Digital Watermark Technology Research Based On Wavelet Transformation

Digital watermarking as a new mean to provide copyright protection and authentication of multimedia data has been developing rapidly since 1990's, and becomes an internationally hot topic at present. A digital watermarking technology allows users to imperceptibly embed a pecifically signal (the watermark) into multimedia data by a certain proposed algorithm in order to protect multimedia data and authentication.The fundamentals, such as basic features, principles, classification and thecurrent development status of digital watermarking are analyzed, and the generalframe of digital watermarking is given, which provide theoretical basis for thedigital watermarking algorithm's proposal, realization and testing.As the base of algorithmic theorem of digital watermarking algorithms, theprocess 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 algorithm such as Arnold transformation is introduced and simulated.A grayscale-image watermarking algorithm based on DWT was proposed. We applied multi-resolution of wavelet transform to embed watermark to the low frequency wavelet coefficient and part of other frequency wavelet of the original image. Experiment results show the algorithm is robust to common processing operations.To strengthen the robustness and security of the watermark, we applied Arnold scramble technology to encryption watermark.