中文摘要：

介绍了Matlab中用于图像数字水印的基本函数，通过设计程序实现了一个DCT城图像数字水印的嵌入和提取算法，并对已嵌入水印的图像实施了攻击（压缩30％）．结果表明，被攻击后的图像仍能成功提取出嵌入的水印信息，具有较好的稳健性和鲁棒性．

英文摘要：

Digital watermarking provide an effective way for overcoming serious problems of digital images on the Internet, including copyright violation, illegal copying and genuine identification, etc. The authors develop a bi-image watermarking method. This paper introduces the commonly used Matlab function in the digital watermarking algorithm and accomplished a new kind of watermark-embedding and detecting algorithm based on the DCT. It has good robustness with the experimental results given that the image embedded watermark after the attack can be extracted successfully.