Detection of Quantization Artifacts and Its Applications to Transform Encoder Identification

Quantization is one of the commonly used techniques in most lossy image source encoders. It is observed that the quantization operation usually introduces some obvious artifacts into the histogram of the corresponding transform coefficients under various compression schemes. By investigating such inherent artifacts over all candidate transform coefficients, it is possible to identify the transform, as well as some parameters previously employed in the transform-based encoder from a decompressed image. In this paper, we first analyze the properties of the quantized coefficients and present a simple yet effective way to detect the quantization artifacts, and then we propose an approach to identify the transform-based encoder based on the quantization artifacts detection. The simulation results evaluated on thousands of natural images with some popular compression schemes demonstrate the effectiveness of our method.