A Digital Watermarking Technology Design And Analyses Based On Airspace And Frequency Space With DCT

In the dissertation, we mainly study the technologies of digital watermarking based on DCT frequency domain.The digital media has become a main way for information communication along with the wide use of network and has played an important role in people's life .As side effects of the popularity of digital representation and distribution over network, some individuals or groups copied transferred ,amended and even sold the digital media without the permission of copyright owners ,which greatly damaged the copyrights and commercial benefits of owners . Therefore, the problem how protect the copyright has become a hot one in research work.In the technology of digital watermarking ,two new methods on digital watermarking are finished: the first is digital image watermarking of based on discrete cosine transform (DCT) domain and the second is a digital audio watermarking algorithm of based on chaos sequence in DCT domain. In the first one, On the basis of establishing the communication model of digital image watermarking is proposed in this paper, and bring in the Human Visual System. Based on discrete cosine transform (DCT) domain is proposed to classify the original image blocks into several classes based on several parameters and different watermarking energy embedded into different blocks to make the algorithm adaptive. At the same time, embed the spread spectrum modulated watermark into the corresponding spatial domain of the digital image, and the error correction coding technique is used to improve the anti-jamming capability of the watermark.Experimental results show that the algorithm improve the robustness and invisibility of the image watermark, and the proposed. In the second one, First, the binary watermarking image should be converted into the one-dimensional sequence in the algorithm. Then the digital audio signal is converted into segments and discrete cosine transform is performed. Finally the watermark is embedded in coefficients in DCT domain by chaos sequence encryption. The experimental results show that the watermark is imperceptible and the algorithm is robust to digital audio signal such as low pass filter, add Gauss noise. Experimental results have proved that the two new methods are robust enough to some image attacking processes.