Digital Watermarking Algorithms Based On HVS For Halftone Images

In many printer and publishing applications,it is desirable to embed data in halftone for copyright and authentication purposes. Therefor,research on digital watermarking techniques for halftoned image is significant.The main problem to research halftone digital watermarking is how to ensures the robust of watermark and the vision of halftone images at the same time. In allusion to the ill-considered method of choosing a pixel to reversal and the slow-pace to embed and extract watermark of an existing algorithm based on HVS, we offer a modified algorithm which solve the problems effectively in this paper.Because the above-mentioned algorithms put the step of embed after halftoning,the data hiding capacity was limited,otherwise the image will be distortional,and when the capacity was few,the robust of watermark was weak. In view of this weakness,we propose a new algorithm which embed watermark and halftoning synchronously,this scheme can increase the capacity and strengthen the robustness.Moreover,the method of this algorithm use to choose pixel was similar to the way in the modified algorithm,so the watermarked image's visual effect was safeguarded.By the quality measurement method based on human visual system,it is proved that the modified algorithm in this paper has improve the quality of image obviously.And experiment results verify that the new algorithm has good data hiding capacity and strong robust when it compare with other algorithms.