基于图像特征的数字水印技术研究-电路与系统专业论文.docxVIP

II II 摘 要 本文以提高数字图像水印的鲁棒性作为研究目的，介绍了数字水印系统的 原理、基本框架、攻击与性能评价；在此基础上深入研究了基于图像特征的数 字水印算法，并进行了分析与总结，提出了基于图像纹理特征与区域相似度的 水印方案。 对原始水印信号作非周期 Arnold 置乱处理，使置乱后的水印信号在恢复过 程中不再具有周期性，此方法显著提高了水印的安全性。 利用小波分析的多分辨率多尺度特性以及人类视觉系统理论（HVS），提出 了依据小波高频系数的方差特征对图像进行纹理分析的方法，将水印优先嵌入 在图像感兴趣区域（ROI）的纹理区域所对应的小波低频系数中，该算法能有效 抵抗诸如噪声、滤波、JPEG 压缩、剪切等常规攻击。 依据图像的局部区域在受攻击前后还会保持较高相似度的特征，同时引入 对数极坐标变换的尺度和旋转不变性，提出了基于区域相似度的水印提取算法。 该算法在抵抗平移、旋转、缩放等几何攻击方面效果明显。 本文所提到的算法及实验都是在 MATLAB（R2007a）环境下进行的，所有 实验结果表明：本文提出的算法能够抵抗噪声、滤波、JPEG 压缩、剪切、平移、 旋转、缩放等常见的图像处理，具有较强的鲁棒性和不可见性。 关键词 数字水印；Arnold 置乱；纹理；区域相似度；几何攻击 III III Abstract Improving the robustness of digital image watermarking as the study purpose, this thesis introduced the system of digital watermarking about principles, basic frames, attack and performance evaluation; it further studied the watermarking algorithm based on image features. After analysis and summary, a watermarking scheme was proposed based on image texture feature and regional similarity. It treated the original watermarking signals using aperiodic Arnold scrambling, then the scrambled signals no longer had the periodicity during the recovery. It was obviously that the safety of the watermarking had been improved using this method. It made good use of multi-resolution, multi-scale characteristic of the wavelet analysis and the human visual system, and gave an analytic method of texture for images according to the variance features of the wavelet high-frequency coefficients, then the watermarking was prior to be embedded in the corresponding wavelet low-frequency coefficients of texture region in ROI image. This method was efficient to resist the common attacks such as noise, filtering, JPEG compression, cutting and so on. It constructed an algorithm of watermarking extraction on the basis of regional similarity, according to the characteristic that the partial region of image would keep high similarity between the original image and the attacked image, and the introduction of an invariant feature of rotati