channel {EBImage} | R Documentation

## Color and image color mode conversions

### Description

`channel` handles color space conversions between image modes. `rgbImage` combines `Grayscale` images into a `Color` one. `toRGB` is a wrapper function for convenient grayscale to RGB color space conversion; the call `toRGB(x)` returns the result of `channel(x, 'rgb')`.

### Usage

    channel(x, mode)
    rgbImage(red, green, blue)
    toRGB(x)

### Arguments

`x` | An `Image` object or an array.
`mode` | A character value specifying the target mode for conversion. See Details.
`red, green, blue` | `Image` objects in `Grayscale` color mode or arrays of the same dimension. If missing, a black image will be used.

### Details

Conversion modes:

`rgb`

  Converts a `Grayscale` image or an array into a `Color` image, replicating RGB channels.

`gray, grey`

  Converts a `Color` image into a `Grayscale` image, using uniform 1/3 RGB weights.

`luminance`

  Luminance-preserving `Color` to `Grayscale` conversion using CIE 1931 luminance weights: 0.2126 * R + 0.7152 * G + 0.0722 * B.

`red, green, blue`

  Extracts the `red`, `green` or `blue` channel from a `Color` image. Returns a `Grayscale` image.

`asred, asgreen, asblue`

  Converts a `Grayscale` image or an array into a `Color` image of the specified hue.

NOTE: `channel` changes the pixel intensities, unlike `colorMode` which just changes the way that EBImage renders an image.

### Value

An `Image` object or an array.

### Author(s)

Oleg Sklyar, osklyar@ebi.ac.uk

### See Also

`colorMode`

### Examples

     x = readImage(system.file("images", "shapes.png", package="EBImage"))
     display(x)
     y = channel(x, 'asgreen')
     display(y)

     ## rgbImage
     x = readImage(system.file('images', 'nuclei.tif', package='EBImage'))
     y = readImage(system.file('images', 'cells.tif', package='EBImage'))
     display(x, title='Cell nuclei')
     display(y, title='Cell bodies')

     cells = rgbImage(green=1.5*y, blue=x)
     display(cells, title='Cells')

[Package EBImage version 4.28.1 Index]