This is the source code of XFD's Pac.Pic. slave, for the curious.

Pac.Pic. is an Amiga picture compression module used in AMOS Basic. It was
created by François Lionet. The code for this slave is based on the
original source code for the picture compactor extension, which came
bundled with AMOS 1.3 all those years ago.

Pac.Pic. is simply an RLE compressor, that re-orders the screen before
compression in a way which favours large vertical lumps of colour. It
RLE-encodes the reordered screen without using a special marker code,
but rather one bit for every byte on the screen to say if it's a repeat
or not. This large list of bits is then itself RLE encoded, which brings
down the size quite a lot.

This XFD slave 'decrunches' the picture to the uncompressed IFF ILBM
picture format.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                  303     475  63.8% -lh5- 8b2f Nov 18  2001 extheader.c
[generic]                  230     406  56.7% -lh5- 2b8d Feb 23  2002 Makefile
[generic]                 1407    2364  59.5% -lh5- fe4a Feb 23  2002 PacPic
[generic]                 3869   11192  34.6% -lh5- 6ce4 Feb 23  2002 PacPic.c
[generic]                  646    1743  37.1% -lh5- c713 Nov 18  2001 SDI_compiler.h
[generic]                  530     970  54.6% -lh5- 4482 Nov 20  2001 xfd_PacPic.readme
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         6 files    6985   17150  40.7%            Aug 24  2002