simple (and a little buggy) click to draw, then when you're finished, click load to watch the script redraw what you drew (imperfectly due to list limits) encode this into a code or something eg: x: 225:336:912:342 y: 998:343:232:131 and run a parser on it, which uses the colons to tell when to separate the values into x and y coordinates respectively
proof of concept
