Additional lossless compression of JPEG images

The task of additional compression of images earlier coded using JPEG is considered. A novel efficient method for coding quantized DCT coefficients is proposed. It is based on coefficient separation into bit planes, taking into account correlation between the values of neighbor coefficients in blocks, between the values of the corresponding coefficients of neighbor blocks as well as between the corresponding coefficients of different color layers. It is shown that the designed technique allows for images already compressed by JPEG to additionally increase compression ratio by 1.3...2.3 times without introducing additional losses.