文中针对图像篡改中最常见的复制粘贴篡改被动取证问题展开图像分析研究，提出了一种基于仿射尺度不变特征变换(ASIFT)和圆投影特征的算法，用于检测图像中是否存在复制粘贴篡改． 实验结果表明:基于仿射尺度不变特征的算法对具有明显角点特征的篡改图像的取证效果较好，而基于改进圆投影特征的算法对不具备明显角点特征的篡改图像(如随机性纹理、平坦区域)的取证效果较好，因此联合使用基于这两种特征的算法对常见的复制粘贴型图像篡改进行被动取证能达到较好效果．

This paper deals with an image analysis method，namely passive forensics，to detect copy-move forgery，the most popular manipulation in digital tampered images． On the basis of ASIFT (Affine Scale-Invariant Feature Transform) and circle projection features，a new algorithm is proposed to detect copy-move forgery in images． The results show that the adoption of ASIFT is effective only in finding the forgery area in a tampered image with obvious corner information，while the adoption of improved circle projection features is effective only in finding the forgery area in a tampered image without such obvious corner information as random textures and flat areas． Thus，it comes to the conclusion that the combination of ASIFT and improved circle projection features is more effective for the pas-sive forensics of copy-move forgery．