  Inconsistency in contrast enhancement can be used to expose image forgeries.
In this work, we describe a new method to estimate contrast enhancement 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 methods, 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 e effective method to to
detect image regions undergone contrast enhancement transformations that are
different from the rest of the image, and use this method to detect composite
images. We perform extensive experimental evaluations to demonstrate the
efficacy and efficiency of our method method.
