Not parent poster, but I did graphs directly in PostScript. The simplest book to start with is the "Blue" book https://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF (from the blog post http://blogs.adobe.com/CCJKType/2016/12/ehandler.html - that book has a lot of examples to really get your feet wet.

I was actually inspired by this blog post: https://www.reddit.com/r/programming/comments/2fwy1y/a_web_s... (page appears to be dead but the conversation is still interesting).

I figured that web servers tend to be pretty fun to write and if someone else has figured out how to do one in PS, I would be clever enough to build one too.

I guess I was wrong about that because I didn't get very far.