Identification of JPEG compressed images saved in uncompressed format (JPEG-U images) is an important issue in forensic analysis. The state-of-the-art JPEG compression detection methods fail to identify such images when subjected to post-processing/anti-forensic operations. In this paper, we propose a novel JPEG compression detector which is robust to post-processing and anti-forensic operations. The detector is based on the difference in the discrete cosine transform (DCT) coefficient distributions in the ac subbands of uncompressed images and JPEG-U images. We show theoretically and empirically that the probability of subband DCT coefficients which lie in the interval $(-0.5,0.5)$ is significantly different for a JPEG-U and the corresponding uncompressed image. This difference is exploited to derive a detection statistic which is compared with a threshold to detect JPEG-U images. The detector makes use of calibration, a technique used in steganalysis, to obtain the detection statistic. The experimental results show that the proposed detector significantly outperforms the state-of-the-art detectors, especially in the presence of post-processing and anti-forensic operations.

鉴定以未压缩格式保存的JPEG压缩图像（JPEG-U图像）是法医分析中的重要问题。现有技术的JPEG压缩检测方法在进行后期处理/取证操作时无法识别此类图像。在本文中，我们提出了一种新颖的JPEG压缩检测器，该检测器对后处理和取证操作具有鲁棒性。该检测器基于未压缩图像和JPEG-U图像的ac子带中离散余弦变换（DCT）系数分布的差异。我们从理论和经验上证明了子带DCT系数在区间内的概率$（-0。5，0。5）$对于JPEG-U和相应的未压缩图像有很大的不同。利用该差异来得出检测统计量，将其与阈值进行比较以检测JPEG-U图像。检测器利用校准（一种用于隐写分析的技术）来获得检测统计信息。实验结果表明，提出的探测器明显优于最新的探测器，特别是在存在后处理和取证操作的情况下。