bitmap_color_depth - Returns the color depth of the specified bitmap. Allegro game programming library.

       Returns the color depth of the specified bitmap (8, 15, 16, 24, or 32).  Example:

          switch (bitmap_color_depth(screen)) {
             case 8:
                /* Access screen using optimized 8-bit code. */
                break;
             default:
                /* Use generic slow functions. */
                break;
          }

       bitmap_color_depth - Returns the color depth of the specified bitmap. Allegro game programming library.

set_color_depth(3alleg4), bitmap_mask_color(3alleg4), ex3d(3alleg4), exlights(3alleg4), exscn3d(3alleg4),
       exswitch(3alleg4), extrans(3alleg4), exupdate(3alleg4), exzbuf(3alleg4)

Allegro                                           version 4.4.3                      bitmap_color_depth(3alleg4)

#include<allegro.h>intbitmap_color_depth(BITMAP*bmp);