Re: Image formats deleted from 3.0?

lilley (lilley@afs.mcc.ac.uk)
Tue, 4 Jul 1995 11:51:18 +0100 (BST)


From: lilley <lilley@afs.mcc.ac.uk>
Message-Id: <4270.9507041051@afs.mcc.ac.uk>
Subject: Re: Image formats deleted from 3.0?
To: wbrooks@trumpet.aix.calpoly.edu (Bill Brooks)
Date: Tue, 4 Jul 1995 11:51:18 +0100 (BST)
Cc: www-html@www10.w3.org
In-Reply-To: <Pine.A32.3.91.950704011500.137605A-100000@trumpet.aix.calpoly.edu> from "Bill Brooks" at Jul 4, 95 01:18:27 am

Bill Brooks said:
> HTML 1.0 specified that image formats should be one of .xbm or .gif.

It was not in the 1.0 "spec", it was in the NCSA documentation if I recall 
correctly. And the three supported image formats were GIF87, XBM, and 
NCSA HDF.

Remember that this was originally a browser specific extension to permit 
an HTML browser to be used in a distributed collaborative Sci Vis environment.

There has never been any standardisation of the supported image formats 
because in theory the browser is supposed to specify what formats it can 
understand, per request, in the accept headers (so it becomesan HTTP issue, 
not an HTML issue).

In practice of course, people generate what they see being widely used and 
servers rarely perform image format conversion - probably as well, since it 
is not trivial and the quality, expiry and consistency issues were never 
talked abnout very much.

So in practice:

GIF87 and 89 are currently almost universally supported. 
XBM is now widely supported but is a fairly poor format for most uses. 
XPM is used by some browsers. 
JPEG is widely used, now that Netscape and Mosaic on most platforms can 
 display inline JPEG one could count it a reasonable choice for inline images
TIFF, EPS, RLE, CGM, IrisRGB etc are not widely supported inline
PNG is not currently widely supported inline

> But I can't find anything in the 3.0 standard that says whether or not 
> JPEG is a supported format. Was this intentional? Or was it just to get 
> around the whole .gif vs. .png issue? Maybe it's in some other section 
> than where I expected to find it. Help me out. 

It is not there, and I suspect it is not likely to be. Go ahead and use 
it; you will not be in conflict with either the spec or with current 
practice.

--
Chris Lilley, Technical Author
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