Research And Application Of Digital Image Watermarking Algorithm Based On DCT Domain

With the rapid development of the communication technology and the multimedia technology, the multimedia information intercommunion has become more extensive and the information transfer has become more expedite. However, the replication of digital information is relatively simple and the digital works has characteristic of easily to be illegal used and tampered. The modified of copyrighted content lead the interests of the owners and issuers to be damage. Though mature cryptology could handle the problem of safe transfer and access control, almost all of encrypted data will be on the verge of dangers with the rapid development of decoding technology. Besides, the cryptography plays a role only in the disseminating process. So the digital media information will be randomly copied and transmitted once it is decoded. The traditional data encryption becomes useless during the follow-up test of the data legality and property right when the data is in its normal usage.Therefore, digital watermarking technology emerges as the times require. Digital watermarking is the implementation for traditional cryptography. Digital watermarking is defined to embed special information, for examples, serial numbers, meaningful text, logos and so on, in digital image, video, audio and texts by signal processing so as to identify the copyright and be used to prove in law as well as to verify the integrity of digital content by testing and analyzing digital watermarking. As an effective means of digital copyright and data security protection, digital watermarking technology has gained wide attention and rapid development, and has become a hot research topic in the field of international information security.On the basis of previous researcher, we study digital image watermarking algorithm based DCT domain with digital image as watermark carrier. And focus on how to embed meaningless and meaningful watermark in DC domain. The main points are as following:1. At first the thesis introduced the digital watermark the domestic and foreign research results as well as the present situation. Then analyzed the development prospects of present digital watermark technology, drew out the significance of selected topic and the prime task. Then we make a recapitulative introduce of the digital watermarking technology including its basic principles, basic characteristics, classification and so on. Then the typical algorithm and main applications of digital watermarking are introduced.2. As the significant component of digital watermarking algorithms, basic definition of discrete cosine transform which is the theoretical basis of realizing DCT domain watermarking algorithm and the technology of digital image scrambling is detail introduced. What is more, the general features and application in the digital watermarking algorithms of the technology of chaotic digital watermarking and human visual system are discussed. Then the watermarking performance assessment and evaluation methods are introduced. They provide a theoretical basis for the test for digital watermarking algorithm.3. As chaotic sequence is extremely sensitive to the initial parameters, even small changes in initial value can lead to different random sequences, a digital watermarking algorithm based on the Pseudo-random watermark signal of the DCT domain of the digital image is proposed in this paper. Chaotic sequence directly as a watermark signal is embedded into the carrier image. The watermark signal is embedded into the carrier image with the embedding strength factor. Lastly experiment result for this watermarking algorithm is given.4. Taking advantage of the characteristics of discrete cosine transform and the human visual system (HVS), considering the texture and the brightness of the image, a digital watermarking algorithm based on DCT domain is proposed, which selects the binary image as the meaningful watermark. In order to improve the safety and unperceivable feature of the robust watermark, Watermark information is encrypted twice. The carrier image was classified according to human visual system and the watermark signal is embedded into the carrier image by comparing the brightness and the texture of the different sub-blocks of original carrier image. Experimental result show that the algorithm has a good transparence of the embedded watermark image and is robust against attacks such as JPEG compression, noise, shear and so on. Lastly, with the software development platform, a digital watermarking system has been completed.