Study And Implementation Of The Adaptive Digital Watermarking Algorithms Based On Wavelet Transformation

With the rapid development of computer networks, the information transmission model has undergone enormous changes, the exchange of information has become more efficient and the form of information has been diversified. Especially, the form of digital image transmission is becoming more prevalent. As digital information can be copied and modified easily, there are a large number of infringement and piracy issues in the network transmission of digital content. Consequently more and more attention has been paid to the protection of intellectual property rights. Digital watermarking as a new information security has attracted people's attention. As one of the important applications of information hiding technology in the computer field, digital watermarking provides a new solution to protect the copyright of multimedia information, and the legitimate use of information. It embeds watermarks into digital multimedia, then by the detection and extraction of watermark to track the use of digital products, thus carries out the functions such as hidden transmission, secret storing, copyright protection.Wavelet analysis has been widely used in image processing due to its multiresolution and multiscale analysis characteristics. In addition, using wavelet analysis can better control the distribution of watermark information in an image, thus resolve the contradiction between robustness and imperceptibility harmoniously.This thesis takes still images as example, firstly expounds basic theory and character of image digital watermarking, and introducts the common algorithms and performance evaluation methods of watermarking, at the same time introduces the basic theory of wavelet analysis and its applications and development prospects in image digital watermarking. By the selection of watermark signal, choosing of wavelet bases, decomposing level and wavelet coefficients, and the use of human visual system(HVS). To solve the contradiction between robustness and imperceptibility of watermarking, an algorithm based on adaptive wavelet digital image watermarking is proposed. The algorithm is tested and capability evaluated through several attacks ,such as cutting, adding noise, filtering, sharpening, fuzzy, the results show that the algorithm has highly robustness to resist general attack and image processing.Finally, the findings have been summarized and the further development of the digital watermarking has been predicted.