Contrast Enhancement Estimation for Digital Image Forensics

Inconsistency in contrast enhancement can be used to expose image forgeries. In this work, we describe a new method to estimate contrast enhancement operations from a single image. Our method takes advantage of the nature of contrast enhancement as a mapping between pixel values and the distinct characteristics it introduces to the image pixel histogram. Our method recovers the original pixel histogram and the contrast enhancement simultaneously from a single image with an iterative algorithm. Unlike previous works, our method is robust in the presence of additive noise perturbations that are used to hide the traces of contrast enhancement. Furthermore, we also develop an effective method to detect image regions undergone contrast enhancement transformations that are different from the rest of the image, and we use this method to detect composite images. We perform extensive experimental evaluations to demonstrate the efficacy and efficiency of our method.