【摘要】 抗几何攻击的鲁棒图像水印算法研究是一项富有挑战性的工作.本文以图像归一化理论为基础,提出了一种可有效抵抗几何攻击的DFT域数字图像水印方案.该方案首先利用基于矩的图像归一化技术将原始载体映射到几何不变空间内,并结合不变质心理论提取出归一化图像的重要区域;然后对重要区域实施分块离散傅立叶变换(DFT);最后结合幅值谱信息自适应确定水印嵌入位置,并利用量化调制策略将数字水印嵌入到重要区域的相位和幅值内.仿真实验结果表明,该数字图像水印方案不仅具有良好的不可感知性,而且具有较强的抵抗常规信号处理及几何攻击的能力.更多还原

【Abstract】 In image watermarking,the watermark′s vulnerability to geometric attacks has long been a difficult problem.In this paper,a Discrete Fourier Transform(DFT) domain robust digital watermarking algorithm based on image normalization is proposed.Firstly,the geometrically invariant space is constructed by using image normalization,and a significant region is obtained from the normalized image by utilizing the invariant centroid theory.Then,the significant region is cut into blocks of 8*8,and DFT is performed on the image blocks.Finally,the digital watermark is adaptively embedded into the significant region by quantizing the magnitude and phase of the selected middle-frequency DFT coefficients.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 etc.更多还原