al_set_separate_blender - Man Page

#include <allegro5/allegro.h>

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

Like al_set_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.

al_set_blender(3), al_get_blender(3), al_get_separate_blender(3)

al_get_separate_blender(3), al_set_bitmap_blender(3), al_set_blender(3), al_set_new_display_option(3).