Quality factor estimation of JPEG compressed images

Abstract : The goal of the paper is to present a new approach to estimate the quality factor value for a JPEG image. This approach is based on the statistical model of variance of blocks 8 × 8 for JPEG images. The variance model follows Gamma distribution, characterized by two parameters which are used to calculate a distance between the first and the second compressions. The distance in case of compressing images twice with the same value of quality factor is exploited as characterized fingerprint for quality factor identification of a JPEG image. Experiments with simulated and real images highlight the relevance of the proposed approach.