R: Color to RGB Conversion

col2rgb {base} | R Documentation

## Color to RGB Conversion

### Description

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

### Usage

    col2rgb(col)

### 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 an integer `i` meaning `palette()[i]`.

### Details

For integer colors, `0` is shorthand for the current `par("bg")`, and `NA` means ``nothing'' which effectively does not draw the corresponding item.

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

### Value

an integer matrix with three 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(1:7)# the ones from the palette()
    stopifnot(col2rgb(0) ==  # col = 0 is the background color:
        print(col2rgb(par("bg"))))

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

    stopifnot(col2rgb("#08a0ff") == c(8, 160, 255))
    ## 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=""))
    stopifnot(grC["red",] == grC["green",],
              grC["red",] == grC["blue",],
              grC["red", 1:4] == c(0,3,5,8))
    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=","))
    str(cl)

     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])
     }

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