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

An apparatus for identifying scale invariant features in an image defined by a plurality of pixels, the apparatus comprising a processor circuit configured to:

• locate said pixel amplitude extrema in difference images by:
• comparing the amplitude of each pixel in an image under consideration, with the amplitudes of pixels in an area about said each pixel in said image under consideration to identify local maximal and minimal amplitude pixels;
• comparing the amplitudes of said local maximal and minimal amplitude pixels with the amplitudes of pixels in a predecessor image to the image under consideration to identify possible maximal and minimal amplitude pixels;
• comparing the amplitudes of said possible maximal and minimal amplitude pixels with the amplitudes of pixels in a successor image to the image under consideration to identify actual maximal and minimal amplitude pixels;
• and
• produce a plurality of component subregion descriptors for each subregion of a pixel region about pixel amplitude extrema in said plurality of difference images.

An apparatus for identifying scale invariant features in an image defined by a plurality of pixels, the apparatus comprising:

• means for locating pixel amplitude extrema in a plurality of difference images produced from said image, said means for locating comprising:
• means for comparing the amplitude of each pixel in an image under consideration, with the amplitudes of pixels in an area about said each pixel in said image under consideration to identify local maximal and minimal amplitude pixels;
• means for comparing the amplitudes of said local maximal and minimal amplitude pixels with the amplitudes of pixels in a predecessor image to the image under consideration to identify possible maximal and minimal amplitude pixels and
• means for comparing the amplitudes of said possible maximal and minimal amplitude pixels with the amplitudes of pixels in a successor image to the image under consideration to identify actual maximal and minimal amplitude pixels;
• and
• means for producing a plurality of component subregion descriptors for each subregion of a pixel region about said pixel amplitude extrema in said plurality of difference images.