@LaurelGreen Gimp and especially Gimp with GMIC can do it with varying degrees of success and human skill involved. Complex images may need to be worked on a bit with, e.g. high pass filters.
I am not a "graphics person" but I have noodled with this.
@b4cks4w thats really helpful! Not exactly what I need but a good pointer , thank you!
@LaurelGreen oh I see you need that be svg or such. There are filters for that too! *rummaging*
@LaurelGreen Okay, I see that the better option (sticking with open source) is an Inkscape autotrace extension. Makes sense because Inkscape is the vector tool. I'll play with it.
https://github.com/Moini/inkscape-centerline-trace
@LaurelGreen Sorry if I'm belaboring this but I got interested. SO: Inkscape's builtin Path tools include Trace Bitmap, and that did pretty well I think on this image. Lots of settings options to try, I kept the defaults.
Eye close-up showing the nodes:
@b4cks4w @LaurelGreen It's the best I've come across and it's hard to beat free.
@b4cks4w Thank you SO much for tracking this down and letting me know! Very much appreciated!
@LaurelGreen Zero knowledge on my part, just clicking "lineart" in GMIC. 'zat the idea?