R: Color to RGB Conversion

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 kind of R colors, i.e., either a color name (an element of `colors()`), a hexadecimal string of the form `"#rrggbb"` or `"#rrggbbaa"` (see `rgb`), or an integer `i` meaning `palette()[i]`. Non-string values are coerced to integer.
`alpha` | logical value indicating whether alpha channel (opacity) values should be returned.

### Details

For integer colors, `0` is shorthand for the current `par("bg")` (and hence is only relevant to base graphics and not grid graphics, and is an error if graphics is not loaded), and `NA` means transparent.

For character colors, `"NA"` is equivalent to `NA`, transparent.

### Value

an integer matrix with three or four rows and number of columns the length (and names if any) as `col`.

### Author(s)

Martin Maechler

### See Also

`rgb`, `colors`, `palette`, etc.

### Examples

    col2rgb("peachpuff")
    col2rgb(c(blu = "royalblue", reddish = "tomato")) # names kept

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

    col2rgb(paste("gold", 1:4, sep=""))

    col2rgb("#08a0ff")
    ## all three kind of colors mixed :
    col2rgb(c(red="red", palette= 1:3, hex="#abcdef"))

    ##-- NON-INTRODUCTORY examples --

    grC <- col2rgb(paste("gray",0:100,sep=""))
    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 2.15.1 Index]