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Availability of image metadata

From: Jim Ley <jim@jibbering.com>
Date: Mon, 22 Jul 2002 20:52:10 -0000
Message-ID: <059a01c231c1$a6961ce0$ca969dc3@emedia.co.uk>
To: <www-svg@w3.org>

Hi,

When including an raster image, there's no way of accessing the metadata
of the image (content-type, height, width, etc.)  Not knowing
height/width of raster images I've already complained about in previous
messages, the content-type is also relevant though.

(Firstly I'm making the assumption that the svg (or other XML based image
format) images DOM is available as a child of the image element in the
parent as even though I can't find a clear statement on this, the
alternative doesn't meet SVG's accessibility features.)

Accessing of content-type is essential to know if the image is being
handled by a new viewport or by scaling of a raster image, also it's
useful to know if the included image is an XML document and if so what
flavour of XML. (SVG, or A.N.Other image type, and the version of each.)
having content-type in the DOM would also be useful for AT's which may
have other tools for particular content-types, which could be brought
into play.

Aswell as this basic metadata though, there is also more complex metadata
stored in images, notably in the Adobe XMP format which embeds RDF
metadata inside the blocks, tools such as the W3's RDFPic and Adobes own
tools can generate such XMP [1] blocks.  I'd like this available because
of the options it opens up, and the simple implementation (with a 5 line
perl script you can add it to SVG/Batik, but that relies on the server
loading the image aswell as the client, which is obviously not the same.)

SVG accessibility requires metadata currently, both
http://www.w3.org/TR/SVG-access/ and Ivan Hermann et al.'s more recent
work rely on it.  As the very same RDF vocabulary can be used to describe
raster images or videos (or flash) it would be very useful from an
accessibility standpoint to have the metadata available directly within
the DOM.

Jim.

[1] XMP - http://www.adobe.com/products/xmp/main.html
Received on Monday, 22 July 2002 16:56:19 GMT

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