[cairo] SVG viewBox misunderstanding
Travis Griggs
tgriggs at cincom.com
Thu Oct 22 21:45:58 PDT 2009
Carl's response, and some further discussion in irc helped me get to
the bottom of things, kind of.
Carl's svg2png trace showed that the svg file does represent the icon
properly, which isn't a surprise (I've attached a lighter/trimmed
version of it again).
What the trace shows is a singular matrix set:
[0.141041 0 1.842245
0 0.144761 3.217366 ]
What I don't get is how it came to that conclusion, *in particular*
the yy value. The 3 inputs from the svg file are:
viewBox ( 0 0 64.424 51.278 )
width&height 16
additional transform matrix (0.6031636, 0, 0, 0.6190702, 7.87836,
5.1860675)
If one runs the number for the XX component of the matrix, it should
be 16 / 64.424 * 0.6031636. Which it is. It's correct. But if one does
16 / 51.278 * 0.619072, it is NOT 0.144761. What seems to be correct,
is to ignore the height of the viewBox attribute, and use the width as
the height instead: 16 / 64.424 * 0.619072.
So what I don't understand, and am begging any SVG gurus to explain,
is why the 64.424 is used for both width and height. That's obviously
what I'm supposed to have done here, but I don't get *why*. I looked
around in librsvg a *little* and didn't see anything obvious right away.
TIA
--
Travis Griggs
Objologist
My Other Machine runs OSX. But then... so does this one.
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