[cairo] [PATCH 0/3] test: Add test for image downscaling

Chris Wilson chris at chris-wilson.co.uk
Fri Jul 12 06:45:10 PDT 2013

On Fri, Jul 12, 2013 at 01:34:07AM +0000, Bryce W. Harrington wrote:
> Hi Chris, for the image downscaling patch Krzysztof Kosiński posted
> a few weeks ago, you mentioned we'd need some corresponding
> tests.  I've taken a shot at that; this patchset includes some simple
> tests for three scaling factors, for each of the filter options.
> I plan to also do downscaling with skew and repeat, but wanted to post
> what I have for your review before I get too far along.  In particular,
> I'm curious what I should do for the reference images; I generated them
> using Gimp as 'truth' but the anti-aliasing results are different, and
> I'm not sure what should be taken as correct behavior.

In this case a visual check that pixman outputs something that looks
reasonable and then use its output as the reference. We can expect to
have discrepancies between all the backends as par for the course.

As for checking that pixman is accurately applying the convolution
matrix, we should write a reference test for pixman comparing use of
the public with manual/alternative computation of the convolution
resampling for a few pixels. And then add as a possible option to
the composite check so that it is part of the randomised smoketesting of
pixman's parameter space.

Chris Wilson, Intel Open Source Technology Centre

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