Advanced stippling
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The following information is retained for historical purposes. Adrian Secord has removed his Weighted Voronoi Stippler program from his website. Two other stipplers based upon Adrian's work and which produce SVG to consider are Evil Mad Science's StippleGen and http://www.saliences.com/projects/npr/stippling/stippling.html.
Unfortunately, there is very little in the way of ready-to-use software packages or plugins for automatically producing stippled images. While tutorials exist, they largely focus on reproducing a specific style of stippled art work (e.g., Hedcut). Such techniques tend to be inappropriate to TSP art as they lack control over the number of stipples used. And, too many stipples lead to artwork which is too detailed for most pen tips. Existing software which permits control over the number of stipples tends to be "research grade". That is, the software's primary design goal was not ease of use, clarity, or robustness. With that in mind, OS X and, maybe, Windows users as well, have the option of trying out Adrian Secord's weighted Voronoi stippler [1].
In the course of his researches, Adrian Secord wrote a program for producing weighted Voronoi stipplings of computer image files. Secord's program allows control of the number of stipples used as well as their diameters. See Secord's NYU research website for information on downloading this program for OS X and Windows,
What follows are some simple notes on using this program.
- After you open an image file, it may take a while before any stippled image appears. It sometimes helps to nudge things along by selecting "Relax Points" or "Jitter" under the "Points" menu item.
- You can control the number of stipples with the "Set num..." item under the "Points" menu.
- You will also want to use a fixed radius for the stipples. Unselect the "Adjust radii automatically" item of the "Points" menu. Then set a specific radius such as 0.002 with the "Set radii..." item of that same menu.
- The program will run for quite some time while seeming to not be doing anything. It's actually trying to refine the picture it has drawn. You can go ahead and tell it to save its work while it is working on its refinements.
- When you have a stippling you like, use the "Save Points" item under the "File" menu. This will write a file containing (x,y) coordinates of each point and their radii. The tspart.py script can read these files as input files. No special options need be set when running tspart.py: it automatically detects the file format.
- If you start seeing blue stipples, that means that you're allowing more stipples than needed. You can decrease the number of allowed stipples.
- On OS X, when you exit the stippler it tends to exit ungracefully [2].
Notes
[*] Stippled images generated with Adrian Secord's weighted Voronoi stippler.
[1] As sources are available for Adrian Secord's stippler, it's possible that the code can be built on Linux as well. Some very minor changes are needed to appease more recent versions of gcc. Contact the original author of this article for a run-down of the few minor edits needed.
[2] Adrian Secord himself points out that the software is "research code". So remember that Secord's focus was not on producing a polished product but rather in accomplishing his own research goals. The author of this wiki article has rebuilt the software on OS X 10.6 and found the issue to persist. The binary version of the program available from Adrian Secord was built with OS X 10.5 but it does run on OS X 10.6.
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