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. Recently, a new class of text compression, namely, Burrows and Wheeler Transformation (BWT) has b een developed which gives promising results for text compression. Here, we propose a sub-block interchange lossless compression method which belongs t o this block sorting class. Our compression results have outperformed GIF i n compression ratios and BWT in compression times when tested with 512x512 pixel 8-bit grey scale images. The comparison of compression ratios and tim es with GIF, BWT and other popular LZ based compression methods are discuss ed.