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From: andrea@hp-sdd.HP.COM (Andrea K. Frankel)
Newsgroups: comp.graphics
Subject: Re: Graphic file formats
Message-ID: <656@hp-sdd.HP.COM>
Date: Wed, 24-Dec-86 16:16:57 EST
Article-I.D.: hp-sdd.656
Posted: Wed Dec 24 16:16:57 1986
Date-Received: Thu, 25-Dec-86 00:38:44 EST
References: <6901@decwrl.DEC.COM> <507@elrond.UUCP> <2824@gitpyr.gatech.EDU>
Reply-To: andrea@hp-sdd.UUCP (Andrea K. Frankel)
Organization: Hewlett-Packard, San Diego Division
Lines: 46
Summary: check out the CGM!

In article <2824@gitpyr.gatech.EDU> robert@gitpyr.UUCP (Robert Viduya) writes:
>GKS Metafile format that ANSI and ISO are supposedly working on.
>I've not been able to find this particular standard in the GaTech
>library (I'm not sure it's even an accepted standard yet)

I think you are referring to the Computer Graphics Metafile (CGM).
This IS in fact an accepted standard!  As of 8/27/86, it is
American National Standard X3.122-1986, available from

    ANSI
    1430 Broadway
    New York, NY   10018

The same document is also an international standard, IS 8632
(accepted just this fall, and still being typeset I believe).

Both standards have four parts:  Part 1 defines the functionality, Part
2 is a Character Encoding (cryptic and compact, good for I/O
transmission), Part 3 is a Binary Encoding (good for file storage), and
Part 4 is a Clear Text Encoding (good if you have to read or edit the
thing).

The CGM was developed to be used by GKS and others for archiving
pictures.  In addition to vector graphics functions, it also
includes a rudimentary raster format (CELL ARRAY), and
"hooks" for putting in implementation-dependent information in the file
(APPLICATION DATA, GENERALIZED DRAWING PRIMITIVE, and ESCAPE).

The CGM is the basis for the CGI (interface to graphics "Virtual
Devices") and for an Extended CGM which will provide GKS audit
trail capability and the CGI's extended raster functionality
(among other things).

By all means, if you want to implement something that has some
chance of being portable between different vendors, and an expected
lifetime longer than the current rev of ,
check out the CGM!

Andrea Frankel, Hewlett-Packard (San Diego Division) (619) 592-4664
 "...like a song that's born to soar the sky..."
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