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Computer Vision with Python 3 by Saurabh Kapur

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SURF keypoint descriptors

Now that we have localized the keypoints, we need to create a descriptor for each, so as to uniquely identify it from the other keypoints. SURF works on similar principles of SIFT, but with lesser complexity. Bay and others also proposed a variation of SURF that doesn't take rotation invariance into account, which is called U-SURF (upright SURF). In many applications, the camera orientation remains more or less constant. Hence, we can save a lot of computation by ignoring rotation invariance.

First, we need to fix a reproducible orientation based on the information obtained from a circular region centered about the keypoint. Then, we construct a square region that is rotated and aligned based on the selected orientation, ...

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