Open source, command line, low "impact", png-producing, full-featured, good-looking graphing on Linux and other Unices?
We are using a script (Tcl, if it matters) to generate a script that will be sent in an email. Right now, we are using gnuplot. It's been a source of problems. No one particular thing, we just often have "issues" generating our graphs, many of them attributable to gnuplot weirdness. I'd like to rewrite it more robustly and eliminate gnuplot (on a three-strikes basis).
The "open source" and "command line" are pretty self explanatory. BTW, I don't really consider gnuplot to be command line, because it has its own shell. Yes, you can script it, but I'm looking for something that will take everything (except the actual data) as command line options.
"Low impact" means "not a lot of extra libs required" and is on the list because we have to manage, build and ship this stuff.
"full-featured" means that something that just draws a squiggle isn't enough. The particular graph we are sending out is actually a multiplot, i.e. two graphs in the same image file. We need to be able to label axes, change colors, set ranges, etc.
"png-producing" I think is non-negotiable. Personally, I would be happy to switch image formats (or better yet, go with SVG), but this email has to meet certain other requirements and I dasn't mess with the format.
"Other Unices" include Solaris and Irix. It doesn't have to ship with those OSes, though, as long as it will compile there painlessly.
As for "good-looking": Plotutils
is actually perfect, except for one problem: The font rendering (actually, rasterizing) is complete ass. As in nearly unreadable even at reasonable sizes. I actually confirmed this with the maintainer that there is no way to make them look better at the present time.