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Posted to batik-users@xmlgraphics.apache.org by James Shaw <he...@btopenworld.com> on 2005/03/18 16:38:23 UTC
Using viewBox for unit conversion
I have been looking for a way to reflect an object about its y axis; I
understand that I need a transform matrix to do this, and that you
cannot translate by cms, ins or other units. The ppl on #svg
recommended using a viewbox.
I've checked on #svg, and I understand that a document like this:
<svg width="20cm" height="10cm" viewBox="0 0 200 100">
<line x1="0" y1="0" x2="20" y2="10" style="stroke: blue;
stroke-width: 1"/>
</svg>
should produce a drawing 20x10cms. However, when I preview this in
squiggle or a JSVGScrollPane, the drawing is about 80x40 pixels. I
would have expected batik to use the screen dpi (or similar measurement)
to correct render the document at 100% zoom.
Am I using viewBox incorrectly, or am I using Batik wrongly?
Thanks in advance
James Shaw
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Re: Using viewBox for unit conversion
Posted by Thomas DeWeese <Th...@Kodak.com>.
Hi James,
James Shaw wrote:
> That's what I would expect, but it doesn't seem to be the case for me --
> the document appears much smaller than I would expect.
If you are using your own frame you may need subclass the canvas and
implement the 'setMySize' method. Here is what the JSVGViewerFrame
does (from squiggle):
public void setMySize(Dimension d) {
setPreferredSize(d);
invalidate();
if (JSVGViewerFrame.this.autoAdjust) {
JSVGViewerFrame.this.pack();
}
}
>> Depending on how complex your object is you might try to use translate
>> and scale tranforms.
>> <svg width="20cm" height="10cm" viewBox="0 0 20 10"
>> style="fill:red;stroke:blue">
>> <g transform="translate(0,10) scale(1,-1)">
>> <line x1="0" y1="0" x2="20" y2="10" style="stroke: blue;
>> stroke-width: 1" />
>> </g>
>> </svg>
>>
>> Patrick
>>
> Thanks for this suggestion. I did try to use scale(1,-1) but it caused
> the object to disappear entirely (am I doing something really stupid
> here?)
I don't know if it's really stupid ;) but the translate is also
important other wise everything will be drawn in the negative
part of the coordinate system. The general thing is to translate
by the height of the viewing area (for vertical flip).
> Also, since switching from hardcoded cms to userspace coords,
> I've noticed discrepancies in line widths between the SVG viewed in a
> JSVGCanvas and via FOP (using the PDFTranscoder). To avoid these
> problems, I would really like to stick with centimetres and find a
> simple way of reflecting objects.
Use translate and scale together...
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Re: Using viewBox for unit conversion
Posted by James Shaw <he...@btopenworld.com>.
Patrick Egan wrote:
> Hi James,
> My understanding is the viewBox attribute defines a mapping between user
> space co-ordinates and the co-ordinates of the svg viewport, and in your
> case you are effectively scaling the image down by a factor of 10 ( 200
> user units=20cm and 100 user units = 10 cm).
That's what I would expect, but it doesn't seem to be the case for me --
the document appears much smaller than I would expect.
>
> Depending on how complex your object is you might try to use translate
> and scale tranforms.
> <svg width="20cm" height="10cm" viewBox="0 0 20 10"
> style="fill:red;stroke:blue">
> <g transform="translate(0,10) scale(1,-1)">
> <line x1="0" y1="0" x2="20" y2="10" style="stroke: blue; stroke-width:
> 1" />
> </g>
> </svg>
>
> Patrick
>
Thanks for this suggestion. I did try to use scale(1,-1) but it caused
the object to disappear entirely (am I doing something really stupid
here?) Also, since switching from hardcoded cms to userspace coords,
I've noticed discrepancies in line widths between the SVG viewed in a
JSVGCanvas and via FOP (using the PDFTranscoder). To avoid these
problems, I would really like to stick with centimetres and find a
simple way of reflecting objects.
Thanks
James Shaw
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Re: Using viewBox for unit conversion
Posted by Patrick Egan <pe...@gresham-forms.co.uk>.
Hi James,
My understanding is the viewBox attribute defines a mapping between user
space co-ordinates and the co-ordinates of the svg viewport, and in your
case you are effectively scaling the image down by a factor of 10 ( 200
user units=20cm and 100 user units = 10 cm).
Depending on how complex your object is you might try to use translate
and scale tranforms.
<svg width="20cm" height="10cm" viewBox="0 0 20 10"
style="fill:red;stroke:blue">
<g transform="translate(0,10) scale(1,-1)">
<line x1="0" y1="0" x2="20" y2="10" style="stroke: blue;
stroke-width: 1" />
</g>
</svg>
Patrick
James Shaw wrote:
> I have been looking for a way to reflect an object about its y axis; I
> understand that I need a transform matrix to do this, and that you
> cannot translate by cms, ins or other units. The ppl on #svg
> recommended using a viewbox.
>
> I've checked on #svg, and I understand that a document like this:
>
> <svg width="20cm" height="10cm" viewBox="0 0 200 100">
> <line x1="0" y1="0" x2="20" y2="10" style="stroke: blue;
> stroke-width: 1"/>
> </svg>
>
> should produce a drawing 20x10cms. However, when I preview this in
> squiggle or a JSVGScrollPane, the drawing is about 80x40 pixels. I
> would have expected batik to use the screen dpi (or similar
> measurement) to correct render the document at 100% zoom.
>
> Am I using viewBox incorrectly, or am I using Batik wrongly?
>
> Thanks in advance
> James Shaw
>
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> To unsubscribe, e-mail: batik-users-unsubscribe@xmlgraphics.apache.org
> For additional commands, e-mail: batik-users-help@xmlgraphics.apache.org
>
>
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