To perform Scale-Invariant Feature Transform
kp=cv_sift(image)
Input Image rgb/grayscale
Keypoints in the image
Scale-Invariant Feature Transform
This function returns keypoints found by sift, it also considers orientation.Please refer http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_feature2d/py_sift_intro/py_sift_intro.html