基于四元数傅里叶变换的彩色图像数字水印算法

目的提高彩色图像数字水印的抗攻击性能,包括缩放、旋转、平移、噪声攻击等。方法基于坐标变换和四元数傅里叶变换提出一种彩色图像数字水印算法。介绍彩色图像四元数表示形式及其双侧傅里叶变换,并分析笛卡尔坐标和极对数坐标之间的变换关系。选择四元数傅里叶变换后实部的中低频部分作为嵌入区域;为提高算法的抗几何攻击能力,给出笛卡尔坐标系和对数极坐标系之间对应点的位置关系;详细论述水印嵌入和提取的流程。结果针对噪声、滤波、剪切等攻击进行了实验研究,结果表明所述算法可以提高提取信息的准确率和水印的抗攻击能力。结论该算法在保证水印隐蔽性的同时能够抵抗一定程度的攻击,满足版权保护和数字防伪的需要。

Color Image Digital Watermarking Algorithm Based on Quaternion Fourier Transform

The work aims to improve the anti-attack performance of color image digital watermarking, including scaling, rotation, translation, noise and so on. A color image digital watermarking algorithm was proposed based on the coordinate transformation and quaternion Fourier transform (QFT). The quaternion color image representation and its bilateral Fourier transform were introduced and the relationship between Cartesian coordinate and polar logarithmic coordinate was analyzed. The low-frequency part of the real component after QFT was chosen as embedded area. In order to improve the algorithm''s ability to resist geometric attacks, the relationship of corresponding points between Cartesian coordinate and logarithmic polar coordinate was given. The watermarking embedding and extracting process was described in details. The experiments were carried out with regard to the attacks, such as noise, filtering, shear and so on. The results showed that the algorithm described could improve the accuracy of extracting information and the ability of watermarking against attacks. The algorithm can guarantee the concealment of the watermarking. At the same time, it can resist attacks to a certain degree. Therefore, it will meet the needs of copyright protection and digital anti-counterfeiting.