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.