基于离散傅立叶变换的图像数字水印算法研究-智能与分布计算实验室

基于离散傅立叶变换的图像数字水印算法研究

姓名	黄丹
论文答辩日期	2007.01.26
论文提交日期	2007.02.02
论文级别	硕士
中文题名	基于离散傅立叶变换的图像数字水印算法研究
英文题名	Research on digital watermarking algorithms based on Discrete Fourier Transform
导师1	卢正鼎
导师2
中文关键词	数字水印;离散傅立叶变换;图像归一化;不变质心
英文关键词	Digital watermarking;Discrete Fourier Transform;image normalization;invariant centroid
中文文摘	随着多媒体技术和因特网技术的迅速发展，数字化产品越来越普及，数字信息的获取、传输和发布变得越来越容易。这一方面便利了人们相互间的信息交流，但另一方面也给未授权的第三方访问并操作多媒体作品提供了渠道，甚至有人不经作者的同意即可对原始作品进行任意的复制和修改，信息所有者正面临着如何保护数据信息知识产权的巨大挑战。数字水印技术作为版权保护的有效手段，已经引起了人们极大的关注。正确合理的系统框架是对数字水印技术进行研究的保证。数字图像水印技术的研究已经取得了很大进展，但抵抗几何攻击仍然是这个领域最大的难点和热点之一。几何攻击破坏了水印与图像之间的同步关系，使水印的提取变得困难，几何攻击也是实际应用中最常见的一种攻击。分析研究了数字水印的一般框架、典型的水印算法，剖析了抗几何攻击的数字水印技术以及对数字水印算法进行客观衡量、定量分析的测评标准。在图像处理的广泛领域中, 傅立叶变换起着非常重要的作用，包括图像的效果增强、图像分析、图像复原和图像压缩等。在图像数据的数字处理中常用的是二维离散傅立叶变换，它能把空间域的图像转变到频率域上进行研究，从而简化处理过程、增强处理效果。研究了连续傅立叶变换、二维离散傅立叶变换、二维离散傅立叶变换的性质以及快速傅立叶变换，并研究了离散傅立叶变换在数字图像中的应用。基于离散傅立叶变换的水印算法原理较为简单，有着其他频率域不可取代的优点。目前基于离散傅立叶变换的数字水印算法要么是只在离散傅立叶变换的幅度成分中嵌水印，要么是只在离散傅立叶变换的相位成分中嵌水印，两种方法各有优点。而同时在离散傅立叶变换的幅度成分和相位成分中嵌水印将会结合两种方法的优点。给出了基于离散傅立叶变换、不变质心，结合图像预处理、图像归一化技术的抗几何攻击的盲数字水印方案。实验表明该方案能有效的抵抗一般的信号处理及一般的几何攻击，对JPEG压缩也有较强的鲁棒性。
英文文摘	With the rapid development of the multimedia technique and the Internet, it becomes more and easier for the transmission, wide distribution, and access of digital data. One side, it brings people conveniences of intercommunion each other. On the other hand, it provides chances that the third party accesses and operates the multimedia product. Someone can copy and tamper the original works arbitrarily under disagree, as infringes the author's copyright. Content providers are facing with the great challenge of how to protect the property right of their digital data. As digital watermarking technology is an effective tool of copyright protection, it has gained more and more concerns. The correct and rational systematic frame is to the assurance of carrying out research on digital watermarking. Although it has made great progress in the research of robust watermarking technique, how to resist the geometric attacks is one of the most difficulties in the watermarking field. So the research of watermarking technique against geometric attacks has now become a focus. Geometric attacks are the most ordinary attacks. Geometric attacks destroy the synchronization between the image and the watermark. The basic request and the systematic frame of digital watermarking algorithms and some representative algorithms of digital watermarking are studied. The attacks to digital watermarking and the countermeasures are also studied. Fourier Transform is very important in image processing. The two-dimension Discrete Fourier Transform is the most ordinary. Analyze Fourier Transform, two-dimension Discrete Fourier Transform, Fast Fourier Transform and the applications of them on digital images. The algorithms of digital watermarking based on Discrete Fourier Transform have some merits which algorithms based on other frequency transforms haven’t. Now, the algorithms of digital watermarking based on Discrete Fourier Transform either embeds watermark only in phase or embeds watermark only in amplitude. These two methods have their merits each. Embed the watermark in the phase and the amplitude simultaneity will combine their merits. A blind digital watermarking scheme based on Discrete Fourier Transform and invariant centroid, combining image preprocess and image normalization is proposed. Experiment results show that the scheme proposed in this paper is very robust to geometric distortions and general image processing techniques.