al_identify_bitmap_f - Allegro 5 API

       Tries  to guess the bitmap file type of the open ALLEGRO_FILE by reading the first few bytes.  By default
       Allegro cannot recognize any file types, but calling al_init_image_addon(3alleg5) will add  detection  of
       (some  of)  the  types  it  can  read.   You  can  also use al_register_bitmap_identifier(3alleg5) to add
       identification for custom file types.

       Returns a pointer to a static string with a file extension for the type, including the leading dot.   For
       example “.png” or “.jpg”.  Returns NULL if the bitmap type cannot be determined.

       al_identify_bitmap_f - Allegro 5 API

al_init_image_addon(3alleg5), al_identify_bitmap(3alleg5), al_register_bitmap_identifier(3alleg5)

Allegro reference manual                                                           al_identify_bitmap_f(3alleg5)

       5.1.12

              #include <allegro5/allegro.h>

              char const *al_identify_bitmap_f(ALLEGRO_FILE *fp)