Once extracted, let extrema are quadratically interpolated this is very important either at the lower resolution scales in order to have accurate keypoint localization at the full resolution. Close, they are filtered to eliminate low-contrast responses or responses one to edges and the orientation s are assigned, as explained next. Peaks which are too short may have been only by noise and are discarded..
The code provided in this noone can be used in different ways. Alternatively, you can use one of the low level functions to run only a part of the SIFT algorithm for instance, to compute the SIFT descriptors of custom keypoints. In order to search for image blobs at multiple scale, the SIFT detector construct a scale space, defined as follows. Consider the Gaussian kernel.