Morphological Opening of a Window
Perform morphological opening of a window
opening.owin(w, r, ...)
- A window (object of class
- positive number: the radius of the opening.
- extra arguments passed to
as.maskcontrolling the pixel resolution
The morphological opening (Serra, 1982)
of a set $W$ by a distance $r > 0$
is the subset of points in $W$ that can be
separated from the boundary of $W$ by a circle of radius $r$.
That is, a point $x$ belongs to the opening
if it is possible to draw a circle of radius $r$ (not necessarily
centred on $x$) that has $x$ on the inside
and the boundary of $W$ on the outside.
The opened set is a subset of
For a small radius $r$, the opening operation has the effect of smoothing out irregularities in the boundary of $W$. For larger radii, the opening operation removes promontories in the boundary. For very large radii, the opened set is empty.
This function computes the opening of the window
as a binary pixel mask. If
w is not already a mask, it is first
converted to a mask by
as.mask. The arguments
"..." determine the pixel resolution. There is a sensible
- Another object of class
"owin"representing the opened window.
Serra, J. (1982) Image analysis and mathematical morphology. Academic Press.
closing.owin for the opposite operation.
data(letterR) v <- opening.owin(letterR, 0.3, dimyx=256) plot(v, main="opening.owin") plot(letterR, add=TRUE)