The Researches Of Digital Image Watermarking Technology

With the development of computer network and multimedia techniques, especially the popularization of Internet, digital multimedia such as digital image, audio, video, has become main means of information communication. People have a quite easy access to digital products through Internet. Because digital products can be easily duplicated and edited illegally, a very critical issue of digital media's information security and copyright protection has emerged. A new technology named digital watermark which is able to protect the information security and copyright efficiently has been proposed in the world. Digital watermarking especial digital watermarking of color image has drawn extensive attention, been studied extensively and been widely applied.This thesis focuses on images. Firstly research backgrounds, basic characteristics, classifications and applications of digital watermarking are introduced. The paper formulates the basic principles and representative algorithms, and the attack of the image digital watermarking is discussed in detail. Then, based on the existing watermarking algorithm, with the chaotic theory, design and implement three amelioration algorithms. The first is the improved watermark-producting algorithm based on the Logistic mapping. The second is the multi-bit plane air space color image digital watermark algorithm based on the chaos. The third is the multi-watermark improvement algorithm which based on the integration of transformation territory and the air space, finally, this thesis confirm the algorithm performance through some common imagery processing technology and attack experiment.1. Several kinds of improved watermark producing algorithm based on Logistic mapping. This thesis builds chaos sequence, which encrypt the watermark image and make the sets sequence at chaotic, using the Logistic chaos mapping. The result of experimental indicated that, these algorithms realizing is simple, the other virtue of these algorithm are higher security of watermark information after encryption,more proportional distribution, better anti-cutting performance.2. The multi-bit plane air space color image digital watermark algorithm based on chaos. This algorithm makes use of the bad sensitivity to blue in the human vision system. Combining chaos technology and the typical air space least significant bit algorithm, we design and realize the algorithm in which the chaos sequence, producting by the Logistic chaos mapping, make the watermark information random inserting to the latter four bit plane of blue color component. The experiment proves that this algorithm has better anti-packing attack capability compare to model air space algorithm, moreover the inserting watermark capacity is big, the anti-cutting attack and the spiced salt noise attack performance is good.3. Multi-watermark improvement algorithm based on the integration of transformation territory and the air space. The multi-watermarks refer to the watermark spliting into the important information and the unimportant information. This algorithm separately inserts the important information and the unimportant information making sufficiently use of strong robustness of the transformation territory and the big inserting capacity of air space. This algorithm has effectively solved the contradiction between the invisibility and the robust, large scale expanded inserting capacity of the watermark information, strengthened the algorithm robustness and security. This algorithm can withdraw more than one watermark informations under JPEG compression, filter, increasing noise, cutting, brightness and contrast gradient transformation. The experiment proved this method has the big inserting capacity, good robustness, easy and feasible and so on.