[Asterisk-Users] Asterisk - fax - spandsp

[Lee Howard]

On Sun, 15 May 2005, Steve Underwood wrote:

> Lee Howard wrote:
> 
> > The other option to color faxing is JBIG compression.  The problem 
> > there, is that JBIG is fairly heavily patented still.  Thus many fax 
> > machines just aren't supporting it yet.
> 
> Thanks Lee. I found that helpful, except the last paragraph which 
> confuses me. I thought JBIG was only a bilevel compression scheme. Am I 
> wrong?

See ITU-T.30 (04/99) Table 2 Notes 34 and 35.  Basically they point you to 
T.43 which basically points you to T.42 and T.82.  But yes, they 
essentially describe a color JBIG compression.

Not surprisingly, these also specify that CIELAB colorspace is used for 
palletized images... which means that it is unlikely that many JBIG 
viewers or JBIG libraries understand it yet... unless someone has 
deliberately developed it for fax support.

Lee.