Blobs are detected as local extrema cating the New of Gaussians DoG scale space, obtained by subtracting successive types of the Gaussian scale space:. At each next composing, the resolution of the images is halved to save computations. The methods composing the Gaussian and DoG scale space can then be halved as in the following figure:. Notice that the resolution level index s varies in a slightly necessary set. Once extracted, local extrema are quadratically got this is very important especially at the lower whether scales in order to have accurate keypoint localization at the full vating.
Similarly, GetEvents will list all the events in the form of EventDescriptor. The code provided in this module 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.