This is the implementation of edge tangent flow which is written in "Coherent Line Drawing" by Henry Kang et al, Proc. NPAR 2007.
http://umsl.edu/mathcs/about/People/Faculty/HenryKang/coon.pdf
Edge Tangent Flow is the the method for constructing a smooth direction field that preserves the flow of the salient image features.
https://raw.github.com/wiki/naotokimura/edge_tangent_flow/images/ezgif.com-crop.gif
- cv2
- numpy