A common type of digital image forgery is the duplication of a region in the same image to conceal something in a captured scene. The detection of region duplication forgeries has been recently addressed using methods based on SIFT features that provide points of the regions involved in the tampering and also the parameters of the geometric transformation between both regions. However, considering this output, there is not yet any information about which of the regions are originals and which are the duplicated ones. A reliable image forensic analysis must provide this information. In this paper, we propose to use a resampling-based method to provide an accurate way to distinguish the original and the tampered regions by analizing the resampling factor of each area. Comparative results are presented to evaluate the performance of the combination of both methods.