| erode.owin {spatstat} | R Documentation |
Perform morphological erosion of a window
erosion.owin(w, r, shrink.frame=TRUE, ..., strict=FALSE) erode.owin(w, r, shrink.frame=TRUE, ..., strict=FALSE)
w |
A window (object of class "owin". |
r |
positive number: the radius of erosion. |
shrink.frame |
logical: if TRUE, erode the bounding
rectangle as well. |
... |
extra arguments to as.mask
controlling the pixel resolution |
strict |
Logical flag determining the fate of boundary pixels. See details. |
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.
The functions erode.owin and erosion.owin are
identical; they compute the erosion of the window w.
If w is not
a rectangle, it must be approximated by a binary pixel image,
and the arguments "..." are passed to as.mask
to determine the pixel resolution. There is a sensible default.
For non-rectangular windows, the erosion consists of all pixels
whose distance
from the boundary of w is strictly greater than r (if
strict=TRUE) or is greater than or equal to r (if
strict=FALSE).
If shrink.frame is false, the resulting window is given the
same outer, bounding rectangle as the original window w.
If shrink.frame is true, the original bounding rectangle
is also eroded by the same distance r.
To simply compute the area of the eroded window,
use eroded.areas.
Another object of class "owin" representing the
eroded window.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner r.turner@auckland.ac.nz
dilate.owin for the opposite operation.
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] ## Not run: v <- erode.owin(w, 0.6) # erosion is empty ## End(Not run)