixels|
Returns an SDL_BlendMode that represents the chosen factors and operations.
The functions SDL_SetRenderDrawBlendMode and SDL_SetTextureBlendMode accept the SDL_BlendMode returned by this function if the renderer supports it.
A blend mode controls how the pixels from a drawing operation (source) get combined with the pixels from the render target (destination). First, the components of the source and destination pixels get multiplied with their blend factors. Then, the blend operation takes the two products and calculates the result that will get stored in the render target.
Expressed in pseudocode, it would look like this:
dstRGB = colorOperation(srcRGB * srcColorFactor, dstRGB * dstColorFactor);dstA = alphaOperation(srcA * srcAlphaFactor, dstA * dstAlphaFactor);
Where the functions
colorOperation(src, dst) and
alphaOperation(src, dst) can return one of the following:
src + dst
src - dst
dst - src
The red, green, and blue components are always multiplied with the first, second, and third components of the SDL_BlendFactor, respectively. The fourth component is not used.
The alpha component is always multiplied with the fourth component of the SDL_BlendFactor. The other components are not used in the alpha calculation.
Support for these blend modes varies for each renderer. To check if a specific SDL_BlendMode is supported, create a renderer and pass it to either SDL_SetRenderDrawBlendMode or SDL_SetTextureBlendMode. They will return with an error if the blend mode is not supported.
This list describes the support of custom blend modes for each renderer in SDL 2.0.6. All renderers support the four blend modes listed in the SDL_BlendMode enumeration.
SDL_BLENDOPERATION_ADDoperation with all factors. OpenGL versions 1.1, 1.2, and 1.3 do not work correctly with SDL 2.0.6.
SDL_BLENDOPERATION_ADDoperation with all factors. Color and alpha factors need to be the same. OpenGL ES 1 implementation specific: May also support
SDL_BLENDOPERATION_REV_SUBTRACT. May support color and alpha operations being different from each other. May support color and alpha factors being different from each other.
SDL_BLENDOPERATION_REV_SUBTRACToperations with all factors.
Some renderers do not provide an alpha component for the default render target. The
SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA factors do not have an effect in this case.
This function is available since SDL 2.0.6.