Created a thread at pixls g'mic site too: https://discuss.pixls.us/t/any-way-to-s ... etch/593/1

Still, if anyone here can help, that would be awesome. My motivation is ceramic reflections as I posted here.

I guess your experiences with Sketch will probably just confirm what I'm about to say but just in case, the slowness of Sketch seems to come from Sketchbw which it uses. Sketchbw runs with a loop within a loop and those loops have some hefty instructions inside.

It runs slower with more "Number of Orientations" so keep that value as low as possible until you think you have a keeper. The inner loop seems to be dependent on the width of the image. If you have a landscape oriented picture, does it look the same if you rotate it into a portrait orientation before running the filter?

You probably know this also but straight strokes should run faster than curved ones.

Beyond that, this look like a case of it needing to be coded in a non-interpreted language.

Souphead.

Wish I was a coder; thanks for your insight on the matter Souphead. I'll experiment with both using portrait orientation and fewer orientations.