Statistical Detection of JPEG Traces in Digital Images in Uncompressed Formats

Abstract

Intrinsic statistical properties of natural uncompressed images are used in image forensics for detecting traces of previous processing operations. In this paper, we propose novel forensic detectors of JPEG compression traces in images stored in uncompressed formats, based on a theoretical analysis of Benford-Fourier coefficients computed on the 8×8 block-DCT domain. In fact, the distribution of such coefficients is derived theoretically both under the hypotheses of no compression and previous compression with a certain quality factor, allowing for the computation of the respective likelihood functions. Then, two classification tests based on different statistics are proposed, both relying on a discriminative threshold that can be determined without the need of any training phase. The statistical analysis is based on the only assumptions of Generalized Gaussian distribution of DCT coefficients and independence among DCT frequencies, thus resulting in robust detectors applying to any uncompressed image. In fact, experiments on different datasets show that the proposed models are suitable for images of different sizes and source cameras, thus overcoming dataset-dependency issues that typically affect state-of-art techniques.

Revealing the traces of histogram equalisation in digital images

“…Recently, due to its wide acceptability, the forensic issues related to JPEG compressed images has received a great attention. Many algorithms have been developed to determine whether a given JPEG image is doubly compressed or not [21][22][23][24][25]. These methods consider double compression as a possible indication of forgery; however, sometimes, images may simply be decompressed and recompressed again without any manipulation, just to satisfy the file-size limitations of uploading.…”

Digital Image Forensic Approach to Counter the JPEG Anti-Forensic Attacks

“…The theoretical analysis of Benford-Fourier coefficients has been extended in [16] to present the forensic detector based on JPEG compression traces in an uncompressed format. A forensic detector based on theoretical analysis of Benford-Fourier coefficients computed on 8 × 8 block in DCT domain is presented in [17]. A feature vector for the detection of JPEG compression is presented in [18] based on Hough line, peaks, and the Harris-Stephens corner features.…”

Morphological Filter Detector for Image Forensics Applications

“…The associate editor coordinating the review of this manuscript and approving it for publication was Wei Zhang. This broad class of specific manipulation detectors includes the identification of pasted regions [12]- [16], resizing [17], [18], re-compression [19], image enhancing [20], inconsistencies in the geometry and illumination of the image due to possible manipulations [21]- [23], and various types of non-linear filtering (especially median) [24]- [35].…”