Abstract: This paper presents a color image watermarking algorithm based on two-dimensional coupled map lattice.It uses two-dimensional coupled map lattice to generate the watermarking.An original image is divided into non-overlapped blocks，fractional box-counting dimension is used to analyze the feature of the image blocks to extract the feature blocks and secondary feature blocks and then one level DWT is used to decompose them.The different strength watermark is adaptively embedded into the low-frequency coefficients of the feature blocks，under the condition that the watermark embedded is invisible，and then is embedded into the secondary feature blocks in the same way.Experimental results demonstrate that the watermarking scheme is strongly robust to different types of attacks such as JPEG compression，noise addition，cropping，filtering and so on.

Key words: digital watermarking, coupled map lattice, fractional box-counting dimension, colour image

摘要： 提出了一种二维耦合映象格子混沌加密的彩色图像自适应水印算法。该算法采用二维离散耦合映象格子混沌系统迭代生成加密水印。在水印嵌人过程中，把彩色图像亮度分量分成互不重叠的图像块，用分数盒维数分析各块的特征，提取特征块和次特征块，对它们分别进行一级小波分解，先将水印以不同强度自适应地嵌入到特征块的小波域低频子图中。在保证隐蔽性的前提下，再次将水印以不同强度自适应地嵌入到次特征块的小波域低频子图中。实验结果表明，该算法对JPEG压缩、加噪、剪切、滤波等具有较强的稳健性。

关键词: 数字水印, 耦合映像格子, 分数盒维数, 彩色图像