Brian Macy
----- Original Message -----
From: Tripp Lilley <tlilley@perspex.com>
To: <sane-devel@mostang.com>
Sent: Saturday, April 24, 1999 4:43 PM
Subject: Re: lineart vrs greyscale
> On Sat, 24 Apr 1999, Nick Lamb wrote:
>
> > To the human eye greyscale will always look better because it reduces
> > aliasing. So if you're just going to look at the results (or use an
> > algorithm which permits greyscale) you should use greyscale.
> >
> > The other advantage of line art is that it returns much less data (of
> > course 8 times less normally, or better with RLE) and so can be saved
> > to a smaller file and transmitted more quickly over SCSI. This might be
> > important for scanning A4 documents at high resolution quickly.
>
> Though greyscale is certainly better for legibility, if you're planning on
> archiving the documents, you'll want to futz around with the
> brightness/contrast settings as mentioned, and stick with lineart. The
> reason, in a nutshell, is that Group 4 Compression (FAX, TIFF, etc.) is
> the "best compromise" compression for archival storage, and it only does
> BW (ie: lineart).
>
> I say it's the "best compromise" because it's not /exactly/ a "general
> purpose" compression algorithm. It was designed for FAX transmission, and
> the designers chose certain constant parameters of the algorithm based on
> statistical analysis of lots of images of text documents in European
> languages. So it doesn't do quite as well on a BW scan of a full page
> magazine ad as it would on a full page of magazine text.
>
> In any case, TIFF or CALS with G4 compression is by far the most pervasive
> encoding in archival document management systems.
>
>
> --
> Tripp Lilley + Innovative Workflow Engineering, Inc. +
(tripp@iweinc.com)
> --------------------------------------------------------------------------
----
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>
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