R: Morphological Dilation

dilation {spatstat} | R Documentation

## Morphological Dilation

### Description

Perform morphological dilation of a window, a line segment pattern or a point pattern

### Usage

     dilation(w, r, ...)
     ## S3 method for class 'owin'
    dilation(w, r, ..., polygonal=NULL, tight=TRUE)
     ## S3 method for class 'ppp'
    dilation(w, r, ..., polygonal=TRUE, tight=TRUE)
     ## S3 method for class 'psp'
    dilation(w, r, ..., polygonal=TRUE, tight=TRUE)

### Arguments

`w` | A window (object of class `"owin"` or a line segment pattern (object of class `"psp"`) or a point pattern (object of class `"ppp"`).
`r` | positive number: the radius of dilation.
`...` | extra arguments passed to `as.mask` controlling the pixel resolution, if the pixel approximation is used; or passed to `disc` if the polygonal approximation is used.
`polygonal` | Logical flag indicating whether to compute a polygonal approximation to the dilation (`polygonal=TRUE`) or a pixel grid approximation (`polygonal=FALSE`).
`tight` | Logical flag indicating whether the bounding frame of the window should be taken as the smallest rectangle enclosing the dilated region (`tight=TRUE`), or should be the dilation of the bounding frame of `w` (`tight=FALSE`).

### Details

The morphological dilation of a set W by a distance r > 0 is the set consisting of all points lying at most r units away from W. Effectively, dilation adds a margin of width r onto the set W.

If `polygonal=TRUE` then a polygonal approximation to the dilation is computed. If `polygonal=FALSE` then a pixel approximation to the dilation is computed from the distance map of `w`. The arguments `"\dots"` are passed to `as.mask` to control the pixel resolution.

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"`.

### Value

If `r > 0`, an object of class `"owin"` representing the dilated region. If `r=0`, the result is identical to `w`.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk

### See Also

`erosion` for the opposite operation.

`dilationAny` for morphological dilation using any shape.

`owin`, `as.owin`

### Examples

      plot(dilation(letterR, 0.2))
      plot(letterR, add=TRUE, lwd=2, border="red")

      X <- psp(runif(10), runif(10), runif(10), runif(10), window=owin())
      plot(dilation(X, 0.1))
      plot(X, add=TRUE, col="red")

[Package spatstat version 1.54-0 Index]