1. A computer-implemented method that uses a processor to perform the processing of: applying a discrete cosine transform (DCT) algorithm to images; diagonally traversing each resultant matrix acquired from applying the DCT algorithm to each image to acquire an index value for each image; and populating a cache with the index values, wherein each index value links to a particular image to which it relates for retrieval from the cache, and wherein when a new image is to be subsequently processed to the cache, a new index value is supplied for the new image and then the cache is searched for a match between the new index value and one of the index values already present in the cache, and assembling the index values in a balanced k-dimensional tree (KD tree) format within the cache, and using a nearest neighbor algorithm to determine the match for the new index value and to acquire a distance metric between the match and the new index value and when the distance metric is more than a threshold value adding the new index value to the KD tree within the cache and acquiring the new image for local linking to the cache.