The Research On Digital Image Watermarking Technique Based On Discrete Multiwavelet Transform

With the prompt development of multimedia and the Internet, the urgent need to safety of digital product and information makes the figure digital watermarking technology has became a hot problem in the field of multimedia information safety. Multimedia watermarking algorithm, based on wavelet, has received much attention in recent years, especially, the appearance of multiwavelet technology brings greater improvement to the research in this field.Multiwavelet analysis, which is the latest international time-frequency analysis tool, has been gradually applied in each field of the digital image processing . It is more free than scalar wavelet, not only has it kept the good time-frequency characteristic that scalar wavelet has, but also it has overcomed the shortcomings of scalar wavelet. It owns a lot of good properties at the mean time, such as the symmetry, compactly support , orthogonality and vanishing moments or higher approximation order. As a result, the multivavelet has more wide application prospect than conventional scalar wavelet.This article focuses its research object on the gray static images and color images, making a thorough research on the robust digital watermarking technology based on multiwavelet, which is used to protect image copyright.The main research work are as follows:1.The thought of multiwavelet is introduced into the digital image watermarking algorithm. The classic watermark algorithm, which is based on discrete wavelet transform proposed by Dugad, is improved. The watermark information is embedded in the original image through three-level decomposition of image by using the GHM multiwavelet, and the threshold value selection formula is improved according to the characteristics of multiwavelet.2.Artificial intelligence technology is used to improve the digital watermark algorithm, and the problem of digital image watermarking is considered as a optimizing program. Based on the present algorithm, a novel multiwavelet image watermarking algorithm which based on Genetic algorithms is proposed in this paper. Watermarking information is embeded in discrete multiwavelet transform domain, genetic algorithms is used to optimize the parameters, and search the optimum embedding threshold value, detecting threshold value and embedding intensity in the each decomposition subgraphs of different frequency domains, thus the robustness of the watermark and the visual quality of watermarked image are both improved.3.For improving robustness, exploring stable characters of an image and taking into account the characters of the human visual system (HVS) are very effective strategies. Based on these ideas,it present a new method of digital watermarking for color images based on discrete multiwavelet transform and human visual system. The algorithm modify multiwavelet coefficients which in multiwavelet decomposition subgraphs of different frequency domains in term of several parameters with the features of HVS ,and adopt repeating embedding technology to improve the watermark robustness.The experimental results show that these three algorithms above can give more robustness to various common attacks and better invisibility of the watermark than base on discrete wavelet transform domain.