Re: CGM deployment? [was: Tables and Charts ]

lilley (lilley@afs.mcc.ac.uk)
Fri, 7 Jul 1995 17:48:47 +0100 (BST)


From: lilley <lilley@afs.mcc.ac.uk>
Message-Id: <16561.9507071648@afs.mcc.ac.uk>
Subject: Re: CGM deployment? [was: Tables and Charts ]
To: connolly@beach.w3.org (Daniel W. Connolly)
Date: Fri, 7 Jul 1995 17:48:47 +0100 (BST)
Cc: lilley@afs.mcc.ac.uk, papresco@calum.csclub.uwaterloo.ca,
In-Reply-To: <199507071418.KAA27180@beach.w3.org> from "Daniel W. Connolly" at Jul 7, 95 10:18:39 am

Dan comnolly writes:
 
> In message <10955.9507071246@afs.mcc.ac.uk>, lilley writes:
> >CGM (ISO/IEC 8632: 1992) is currently being registered as an Internet 
> >Media Type.
> 
> What sort of support for CGM is in various authoring tools? e.g. can
> I easily save FrameMaker drawings in CGM? How about stuff like MacDraw,
> etc.?

There is a Frame Filter Pack which will import and export CGM.

Many CAD packages can produce CGM

CorelDraw can produce CGM, so I am told can Harvard Graphics.

There is software called Graphporter you can get for a Mac that looks 
like another printer, but when you print to it a CGM file gets generated 
instead of PostScript. See:

gopher://nisp.ncl.ac.uk:70/0R0-2587-/lists/chest-cgm/archives/1995-02
 
> Does anybody know how CGM interacts with fonts? If it has a nice clean
> font story,

As far as I am aware, CGM:1992 covers font naming, control, and aliasing 
using concepts from ISO 9541-1 Font Information Exchange. That was a DIS 
when I got the information, but I expect it has become a full IS by now.

Dan: if you have technical queries at the W3C level I suggest you mail
Dr Anne Mumford <A.M.Mumford@lut.ac.uk>

Anne is the contact point for the CGM Rapporteur Group of ISO/IEC JTC1 SC24
(damn these cryptic committee numbers) and you will be able to get an 
authoritative answer from her.

> that would put it way ahead of EPS for this sort of thing.

Talking of competing with PostScript ;-) I see the feature list now includes 
external symbol libraries, compound paths for clipping to arbitrary shapes, 
NURBS, colour calibration, use of CIELUV and CIELAB colour spaces, and 
control over line termination, joining and mitring.

A useful summary of recent developments in CGM is at:

gopher://nisp.ncl.ac.uk:70/0R14133-23085-/lists/chest-cgm/archives/1994-08

which is also reachable from the archives of the chest-cgm mailing list :

gopher://nisp.ncl.ac.uk:70/11/lists-a-e/chest-cgm

> The consortium has been approached by somebody who's willing to give
> away source to a CGM viewer. If there were free CGM viewers available
> via w3.org, do you think it would take off?

Certainly, provided the viewers were of reasonable quality and implemented
enough of the 1992 standard to ensure they could read most CGMs on the Web 
without problems.

Incidentally,  is that the RALCGM viewer or another one I don't know 
about yet? Is it something Bruce Garner has written? Or a freebee from
Carberry Technology? (Itching to know).

To achieve the best Web acceptance of CGM, what is needed (IMHO) is:

* a fully PD (ie, including commercial use) platform independent,
  C++ compatible, C library for CGM, after the fashion of the TIFF, JPEG
  and PNG libraries
* freely distributable Mac, MS-Windows and X-Windows viewers that use
  this library. These should view CGMs, allow easy (rubberband box)
  zooming and panning, and provide a means to load and save files.

This way, there are immediate viewers for *external* CGM files to get the
ball rolling.  The benefit of a truly Public Domain CGM library is that
browser vendors can use it to do inline CGM, and other implementors can
use it to make value-added CGM viewers or to add CGM capability to
existing image viewers.

Inline CGM, in HTML 3.0 FIGures, would be a good enabling technology for
large sections of the scientific and engineering Web user community.  At
present there does not seem to be a clear leader in the various
competing technologies for helper application integration (W3A etc) so a
library is currently the best way to allow browser developers to add a
new inline graphics type.  

I hope that browsers will handle inline CGM files intelligently, ie allow
zooming, panning and paging operations. CGMs are not fixed raster images 
(although they may contain image data mixed in with the vector stuff).

-- 
Chris Lilley, Technical Author
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