Method and apparatus for identifying scale invariant features in an image and use of same for locating an object in an image

Abstract

A method and apparatus for identifying scale invariant features in an image and a further method and apparatus for using such scale invariant features to locate an object in an image are disclosed. The method and apparatus for identifying scale invariant features may involve the use of a processor circuit for producing a plurality of component subregion descriptors for each subregion of a pixel region about pixel amplitude extrema in a plurality of difference images produced from the image. This may involve producing a plurality of difference images by blurring an initial image to produce a blurred image and by subtracting the blurred image from the initial image to produce the difference image. For each difference image, pixel amplitude extrema are located and a corresponding pixel region is defined about each pixel amplitude extremum. Each pixel region is divided into subregions and a plurality of component subregion descriptors are produced for each subregion. These component subregion descriptors are correlated with component subregion descriptors of an image under consideration and an object is indicated as being detected when a sufficient number of component subregion descriptors (scale invariant features) define an aggregate correlation exceeding a threshold correlation with component subregion descriptors (scale invariant features) associated with the object.