Abstract: In this paper，a digital image spread spectrum watermarking algorithm in dual transform domains of combination of Discrete Wavelet Transform（DWT） and Discrete Cosine Transform（DCT） based on chaos is proposed.The algorithm uses a binary image as a watermark，increasing the embedded information capacity.The simulation results indicate that the algorithm not only has good security，invisibility and robustness property but also doesn’t need the carrier image when extracting the watermark image，so it has some practical value for copyright protection.

Key words: digital image watermarking, Discrete Wavelet Transform, Discrete Cosine Transform, chaos, spread spectrum

摘要： 提出了一种基于混沌的离散小波和离散余弦双重变换域数字图像扩频水印算法。算法采用二值图像作为水印，增加了嵌入的信息量。仿真结果表明，算法不仅具有较好的安全性、不可见性和鲁棒性，而且在水印的提取过程中不需要载体图像，在版权保护方面具有一定的应用价值。

关键词: 数字图像水印, 离散小波变换, 离散余弦变换, 混沌, 扩频