Color and image color mode conversions

Description

channel allows to convert colors of images and color values given in vectors, arrays or matrices from one mode to another. The supported source and target modes are TrueColor (data of type: integer) and Grayscale (numeric) and X11 strings (character).

The mode of the argument is determined automatically from its type.

Usage

 
  ## S4 methods for signatures 'x=Image,mode=character'
  ## and 'x=ANY,mode=character'
  channel(x, mode, ...)
  
  rgbImage(r, g, b)
  channelMix(r, g, b)

Arguments

Details

Conversion modes:

rgb

The result is a true color representation of the input. Its class is or includes integer, i.e. an integer array or a TrueColor integer-based image.

gray

The result is a gray scale representation of the input. Its class is or includes numeric. Synonym: grey

red, green, blue

The result is a gray scale representation of the input from only the red, the green or the blue channel was extracted, correspondingly. The result's class is numeric-based. As synonyms single letters r, g, b can be used correspondingly.

asred, asgreen, asblue

The result is a true color with all the data in one channel only, the red, green or blue, correspondingly. The result's class is integer-based. As synonyms 2r, 2g, 2b can be used.

x11

The result is a character, which elements represent the input colors as X11 strings, i.e. RGB hex codes starting with a sharp sign.

Conversion modes are case insensitive!

If the input is a character vector, its values may contain color names instead of color hex codes, like red, purple, white etc. However, the result of the X11 mode will always contain hex codes.

channelMix uses the following formula to calculate the mix: mix = sqrt(r^2+g^+b^2). Any of the values can be missing.

Value

For an argument of Image the function returns a new object of Image in all modes except 'X11'. In case of 'X11' it returns a character vector of the same length as the image.
For vectors the function returns a vector of the same size in the target mode.
rgbImage generated a TrueColor image using r, g and b as values for red, green and blue channels correspondingly.
channelMix generates a grayscale image as if the image was converted from a TrueColor one that was composed using r, g and b.

Author(s)

Oleg Sklyar, osklyar@ebi.ac.uk

See Also

Image, readImage, writeImage

Examples

  cl <- channel("pink", "rgb")
  r <- channel( channel(cl, "red"), "asred")
  g <- channel( channel("pink", "green"), "asgreen")
  b <- channel( channel(cl, "blue"), "asblue")
  rgb <- r + g + b
  print( rgb == cl )
  clg <- channel(cl, "gray")
  print( channel(cl, "x11"))
  
  ## further example in 'paintObjects'