A lot of work has been done on this. For instance, see also <a href="http://tex.stackexchange.com/questions/39296/simulating-hand-drawn-lines" rel="nofollow">http://tex.stackexchange.com/questions/39296/simulating-hand...</a> and <a href="http://tex.stackexchange.com/questions/74878/create-xkcd-style-diagram-in-tex" rel="nofollow">http://tex.stackexchange.com/questions/74878/create-xkcd-sty...</a>.