Description Usage Arguments Details Value Author(s) See Also Examples

Perform morphological erosion of a window, a line segment pattern or a point pattern by a disc.

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`w` |
A window (object of class |

`r` |
positive number: the radius of erosion. |

`shrink.frame` |
logical: if |

`...` |
extra arguments to |

`strict` |
Logical flag determining the fate of boundary pixels, if pixel approximation is used. See details. |

`polygonal` |
Logical flag indicating whether to compute a polygonal
approximation to the erosion ( |

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*.

If `polygonal=TRUE`

then a polygonal approximation
to the erosion is computed.
If `polygonal=FALSE`

then a pixel approximation
to the erosion is computed from the distance map of `w`

.
The arguments `"\dots"`

are passed to `as.mask`

to control the pixel resolution.
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`

).

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"`

.

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`

.

If `r > 0`

, an object of class `"owin"`

representing the
eroded region (or `NULL`

if this region is empty).
If `r=0`

, the result is identical to `w`

.

`dilation`

for the opposite operation.

`erosionAny`

for morphological erosion using any shape.

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