Exposing duplicated regions affected by reflection, rotation and scaling

A commonly considered image manipulation is to conceal undesirable objects or people in the scene with a region of pixels copied from the same image. Forensic mechanisms aimed at detecting this type of forgeries must also consider other potential types of post-processing, including geometric distortions. In this paper, a new method is proposed to detect duplicated regions, even when the cloned region has undergone reflection, rotation and scaling. The algorithm uses colour-dependent feature vectors to reduce the number of comparisons in the search stage, and one-dimensional (1-D) descriptors, invariant to reflection and rotation, to perform an efficient search in terms of memory usage. Comparison results are presented to evaluate the effectiveness of the proposed method and two existing schemes.