Ваш код выше вызывает исключение (opencv 2.3.1):
OpenCV Error: Unsupported format or combination of formats () in calcHist, file /usr/ports/graphics/opencv-core/work/OpenCV-2.3.1/modules/imgproc/src/histogram.cpp, line 632
Traceback (most recent call last):
File "ocv.py", line 8, in <module>
cv.CalcHist([cv.GetImage(cv.fromarray(np.array([x]))) for x in [angles, magnitudes]], hist)
cv2.error
Использование np.float32 для углов и величины решает проблему:
hist = cv.CreateHist([3, 3], cv.CV_HIST_ARRAY, [[0, 1], [0, 1]])
angles =np.random.rand(100).astype(np.float32)
magnitude = np.random.rand(100).astype(np.float32)
cv.CalcHist([cv.GetImage(cv.fromarray(np.array([x]))) for x in [angles, magnitudes]], hist)
print np.array(hist.bins)
...
[[ 11. 9. 7.]
[ 10. 11. 15.]
[ 11. 14. 12.]]