目前，大多数鲁棒图像水印所面临的最大问题就是几何攻击，而几何攻击又以仿射变换为主，攻击者只需对目标图像做轻微的几何形变就可以使嵌入其中的水印信息失效。本文在PingDong等人提出的基于图像归一化方法的抵抗任意仿射变换攻击的鲁棒数字水印的基础上[1]，改进了原有的归一化方法，去掉了归一化过程中的约束条件，简化了归化的过程。并且在此基础上提出一种新的水印嵌入方案，克服了文献[1]中水印方案水印不可见性较差的问题。实验证明，本文提出的方案对仿射变换攻击具有很好的鲁棒性，嵌入的水印容量较大且水印图像的质量较高。

A new image data compression method using fractals and the discrete cosine transforms (DCT) is presented. The original image is first encoded by fractals in the DCT domain, then the error image is encoded using the DCT. Experiments show that the method can achieve high fidelity at a high compression ratio.

分形图像编码是近几年发展起来的一种新的图像编码方法，目前对其研究较为广泛。本文介绍了分形图像压缩编码的数学原理、基本特性，着重介绍了当今这一领域的发展成果，比较了各种方案的优缺点，分析了目前编码方案所存在的缺点、原因及未来的发展方向。

In Fractal image coding (FIC), a parti-tioning of the original im age into ranges and domains is required, which greatly afects the coding performance. Usually, the more adaptive to the image content the partition is, the higher performance it can achieve. Nowadays, some alleged Region-based fractal coders (RBFC) using split-and-merge strategy can achieve better adaptivity and perform ance com pared with traditional rectangular block partitions. However, the regions are still with linear con. tour. In this paper, we present a Freely-shaped Region-based fractal coder rFs. (RBFC) using a two-step partitioning, i. e. coarse partitioning bas ed on fractal dim ension and fine partitioning based on region growth, which brings freely-shaped regions. Our highly im age-adaptive scheme can achieve better rate. distortion curve than conventional scheme, even more visually pleasing resultsat the same perform ance.

该文实现丁一种抵抗几何攻击的数字图像水印方案，水印信号为根据密钥产生的服从正志分布的实数序列，对水印信号作璜处理井进行周期化之后在空域将其嵌入数字图像中。检测端不需要原始图像，根据预测水印的自相关函数(ACF) 判断水印图像遭受的几何变换攻击并进行逆变换，然后进行水印检测。实验表明该方案对压缩、滤波，剪切等常见的图像处理攻击同样具有很高的鲁棒性。