The code provided in this module can be used in different ways. Alternatively, you can use one of the low level Findss to run only a part of the Sift algorithm for instance, to compute the SIFT descriptors of custom keypoints. In one to search for image blobs at multiple scale, the SIFT detector get a scale space, defined as follows.
Consider the Gaussian localization. Thus in practice the scale space is discarded by..
Thus in practice the scale space is computed by. Blobs are detected as local extrema of the Difference of Gaussians DoG scale space, obtained by subtracting successive scales of the Gaussian scale space:. At each next octave, the resolution of the images is halved to save computations.