[cairo] SVG Misunderstanding?

[Travis Griggs]

I apologize for this being possibly off topic. I'm trying to use Cairo  
to draw an SVG file (the one attached for example). And something's  
not going right. I must be missing something obvious.

When rendered as an icon from Inkscape, I end up with a 16x16 icon,  
with 9 little orange gradient squares. They're nicely pixel aligned to  
keep it crisp. If I understand the SVG correctly, I should be able to  
do the following cairo stuff in pseudo code:

// These values derived from the height/width and the viewBox of the  
root svg node
scale( cr , 16 / 64.424 , 16 / 51.278 );
// apply the transform found at the g4466 node
matrix.xx = 0.6031636;
matrix.yx = 0;
matrix.xy = 0;
matrix.yy = 0.6190702;
matrix.x0 = 7.87836;
matrix.y0 = 5.1860675;
set_matrix( cr , &matrix );
// rect3654
rectangle(cr,
	-5.9716139,
	-15.317435,
	-5.9716139 + 28.360464,
	-15.317435 + 27.631762);
//set a source and fill after this

Unfortunately, this doesn't end up right. If I work the numbers by  
pencil myself, at least for the origin of the rectangle, I get:

(-5.9716139 * 0.6031636 + 7.87836) * (16 / 64.424) --> 1.06209
(-15.317435 * 0.6190702 + 5.1860675) * (16 / 51.278) --> -1.34061

I could almost believe that the 1.06 was just rounding error (rather  
severe actually), but the y value shouldn't be negative at all, and  
it's not at all near integral.

I don't know what I'm doing wrong. I'm wondering at this point, if  
I've mixed something in the application of viewBox.

Any helps or hints would be hugely appreciated.

--
Travis Griggs
Objologist
One man's blue plane is another man's pink plane.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: Array.svg
Type: image/svg+xml
Size: 301695 bytes
Desc: not available
Url : http://lists.cairographics.org/archives/cairo/attachments/20091021/204c032d/attachment-0001.svg