Study And Application Of Dual-tree Complex Wavelet In Digital Watermarking

With rapid development of computer and network technologies, it is more and more convenient to spread and copy digital works. As a result, the information safety and copyright of these digital works urgently need protecting. Digital watermarking is a new solution to protect copyright in the information security field. In order to prevent pirated copy and interpolation to the digital products, the digital watermarking inlays some information into the original data to provide complete and reliable evidence for the integrity and ownership of copyrighted digital works. The development of digital watermarking demonstrates the excellent time-frequency localization, multi-scale analysis and compatibility with JPEG compression standard of wavelet transform, which makes the wavelet watermarking technology the future of data security and copyright protection and also the hot spot of watermarking technology research. As a new star of wavelet transform, the dual-tree complex wavelet transform not only bears the advantages of traditional wavelet transform analysis but also is endowed with the multi-direction, translation invariance, limited redundancy and other characters that do not possessed by the traditional wavelet, providing a greater chance to develop large capacity of watermarking with better visual traits. This paper specifies the research works in the following aspects.1) Fundamental theories of digital watermarking is studied, including basic framework of watermarking system, inlay technology of watermarking, extraction (examination) of watermarking, regular attacks to watermarking system and their solutions and main applications of watermarking. And analyzing the regular problem of watermarking system - contradictions among its invisibility, robustness and watermarking capacity.2) Basic theories of dual-tree complex wavelet is studied. The dual-tree complex wavelet transform with stressed traits of multi-direction, translation invariance, limited redundancy, etc. for traditional wavelet analysis solution has been introduced based on the traditional wavelet transform with its advantages and limitations analyzed; meanwhile, current research achievements on dual-tree complex wavelet in watermarking technique are summarized as well.3) A self-adaptive digital watermarking scheme based on dual-tree complex wavelet is put forward, which eases contradictions among non-visibility, robustness and watermarking capability encountered by ordinary watermarking scheme. This watermarking inlay scheme is featured with the masking to the self-adaptive original image; therefore, although in huge capability of watermarking inlay, this scheme can maintain its outstanding invisibility, which enables quantification to blind watermark extraction. The registration with quantification steps as secret keys can validate digital works'copyrights without original images in watermark extraction process. Considering discrepant original images as well as sizes of watermarks and inlay strategy of different wavelet decomposition layers, the design of dynamic steps will facilitate its application in business.4) Successful applications of document research achievements to copyright protection of the digital rubbings provide historical literatures'copyright protection with practical solutions...