closing
Morphological Closing
Perform morphological closing of a window, a line segment pattern or a point pattern.
Usage
closing(w, r, …) # S3 method for owin
closing(w, r, …, polygonal=NULL)
# S3 method for ppp
closing(w, r, …, polygonal=TRUE)
# S3 method for psp
closing(w, r, …, polygonal=TRUE)
Arguments
- w
A window (object of class
"owin"or a line segment pattern (object of class"psp") or a point pattern (object of class"ppp").- r
positive number: the radius of the closing.
- …
extra arguments passed to
as.maskcontrolling the pixel resolution, if a pixel approximation is used- polygonal
Logical flag indicating whether to compute a polygonal approximation to the erosion (
polygonal=TRUE) or a pixel grid approximation (polygonal=FALSE).
Details
The morphological closing (Serra, 1982) of a set \(W\) by a distance \(r > 0\) is the set of all points that cannot be separated from \(W\) by any circle of radius \(r\). That is, a point \(x\) belongs to the closing \(W*\) if it is impossible to draw any circle of radius \(r\) that has \(x\) on the inside and \(W\) on the outside. The closing \(W*\) contains the original set \(W\).
For a small radius \(r\), the closing operation has the effect of smoothing out irregularities in the boundary of \(W\). For larger radii, the closing operation smooths out concave features in the boundary. For very large radii, the closed set \(W*\) becomes more and more convex.
Value
If r > 0, an object of class "owin" representing the
closed region. If r=0, the result is identical to w.
References
Serra, J. (1982) Image analysis and mathematical morphology. Academic Press.
See Also
opening for the opposite operation.
Examples
# NOT RUN {
v <- closing(letterR, 0.25)
plot(v, main="closing")
plot(letterR, add=TRUE)
plot(closing(cells, 0.1))
points(cells)
# }