An image based watermark string detection system for document security checking

Document security is a very important topic in information management. In this paper, an image based watermark string detection system is proposed to detect the documents that include printed keyword strings as the watermark in the background. Therefore, the disclosure of the sensitive documents can be monitored automatically. Since the documents are represented in image format, the watermark string is detected by a parts based object recognition strategy. The two key contributions of our paper are cross validation based image registration and theMaximum Clique (MC) based object parts recognition. Experiments on PPT and WORD document pages with 5 different watermark keywords show the excellent performance of our system.