convertColor | R Documentation |
Convert colours between their representations in standard colour spaces.
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. The function will also accept a data frame, but will silently convert to a matrix internally. |
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 von Kries chromatic adaptation algorithm is used
for this. Prior to R 3.6, color conversions involving color spaces
created with make.rgb
were carried out assuming a D65
illuminant, irrespective of the actual illuminant used in the creation of the
color space. This affected the built-in "CIE RGB"
color space.
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.
For the named color spaces color
must be a matrix of values in
the from
color space: in particular opaque colors.
A 3-column matrix whose rows specify the colors.
For all the conversion equations http://www.brucelindbloom.com/.
For the white points https://web.archive.org/web/20190613001950/http://efg2.com/Lab/Graphics/Colors/Chromaticity.htm.
col2rgb
and colors
for ways to specify
colors in graphics.
make.rgb
for specifying other colour spaces.
## The displayable colors from four planes of Lab space ab <- expand.grid(a = (-10:15)*10, b = (-15:10)*10) require(graphics); require(stats) # for na.omit par(mfrow = c(2, 2), mar = .1 c(3, 3, 3, .5), mgp = c(2, .8, 0)) 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())); rownames(cols) <- palette(); cols zapsmall(lab <- convertColor(cols, from = "sRGB", to = "Lab", scale.in = 255)) stopifnot(all.equal(cols, # converting back.. getting the original: round(convertColor(lab, from = "Lab", to = "sRGB", scale.out = 255)), check.attributes = FALSE))
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