Returns a copy of the two-dimensional numerical array
which is dilated using a 3 by 3 square mask. Only the properties "equal
to zero" and "unequal to zero" of the data values are regarded. If any
of the nine data elements centered on the element of interest are
unequal to zero, then a 1 is returned for the element of interest, and a
0 otherwise. On the one-element-wide edges a 1 is returned if the
element of interest is unequal to zero, or a 0 otherwise.
See also: erode