Man pages matching name al_grab_font_from_bitmap in section 3alleg5:

al_grab_font_from_bitmap.3alleg5.en	debian 10 / allegro5-doc
al_grab_font_from_bitmap.3alleg5.en	debian 11 / allegro5-doc
al_grab_font_from_bitmap.3alleg5.en	debian 12 / allegro5-doc