dilation
Morphological Dilation
Perform morphological dilation of a window, a line segment pattern or a point pattern
Usage
dilation(w, r, …)
# S3 method for owin
dilation(w, r, …, polygonal=NULL, tight=TRUE)
# S3 method for ppp
dilation(w, r, …, polygonal=TRUE, tight=TRUE)
# S3 method for psp
dilation(w, r, …, polygonal=TRUE, tight=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 dilation.
- …
extra arguments passed to
as.maskcontrolling the pixel resolution, if the pixel approximation is used; or passed todiscif the polygonal approximation is used.- polygonal
Logical flag indicating whether to compute a polygonal approximation to the dilation (
polygonal=TRUE) or a pixel grid approximation (polygonal=FALSE).- tight
Logical flag indicating whether the bounding frame of the window should be taken as the smallest rectangle enclosing the dilated region (
tight=TRUE), or should be the dilation of the bounding frame ofw(tight=FALSE).
Details
The morphological dilation of a set \(W\) by a distance \(r > 0\) is the set consisting of all points lying at most \(r\) units away from \(W\). Effectively, dilation adds a margin of width \(r\) onto the set \(W\).
If polygonal=TRUE then a polygonal approximation
to the dilation is computed.
If polygonal=FALSE then a pixel approximation
to the dilation is computed from the distance map of w.
The arguments "\dots" are passed to as.mask
to control the pixel resolution.
When w is a window, the default (when polygonal=NULL)
is to compute a polygonal approximation if
w is a rectangle or polygonal window, and to compute a
pixel approximation if w is a window of type "mask".
Value
If r > 0, an object of class "owin" representing the
dilated region. If r=0, the result is identical to w.
See Also
erosion for the opposite operation.
dilationAny for morphological dilation using any shape.
Examples
# NOT RUN {
plot(dilation(redwood, 0.05))
points(redwood)
plot(dilation(letterR, 0.2))
plot(letterR, add=TRUE, lwd=2, border="red")
X <- psp(runif(10), runif(10), runif(10), runif(10), window=owin())
plot(dilation(X, 0.1))
plot(X, add=TRUE, col="red")
# }