al_create_sub_bitmap(3alleg5)                    al_create_sub_bitmap(3alleg5)

       al_create_sub_bitmap - Allegro 5 API

              #include <allegro5/allegro.h>

              ALLEGRO_BITMAP *al_create_sub_bitmap(ALLEGRO_BITMAP *parent,
                 int x, int y, int w, int h)

       Creates a sub-bitmap of the parent, at the specified coordinates and of
       the specified size.  A sub-bitmap is a bitmap that shares drawing
       memory with a pre-existing (parent) bitmap, but possibly with a
       different size and clipping settings.

       The sub-bitmap may originate off or extend past the parent bitmap.

       See the discussion in al_get_backbuffer(3alleg5) about using
       sub-bitmaps of the backbuffer.

       The parent bitmap's clipping rectangles are ignored.

       If a sub-bitmap was not or cannot be created then NULL is returned.

       When you are done with using the sub-bitmap you must call
       al_destroy_bitmap(3alleg5) on it to free any resources allocated for

       Note that destroying parents of sub-bitmaps will not destroy the
       sub-bitmaps; instead the sub-bitmaps become invalid and should no
       longer be used for drawing - they still must be destroyed with
       al_destroy_bitmap(3alleg5) however.  It does not matter whether you
       destroy a sub-bitmap before or after its parent otherwise.


Allegro reference manual                         al_create_sub_bitmap(3alleg5)