The number of element in the original structuring element is 25, but the total
number of element in the row-column decomposition is only 10.This means
that dilation with the row structuring element first, followed by dilation with
the column element, can be performed 2.5 times faster than dilation with the
5 x 5 array of 1s. In practice, the speed-up will be somewhat less because there
is usually some overhead associated with each dilation operation, and at least
two dilation operations are required when using the decomposed form. However,
the gain in speed with the decomposed implementation is still significant