Confirmed boundary pattern matching

DETAILED DESCRIPTION It is an object of this invention to provide a signal processing technique for registering two images.
It is a further object of this invention to provide a signal processing technique to register two images when the viewing angles of the images differ.
It is another object of this invention to provide a signal processing technique for registering two images using relatively quick and simple processing.
The foregoing and other objects of this invention are obtained by processing the first of two images to create a reference template.
The reference template is compared to each area of the second image to find the area of the second image matching the reference template.
The reference template is formed by filtering the first image to reduce noise and enhance the contrast between different regions in the image.
Two maps are then formed from the filtered image.
The first map contains an indication of the location of edges of objects in the image and is formed by finding places in the image where the intensity changes suddenly.
The second map is formed by setting the intensity of each pixel in the filtered image to one of a very small number of image intensities and then indicating an edge at every pixel adjacent to a pixel of different intensity.
The two maps are then compared to form a new map containing only the edges formed in both maps.
Additional processing adds edges to the new map corresponding to edges appearing in only one of the maps provided those edges meet additional criteria suggesting they are true edges.
The resulting map is then encoded as a template, allowing quick comparison to the second image.
More particularly, the first map is formed by operating on subarrays of pixels in the first image.
Each subarray is divided into two equisized groups of adjacent pixels.
The sum of the intensities of the pixels in each group is computed and the ratio between the two sums is computed.
Each subarray is divided four different ways and the division which produces the largest ratio is selected