Earth mover distance for 2 numpy histograms (uses OpenCV's calcEMD2)

gistfile1.py

#extended from http://stackoverflow.com/questions/15706339/how-to-compute-emd-for-2-numpy-arrays-i-e-histogram-using-opencv
#Earth Mover Distance = histogram similarity metric.  Weights are optional.
def histEMD(hist1, hist2, hist1weights = [], hist2weights = []):
    if not len(hist1weights):
        hist1weights = np.ones(len(hist1))
    
    if not len(hist2weights):
        hist2weights = np.ones(len(hist1))
    
    a64 = cv.fromarray(np.dstack((hist1weights, hist1))[0].copy())
    a32 = cv.CreateMat(a64.rows, a64.cols, cv.CV_32FC1)
    cv.Convert(a64, a32)

    b64 = cv.fromarray(np.dstack((hist2weights, hist2))[0].copy())
    b32 = cv.CreateMat(b64.rows, b64.cols, cv.CV_32FC1)
    cv.Convert(b64, b32)
    
    return cv.CalcEMD2(a32,b32,cv.CV_DIST_L2)