The Research Of Figure Watermark Base On Fractal Image Coding

With quick development technology of computer network and multi-media, the protection for copyright of digital products becomes one of the most important issues in the information technology field. As an important application for the information hiding techniques in computer field, digital watermarking provides a new way to resolve the copyright protection of multi-media information and legal usage of information.The design of digital watermarking system should include three parts, namely, formation, embedding, extraction. The formation of watermark is one of the cores in the thesis. The main idea of it is to draw some complicate point set produced by the complex dynamic system in the image applying the formation principle of JULIA set, causing the character of non-zero point in the image having identical parameter of iteration formula. Then the parameter is corresponded to one of word-symbols of aiming coding copyright information. Due to not only having single word-symbol in copyright information, it adopts various parameters which are similar to the image to superpose, and uses the thought of strong first impression to deal with hitting point conflict problems, finally, forms the fractal image coding watermark with complete copyright information. The embedding watermark is anther important part in the thesis. Owing to the character of real transform, the high quality capacity of compressing energy and solution relativity, and the merit of calculation by fast algorithm, discrete cosine transform has strong attraction to the research of digital watermarking embedding algorithm. Therefore, the thesis provides an embedding algorithm which hides watermark at DCT field utilizing comparative method. In the other words, the original image matrix is divided into blocks, and transformed by DCT. According to stochastic blocks array engendered by secret key, the watermark information adopting compare method are embedded into the blocks of original image one by one. The extraction algorithm of watermark is similar to the embedding algorithm, the different between them is to conserve the information of'0','1'transformed by the result which is compared, that is forming the watermark image where the reduced copyright information is got. The experiment indicates that the watermark image formed by the algorithm is imperceptible, and has low wrong alarm rate when it is extracted. In addition, it also manifests high Robustness when it is attacked by various means of watermark. On the basis of fractal principle, the research provides a high secret coding method, meanwhile it offers a new pattern for digital watermarking field application.