Research On The Algorithm Of Digital Watermark About Image In Frequency Domain

With the rapid development of digital communication network and multimedia technology, more and more multimedia products have been issued through network form, which also have made the issuance and transfer of information become not only convenient but also quick. But there are properties such as being copied and interpolated illegally in digital products. Anybody can copy and issue what is protected by the intellectual property rights in batches for free and without any quality loss, which have critically threatened the copyright protection of digital products. In recent years, there are more and more copyright dispute cases of digital products and the act of tort become rampant day by day. Right infringements of copy behaviors have been laid store by the industry of video, film and publication. So the digital watermark technology which is regarded as the powerful complementarily of the traditional cryptology was born. The digital watermark technology provides a brand-new idea for realizing effective information copyright protection method and it also becomes a hot topic in the research area of multimedia information security. It is playing a good role in questions of information security, pirate and copyright dispute, copyright protection and content distinction of multimedia, and so on.Two kinds of digital watermark methods about image based on DCT and DWT in frequency domain were mainly researched in this article. In the design of the watermark algorithms, all kinds of factors affecting watermark performance were synthesized and the influence of position watermark embedded to watermark performance at different frequency domain was analyzed with emphasis.In this article a meaningful public watermark algorithm based on DCT was realized. An idea of controlling the position embedded by the random series was inducted which improved the algorithm. Algorithm uses Logistic chaotic series as the random series generator, selects coefficients according to the luminance quantization value of compression and chooses controlled variable to do the coefficients modulation, which will make the watermark system be of good performance. Compared to the original algorithm, the security and the ability of resisting some attacks such as cutting and JPEG compression were obviously enhanced in the watermark system. Otherwise, the embedded mode of traditional watermark doesn't been adopted, which avoids the model attack problems under the traditional watermark. The extract process of watermark signal doesn't have to resort to the original image to satisfy with the requirement of blind extract. A kind of digital watermark method about image based on DWT was realized in this paper, combining the JPEG2000 which a new image compression standard and HVS. The high frequency coefficients under high scale decomposition according to multi-resolution characteristic of wavelet transfer were chosen in the algorithm, which is advantageous to satisfy the requirements of watermark system to robustness and invisible and manifests the advantages of digital watermark in wavelet domain. It sets two more appropriate threshold values to control the selection of the coefficients through analyzing DWT coefficients and being confirmed by massive experiments. The watermark embedded in this algorithm is concerned with the characteristic of image statistic and the watermark system can self-adapt to the image.