基于直流分量和低频分量的DCT域数字水印嵌入算法

提出了两种数字水印嵌入算法．一是对原始图像作整体DCT变换后在低频分量上嵌入水印，水印是一符合标准正态分布的随机序列；二是利用人类视觉掩蔽特性，对原始图像作分块DCT变换后选取直流分量嵌入水印，水印是一个在视觉上具有直观意义的数字图像，并采用图像置乱的方法增强水印的安全性．实验结果表明提出的两种水印算法均具有较好的不可见性，且能够成功地抵抗JPEG有损压缩、缩放、中值滤波、加噪、剪切等常见的图像处理操作，具有较强的鲁棒性．

Digital Watermarking Embedded Algorithm in DCT Domain Based on DC and Lower Frequency Component

The two embedded algorithms of digital watermarking are proposed in this paper.The first algorithm is that watermark is embedded in lower frequency part after an original image has been transformed based on DCT and the watermark is a random sequence according to standard normal distribution.The second algorithm is that DC component is chosen as watermark embedded area utilizing the human visual characteristic,after an original image has been transformed by separated block DCT,the watermark is a digital image having a significant intuitively and scrambled to enhance the security of the watermark.The results of the experiment show that the two watermarking algorithms have perfect imperceptibility,and can successfully resist image processing operations such as JPEG lossy compression,resizing,median filtering,plus noise and cropping,so the thesis' algorithms have good robustness.