undesired grid in ps/eps outputs generated by filled.contour or image

Hi!

Whenever I save a graphic in ps/eps format generated by filled.contour or
image, an undesired grid is added to it (not visible on the X11 screen). For
example:

postscript("volcano.eps")
filled.contour(volcano,col=gray(seq(0,1,,50)),levels=seq(min(volcano),max(volcano),,50))
dev.off()

Any ideia how to eliminate this grid?

Thanks,
Rachel

I can confirm the problem, running:

  R version 2.8.1 Patched (2009-01-24 r47726)

on Fedora 10.

The problem is actually worse if using the pdf() device, with additional
artifacts present.

There was a posting about this back in 2003:

  https://stat.ethz.ch/pipermail/r-help/2003-August/037348.html

with no replies. There is a bug report here from 2004:

  http://bugs.r-project.org/cgi-bin/R/Graphics?id=6763

that seems to be related. So it seems the issue has been around for a while.

I tried increasing the granularity of the color scale, though without
any benefit.

Will have to defer to the graphics device wizaRds on this one.

Marc Schwartz