A Study Of Digital Watermarking Algorithm On Halftone Images To Resist Hard-copy Attack

Along with the need of copyright protection and certification for printed paper publications, in this paper halftone watermarking algorithms and the techniques to resist hard-copy attack in the practical application have been studied. This paper presents a digital watermarking algorithm which is effective resistance to the hard-copy attack.Firstly, this paper analyzes the research status of halftone watermarking algorithms and pointed out the advantages and disadvantages of the existing algorithms. A halftone watermark algorithm based on convex optimization theory is proposed. Experimental results show that the algorithm has a good robustness to the attacks in both space and frequency domain.Then, on the basis of the algorithm the typical hard-copy devices——printers and scanners models have been studied in this paper. This article uses the methods of autonomous control of the printing process, avoiding the attack to the images in the processing inside the printer. Then the image correction method is effective to repair the damage caused by the scanner in the spatial domain. Through the print-scan test, the algorithm presented in this paper is able to resist attacks on hard-copy device in a certain extent and the watermark information can be identified.