al_get_pixel_format_bits - Allegro 5 API

       Return  the  number  of  bits  that  a  pixel  of  the  given format occupies.  For blocked pixel formats
       (e.g. compressed formats), this returns 0.

       al_get_pixel_format_bits - Allegro 5 API

ALLEGRO_PIXEL_FORMAT(3alleg5), al_get_pixel_size(3alleg5)

Allegro reference manual                                                       al_get_pixel_format_bits(3alleg5)

              #include <allegro5/allegro.h>

              int al_get_pixel_format_bits(int format)