Document image similarity and equivalence detection

Abstract.

An algorithm is presented for determining the similarity and equivalence of document images. Features extracted from the CCITT fax-compressed representations of two images are compared to determine their visual similarity and whether they are equivalent (i.e., scanned from the same original). Pass codes in the compressed data are used as features. A fixed grid is imposed on the image and a feature vector is derived from the number of pass codes in each grid cell. The features vectors are compared to locate a group of documents that are visually similar to the input image. The equivalence of two documents is determined by applying the Hausdorff distance to the two-dimensional arrangement of pass codes in small patches of each image.