thresh {EBImage} | R Documentation

## Image and color channel thresholding

### Description

Functions to threshold images and color channels of images.

### Usage

      ## S4 method for signature 'Image':
      thresh(x, w=5, h=5, offset=0.01, ...)
      ## S4 method for signature 'Image':
      athresh(x, w=10, h=10, offset=0, ...)
      ## S4 method for signature 'Image':
      cthresh(x, threshold=0, ...)

### Arguments

`x` | An object of `Image`. For `thresh` it must be in the `Grayscale` mode.
`w, h` | Thresholding frame width and height in pixel.
`offset` | Threshold offset from the mean value.
`threshold` | Threshold value for channel thresholding (uniform).
`...` | Reserved.

### Details

If `thresh` and `athresh` are adaptive thresholind functions. While `athresh` can be used on both `Grayscale` and `TrueColor` images, `thresh` can only be used on `Grayscale` images, however it is significantly faster on them.

The value of `offset` in `thresh` is on the same scale as data, i.e. the default value is selected assuming data in the range `[0,1]`. This value for `athresh` should be selected empirically, as this function uses `AdaptiveThreshold` of `ImageMagick` and the scale of this parameter was not documented; the reasonable values are usually in the orders of 500, 1000 or avobe (at least to obtain similar thresholding to that of 0.01 with `thresh` on cytomicroscopic images. ).

### Value

A new instance of `Image` in the same color mode as input.

### Author(s)

Oleg Sklyar, osklyar@ebi.ac.uk, 2005-2007

### References

ImageMagick: http://www.imagemagick.org.

### See Also

`Image, Image, distmap, segment, [,Image-method`

### Examples

      ## see example(watershed)

[Package EBImage version 2.4.0 Index]