Digital BW, The Print

The Wogster writes:

> For archiving though, where you are not looking at the image on a
> regular basis, you can use other compression mechanisms.  For example if
> you can compress a 600MB file down to say 50MB for archiving, and then
> decompress it again later, who cares?  Even if it takes an hour to 
> compress/decompress.

Agreed.  But what file formats would be in this category?

Theoretically, you could compress most image files enormously with no
loss, given time and space to do an absolutely optimal compression.
I've never heard of a file format that is designed for this purpose,
though.