col2rgb              package: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 an integer 'i' meaning
          'palette()[i]'.  Non-string values are coerced to integer.

   alpha: logical value indicating whether alpha channel 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 'NA' means
     transparent.

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

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)

