# erode.owin

##### Erode a Window

Perform morphological erosion of a window

- Keywords
- spatial

##### 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
```

*Documentation reproduced from package spatstat, version 1.5-9, License: GPL version 2 or newer*