paths <- PSimport("tiger.ps.out")
# drop the first element (just a bounding rect?)
paths <- paths[-1]

# normalise the locations
minoutlinex <- function(x) {
  min(x@x, na.rm=TRUE)
}
minx <- min(sapply(outlines, minoutlinex))
minoutliney <- function(x) {
  min(x@y, na.rm=TRUE)
}
miny <- min(sapply(outlines, minoutliney))
maxoutlinex <- function(x) {
  max(x@x, na.rm=TRUE)
}
maxx <- max(sapply(outlines, maxoutlinex))
maxoutliney <- function(x) {
  max(x@y, na.rm=TRUE)
}
maxy <- max(sapply(outlines, maxoutliney))
cx <- mean(c(minx, maxx))
cy <- mean(c(miny, maxy))
range <- max(maxx - minx, maxy - miny)
normalise <- function(x, c) {
  unit(0.5 + (x - c)/range, "npc")
}

setGeneric("norm", function(x) { standardGeneric("norm") })
setMethod("norm", signature(x="PSstroke"),
          function(x) {
            linesGrob(normalise(x@x, cx), normalise(x@y, cy), 
                      gp=gpar(lwd=x@lwd, col=x@rgb))
          })
setMethod("norm", signature(x="PSfill"),
          function(x) {
            polygonGrob(normalise(x@x, cx), normalise(x@y, cy), 
                        gp=gpar(col=NA, fill=x@rgb))
          })           

# Produce a plot of tiger populations with picture as background
# Source: http://www.globaltiger.org/population.htm
year <- c(1993, 1996, 1998, 2001)
minpop <- c(20, 50, 50, 115)
maxpop <- c(50, 240, 240, 150)
# Draw a plot
pdf("tiger.pdf", version="1.4")
grid.rect(gp=gpar(col=NA, fill="light grey"))
pushViewport(plotViewport(),
             viewport(xscale=c(1991, 2003), yscale=c(0, 250)))
# tiger backdrop
pushViewport(viewport(width=0.95, height=0.95),
             viewport(width=unit(1, "snpc"), height=unit(1, "snpc")))
grid.draw(do.call("gList", lapply(outlines, norm)))
popViewport(2)
# translucent cover
grid.rect(gp=gpar(fill=rgb(1, 1, 1, 0.8)))
grid.xaxis(at=year)
grid.yaxis()
grid.rect(x=unit(year, "native"), y=0,
          width=unit(1, "native"), height=unit(maxpop, "native"),
          just="bottom",
          gp=gpar(fill=rgb(0, 0, 1, 0.2)))
grid.text("Estimated Population (max.) of Bengal Tigers\n(in Bhutan)",
          y=unit(1, "npc") + unit(2, "lines"))
popViewport(2)
grid.text("Source: http://www.globaltiger.org/population.htm",
          x=unit(1, "npc") - unit(2, "mm"),
          y=unit(1, "lines"), just="right",
          gp=gpar(fontfamily="mono", cex=0.5))
dev.off()