Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!decwrl!bacchus.pa.dec.com!rust.zso.dec.com!shlump.nac.dec.com!ryn.esg.dec.com!uninet!uninet.dec.com!morris
From: morris@uninet.dec.com (Tom Morris)
Newsgroups: comp.std.internat
Subject: Re: CCITT Group 3 question: "early" EOL
Message-ID: <1990Sep3.155358@uninet.dec.com>
Date: 3 Sep 90 15:03:12 GMT
References: <1990Aug29.194009.6820@sdd.hp.com>
Sender: news@uninet.vbo.dec.com
Reply-To: morris@casee.enet.dec.com
Distribution: comp
Organization: Digital Equipment Corporation, Valbonne, France
Lines: 34

In article <1990Aug29.194009.6820@sdd.hp.com>, andrea@sdd.hp.com 
(Andrea K. Frankel) writes:

[in reference to `early EOLs' in G3 fax encoding]
|> 
|> 	-  Is this a valid, conforming implementation?  
|> 
|> 	-  Or should a robust implementation be able to decode
|> 	Group 3 files where some rows are ended "early" with an EOL 
|> 	(in which case presumably the rest of the row is white)?
|> 

Your two options aren't mutually exclusive.  Do you simply want a `valid,
conforming implementation' or do you want a robust implementation which is
useful to your customers?

I think that this is case where you want to apply different standards for
your encoder and decoder.  The encoder should generate files which conform
to the letter of the law, but your decoder should make all reasonable attempts
to decode anything it is given.  For one thing, if this is a real fax which
came from the error-prone analog world instead of our nice clean digital 
world, there is no guarantee that it hasn't been corrupted in transmission.

If you can assume that you are dealing with an error free image from a known
source, than you can probably take some short cuts which will speed things up,
but you risk getting burned later when you start getting images from a 
different source.

------------------------------------------------------------------------
Tom Morris				morris@casee.enet.dec.com
Digital Equipment,
Centre Technique Europe S.A.R.L		DTN 828-5729
B.P. 129 - Sophia Antipolis 		Tel. +33 92 95 57 29
06561 Valbonne Cedex - France		Fax  +33 93 65 41 58