col2rgb {grDevices}R Documentation

Color to RGB Conversion

Description

R color to RGB (red/green/blue) conversion.

Usage

col2rgb(col, alpha = FALSE)

Arguments

col

vector of any of the three kinds of R color specifications, i.e., either a color name (as listed by colors()), a hexadecimal string of the form "#rrggbb" or "#rrggbbaa" (see rgb), or a positive integer i meaning palette()[i].

alpha

logical value indicating whether the alpha channel (opacity) values should be returned.

Details

NA (as integer or character) and "NA" mean transparent.

Values of col not of one of these types are coerced: real vectors are coerced to integer and other types to character. (Prior to R 3.0.2 factors were coerced to their integer codes: in all other cases the class is still ignored when doing the coercion.)

Prior to R 3.0.0, col = 0 could be used to refer to the background color of the current device in base graphics: this is now an error.

Before R 3.0.0 negative integer values were accepted and wrapped around to colors in the palette: this was not how either the base or grid graphics systems usually resolved such values. They are now always an error.

Value

An integer matrix with three or four (for alpha = TRUE) rows and number of columns the length of col. If col has names these are used as the column names of the return value.

Author(s)

Martin Maechler and the R core team.

See Also

rgb, colors, palette, etc.

The newer, more flexible interface, convertColor().

Examples

col2rgb("peachpuff")
col2rgb(c(blu = "royalblue", reddish = "tomato"))  # note: colnames

col2rgb(1:8)  # the ones from the palette() (if the default)

col2rgb(paste0("gold", 1:4))

col2rgb("#08a0ff")
## all three kinds of color specifications:
col2rgb(c(red = "red", hex = "#abcdef"))
col2rgb(c(palette = 1:3))

##-- NON-INTRODUCTORY examples --

grC <- col2rgb(paste0("gray", 0:100))
table(print(diff(grC["red",])))  # '2' or '3': almost equidistant
## The 'named' grays are in between {"slate gray" is not gray, strictly}
col2rgb(c(g66 = "gray66", darkg =  "dark gray", g67 = "gray67",
          g74 = "gray74", gray  =       "gray", g75 = "gray75",
          g82 = "gray82", light = "light gray", g83 = "gray83"))

crgb <- col2rgb(cc <- colors())
colnames(crgb) <- cc
t(crgb)  # The whole table

ccodes <- c(256^(2:0) %*% crgb)  # = internal codes
## How many names are 'aliases' of each other:
table(tcc <- table(ccodes))
length(uc <- unique(sort(ccodes))) # 502
## All the multiply named colors:
mult <- uc[tcc >= 2]
cl <- lapply(mult, function(m) cc[ccodes == m])
names(cl) <- apply(col2rgb(sapply(cl, function(x)x[1])),
                   2, function(n)paste(n, collapse = ","))
utils::str(cl)
## Not run: 
 if(require(xgobi)) { ## Look at the color cube dynamically :
   tc <- t(crgb[, !duplicated(ccodes)])
   table(is.gray <- tc[,1] == tc[,2] & tc[,2] == tc[,3])  # (397, 105)
   xgobi(tc, color = c("gold", "gray")[1 + is.gray])
 }

## End(Not run)

[Package grDevices version 2.15.3 Index]