General Shape Analysis Applied to Stamps Retrieval from Scanned Documents

Abstract

The main purpose of the paper is to present a method of detection, localization and segmentation of stamps (imprints) in the scanned document. It is a very actual topic these days since more and more traditional paper documents are being scanned and stored on digital media. Such digital copy of a stamp may be then used to print a falsified copy of another document. Thus, an electronic version of paper document stored on a hard drive can be taken as a forensic evidence of possible crime. The process of automatic image retrieval on a basis of stamp identification can make the process of crime investigation more efficient. The problem is not trivial since there is no such thing like ,,stamp standard”. There are many variations in size, shape, complexity and ink color. It should be remembered that the scanned document may be degraded in quality and the stamp can be placed on relatively complicated background. The algorithm consists of several steps: color segmentation and pixel classification, regular shapes detection, candidates segmentation and verification. The paper includes also some results of selected experiments on real documents having different types of stamps.