Research Of Digital Watermarking Technology Based On Spread Spectrum Technology And DCT

With the rapid development of information and internet technology, It's becoming more convenient for people to store, copy and transmit the digital multimedia information. People can get multimedia information through Internet or CD-ROM and get the original copy products of others easily, and can edit , modify, copy and spread those music and images randomly, which must threaten the creators' copyright and economical benefits undoubtedly. As a result, the problems of security issue, pirate and copyright dispute become more serious.Digital watermark technology opened up a brand new information security way, it embedded some secret information in digital objects to prove the ownership of copyright or track the tortious behaviors, which provide an effective and potential solution copyright protection. Therefore, the research work in this article is of great value and practical significance.This paper is mainly concerned about watermark technology of digital image research and a new watermark algorithm of digital image. The innovations in this algorithm are manifested in the following aspects : (1) Processing the watermark image with Gaussian pyramid decomposition, and using the spread spectrum technology modulated the watermark sequence, and distributing to the entire image in the different blocks with groups, which realized the whole distribution of watermark. Experiment showed that it had very strong robustness to the processing of images., particularly in the cropping. (2) We chose the embedding intensity based on the relations of energy and variance, and embedded watermark sequence into intermediate frequency which is near to low frequency in discrete cosine transform domain by different embedding intensities, which realized self-adaptive embedding. (3) This algorithm not only fit the gray image but also fit the color image, in this article, we also offered the watermark algorithm in color image. Experiment results show that the watermark is with invisibleness and fairly robustness.