基于归一化和非下采样Contourlet变换的数字水印方案

在研究非采样Contourlet变换和归一化理论的基础上，提出了一种新的数字图像水印算法。先将原始图像经过非下采样Contourlet变换处理，提取出图像的低频区域，然后依据人眼的视觉特性以及嵌入水印前、后系数的相关性，将水印信息嵌入对低频区域进行归一化重要区域中。无须借助于原始图像，就能进行水印提取，实现真正的盲检测。实验结果表明，本文算法对平移变换的抵抗力最强，对旋转和缩放也有很好的抵抗力，而且经过JPEG压缩之后，数字水印也不会失真。 

A Watermarking Scheme Based on Normalization and Nonsubsampled Contourlet Transform

A new watermarking algorithm scheme was presented based on normalization and nonsubsampled Contourlet transform knowledge, extracting low frequency sub-band of the image with nonsubsampled Contourlet transform, and then embedding the low frequency sub-band in a significant region for normalization according to the human visual system (HVS) and the correlation between the coefficients of the embedded watermark before and after. Without the aid of the original image, the watermark can be extracted and the real blind detection can be realized. The experimental results show that, the proposed watermarking algorithm has the best resistance to shift transform, and has the better resistance to rotation and zoom. After JPEG compression, the digital watermark is not distorted.