Blind estimation of pixel brightness transform

Pixel brightness transforms (PBT), examples of which include gamma correction, sigmoid stretching and histogram equalization, are common operations on digital images, and it is practically useful to estimate such transforms directly from an image. In this work, we describe an effective and efficient method to estimate PBT from images, which takes advantage of the nature of PBT as a mapping between integral pixel values and the distinct characteristics it introduces to the pixel value (PV) histograms of the transformed image. Our method recovers the original PV histogram and the PBT simultaneously with an efficient iterative algorithm, and can effectively handle perturbations due to noise and compression. We perform experimental evaluation to demonstrate the efficacy and efficiency of the proposed method.