al_lock_bitmap_region_blocked - Man Page

#include <allegro5/allegro.h>

ALLEGRO_LOCKED_REGION *al_lock_bitmap_region_blocked(ALLEGRO_BITMAP *bitmap,
   int x_block, int y_block, int width_block, int height_block, int flags)

Like al_lock_bitmap_blocked(3), but allows locking a sub-region, for performance. Unlike al_lock_bitmap_region(3) the region specified in terms of blocks and not pixels.

5.1.9

al_lock_bitmap_region(3), al_lock_bitmap_blocked(3)

al_lock_bitmap(3), al_lock_bitmap_blocked(3), al_unlock_bitmap(3).