Lossy plus lossless residual encoding with dynamic preprocessing for Hubble Space Telescope fits images

In this paper we present an innovative lossy plus lossless residual encoding scheme consisting of the following steps: (A) Dynamic pre-processing applied either to the original image in order to separate homogeneous parts of it; or to the histogram of the pixel values in order to generate three images each with the same size of the original one that superposed reconstruct exactly the source image. (B) Use of an efficient lossy compression scheme to pre-processed data in order to generate low bit rate images. (C) Definition of residuals by computing the differences between the lossy reconstructions and the pre-processed images. (D) Encode the residuals using an appropriate lossless technique. We applied this double scheme, with the two different pre-processing techniques, to some HST FITS images, obtaining from 1:4 to 1:6.4 lossless compression ratios.