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SVG 1.2 10 Alternate content based on display resolutions

From: Jim Ley <jim@jibbering.com>
Date: Fri, 9 May 2003 08:34:29 -0000
To: www-svg@w3.org
Message-ID: <b9g2te$er0$7@main.gmane.org>

I think in general the Alternate content section could be simply extended to
cope with low bandwidth aswell as different display resolutions - it may
also be possible to extend it in such a way that you can specify different
images for different sub-regions for when zooming in/out without forcing the
download of a complete more accurate map and the bandwidth costs of that.
(basically doing what we do in Level-of-Detail script changing situations)

Exactly how that extension might be managed I'm not sure...  For the
bandwidth case, a simple advisory content-size attribute on the subImage
element would provide a hint to the UA, which it could then use in the
decision making process.

For the more complicated LOD regional part, then the subImage elements could
also have x/y/w/h  attributes defining the region of the parent Image
element that they refer to, looking something like this:

<image x="200" y="200" width="100px" height="100px"
         min-pixel-size="1" max-pixel-size="1"
    <subImage xlink:href="myimage-lg.png"
              min-pixel-size=".5" max-pixel-size=".5"
              x="25px" y="25px" height="50px" width="50px">
       <desc>An alternative image for the central portion of the parent

The UA can then choose to switch to the subIamge if the zoomed region would
be better served by it.  This would give us Level-of-detail functionality
without needing scripting.

What would happen in situations where the zoom overlaps regions which don't
have a subImage is something else I don't know about, rendering both images
would be possible, or you could just use the parent one.

Received on Friday, 9 May 2003 08:40:50 UTC

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