PNG is a lot more complicated than GIFs, but then again, it
does a lot more. If it is truly rectangular, and these
are being output to the web, you can make some very small
and very quick-loading GIF images by having perl output an
IMG tag to a small GIF, and changing the HEIGHT and WIDTH
tags. If not on the web, the GD option mentioned above (thanks
!)
may be your best bet. But the HEIGHT and WIDTH trick (along
with some other HTML tweaking) can produce really nice looking results.