OpenCV Python and SIFT features
I know there is a lot of questions about Python and OpenCV but I didn't find help on this special topic.
I want to extract SIFT keypoints from an image in python OpenCV.
I have recently installed OpenCV 2.3 and can access to SURF and MSER but not SIFT.
I can't see anything related to SIFT in python modules (cv and cv2) (well I'm lying a bit: there are 2 constants: cv2.SIFT_COMMON_PARAMS_AVERAGE_ANGLE and cv2.SIFT_COMMON_PARAMS_FIRST_ANGLE).
This puzzles me since a while. Is that related to the fact that some parts of OpenCV are in C and other in C++? Any idea?
P.S.: I have also tried pyopencv (another python binding for OpenCV <= 2.1) without success.
Answer
Are you sure OpenCV is allowed to support SIFT? SIFT is a proprietary feature type, patented within the U.S. by the University of British Columbia and by David Lowe, the inventor of the algorithm. In my own research, I have had to re-write this algorithm many times. In fact, some vision researchers try to avoid SIFT and use other scale-invariant models because SIFT is proprietary.