Computes the descriptors for a set of keypoints detected in an image or image set.

[descriptors, keypoints] = obj.compute(img, keypoints)
[descriptors, keypoints] = obj.compute(imgs, keypoints)

Input

• img Image (first variant), 8-bit grayscale image.
• imgs Image set (second variant), cell array of images.
• keypoints Input collection of keypoints. Keypoints for which a descriptor cannot be computed are removed. Sometimes new keypoints can be added, for example: cv.SIFT duplicates keypoint with several dominant orientations (for each orientation). In the first variant, this is a struct-array of detected keypoints. In the second variant, it is a cell-array, where keypoints{i} is a set of keypoints detected in images{i} (a struct-array like before).

Output

• descriptors Computed descriptors. In the second variant of the method descriptors{i} are descriptors computed for a keypoints{i}. Row j in descriptors (or descriptors{i}) is the descriptor for j-th keypoint.
• keypoints Optional output with possibly updated keypoints.