Erode a Window
Perform morphological erosion of a window
erode.owin(w, r, shrink.frame=TRUE, ...)
- A window (object of class
- positive number: the radius of erosion.
- logical: if
TRUE, erode the bounding rectangle as well.
- extra arguments to
as.maskcontrolling the pixel resolution
The morphological erosion of a set $W$ by a distance $r > 0$ is the subset consisting of all points $x \in W$ such that the distance from $x$ to the boundary of $W$ is greater than or equal to $r$. In other words it is the result of trimming a margin of width $r$ off the set $W$.
This function computes the erosion of the window
w is not
a rectangle, it must be approximated by a binary pixel image,
and the arguments
"..." are passed to
to determine the pixel resolution. There is a sensible default.
shrink.frame is false, the resulting window is given the
same outer, bounding rectangle as the original window
shrink.frame is true, the original bounding rectangle
is also eroded by the same distance
To simply compute the area of the eroded window,
- Another object of class
"owin"representing the eroded window.
library(spatstat) w <- owin(c(0,1),c(0,1)) v <- erode.owin(w, 0.1) # returns rectangle [0.1, 0.9] x [0.1,0.9] v <- erode.owin(w, 0.6) #fails - erosion is empty