ENCODING-INTERLEAVED HIERARCHICAL INTERPOLATION FOR LOSSLESS IMAGE COMPRESSION

In this correspondence an improved version of the Hierarchical INTerpo lation (HINT) algorithm is proposed for multiresolution reversible com pression of still images. The efficiency of the basic scheme is increa sed by splitting the nonseparable interpolation process into two casca ded directional steps interleaved with encoding. Interpolation errors from the former are encoded to yield error-free pixel values, from whi ch the left-over pixels are interpolated in the latter step. The outco me benefit is twofold: interpolation is executed starting from all err or-free pixel values, and different directional correlations may be ex ploited. In addition, the differences between true and interpolated pi xel values are encoded cyclically with respect to the range of pixel v alues within square blocks, thus saving extra bits compared to plain e ntropy coding. Results and comparisons witness the improved coding per formance. (C) 1997 Published by Elsevier Science B.V.