al_set_separate_bitmap_blender - Man Page

#include <allegro5/allegro.h>

void al_set_separate_bitmap_blender(int op, int src, int dst, int alpha_op, int alpha_src, int alpha_dst)

Like al_set_bitmap_blender(3), but allows specifying a separate blending operation for the alpha channel. This is useful if your target bitmap also has an alpha channel and the two alpha channels need to be combined in a different way than the color components.

5.2.5

al_set_bitmap_blender(3), al_reset_bitmap_blender(3)