Re: wherefore CGM?

David Perrell (
Sun, 8 Dec 1996 13:30:37 -0800

Message-Id: <>
From: "David Perrell" <>
To: "Joel N. Weber II" <>,
Cc: <>
Subject: Re: wherefore CGM?
Date: Sun, 8 Dec 1996 13:30:37 -0800

Joel N. Weber II wrote:
> Note also that encapsulated postscript files often include a preview;
> essentially they store the postscript code needed to generate a
> high-quality image as well as a bitmap.  Try two versions of the
> postscript, one with a preview and one without.  So that brings
> the total to twelve formats.

Moving back to the original argument...

Binary CGM is a relatively compact representation of 2D objects on a
plane, and includes vectors, regular shapes, spline curves, and bitmap
tiling. It's good for representing images composed of lines and filled
shapes. Diagrams and maps that now must be represented as huge bitmaps
could be a fraction of the size in CGM, and users could zoom into such
drawings for greater detail.

3DMF may be an efficient representation of both 2D and 3D objects, but
all objects exist in a 3D coordinate system. In addition to object
shape and color, surface characteristics, viewport, and lighting must
be considered.

The next version of PostScript may have a more efficient binary
incarnation, but CGM might still have more pre-defined elements and
therefore smaller file sizes.

I still say universal graphical UA support for inline CGMs would be a
good thing (though if the spec is unavailable anywhere but from the
grasping toll-takers of the ISO I might reconsider).

David Perrell