minfilter(x [[, axes], widths])
Applies a minimum filter to one or more dimensions
widths elements. If
is not specified, then
x is treated as a 1d array.
widths must be a scalar or an array with the same number of
widths and must contain only positive numbers.
widths defaults to scalar
3. For elements too close
to the edge to yield full-width results, the nearest full-width result
ordfilter(/minimum) yields the same results as
minfilter(), but is much slower.