Posted on 31 January 2010

Paper details:

Our TIFS paper was the first work to offer a unified forensic framework that can identify the compression method used upon an image. Among these compression methods are transform coders — compression methods that apply some form of entropy coding in the transform domain (e.g., via discrete cosine transform, wavelet transform, etc.). Transform coding is undoubtedly the most popular category of image coders in use today. Therefore, the forensic problem of transform coder classification deserves attention.

In this paper, we propose a method that can identify which transform was used upon an image during the compression process. By analyzing the transform coefficient histogram obtained after applying a candidate transform, we can determine if the image was compressed using the transform tested. Results show that forensic classification accuracy is high when testing from among six well-known transforms.

To our knowledge, this work is the first to address the problem of transform coder classification and propose a working solution.