针对数字图像版权的保护，本文提出了一种小波域内基于分形理论的零水印算法。首先对载体图像进行Haar 小波变换，接着对小波低频系数进行分形编码，通过分形匹配获得图像的重要特征信息；然后建立特征信息与图像水印之间的 关系，进行水印的双重嵌入；由于算法没有对图像进行任何修改就完成了水印的嵌入，很好地解决水印鲁棒性与不可见性之间 的矛盾。仿真实验结果表明，算法对常见的图像处理及几何攻击有较强的鲁棒性。

In order to protect the copyright of the image, this paper proposes one kind of zero-watermark algorithm in DWT domain based on fractal theory. Firstly, the original image is transformed via DWT. Then, the vital features of the original image are generated by fractal matching in the domain of low frequency. After that, the dual watermark is embedded in the original image by establishing the relationship between the vital features and digital watermark image. The algorithm ideally solves the conflict between the watermark robustness and invisibility without modifying the data of original image. Meantime, simulation results show that it is also robust against common image processing and geometric distortion.