[R] latex, eps graphics and transparent colors

[Jim Lemon]

On 04/14/2011 03:30 AM, Michael Friendly wrote:
> I have a diagram to be included in latex, where all my figures are .eps
> graphics (so pdflatex is not an
> option) and I want to achieve something
> like the following: three concentric filled circles varying in lightness
> or saturation. It is easiest to do this using
> transparency, but in my test using the postscript driver, the
> transparent color fills do not appear. Is it
> correct that postscript() does not support transparency?
>
> circle <-function (radius = 1, segments=61) {
> angles <- (0:segments)*2*pi/segments
> radius * cbind( cos(angles), sin(angles))
> }
>
> plot(1:5, 1:5, type='n', xlim=c(-1,5), ylim=c(-1,5), xlab='', ylab='',
> asp=1, xaxt="n", yaxt="n")
>
> #clrs <- trans.colors("lightblue", alpha=c(.2, .4, .6)) ## from heplots
> package
> clrs <- c("#ADD8E633", "#ADD8E666", "#ADD8E699")
>
> c1 <- circle(3)
> polygon( c1, col=clrs[1], border="lightblue")
> polygon(.67*c1, col=clrs[2], border="lightblue")
> polygon(.33*c1, col=clrs[3], border="lightblue")
>
> arrows(-1, 0, 5, 0, angle=10, length=.2, lwd=2, col="darkgray")
> arrows( 0, -1, 0, 5, angle=10, length=.2, lwd=2, col="darkgray")
>
> One alternative that sort of works is to use the png() driver, and then
> convert fig.png fig.eps
> but I need very high resolution to make the real diagram legible.
>
> It might suffice to use hcl() colors to approximate what I've done with
> transparency,
> but I don't know how to start with a given color ("lightblue") and
> achieve roughly
> similar resuts.
>
Hi Michael,
For a "one off" job, I would probably do the transparent overlays in the 
pdf device, open the result in xpdf or Acrobat and then use the GIMP to 
identify the resulting colors from a screen shot. Then redo the plot in 
the postscript device using the opaque colors. This is only an 
approximation, of course, but it gets the job done.

Jim