One of the main drawbacks of fractal im-age coding (FIC) is its time-consuming encoding process. So how to speed up the encoding process is a challenging issue of FIC research. As both sequential solutions and parallel ones have their advantages and disadvantages, we combine them together to further speed up the encoding phase. In this paper a derivative tree topology is first pro-posed to provide support for complex parallelism. Then a dual-classification technique is designed for speeding up the fractal image coding with Same-Sized Block Mapping, which improves the decoded image quality. Finally, some experimental results with good performance are presented.

The fractal image coding technique has attracted a degree of interest for its low bit rate. But the reconstructed image is of medium quality. This problem has prevented the fractal technique from being practically used. In order to improve the compression fidelity, a new affine ransformation is roposed in this paper. Meanwhile, its contractivity requirement is analyzed, and the optimal parameters are derived using the least square method. The new affine transformation has been practically used in image coding. Experiments show that the PSNR can reach 28.7dB at a compression ratio (CR) of 16.4 for the 256 256 8 "Lena" image. Comparison with other fractal coding schemes shows that the new affine transformation can improve the reconstructed image quality efficiently.

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.

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.

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。

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。

相关反馈方法是对基于内容图像检索系统的有效改进，它将人类视觉特性逐步引入检索过程，有效地减小了图像低层特征表示与图像语义理解之问的差异。但传统的相关反馈算法存在反馈次数多，且无法积累用户反馈信息等缺点。本文针对这些缺点，在相关反馈图像检索系统中引入了可更新特征库。即在原始特征索引库的基础之上引入了一个用户可修改的特征索引库，系统可以将用户多次反馈的信息逐步嵌入到这个特征索引库中。与此同时，我们提出了一种基于多分辨率分析的彩色图像纹理特征描述方法，并将其用于特征库的构建中。我们在一个含有10 000幅图像的图像库上所做的测试结果表明：与Illinois大学的MARS系统相比[1]，本系统可明显提高系统检索准确率和相关反馈的收敛速度。

Abstract. In conventional fractal image coding (FIC) schemes, domain blocks are constrained to be twice as large as range blocks to ensure the convergence of their iterative decoding stage. However, this constraint has limited the fractal encoder to exploit the self-similarity at the same resolution scale of natural images. To overcome the shortcoming, a novel scheme using same-sized range and domain blocks is proposed. Further, a recursive scheme feeding the coding results back to the input during the encoding procedure is used to improve the decoded image quality. Experimental results show our method gives significant improvement over Fisher's FIC.

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。

The robustness against geometrical attacks remains one of the most challenging issues in watermarking of images and video. This Paper presents several improvements of the video watermarking approach presented in [1], namely (i) using a temporally low-pass watermark and (ii) synchronization to resist attacks along the temporal axis. In order to improve the watermark detection performance. we propose: to rose to use an amplitude. limiting filter and a whitening filter during the watermark extraction process. Experimental results show that the proposed techniques achieve good performanee.