Reverse engineering of double JPEG compression in the presence of image resizing

In this paper, we propose a forensic technique for the reverse engineering of double JPEG compression in the presence of image resizing between the two compressions. Our approach is based on the fact that previously JPEG compressed images tend to have a near lattice distribution property (NLDP), and that this property is usually maintained after a simple image processing step and subsequent recompression. The proposed approach represents an improvement with respect to existing techniques analyzing double JPEG compression. Moreover, compared to forensic techniques aiming at the detection of resampling in JPEG images, the proposed approach moves a step further, since it also provides an estimation of both the resize factor and the quality factor of the previous JPEG compression. Such additional information can be used to reconstruct the history of an image and perform more detailed forensic analyses.