论文标题:基于灰度图像的数字水印技术的研究
The Study of the Digital Watermarking Technology Based on Gray Image
论文作者 李淑明
论文导师 覃团发,论文学位 硕士,论文专业 计算机应用技术
论文单位 广西大学,点击次数 97,论文页数 78页File Size5116k
2005-05-01论文网 http://www.lw23.com/lunwen_665097692/ 数字水印;离散余弦变换;离散小波变换;图像置乱;奇异值分解;人眼视觉特性;混沌序列
Digital Watermarking; DCT; DWT; Digital Image Scrambling; SVD; HVS; Chaos sequence
随着多媒体技术和计算机网络技术的发展,数字产品的版权保护问题显得尤为重要,如何确保数字产品的安全已经成为国内外研究的热点。数字水印技术作为一种新的版权保护方法,从20世纪90年代提出至今,已经受到广大科技工作者和用户越来越多的关注,研究成果也层出不穷。但是这个技术远未成熟,许多问题亟待解决。 本文对灰度图像数字水印技术进行了研究,主要工作如下: (1)分析数字水印技术的基本理论,总结水印算法中所涉及的图像置乱、离散余弦变换(DCT)和离散小波变换(DWT)等技术。 (2)提出一种基于混沌加密的图像数字水印算法。本算法采用混沌序列作为密码序列,对二值图像水印进行加密,以保证水印自身的安全性。然后,根据人的视觉特性把原始图像DCT块分成五类,把不同强度的水印分量自适应地嵌入到中频系数中,使嵌有水印的图像具有良好的视觉不可见性。实验结果表明,水印对高斯噪声和椒盐噪声、均值滤波、图像剪切、JPEG压缩等水印攻击方法具有较好的鲁棒性。 (3)提出一种基于DWT域的灰度图像数字水印算法。该算法在对原始图像进行离散小波变换之前,首先将它进行Arnold置乱变换,然后再进行小波分解,把分解后得到的高频子带系数(LH_3)组成一个矩阵,对该矩阵进行奇异值分解(SVD),在奇异值分解的对角阵中嵌入水印。该算法采用有意义的灰度图像作为水印,极大地增加了嵌入水印的信息量。实验
With the development of multimedia and network techniques, the Copyright Protection of digital media is becoming more and more important. How to ensure the security of digital media has become the focus of research work all over the world. As a new method of Copyright Protection, digital watermarking technique has attracted more and more attention of researchers and users since it was proposed in 1990s. More and more research results are obtained. However, technology of digital watermarking is still in its infancy, and there are still many problems to settle.In this dissertation, we study gray image digital watermarking. The main contributions are as follows:(1) The basic theories of digital watermarking technique are analyzed. Also we summarize the techniques of digital image scrambling, Discrete Cosine Transformation (DCT) and Discrete Wavelet Transformation (DWT) etc.(2) A new algorithm of image digital watermarking based on chaotic encryption is proposed. In this algorithm, Chaotic sequences are used as cipher sequence to encrypt binary image for ensuring the security of watermark. Then the DCT blocks of original image are classified into five categories according to the visual masking and texture characteristics of Human Visual System (HVS). Consequently, watermark components with different strength are adaptively embedded into some mid-frequency coefficients of original image to ensuregood invisibility. The experimental results show that the watermark has a good robustness against Gaussian noise, Salt & Pepper noise, Low pass, crop, JPEG procession etc.(3) A new algorithm with gray image digital watermarking based on DWT is proposed. Firstly, the original image is scrambled by Arnold transformation before DWT. Secondly, some high frequency coefficients are selected (such as LH_3) to form a matrix. This matrix is processed by Singular Value Decomposition (SVD). Lastly, the gray watermark is embedded into diagonal matrix of SVD. This algorithm uses meaningful gray image as watermark, so it greatly increases the information embedded in this algorithm. The experimental results show that the watermark has better robustness against common attacks of image.
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