Image Digital Watermarking Algorithms In Wavelet Domain

With the development at full speed of the multimedia technology and network technology, people obtaining to digital products is extremely fast and convenient. At the same time, problems about copyright protection and integrity authentication of digital media have attracted more and more attention. Traditional security systems can only protect information in transmitting but not meet the requirements under new conditions. In recent years, lots of scholars put their interests in Digital watermarking technology, which is an emerging technique to protect data security and intellectual property right.Early research of digital watermarking dwelled on space field of images, but it is proved not robust. It is proved that human vision has different sensitivity towards different part of images. In order to improve the robusticity of digital watermarking, the watermark should be embedded into the important visual parts of the images. It leads to the development of the transformation field watermarking. Recently the watermarking algorithms based on Discrete Wavelet Transform (DWT) have attracted more and more attention. One of the reasons is that some features of image wavelet decomposition are similar to the Human Visual System (HVS). Thus the research of HVS model can be exploited to improve the watermarking schemes based on DWT.In this thesis, the application of wavelet transform into image digital watermarking technology has been theoretically analyzed and experiment researched. It is organized as follows:First, introduce the need background of the digital watermark and the present study status domestic and abroad. Synoptically discuss the concept, basic characteristics, classification and evaluation of watermark.Secondly, the thesis discusses the definition and properties of wavelet, studies the idea and mathematical theory of multi-resolution wavelet analysis on digital watermarking technology, two-dimensional wavelet transform of image, and the characteristics of human visual system related theory used in digital watermarking technology.Thirdly, According to the theories suggested above, Two multipurpose digital watermarking algorithms based on Dual-Tree Complex Wavelet Transform (DT CWT) are proposed for two purposes: to notify the copyright owner with a visible watermark, and to protect the copyright with an invisible watermark. Experimental results show that both two algorithms have high capacity to make the visible watermark hard to remove and the invisible watermark robust.Finally, we make some primary discussion and attempt on watermarking algorithm based on dirty paper coding. Introducing the basic theories of dirty paper coding into image digital watermarking, we present a correlation-based watermarking algorithm employing dirty paper coding with side-information.