The Digital Watermarking Based On Non-linear Theory

In this paper, based on the chaos and fractal theory, the research has studied the application of the non-linear theory in digital watermarking as follows:Firstly, based on the Hilbert fractal curve and Iterative Chaotic Map with Infinite Collapses (ICMIC) a novel image spatial domain digital watermarking algorithm is proposed.The proposed scheme considers the features of the human vision system (HVS) very richly. Because the sensitivity of the flat region outbalances the texture one by dealing with the original image the texture domain can be separated from the original image very easily. The watermarks are embedded in these regions. This scheme does not cause any distortion of the original image and has high fidelity.The original watermarking is scrambled by using a simple and reversible method. The chaos map has the trait of randomicity and sensitivity to the initial value. The embedding place is determined by the chaos map. By using the character of the chaos the security is improved very obviously.By using the strategy of minimizing changes of host image pixels and statistical method, we achieve the results that the digital watermarking is sightless. When abundant watermarking is embedded we also achieve the unification of the sightlessness and the robustness. The experimental results show that the watermark is robust against the cut attack, salt-pepper noise attack, LSB (least significant bit) attack, many of low bits damage attack and winner attack.Secondly, based on the fractal image encoding and decoding theory, a novel fractal image digital watermarking algorithm is presented. The watermarks are embedded into every pixel of the range block which makes the tampering become very hard. Using the strategy of the best match in the embedding process, the complexity is minished. The reconstructed image has been showed very clearly. Simulation results show the superior performance of the methods and demonstrate the robustness against the image attack.Lastly, the usage of the digital watermarking in the copyright protection has been discussed.