Quantisation error reduction for reducing Q-factor JPEG recompression

This paper studies the mechanism of recompression using the reduced Q-factor JPEG compression and highlights the areas which contribute to image distortion during recompression. A quantisation error reduction algorithm with the aim to preserve the originality of the image against recompression was presented. Statistical information from a typical image was collected which was then used as the threshold in the run time criteria of the algorithm. The algorithm works with the approach of adjusting the discrete cosine transformation coefficients to correct the quantisation errors. The algorithm was found work well for both images consisting of low frequency and high frequency components.