make.rgb {grDevices} | R Documentation |
These functions specify colour spaces for use in
convertColor
.
make.rgb(red, green, blue, name = NULL, white = "D65", gamma = 2.2) colorConverter(toXYZ, fromXYZ, name, white=NULL)
red,green,blue |
Chromaticity (xy or xyY) of RGB primaries |
name |
Name for the colour space |
white |
Character string specifying the reference white (see Details) |
gamma |
Display gamma (nonlinearity). A positive number or the
string "sRGB" |
fromXYZ |
Function to convert from XYZ tristimulus coordinates to this space |
toXYZ |
Function to convert from this space to XYZ tristimulus coordinates. |
An RGB colour space is defined by the chromaticities of the red, green and blue primaries. These are given as vectors of length 2 or 3 in xyY coordinates (the Y component is not used and may be omitted). The chromaticities are defined relative to a reference white, which must be one of the CIE standard illuminants: "A", "B", "C", "D50", "D55", "D60", "E" (usually "D65").
The display gamma is most commonly 2.2, though 1.8 is used for Apple RGB.
The sRGB standard specifies a more complicated function that is close
to a gamma of 2.2; gamma="sRGB"
uses this function.
Colour spaces other than RGB can be specified directly by giving
conversions to and from XYZ tristimulus coordinates.
The functions should take two arguments. The first is a vector giving the
coordinates for one colour. The second argument is the reference
white. If a specific reference white is included in the definition of
the colour space (as for the RGB spaces) this second argument should
be ignored and may be ...
.
An object of class colorConverter
Conversion algorithms from http://www.brucelindbloom.com
(pal <- make.rgb(red= c(0.6400,0.3300), green=c(0.2900,0.6000), blue= c(0.1500,0.0600), name = "PAL/SECAM RGB")) ## converter for sRGB in #rrggbb format hexcolor <- colorConverter(toXYZ = function(hex,...) { rgb <- t(col2rgb(hex))/255 colorspaces$sRGB$toXYZ(rgb,...) }, fromXYZ = function(xyz,...) { rgb <- colorspaces$sRGB$fromXYZ(xyz,..) rgb <- round(rgb,5) if (min(rgb) < 0 || max(rgb) > 1) as.character(NA) else rgb(rgb[1],rgb[2],rgb[3])}, white = "D65", name = "#rrggbb") (cols <- t(col2rgb(palette()))) (luv <- convertColor(cols,from="sRGB", to="Luv", scale.in=255)) (hex <- convertColor(luv, from="Luv", to=hexcolor, scale.out=NULL)) ## must make hex a matrix before using it (cc <- round(convertColor(as.matrix(hex), from= hexcolor, to= "sRGB", scale.in=NULL, scale.out=255))) stopifnot(cc == cols)