基于图像归一化的Contourlet域数字水印方案

Contourlet变换是一种全新的高维信号奇异性分析工具,其不仅具有良好的方向性和各向异性,而且能够高效率捕获图像几何结构.本文以Contourlet变换理论及图像归一化技术为基础,提出一种基于图像归一化的Contourlet域数字水印方案.该方案首先利用图像归一化技术将原始载体映射到几何不变空间内,并提取出归一化图像的重要区域;然后对重要区域实施Contourlet变换;最后根据人眼视觉特性及系数相关性,利用量化调制策略将水印信息嵌入到Contourlet域低频子带内.仿真实验结果表明,该数字图像水印方案不仅具有良好的透明性,而且具有较强的抵抗常规信号处理及几何攻击的能力.

Image Normalization Based Robust Digital Watermarking Scheme in Contourlet Domain

Contourlet transform is an efficient anisotropy analysis tool in high dimensions, which not only possess the main features of directionality and anisotropy, but also can effectively capture the intrinsic geometrical structures such as smooth contours (at different scales and directions) in natural images. In this paper, an image normalization based robust digital watermarking scheme in Contour-let domain is proposed. Firstly, the geometrically invariant space is constructed by using image normalization and the significant region is obtained from the normalized image by utilizing the invariant centroid theory. Then, the Contourlet transform is performed on the significant region. Finally, the digital watermark is adaptively embedded into the significant region by quantizing the low-frequency Contourlet coefficients according to the Human Visual System (HVS). Especially, the predistortion compensation technique is used to reduce image distortion generated by image normalization. Experimental results show that the proposed scheme is not only invisible and robust against common signals processing such as sharpening, noise adding, and JPEG2000 compression, but also robust against the geometric distortion such as rotation, translation, scaling, row or column removal, cropping, and local random bending.