\HeaderA{col2rgb}{Color to RGB Conversion}{col2rgb}
\keyword{color}{col2rgb}
\keyword{dplot}{col2rgb}
\begin{Description}\relax
\R{} color to RGB (red/green/blue) conversion.
\end{Description}
\begin{Usage}
\begin{verbatim}
col2rgb(col, alpha = FALSE)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{col}] vector of any of the three kind of \R{} colors, i.e., either
a color name (an element of \code{\LinkA{colors}{colors}()}), a hexadecimal
string of the form \code{"\#rrggbb"}, or an integer \code{i} meaning
\code{palette()[i]}.  Non-string values are coerced to integer.
\item[\code{alpha}] logical value indicating whether alpha channel
values should be returned.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
For integer colors, \code{0} is shorthand for the current
\code{par("bg")} (and hence is only relevant to base graphics), and
\code{\LinkA{NA}{NA}} means transparent.

For character colors, \code{"NA"} is equivalent to \code{NA} above.
\end{Details}
\begin{Value}
an integer matrix with three or four rows and number of columns the length
(and names if any) as \code{col}.
\end{Value}
\begin{Author}\relax
Martin Maechler
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{rgb}{rgb}}, \code{\LinkA{colors}{colors}}, \code{\LinkA{palette}{palette}}, etc.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
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)
\end{ExampleCode}
\end{Examples}

