Studies Of Digital Watermarking On Still Image

The digital media has become a main way for information communication along with the wide use of network. At the same time, multimedia information security problems including copyrights piracy emerged as side effects of the popularity of digital representation and distribution over network. Digital watermarking technology provides novel ways to solve these security problems for multimedia information. In this dissertation, we study the technologies and application of multimedia information security in the area of digital watermarking.Firstly, the history of watermarking and the relevant glossary are talked, and the basic theory and framework of watermarking algorithm have been roughly analyzed, then watermarking patterns are classified and the popular watermarking algorithms have been concluded.Secondly, with the basis of thinking of watermarking communication, the ACF of the CDMA watermarking algorithms is analyzed under geometry attack. Taking advantage of the communication theory and pre-noise-removed technology, a new spread spectrum-watermarking algorithm based on Code-Division Multiple Accesses is proposed. It uses the perceptual masking to accomplish embedding the watermarking in the wavelet domain, as the experiments given; it's proved to be invisible and robustness.A method of watermarking which bases on the digital signature is also proposed. The signature is a authentic method of the communication between applications. We consider the Image Hash as the signature, which was extracted from the image by Radon transform and L-level DWT. As combines of signature's security and watermarking's invisibility. It provides a new way for Image Authentication.