al_set_separate_bitmap_blender - Allegro 5 API

       Like  al_set_bitmap_blender(3alleg5),  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.

       al_set_separate_bitmap_blender - Allegro 5 API

al_set_bitmap_blender(3alleg5), al_reset_bitmap_blender(3alleg5)

Allegro reference manual                                                 al_set_separate_bitmap_blender(3alleg5)

       5.2.5

              [UnstableAPI]: New API.

              #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)