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% File src/library/grDevices/man/make.rgb.Rd
% Part of the R package, http://www.R-project.org
% Copyright 1995-2007 R Core Development Team
% Distributed under GPL 2 or later

\name{make.rgb}
\alias{make.rgb}
\alias{colorConverter}
\title{Create colour spaces }
\description{
  These functions specify colour spaces for use in
  \code{\link{convertColor}}.
}
\usage{
make.rgb(red, green, blue, name = NULL, white = "D65",
         gamma = 2.2)

colorConverter(toXYZ, fromXYZ, name, white=NULL)
}
\arguments{
  \item{red,green,blue}{Chromaticity (xy or xyY) of RGB primaries}
  \item{name}{Name for the colour space}
  \item{white}{Character string specifying the reference white (see
    \sQuote{Details}.)}
  \item{gamma}{Display gamma (nonlinearity). A positive number or the
    string \code{"sRGB"} }
  \item{fromXYZ}{Function to convert from XYZ tristimulus coordinates
    to this space}
  \item{toXYZ}{Function to convert from this space to XYZ tristimulus
    coordinates.}
}
\details{
  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; \code{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 \code{...}.
}
\value{
  An object of class \code{colorConverter}
}
\references{Conversion algorithms from \url{http://www.brucelindbloom.com}}
\seealso{\code{\link{convertColor}}
}
\examples{
(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)
}
\keyword{color}