Patent ID: 6256416
Filing Date: 2001-07-03
Classification: G06T,H04N

Abstract:
A method of determining if an image is compressed, comprising the steps of:(a) determining a block grid within the image;(b) establishing blocks from the determined grid;(c) for a predetermined number of blocks, computing a first set of differences from four adjacent pixels located within each of the predetetermined number of blocks;(d) for each of the predetermined number of blocks, computing a second set of differences from four adjacent pixels, each pixel being located in a corner of four adjacent blocks, one of the four adjacent blocks being one of the predetermined number of blocks;(e) computing histogram H(n) for the first set of differences and histogram H'(n) for the second set of differences;(f) normalizing the histograms; and(g) determining if the image is compressed based on a difference between the two normalized histograms.