Grayscale Image Digital Watermarking Research And Application

Digital watermarking is a technique which can protect the copyright of multimedia data and prevent digital material from being tampered and distributed unauthorizedly etc. Digital watermarking can be traced back as far as 1990. Since that time, it has won more and more recognition from scholars and consumers, and a number of watermarking technologies have been developed and deployed for a variety of applications. Now digital watermarking has become a very active area of research. But, though considerable process has been made in the last ten years, digital watermarking is still in its infancy, and much interesting work remains to be doneThis thesis addresses some problems in the gray-scale image digital watermarking that are summarized below:1) Whereas the basic theory of digital watermarking is still very poor, a digital watermarking mathematic model based on imperceptibility and robustness is presented by analysising the characteristic of digital watermarking;2) Based on the model constructed above, by defining the measures of capacity and robustness of digital watermarking, an objective method for evaluating the digital watermarking is introduced and used to analysis some algorithms;3) Whereas geometric distortion always influences the restoration of watermark, we advocate to enhance the robustness against geometric distortion by restoring the image which has been distorted by geometric transformation, and a method is designed for estimating the parameters of geometric transformation;4) Based on the conclusion discussed above, and combined with the masking effects of HVS, a novel public meaningful gray-scale image digital watermarking is designed by analysising the characteristics of image gray-scale interpolation and Haar wavelet transformation. The experimental results show that the method is indeed powerful;5) Whereas many image digital watermarking schemes, which embed watermark by modifying the values of pixels in spatial domain and transformed domain, are confronted with the conflict between the imperceptibility and robustness, we advocated to use some stable digital characteristics of host image as watermark and a algorithm based on Hermite matrix is designed. The experimental results show the proposed algorithm is effective.