A requantization-based method for recompressing JPEG images
Heinz H. Bauschke, Chris H. Hamilton, Mason S. Macklem, J.S. McMichael, Nicholas R. Swart · IEEE International Conference on Acoustics Speech and Signal Processing · 2002
We propose a new method for requantizing JPEG images, based on the well-known Laplacian distribution of the AC discrete cosine transform (DCT) coefficients and on an analysis of the error introduced by requantization. The resulting images have improved perceptual image quality over a “blind” requantization approach, that is, one that does not consider the properties of the quantization matrices.