Improvement of the lossless compression of images with quasi-sparse histograms

Off-line histogram packing is a known method which is capable of producing improvements if applied prior to the lossless compression of images having sparse histograms. However, this technique becomes useless if the image possesses a quasi-sparse histogram, even if it differs from the strictly sparse case only by a minimal margin. In this paper, we present a technique that is able to overcome this drawback and we present results showing its effectiveness.