Hi, I wonder if you know "IPOL": http://www.ipol.im They publish articles on image processing, featuring implementations (in C/C++). I made bindings for their SIFT and SURF feature extractions & image alignment (only 2 img for now). My cython code could be released under BSD if you wish ... but beside this I don't know the license of (all) the original C++ code: "The implementation of IPOL algorithms is distributed under a free software license, usually GPL, AGPL, LGPL or BSD." It also includes Eigen: Eigen is Free Software. It is licensed under the LGPL3+. As an alternative license choice, Eigen is also licensed under the GPL2+. So LGPL3 seems to be the most permissive license achievable :-/ If it does not make sense for skimage ... I will release it elsewhere but it can interest some of yours. Cheers, -- Jérôme Kieffer <google@terre-adelie.org> the code is here: https://github.com/kif/surf/tree/master/features