dilation: extends white objects. One layer
is added to an object in 1 iter(ation).
Holes < #iter x 2 are filled.
cmd : dilation # iter,bitpl,connec,edge,im 
dflt: dilation     1 ,  1  ,   6  ,  0 , B
range:        <1,512>,<1,8><4,6,8><0,1><AD>
