Miscellany

k= find_cluster(PIXEL_TOP_LEFT)    + find_cluster(PIXEL_TOP)    + find_cluster(PIXEL_TOP_RIGHT) +                                         
   find_cluster(PIXEL_LEFT)        +            1               + find_cluster(PIXEL_RIGHT)     +
   find_cluster(PIXEL_BOTTOM_LEFT) + find_cluster(PIXEL_BOTTOM) + find_cluster(PIXEL_BOTTOM_RIGHT);