Path: utzoo!attcan!uunet!mcsun!ukc!pyrltd!advsys!graham
From: graham@advsys.UUCP (Graham Underwood)
Newsgroups: comp.graphics
Subject: Re: File Formats
Message-ID: <852@advsys.UUCP>
Date: 12 Jul 90 08:44:44 GMT
References: <8437@arctic.nprdc.arpa>
Reply-To: graham@advent.co.uk (Graham Underwood)
Organization: Advent Systems Ltd., Wokingham, England
Lines: 18
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In article <8437@arctic.nprdc.arpa> armfield@nprdc.navy.mil (Sylvia Armfield) writes:
>
>   I still haven't figured out how to identify the following file 
>formats:
>           CITT FAX4  

CCITT [sic] Group 4 is not a file format, it is an image compression
standard.  The encoded data is therefore dependent on the image you are
compressing and there is no way to determine that it is Group 4 data. 
(Other than starting to decompress it and seeing if you get something
inteligible - but thats probably for comp.ai enthusiasts).

Group 4 data alone does not contain sufficient information for you to
decode it - e.g.  you have to know the pixel width of the image.  You
will probably find that the Group 4 data is wrapped up inside a file
format such as TIFF which enables the other information to be specified. 

Graham.