1. A computer-readable storage medium storing computer-executable instructions to process a JPEG image, the computer-executable instructions comprising: receiving the JPEG image for analysis; extracting a 2-dimensional (2-D) array of JPEG coefficients from the JPEG image; generating a 2-D difference array based on the 2-D array of JPEG coefficients, wherein entries in the 2-D difference array reflect relative changes in values of pairs of entries in the 2-D array of JPEG coefficients; modeling the 2-D difference arrays using a Markov random process; and evaluating whether the random process reveals statistical artifacts in the JPEG image, the statistical artifacts resulting from double JPEG impression performed on the JPEG image.