目前，大多数图像取证方法对彩色图像的处理是将其转换为灰度图像，从而导致了彩色图像的颜色信息不能被有效且充分地利用.针对此问题提出一种基于四元数主成分分析（quaternion principal component analysis，QPCA）的复制粘贴篡改检测方法.该方法充分利用了彩色图像的各个颜色通道及它们之间的相关性，能够有效提高篡改区域的识别度.运用基于图像块的检测方法，首先将图像分块后对所有块进行QPCA计算以提取特征，然后用字典排序获取相似块的移位向量，最后根据移位向量频数与阈值的比较确定篡改区域.实验结果表明，所提方法的误检漏检率低于现有方法，检测准确率有较大提高.
Currently, in order to deal with color images, most forensics methods transform color images into gray images,which results in the color property not being fully used. Aimed at this problem, a copy-move forgery detection scheme based on quaternion principal component analysis (QPCA) is proposed in this paper. The scheme makes full use of the color property and the relationship among all color channels, which improves the accuracy in forged area effectively. The proposed scheme is block-based and frstly it divides images into overlapping blocks and performs QPCA of all the blocks to extract features. Then the features are lexicographical ordered to obtain shift vector and its frequency. Finally we compare the shift vector frequency to the threshold to locate the forged region. Experiments show that the missing-false alarm rate in the proposed method is lower than the existing methods and has a better accuracy.
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