The Research Of The Digital Watermarking Technology Based On Transformation Domain

With the development of network technology, the digital products transmitted through the Internet are easier to be modified or copied by vicious people at will without authorization. The digital watermarking technology was presented several years ago to resolve this problem. Though researchers pay out a mass of vigor for this technology and acquire some achievements, the digital watermarking technology is still on road to development and many existing problems hold back its application.The digital watermarking technology is studied from three different points of view to improve the robustness under the precondition of invisibility. The primary contributions of this paper contain the following points:(1) Two algorithms are presented using chaotic system and discrete Kolmogorov flows to create watermark sequences .The algorithms have good security and the mean of watermark sequences is close to zero, preparing for following two algorithms.(2) The proposed method is an adaptive watermarking technology based on Discrete Cosine Transformation (DCT). This method discerns the edge blocks using the edge detection method and texture blocks using the deviations of DCT coefficients at first, and then the DCT blocks of image are classified into 6 blocks based on Human Visual System (HVS). Watermark components with different strengths are adaptively embeded into some low-frequency coefficients according to the classification to ensure good robustness against attacks. The experimental results show this algorithm possesses better robustness than the similar algorithms.(3) A public watermarking technology based on Discrete Wavelet Transformation (DWT) is proposed, which introduces Chaos systems into the modified public watermarking model. The watermark is embedded into the low-frequency coefficients ofDWT domain and an index factor is used in this technology. In the experiment, this paper analyses the robustness of watermark against attacks using the different index factors and concludes when the value of the index factor is between 0.1 and 0.2,the robustness of watermark against attacks is better.