al_load_bitmap_font
ALLEGRO_FONT *al_load_bitmap_font(const char *fname)
Load a bitmap font from. It does this by first calling al_load_bitmap and then al_grab_font_from_bitmap. If you want to for example load an old A4 font, you could load the bitmap yourself, then call al_convert_mask_to_alpha on it and only then pass it to al_grab_font_from_bitmap.
Examples: ex_mouse_cursor
Most helpful discussions: