[cairo] A better image comparison tool
taraben.a at st-innovation.com
Wed Sep 24 00:51:10 PDT 2008
in the Inkscape team we had a GSOC project that set-up some rendering
tests. Currently there is only binary compare of the images (sounds
There is also a tool for perceptual image difference
I think/assume that this tool detects only "visible" differences using
hard stuff mathematics ;-) You might look at this tool too.
1.) perceptualdiff does not handle transparency in images.
2.) Also what I need is to define some exclude and/or include regions.
- Some test images have text that I would not like to take into
- Or I would like to specifically point to that line-caps only.
Those are my 2ct :-)
Antoine Azar wrote:
> Hey all,
> this is something we discussed during the Cairo Summit, and I wanted to
> take some feedback and ideas on the list before I start working on it.
> The idea is to have a better image comparison tool in the Cairo test
> suite instead of simply checking for any pixel discrepancy. Carl pointed
> out we currently have several reference image sets to compensate for
> differences across backends. Such a tool would ideally eliminate these
> multiple images as much as possible. Another advantage of such a tool
> would be some integration in the build/test bot machines Mozilla is
> setting up. If a given patch changes the results of a render in a (new)
> correct way, instead of seeing a broken test suite, we would see e.g. a
> 90% similarity score for the given test.
> I am considering a couple approaches. The first one I want to try out is
> a pretty simple square sum of differences or sum of absolute
> differences. There are more fancy algorithms like cross correlation and
> mutual information, which I'll probably try out too. We can then set
> custom thresholds for what should appear as "OK", "Warning" and "Error".
> cairo mailing list
> cairo at cairographics.org
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