Hello Jasper,
Wednesday, October 16, 2013, 9:20:46 AM, you wrote:
The W3C reference images are (if I remember correctly, and this may have changed with the new test suite) essentially unsuitable for automated testing with Inkscape.
Yes, they are not intended for regression testing. In particular SVG allows the 0.5 pixel slop on "where is the middle of the pixel" and also does not specify anti-aliasing algorithms, text hinting, and suchlike which will produce per-implementation differences.
There are simply too many small differences between Inkscape and what they used (Batik I think)
Batik if it passes. Something else (another renderer, or a patch SVG that gives the correct result) if not.
to make a direct comparison. The one pixel off rule might help (if we implemented something for using that), but since Inkscape is systematically half a pixel off compared to Batik... Inkscape considers a pixel to be at (x+0.5,y+0.5) while Batik considers it to be at (x,y), if I'm not mistaken (just compare the black border around the tests to see what I mean).
If you are making your own version of the test suite, have you considered wrapping everything in a
<svg start tag copied from the test> <g transform="translate(-0.5,-0.5)"> svg the test here </g> </svg>