中文摘要：

为了在不降低数字水印鲁棒性的前体下提高嵌入容量，采用了在变换域中对DCT系数的修改来添加灰度图像数字水印。数字水印通过DWT变换并提取其低频分量实现数据压缩，用低频系数代替载体图像中的部分中频系数来实现水印嵌入。在DcT域中对其中频系数的修改算法可以保证水印的鲁棒性，同时又有较大的嵌入容量。实验结果表明，这一算法对JPEG压缩、剪切、加噪都具有较好的鲁棒性。

英文摘要：

Common digital watermarking will reduce the robust performance and invisibility when the embedded information volume is improved. A gray level digital watermarking was embedded in the DCT transformation domain by exchange the DCT coefficient in order to improve the information volume without decreasing the robust performance. The embedded watermarking is a high compression edition of watermarking image with DWT transformation and the carrier image middle frequency DCT coefficient is replaced with the low frequency coefficient. The algo- rithm with modification of middle frequency DCT coefficient can promise the robust performance and large information volume. Results show that the algorithm improved the robust performance when it was attacked with JPEG compression, cutting and adding some noises.