R: Convert Window to Pixel Image

pixellate.owin {spatstat} | R Documentation

## Convert Window to Pixel Image

### Description

Convert a window to a pixel image by measuring the area of intersection between the window and each pixel in a raster.

### Usage

    ## S3 method for class 'owin'
    pixellate(x, W = NULL, ..., DivideByPixelArea=FALSE)

### Arguments

`x` | Window (object of class `"owin"`) to be converted.
`W` | Optional. Window determining the pixel raster on which the conversion should occur.
`...` | Optional. Extra arguments passed to `as.mask` to determine the pixel raster.
`DivideByPixelArea` | Logical value, indicating whether the resulting pixel values should be divided by the pixel area.

### Details

This is a method for the generic function `pixellate`.

It converts a window `x` into a pixel image, by measuring the amount of `x` that is inside each pixel.

(The related function `as.im` also converts `x` into a pixel image, but records only the presence or absence of `x` in each pixel.)

The pixel raster for the conversion is determined by the argument `W` and the extra arguments `...`.

- If `W` is given, and it is a binary mask (a window of type `"mask"`) then it determines the pixel raster.

- If `W` is given, but it is not a binary mask (it is a window of another type) then it will be converted to a binary mask using `as.mask(W, ...)`.

- If `W` is not given, it defaults to `as.mask(as.rectangle(x), ...)`

In the second and third cases it would be common to use the argument `dimyx` to control the number of pixels. See the Examples.

The algorithm then computes the area of intersection of each pixel with the window.

The result is a pixel image with pixel entries equal to these intersection areas.

### Value

A pixel image (object of class `"im"`).

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz

### See Also

`pixellate.ppp`, `pixellate`, `as.im`

### Examples

       data(letterR)
       plot(pixellate(letterR, dimyx=15))
       W <- grow.rectangle(as.rectangle(letterR), 0.2)
       plot(pixellate(letterR, W, dimyx=15))

[Package spatstat version 1.63-3 Index]