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From "Philip Feldman" <pfeld...@proteus-technologies.com>
Subject RE: Acccessing pixels in an <image>
Date Tue, 02 May 2006 18:46:18 GMT
Sometimes ya just gotta touch pixels... This is for a panel that is
displaying a "high level view" of a large system - something on the
order of 100,000 - 200,000 points. It's far easier to put an image in
the display than to draw things directly. Think of it as a streaming
texture map.

Anyway, I'm wondering where you get the BridgeContext. Do I create a new
UserAgent and then a new BridgeContext? Or access the (protected)
JSVGCanvas.CanvasUserAgent somehow? Or is there an accesable
BridgeContext I can use directly?

Thanks!

Phil

> I am reading an image in as part of an SVG file that I need to do some

> processing on (changing the color of some pixels periodically). I see
that 
> Batik maps the <image> tag to an SVGOMImageElement. Is there any way 
> to
get at
> the pixels directly?

   It isn't very easy.  From the SVGOMImageElement you can use the
BridgeContext getGraphicsNode method to get the GraphicsNode that is the
'peer' to the Image element.  You can then poke around it's subtree, and
find the RasterImageNode child (assuming the image references a raster
format).  The RasterImageNode has a 'Filter' which is the image - but it
is a resolution independent view of the image.  You can get this
rendered to a fixed size and use the RenderedImage interface to get data
out of it.

   I would suggest that manipulations of the graphic display are best
done using svg rather than trying to twiddle raster images...


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