\name{imageMap-methods}
\docType{methods}
\alias{imageMap}
\alias{imageMap-methods}
\alias{imageMap,Ragraph-method}
\alias{imageMap,graph-method}
\alias{imageMap,Ragraph,connection,list,character-method}
\alias{imageMap,graph,connection,list,character-method}
\title{Write an HTML IMG tag together with a MAP image map.}
\description{Write an HTML IMG tag together with a MAP image map.}
\usage{
\S4method{imageMap}{Ragraph,connection,list,character}(object, con, tags, imgname, width, height, usr = par("usr"))
\S4method{imageMap}{graph,connection,list,character}(object, con, tags, imgname, width, height)
}
\arguments{
\item{object}{The graph layout for which we want to create an image map.}
\item{con}{Connection to which the image map is written.}
\item{tags}{Named list whose elements are named character vectors.
Names must correspond to node names in \code{object}. See details.}
\item{imgname}{Character. Name of the image file (for example PNG
file) that contains the plot.}
\item{width}{Width of the image.}
\item{height}{Height of the image.}
\item{usr}{Numeric vector of length 4. The user coordinates in the
plot window that \code{object} was plotted into.}
}
\details{The most important tags are \code{TITLE}, \code{HREF},
and \code{TARGET}. If the list \code{tags} contains an element
with name \code{TITLE}, then this must be a named character vector
containing the tooltips that are to be displayed when the mouse moves
over a node. The names of the nodes are specified in the \code{names}
attribute of the character vector and must match those of
\code{object}.
Similarly, \code{HREF} may be used to specify hyperlinks that the
browser can follow when the mouse clicks on a node, and \code{TARGET}
to specify the target browser window.
Currently, only rectangular regions are implemented; the actual
shape of the nodes as specified in \code{object} is ignored.
Also, tags for edges of the graph are currently not supported.
This function is typically used with the following sequence
of steps:
\enumerate{
\item Create a graph layout with \code{\link[Rgraphviz::agopen]{agopen}}
\item Plot it into a bitmap device, e.g. \code{\link{jpeg}}
or \code{\link{png}}.
\item Write HTML header.
\item Call the \code{\link{imageMap}} function.
\item Optionally, write further text into the HTML connection.
\item Close HTML file.
}
The new API for plotting of graphs now also allows for this
alternative procedure:
\enumerate{
\item Lay out the graph object \code{foo} using
\code{\link[Rgraphviz::layoutGraph]{layoutGraph}}
\item render the graph on a bitmap device using
\code{\link[Rgraphviz::rendderGraph]{renderGraph}} like this:
\code{foo <- renderGraph(foo)}
\item Write HTML header.
\item Call the \code{\link{imageMap}} on the graph object \code{foo}.
\item Optionally, write further text into the HTML connection.
\item Close HTML file.
}
}
\value{The function is called for its side effect, which is writing text into
the connection \code{con}.}
\seealso{\code{\link[Rgraphviz::agopen]{agopen}},
\code{\link[prada::openHTMLpage]{openHTMLpage}}}
\author{Wolfgang Huber \url{http://www.ebi.ac.uk/huber}}
\keyword{iplot}
\examples{
fhtml = paste(tempfile(), ".html", sep="")
fpng =paste(tempfile(), ".png", sep="")
if(capabilities()["png"] && interactive()) {
## Create a random graph, make tooltips and hyperlinks
set.seed(123)
g = randomEGraph(letters[14:22], 0.2)
tooltip = paste("This is node", nodes(g))
url = paste("This could be a link for node", nodes(g))
names(url) = names(tooltip) = nodes(g)
## Open plot device
width = height = 512
png(fpng, width=width, height=height)
par(mai=rep(0,4))
## Layout and render
lg = agopen(g, name="My layout")
plot(lg)
## Write an HTML file with the image map
con = file(fhtml, open="wt")
writeLines("<html><head><title>Click Me</title></head><body>\n", con)
imageMap(lg, con, fpng, tags=list(HREF=url, TITLE=tooltip), width=width, height=height)
writeLines("</body></html>", con)
close(con)
dev.off()
cat("Now have a look at file", fhtml, "with your browser.\n")
browseURL(fhtml)
}
}