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[Bug 5560] Image inclusion with <image> depends on referent's coords

From: <bugzilla@wiggum.w3.org>
Date: Tue, 11 Mar 2008 22:28:26 +0000
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To: www-svg@w3.org
Message-Id: <E1JZCxO-0002k2-TL@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=5560

           Summary: Image inclusion with <image> depends on referent's
                    coords
           Product: SVG
           Version: SVG 1.1 Full
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Coordinate Systems
        AssignedTo: schepers@w3.org
        ReportedBy: mark@kli.org
         QAContact: www-svg@w3.org


You can include an image in an SVG, and if it is a raster image, you can
specify its size and position in the local (referring) SVG's coordinate system
and everything will scale just right no matter what size the actual PNG is. 
e.g., <image x="-50" y="-50" width="100" height="100" xlink:href="pic.png"/>
will have the picture centered on (0,0) in the current co-ordinate system and
stretching from -50 to 50 in whichever dimension is its largest, no matter how
big pic.png really is.  This cannot be done if the included image is an SVG,
making SVGs actually *less* scalable and portable than raster images, which
seems to defeat their purpose.  The specs say:

"The value of the 'viewBox' attribute to use when evaluating the
preserveAspectRatio attribute is defined by the referenced content. For content
that clearly identifies a viewBox (e.g. an SVG file with the 'viewBox'
attribute on the outermost svg element) that value should be used."

Which is probably necessary for some applications, but it should be defeasible.
 There ought to be a way for the referring SVG to force the viewBox to be
scaled into its own co-ordinates, so we can do the same sort of thing as can be
done with raster images.  The SVG being included might not be under the same
control and authorship as the referring SVG, and the spec seems to assume it
is.  Maybe something like a "useLocalCoords='yes'" attribute or something?
Received on Tuesday, 11 March 2008 22:28:34 GMT

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