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Posted to batik-users@xmlgraphics.apache.org by Jean-Christophe Arnu <ar...@paratronic.fr> on 2005/06/22 12:20:53 UTC
getCurrentTranslate() getCurrentScale().... I'm confused!
Hi,
on the confusing road of transforms (once again) I would like to
know what is the coordinate system (element/user or viewport) I get
while using getCurrentTranslate() getCurrentScale() methods on the
document.getRootElement().
If I'm logical this should be in "user" coordinate system.
let's have an exemple :
The SVG file :
<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20000303 Stylable//EN"
"http://www.w3.org/TR/2000/03/WD-SVG-20000303/DTD/svg-20000303-stylable.dtd">
<svg xml:space="preserve" width="1024px" height="400px"
viewBox="617621.000000 1782627.700000 413374.400000 358857.300000" >
<g id="Carte" style="font-size:12;"
transform="matrix(1,0,0,-1,0,3924112.700000)" >
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</svg>
I use then zoom + pan interactor to view a part of this document.
When I apply getCurrentTranslate() I get the following point :
-6124.4717,-2116.2705
and getCurrentScale() : 7.4779873
What is the currentTranslate/scale coordinate system space?
How do I get real (cartographic) data (the one the viewBox is expressed
in) from my translation and scale?
I guess scale is ok (real zoom)
But what about the translate? (IIRC, I have to make some calculation
adding/substracting the viewBox coordinates). Are these translate/scale
bound to the viewport size or is it independant?
Does screenCTM has some relations to this?
I'm quite confused, I hope someone could give me some path to follow to
avoid asking such confused/dumb questions.
Thanks !
--
Jean-Christophe Arnu
Paratronic
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Re: getCurrentTranslate() getCurrentScale().... I'm confused!
Posted by Thomas DeWeese <Th...@Kodak.com>.
Jean-Christophe Arnu wrote:
> on the confusing road of transforms (once again) I would like to know
> what is the coordinate system (element/user or viewport) I get while
> using getCurrentTranslate() getCurrentScale() methods on the
> document.getRootElement().
>
> If I'm logical this should be in "user" coordinate system.
Current scale/translate is roughly the mapping between screen
pixels and the width/height attributes on the root svg Element.
> The SVG file: [...]
> <svg xml:space="preserve" width="1024px" height="400px"
> viewBox="617621.000000 1782627.700000 413374.400000 358857.300000" >
> I use then zoom + pan interactor to view a part of this document.
> When I apply getCurrentTranslate() I get the following point :
> -6124.4717,-2116.2705
> and getCurrentScale() : 7.4779873
>
> What is the currentTranslate/scale coordinate system space?
> How do I get real (cartographic) data (the one the viewBox is expressed
> in) from my translation and scale?
Use getScreenCTM on the root SVG element. This will give you
the matrix from the userspace (after the application of the viewBox)
to screen pixels. You can then use the inverse of this
(SVGMatrix.inverse()) to get the mapping from Screen to userspace.
> I guess scale is ok (real zoom)
> But what about the translate? (IIRC, I have to make some calculation
> adding/substracting the viewBox coordinates). Are these translate/scale
> bound to the viewport size or is it independant?
It is independent you could roughly divide the translate by the
scale to get the translation in terms of the width and height of
the SVG element (so you would have been looking at the lower right
hand corner of the content).
> Does screenCTM has some relations to this?
screenCTM is what you really want. Most people don't need
to muck with currentScale/Translate other than to tie into the
UserAgent's pan/zoom facilities.
> I'm quite confused, I hope someone could give me some path to follow to
> avoid asking such confused/dumb questions.
Well all of this is explained in the SVG specification.
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