Sub-block interchange for lossless image compression

Lempel-Ziv-Welch (LZW) technique for text compression has been successfully modified to lossless image compression such as GIF. A new class of text compression, namely, Burrows and Wheeler (1994) transformation (BWT) has been developed which gives promising results for text compression. Here, we propose a sub-block interchange lossless compression method which belongs to this block sorting class. Our compression results have outperformed GIF in compression ratios and BWT in compression times when tested with 512/spl times/512 pixel 8-bit grey scale images. The comparison of compression ratios and times with GIF, BWT and other popular LZ based compression methods are discussed.