The Pascal VOC Toolkit comes with a Matlab/C implementation of HOG features by Pedro Felzenszwalb, Deva Ramanan and presumably others. Since I'm not very fond of Matlab I replaced the Matlab-specific parts for their Numpy equivalents. It works, but it's not very efficient because it copies the array into a Fortran-ordered version. That should be easy to fix.
See an example of here: http://nbviewer.ipython.org/github/dimatura/pyhog/blob/master/pyhog_example.ipynb
Daniel Maturana - dimatura@cmu.edu 2012