Vq-based Digital Image Watermarking Algorithm

The multimedia and the network technology are developing quickly. The security of multimedia has becoming urgent problem worldwide. Because there are shortcomings of encrypt and digital signature technology, which are first generation of copyright protection. As the times require, the watermarking technology emerges, becoming a new copyright protection technology. Digital watermarking technology becomes an important method of copyright protection, and the study of it becomes a focus in the academic world.Digital watermark is a method for imperceptibly embedding an identification code into multimedia for the purpose of proving ownership. The watermark is as one part of multimedia and strong enough to survive after some purchase.This thesis has mainly studied digital watermarking without original image for still image. The main work finished includes the following aspects:First, this thesis gives a review of digital watermarking technology and information hiding technology based on vector quantization. Based on the summarization of the current copyright problems of the digital library, this thesis analyses the relative thesis in CNKI, and then studies the application of digital watermarking technology in digital libraries.Second, this thesis introduces the related basic theory research and key technology. On the one hand, introduces the basic model, characteristics, classification and performance evaluation of digital watermarking technology; On the other hand, give out the principle of vector quantization technology and introduces two key technologies in the world:code book designing and code word searching. Then the typical code book generation algorithm LBG is studied.Third, based on the classification of digital watermarking algorithms, now available algorithms are summarized. Then some typical algorithms are studied.Fourth, a digital image watermarking based on VQ (Vector Quantization) is provided. The side-match victor quantization (SMVQ) is executed for the side blocks, and the traditional VQ (TVQ) for seed blocks. In order to reduce codeword waste and increase watermarking payload capacity, two tricks are introduced into VQ encoding. They are 'codeword moment' and 'data reuse'.This thesis focuses on the copyright protection for image and proposes a VQ-based digital image watermarking algorithm. In the algorithm,'codeword moment' and 'data reuse' are introduced. As experimental results showing, the algorithm has higher load capacity and bigger compression ratio.