Prioritized DCT for compression and progressive transmission of images

In this paper a new approach based on the block discrete cosine transform (DCT) for compression and progressive transmission of images is presented. The novelty of this approach is that the transform coefficients of all image blocks are coded and transmitted in absolute magnitude order. The resulting ordered-by-magnitude transmission is accomplished without sacrificing coding efficiency by using partition priority coding (PPC a new source coding method that allows the transmission of an ordered data source without coding overhead due to prioritization. Using this approach, coding and transmission are adaptive to the characteristics of each individual image, and therefore, very efficient. Another advantage of this approach is its high progression effectiveness. Since the largest transform coefficients that capture the most important characteristics of images are coded and transmitted first, this method is well suited for progressive image transmission (PIT). Further compression of the image data is achieved by utilizing multiple distribution entropy coding (MDEC. MDEC is a new coding technique based on arithmetic coding. Experiments are presented where the new DCT approach was tested. It is shown that it compares favorably with previously reported DCT and subband image codecs and is also very effective for PIT.