 In practice, however, most corner detectors are sensitive not specifically to corners, but to local image regions which have a high degree of variation in all directions.The use of interest points also goes back to the notion of regions of interest, which have been used to signal the presence of objects, often formulated in terms of the output of a blob detection step.While blob detectors have not always been included within the class of interest point operators, there is no rigorous reason for excluding blob descriptors from this class.