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 |
scale.in , scale.out |
Input is divided by |
clip |
If |
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.
require(graphics); require(stats) # for na.omit
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))