The PDF library I use gives you the dimensions of a certain letter (via FreeType I believe). I just plot 'X' (or any char for monospace) and get it's width, height.

You could support ignoring binary/generated code with a Linguist(https://github.com/github/linguist) wrapper(ruby).

Hope it didn't sound like criticism, just wanted to talk about it. Not everyone wants to talk about generating posters :)