$map = parse_ini_section("ra_4_corners.mpr", "PreviewPack", COLLAPSE);
$preview_pack = base64_decode($map["PreviewPack"]);
echo hex_dump($preview_pack);

Gives me:

http://eth0.org/ra_4_corners.txt

I thought it was a PCX but now that I've been reading up on PCX it don't apear to be...