Patent ID: 8670619

Claim:
A method for determining an interest point in an image having a plurality of pixels suitable for working at different scales and/or rotations, the method comprising: filtering the image using at least three digital filters, and selecting an interest point based on determining a measure resulting from application of the at least three digital filters, the measure being a non-linear combination of the outputs of the at least three digital filters, the measure capturing variations of an image parameter in more than one dimension or direction, the at least three digital filters being a combination of box filters, a first digital filter having a central lobe of one binary polarity, two zero crossing and two outer lobes of the opposite binary polarity and having a spatial extent greater than one pixel and a second digital filter wherein the central pixel has a zero value and there are two positive lobes along a diagonal and there are two negative lobes along the other diagonal, and a third digital filter that is a rotated version of the first filter.