JB2 is the bitonal compression algorithm of DjVu.


With DjVuLibre, you can extract a raw JB2 chunk from a DjVu file by

    djvuextract input.djvu Sjbz=output.jb2

and assemble it back to DjVu with
    
    djvumake output.djvu Sjbz=input.jb2
