This function computes the perimeter (length of the boundary) of the
window w
. If w
is a rectangle or a polygonal window,
the perimeter is the sum of the lengths of the edges of w
.
If w
is a mask, it is first converted to a polygonal window
using as.polygonal
, then staircase edges are removed
using simplify.owin
, and the perimeter of the resulting
polygon is computed.