Research On Resisting Geometric Attacks In Digital Image Watermarking

The prevalence of multimedia resources is getting more and more seriously withthe rapid development of information technology and network technology. The digitalwatermarking technique appears accordingly and has been regarded as a promising wayto protect the copyright of digital products. However, the research on anti-geometrictransform attacks has been considered as a difficult and tough issue to improve therobustness of image watermarking algorithm. As a result, it is of great practicalsignificance and application value to design digital watermarking schemes with theability to resist geometric attacks.This thesis focuses on the research on resisting geometric attacks in digital imagewatermarking. The major works and contributions can be summarized as follows:(1) In-depth analysis is conducted on digital image watermarking algorithmresisting geometric attacks. First, principles and advantages and disadvantages ofvarious types of digital image watermarking schemes against geometric attacks areanalyzed systematically. Second, several typical image moments and these applicationsin the watermarking technology are introduced in detail with its development status ofimage moments theory.(2) The existing watermarking algorithms against geometric attacks are sensitivefor scaling and high complexity in the procession of watermark insertion. To solve theseproblems, a robust digital image watermarking scheme is presented by introducing thePolar Harmonic Transform (PHT). During embedding, a subset of the optimal PHTs aremodified according to the binary watermark sequence. Then the difference vector isreconstructed. The final watermarked image is obtained by adding the compensationimage to the original image. In detection, the PHTs of possibly attacked image arecomputed. And the watermark can be retrieved from the subset of the optimal PHTs.Experimental results show that compared to similar methods the proposed scheme hasbetter robustness and higher embeddings capacity.(3) The scheme based on digital watermarking technology is transplanted to thesecret communication transmission system in the Microsoft Windows platform usingVC++.