\name{munsell2rgb}
\Rdversion{1.1}
\alias{munsell2rgb}
\title{
Convert Munsell Notation to RGB
}
\description{
Color conversion based on a look-up table of common soil colors.
}
\usage{
munsell2rgb(the_hue, the_value, the_chroma, alpha=1, 
maxColorValue=1, return_triplets=FALSE)
}
\arguments{
  \item{the_hue}{a vector of one or more more hues, upper-case}
  \item{the_value}{a vector of one or more values}
  \item{the_chroma}{a vector of one or more chromas}
  \item{alpha}{alpha channel value (for transparency effects)}
  \item{maxColorValue}{maximum RGB color value (see \code{\link{rgb})}}
  \item{return_triplets}{should the function return raw RGB triplets instead of an R color}
}
\details{This function generalizes to vectorized usage, as long as the length of each argument is the same.}
\note{Care should be taken when using the resulting RGB values; they are close to their Munsell counterparts, but will vary based on your monitor and ambient lighting conditions. Also, the value used for \code{maxColorValue} will affect the brightness of the colors. Th default value (1) will usually give acceptable results, but can be adjusted to force the colors closer to what the user thinks they should look like.}
\value{
A vector of R colors is returned that is the same length as the input data. If \code{return_triplets} is \code{TRUE}, then a dataframe (of sample length as input) of r,g,b values is returned.
}
\references{
\url{http://casoilresource.lawr.ucdavis.edu/drupal/node/201}
\url{http://www.brucelindbloom.com/index.html?ColorCalcHelp.html}
\url{http://www.cis.rit.edu/mcsl/online/munsell.php}
}
\author{Dylan E. Beaudette}

\section{Warning}{As of \code{plyr} 1.6 (CRAN), there are cases when this function will fail (\url{https://github.com/hadley/plyr/issues/43}). The next version of \code{plyr} should address this problem. Until then, be sure not to pass in Munsell (hue, value, chroma) as factors.}


\examples{
# basic example: no factors!
d <- expand.grid(hue='10YR', value=2:8, chroma=1:8, stringsAsFactors=FALSE)
d$color <- with(d, munsell2rgb(hue, value, chroma))

# similar to the 10YR color book page
plot(value ~ chroma, data=d, col=d$color, pch=15, cex=3)

# multiple pages of hue:
hues <- c('2.5YR','5YR','7.5YR','10YR')
d <- expand.grid(hue=hues, value=2:8, chroma=seq(2,8,by=2), stringsAsFactors=FALSE)
d$color <- with(d, munsell2rgb(hue, value, chroma))


# plot: note that we are setting panel order from red-->yellow
library(lattice)
xyplot(value ~ factor(chroma) | factor(hue, levels=hues),
main="Common Soil Colors", layout=c(4,1), scales=list(alternating=1),
strip=strip.custom(bg=grey(0.85)),
data=d, as.table=TRUE, subscripts=TRUE, xlab='Chroma', ylab='Value',
panel=function(x, y, subscripts, ...)
{
panel.xyplot(x, y, pch=15, cex=4, col=d$color[subscripts])
}
)

# try again, this time annotate with LAB coordinates:
if(require(colorspace))
  {
  d.rgb <- with(d, munsell2rgb(hue, value, chroma, return_triplets=TRUE))
  d.lab <- as(with(d.rgb, RGB(r,g,b)), 'LAB')
  d <- data.frame(d, d.lab@coords)
  
  xyplot(value ~ factor(chroma) | factor(hue, levels=hues),
  main="Common Soil Colors - Annotated with LAB Coordinates", layout=c(4,1), 
  scales=list(alternating=1), strip=strip.custom(bg=grey(0.85)),
  data=d, as.table=TRUE, subscripts=TRUE, xlab='Chroma', ylab='Value',
  panel=function(x, y, subscripts, ...) {
    panel.xyplot(x, y, pch=15, cex=7, col=d$color[subscripts])
    lab.text <- with(d[subscripts, ], paste(round(L), round(A), round(B), sep='\n'))
    panel.text(x, y, labels=lab.text, cex=0.75, col='white', font=2)
    }
  )
  
  # also demonstrate A ~ hue for each slice of chroma
  xyplot(A ~ factor(hue, levels=hues) | factor(value), groups=chroma, data=d,
  scales=list(alternating=1), strip=strip.custom(bg=grey(0.85)),
  main="A-coordinate vs. Munsell Hue", sub='panels are Munsell value, colors are Munsell chroma',
  xlab='Munsell Hue', ylab='A-coordinate', pch=16,
  type='b', as.table=TRUE, auto.key=list(lines=TRUE, points=FALSE, columns=4))
  
  }



# soils example
data(sp1)

# convert colors
sp1$soil_color <- with(sp1, munsell2rgb(hue, value, chroma))

# simple plot, may need to tweak gamma-correction...
image(matrix(1:nrow(sp1)), axes=FALSE, col=sp1$soil_color, main='Soil Colors')

# convert into a more useful color space
# you will need the colorspace package for this to work
if(require(colorspace))
{
# keep RGB triplets from conversion
sp1.rgb <- with(sp1, munsell2rgb(hue, value, chroma, return_triplets=TRUE))

# convert into LAB color space
sp1.lab <- as(with(sp1.rgb, RGB(r,g,b)), 'LAB')
plot(sp1.lab)
}

}

% Add one or more standard keywords, see file 'KEYWORDS' in the
% R documentation directory.
\keyword{manip}