Pekka Paalanen 97359ba5c5 tests: add output transform tests ...

This goes through all output transforms with two different buffer transforms
and verifies the visual output against reference images.

This commit introduces a new test input image 'basic-test-card.png'. It is a
small image with deliberately odd and indivisible dimensions to provoke bad
assumptions about image sizes. It contains red, green and blue areas which are
actually text that makes it very obvious if you have e.g. color channels
swapped. It has a white thick circle to highlight aspect ratio issues, and an
orange cross to show a mixed color. The white border is for contrast and a 1px
wide detail. The whole design makes it clear if the image happens to be rotated
or flipped in any way.

The image has one pixel wide transparent border so that bilinear sampling
filter near the edges of the image would produce the same colors with both
Pixman- and GL-renderers which handle the out-of-image samples fundamentally
differently: Pixman assumes (0, 0, 0, 0) samples outside of the image, while
GL-renderer clamps sample coordinates to the edge essentially repeating the
edge pixels.

It would have been "easy" to create a full matrix of
every output scale & transform x every buffer scale & transform, but that
would have resulted in 2 renderers * 8 output transforms * 3 output scales *
8 buffer transforms * 3 buffer scales = 1152 test cases that would have all
ran strictly serially because our test harness has no parallelism inside one
test program. That would have been slow to run, and need a lot more reference
images too.

Instead, I chose to iterate separately through all output scales & transforms
(this patch) and all buffer scales & transforms (next patch). This limits the
number of test cases in this patch to 56, and allows the two test programs to
run in parallel.

I did not even pick all possible scale & transform combinations here, but just
what I think is a representative sub-set to hopefully exercise all the code
paths.

https://gitlab.freedesktop.org/wayland/weston/issues/52

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

2020-02-28 15:07:51 +02:00

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