Digital Watermark Algorithm Based On Wavelet Transfomation

On the base of research and discussion of digital watermarking algorithms, the thesis designs and realizes digital watermarking algorithm of the still image in spatial and frequency domain, and the robustness is also tested.The fundamentals, such as basic features, principles, classification and the current development status of digital watermarking are analyzed, and the general frame of digital watermarking is given, which provide theoretical basis for the digital watermarking algorithm's proposal, realization and testing.As the base of algorithmic theorem of digital watermarking algorithms, the process of development, basic definition, multi-resolution analysis of wavelet, Mallat algorithm and its application in the image processing are introduced. What's more, two-dimension wavelet decomposition and reconstruction algorithms for the still image are given. As the processing of watermarking-scrambling is taken into account, image-scrambling algorithms such as Arnold transformation is introduced and simulated.Although spatial algorithm's robustness is not good, it is important in the secret communication. The algorithms based on MSB and LSB are given and tested.For color image, the author proposed an algorithm which embedding watermarking information into red, green, blue components decomposed DWT transformation by different ratios. The watermarking information embedded in the different components have different performance facing different image attacks, and it is tested by experiments that the algorithms is quite robust.With the proposition of lifting scheme of wavelet, the wavelet decomposition and the restructuring algorithm no longer relies on the Fourier transformation, and this enormously simplify algorithm's computation. In this chapter a kind of digital watermark algorithm based on the lifting scheme wavelet is proposed.