erode.owin
Erode a Window
Perform morphological erosion of a window
Usage
erode.owin(w, r, shrink.frame=TRUE, ...)
Arguments
- 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
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 $W$.
This function computes 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.
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
.
Value
- Another object of class
"owin"
representing the eroded window.
See Also
Examples
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