Identifying high quality JPEG compressed images through exhaustive recompression technique

An important step in digital image forensics is to identify whether a given image is JPEG compressed or not. Most of state-of-the-art image forensic methods fail to differentiate between an uncompressed and a high quality compressed (near lossless) images. In this paper we propose a method to efficiently differentiate an original uncompressed image from high quality JPEG compressed images (but saved as TIFF or BMP) by analyzing the changes in the DCT coefficients after recompression. We define a new parameter and experimentally show that it acquires a very small value for uncompressed images compared to the JPEG compressed counterpart. Simulation results verify that the proposed method significantly outperforms other methods, for images taken from various sources.