Message-ID: 38453875.D7E95579@ina.de
To: TIFF Mailing List <tiff@olympiakos.com>
Subject: Re: libtiff 3.5.3 release.
From: Klaus Bartz <bartzkau@ina.de>
Date: Wed, 01 Dec 1999 16:02:13 +0100
References: <3.0.5.32.19991130230733.00b22520@mailhost.cam.harlequin.co.uk> <38452BE7.3F5019C3@petris.com>
Sender: owner-tiff@olympiakos.com


CCITT T.4 ( G3 ) and CCITT T.6 ( G4 ) are lossless, but only defined for
images with 1 bit per pixel and are TIFF extensions. The only baseline
losless compression format is PackBits ( also it has a private number for 
the TAG :-) ).
LZW was in TIFF Revision 5.0 a baseline compression format, in 
Revision 6.0 it is NOT because the patent problems ( it's a TIFF
extension ).
Since 7 years there is no new Revision. Else there will be a new
baseline losless compression format - may be deflate or Burrows-Wheeler
( that what compresses in bzip2 ).
Why not use deflate ( name it ZIP if you want) jet ? It compress 
better than LZW.

Klaus


Bruce Cameron wrote:
> 
> Most of the image I handle use CCITT compression, which I have presumed
> is lossless.  It may be that the reason I get good small images is that
> for the most part I am operating on greyscale or binary images.  Is
> CCITT not lossless, or is it that it is a 'non-standard' compression?
> 
> Martin Bailey wrote:
> >
> > At 17:23 30/11/99 -0500, Michael L. Welles wrote:
> >
> > >Unfortunatly, the compression removal means that saved image size has
> > >grown dramatically.  Without a change in the TIFF spec to support
> > >another lossless compression format, this is unavoidable.

-- 
-------------------------------------------------------------------
Dr. Klaus Bartz                                     bartzkau@ina.de
COI GmbH / Abt. KOS3    Industriestr. 1-3    D-91072 Herzogenaurach
Tel: +49 (9132) 82-3433                        Fax: +49-9132-824959

