1. A method to find a specified number of corners in a digital image, the method comprising: receiving the digital image containing a plurality of candidate corners; directly calculating a threshold score (S) for a plurality of center pixels to form a plurality of scores, wherein each center pixel corresponds to a distinct individual candidate corner in the plurality of candidate corners; sorting, by the plurality of scores, the plurality of candidate corners to form a sorted list; and selecting corner locations sequentially from the sorted list based on the specified number of corners.