5 ms·

Only tangentially related to this post, but does anyone know what sort of algorithm I would use to create pen plots from photos, something like this? https://t

Only tangentially related to this post, but does anyone know what sort of algorithm I would use to create pen plots from photos, something like this? https://twitter.com/PhotoPuck/status/1412540641066749953 https://twitter.com/PhotoPuck/status/1412540641066749953 The basic algorithm is some sort of halftoning I guess, but I'm impressed by the way the lines follow the contours of the objects in the scene, they're not just random squiggles trying to reach a certain darkness. So if there's an object with obviously vertical lines, it'll be drawn by the plotter using vertical lines as well. How might I achieve something similar?

mkl 5y ago
I'm not sure how the curvy shading was done, but the lines following edges looks like the results of vectorising the output of an edge detector: https://en.wikipedia.org/wiki/Edge_detection https://en.wikipedia.org/wiki/Edge_detection
- lemming 5y ago
  Thanks, I'd figured it was something like that. It's very impressive how it works, he has more examples in his feed. Sometimes it looks more like there's a conversion to a sort of "visual direction" in the image which the lines follow, not just edges.
  - mkl 5y ago
    If you follow level curves as well as edges, you can get that visual direction effect. I think people may also do shading in directions similar to nearby edges.
raphlinus 5y ago
I think coming up with an appropriate stippling algorithm is part of what makes it art; different techniques make different textures. But here's an example that comes with full source and is not too complicated: https://greweb.me/plots/236 https://greweb.me/plots/236 And another approach (from the makers of the AxiDraw) that's more dot-like: https://wiki.evilmadscientist.com/StippleGen https://wiki.evilmadscientist.com/StippleGen
- lemming 5y ago
  Great, thanks for the links!
paulgb 5y ago
This doesn’t really answer your question, but I think people interested in this question would like the book Opt Art. It introduces a number of techniques for using constraint solvers to arrange lines such that they look like a source image. https://press.princeton.edu/books/hardcover/9780691164069/opt-art https://press.princeton.edu/books/hardcover/9780691164069/op...
- joshu 5y ago
  and he's on twitter here: https://twitter.com/baabbaash https://twitter.com/baabbaash

mkl 5y ago

I'm not sure how the curvy shading was done, but the lines following edges looks like the results of vectorising the output of an edge detector: https://en.wikipedia.org/wiki/Edge_detection https://en.wikipedia.org/wiki/Edge_detection

lemming 5y ago
Thanks, I'd figured it was something like that. It's very impressive how it works, he has more examples in his feed. Sometimes it looks more like there's a conversion to a sort of "visual direction" in the image which the lines follow, not just edges.
- mkl 5y ago
  If you follow level curves as well as edges, you can get that visual direction effect. I think people may also do shading in directions similar to nearby edges.

raphlinus 5y ago

I think coming up with an appropriate stippling algorithm is part of what makes it art; different techniques make different textures. But here's an example that comes with full source and is not too complicated: https://greweb.me/plots/236 https://greweb.me/plots/236 And another approach (from the makers of the AxiDraw) that's more dot-like: https://wiki.evilmadscientist.com/StippleGen https://wiki.evilmadscientist.com/StippleGen

lemming 5y ago
Great, thanks for the links!

paulgb 5y ago

This doesn’t really answer your question, but I think people interested in this question would like the book Opt Art. It introduces a number of techniques for using constraint solvers to arrange lines such that they look like a source image. https://press.princeton.edu/books/hardcover/9780691164069/opt-art https://press.princeton.edu/books/hardcover/9780691164069/op...

joshu 5y ago
and he's on twitter here: https://twitter.com/baabbaash https://twitter.com/baabbaash