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Subject: AW: RE: [cgmo-webcgm] Z compression research


Dave,

This is no problem. Once you have decompressed the (unknown) file, you can then examine the first couple of bytes to detect the format.
If we use cgmz as the extension you would know anyway ahead of time.

Dieter
Send from my BlackBerry

-----Original Message-----
From: Cruikshank, David W <david.w.cruikshank@boeing.com>
To: DULUC, Franck <franck.duluc@airbus.com>; Don Larson <dlarson@cgmlarson.com>; CGM Open WebCGM TC <cgmo-webcgm@lists.oasis-open.org>
Sent: Thu Sep 20 09:56:21 2007
Subject: RE: [cgmo-webcgm] Z compression research

I guess I also raises the question of if you find the "magic number" for zcompress how do you know it's not an svgz file instead of a cgmz file?

Thx...Dave


Technical Fellow - Graphics/Digital Data Interchange
Boeing Commercial Airplane
206.544.3560, fax 206.662.3734
david.w.cruikshank@boeing.com

-----Original Message-----
From: DULUC, Franck [mailto:franck.duluc@airbus.com] 
Sent: Thursday, September 20, 2007 6:31 AM
To: Don Larson; CGM Open WebCGM TC
Subject: RE: [cgmo-webcgm] Z compression research

i think it is the same for VRML.

Franck

-----Message d'origine-----
De : Don Larson [mailto:dlarson@cgmlarson.com] Envoyé : mercredi 19 septembre 2007 23:07 À : CGM Open WebCGM TC Objet : [cgmo-webcgm] Z compression research


All,

After researching Z compression, I have determined that the file format used for compressed SVG is the same used by "gzip" an open source software. And that there indeed is a magic number in first 2 bytes indicating Z compression.

The complete specification for the gzip file format can found here:
http://www.ietf.org/rfc/rfc1952.txt

Further details on gzip and source code can be found at:
http://www.gzip.org/


Regards,
Don Larson

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