| convertColor {grDevices} | R Documentation |
Convert colours between standard colour space representations. This function is experimental.
convertColor(color, from, to, from.ref.white, to.ref.white,
scale.in=1, scale.out=1, clip=TRUE)
color |
A matrix whose rows specify colors |
from,to |
Input and output color spaces. See Details below |
from.ref.white,to.ref.white |
Reference whites or NULL
if these are built in to the definition, as for RGB
spaces. D65 is the default, see Details for others
|
scale.in, scale.out |
Input is divided by scale.in, output
is multiplied by scale.out. Use NULL to suppress
scaling when input or output is not numeric. |
clip |
If TRUE, truncate RGB output to [0,1],
FALSE return out-of-range RGB, NA set out of range
colors to NaN. |
Color spaces are specified by objects of class colorConverter,
created by colorConverter or
make.rgb. Built-in color spaces may be referenced by
strings: "XYZ", "sRGB", "Apple RGB", "CIE RGB",
"Lab", "Luv". The converters for these colour spaces are
in the object colorspaces.
The "sRGB" color space is that used by standard PC monitors.
"Apple RGB" is used by Apple monitors. "Lab" and
"Luv"
are approximately perceptually uniform
spaces standardized by the Commission Internationale
d'Eclairage. XYZ is a 1931 CIE standard capable of representing
all visible colors (and then some), but not in a perceptually uniform
way.
The Lab and Luv spaces describe colors of objects, and
so require the specification of a reference “white light”
color. Illuminant D65 is a standard indirect daylight,
Illuminant D50 is close to direct sunlight, and Illuminant
A is the light from a standard incandescent bulb. Other
standard CIE illuminants supported are B, C, E and
D55. RGB colour spaces are defined relative to a particular
reference white, and can be only approximately translated to other
reference whites. The Bradford chromatic adaptation algorithm is used
for this.
The RGB color spaces are specific to a particular class of display.
An RGB space cannot represent all colors, and the clip option
controls what is done to out-of-range colors.
A 3-row matrix whose columns specify the colors.
For all the conversion equations http://www.brucelindbloom.com/
For the white points http://www.efg2.com/Lab/Graphics/Colors/Chromaticity.htm
col2rgb and colors for ways to specify
colors in graphics.
make.rgb for specifying other colour spaces.
par(mfrow=c(2,2)) ## The displayable colors from four planes of Lab space ab <- expand.grid(a=(-10:15)*10,b=(-15:10)*10) Lab <- cbind(L=20,ab) srgb <- convertColor(Lab,from="Lab",to="sRGB",clip=NA) clipped <- attr(na.omit(srgb),"na.action") srgb[clipped,] <- 0 cols <- rgb(srgb[,1],srgb[,2],srgb[,3]) image((-10:15)*10,(-15:10)*10,matrix(1:(26*26),ncol=26),col=cols, xlab="a",ylab="b",main="Lab: L=20") Lab <- cbind(L=40,ab) srgb <- convertColor(Lab,from="Lab",to="sRGB",clip=NA) clipped <- attr(na.omit(srgb),"na.action") srgb[clipped,] <- 0 cols <- rgb(srgb[,1],srgb[,2],srgb[,3]) image((-10:15)*10,(-15:10)*10,matrix(1:(26*26),ncol=26),col=cols, xlab="a",ylab="b",main="Lab: L=40") Lab <- cbind(L=60,ab) srgb <- convertColor(Lab,from="Lab",to="sRGB",clip=NA) clipped <- attr(na.omit(srgb),"na.action") srgb[clipped,] <- 0 cols <- rgb(srgb[,1],srgb[,2],srgb[,3]) image((-10:15)*10,(-15:10)*10,matrix(1:(26*26),ncol=26),col=cols, xlab="a",ylab="b",main="Lab: L=60") Lab <- cbind(L=80,ab) srgb <- convertColor(Lab,from="Lab",to="sRGB",clip=NA) clipped <- attr(na.omit(srgb),"na.action") srgb[clipped,] <- 0 cols <- rgb(srgb[,1],srgb[,2],srgb[,3]) image((-10:15)*10,(-15:10)*10,matrix(1:(26*26),ncol=26),col=cols, xlab="a",ylab="b",main="Lab: L=80") (cols <- t(col2rgb(palette()))) (lab <- convertColor(cols,from="sRGB",to="Lab",scale.in=255)) round(convertColor(lab,from="Lab",to="sRGB",scale.out=255))