数字水印是一种嵌入到图象、视频或者音频数据中的不可见标志，通过对水印信息的检测可达到保护多媒体数据版权的目的.为了提高数字水印系统的鲁棒性，提出了一种基于 CL 多小波变换的图象数字水印嵌入和检测模型.该 CL 多小波变换可将图象的能量集中在其最低分辨率子图象上，同时，能使最低分辨率子图象的能量进一步汇聚于其第 1个分量之上.由于最低分辨率子图象受压缩、滤波等变换的影响较小，因此在 CL 小波变换域嵌入数字水印可以改善水印系统的鲁棒性.为了提高水印的透明性和不可统计性，在嵌入水印之前需要对水印图象进行相应的预处理.实验表明，该水印系统具有良好的鲁棒性和透明性.

Digital watermark is invisible mark embedded in digital image, video or audio documents, which can be detected to protect copyright of multimedia data. The thesis describes a watermarking scheme based on CL multi-wavelets. After the CL multi-wavelet transformation of an image, most energy of the image is mainly concentrated on its lowest resolution sub-image. Moreover, most energy of the lowest resolution sub-image is further concentrated on its first component. Because lowest resolution sub-image can survive from some transformation such as compression, this scheme can improve robust of embedded watermark. But the invisibility of watermark is reduced at that time because of the sensitivity of the lowest resolution sub-image to HVS(Human Visual Model). The position to embed watermark is selected with a trade-off between robustness and invisibility. And preprocessing of the watermark image is here for declining the difference between the watermarked and original image. To deal with attack of counterfeit, it uses not additive method but replacement algorithm when embedding watermark. The correlation between the original and extracted watermark is computed to tell whether there exists watermark in the image. The performance of the proposed watermarking is invisible to HVS and robust to a variety of signal distortions, such as JPEG compression, filtering, cropping and incorporating attacks.