You all remember this thread: http://gimpchat.com/viewtopic.php?f=22&t=1128
Well, the voronoi technique just wasn't cutting it so I went back to the 90% solid white technique which still wasn't quite adequate enough, but then I remember the burn layer property so here is the flow. First copy your source twice and a solid white fill layer in the middle set to 90% opacity. Set the top layer to burn and then go to the channels dialoge, right click inside one of the channels and choose add to selection option and then do <CTRL> X a few times. Now do Mode>Index with with 1-bit option and Floyd-Steinberg Normal setting to create the dots. Save the file as a PBM and use it with the Python TSP Script as before.
Click on the image for it's Flickr and links to larger rez version.