Stefan, I found the algorithm implemented in CGAL ipelet demo package, so except the implementation it can be applied in ipe GUI. I'm impressed by those ipelets, as they make this vector drawing program magical, allowing computational geometry algorithms in vector application. I also went the route with Python, and it doesn't look that hard as expected. Triangulation can be applied on binary image as is, but it's better if contours are sampled. "Only" thing left for me to do is applying the crust i.e filtering the triangulation, which I interrupted as I was introduced to this huge package CGAL. Cheers