Marks cracks on photographs for a damage report, without painting over the evidence. A red contour is drawn as a ring held a fixed clear distance from the crack centreline, so the crack itself stays fully visible inside the outline.
Two ideas do the actual work:
1. Snap, don't trace. You supply rough waypoints along a crack — they can be off by
tens of pixels. snap.py runs a Viterbi search along the path normals over a Sato