Prior Image Jpeg-Compression Detection

The paper presents two methods of prior JPEG-compression detection. In the first method the histogram of chrominance is analysed. In JPEG-compressed images the histogram contains significantly more local maxima than in uncompressed files. The second method is based on neighbouring pixel Ø value difference. In JPEG-compressed image the distribution of these values is different than the distribution counted on the edges of compression 8x8 blocks. These differences are summed up to create a classifier that allows to assess if the image was compressed.