[gdal-dev] Test Failures

[Even Rouault]

> Do you have any idea why the differences exist? Is it worth investigating?

Quite likely subtle differences in behavior of the JPEG compression 
library. Mine on ubuntu 20.04 is libjpeg-turbo 2.0.3 with IJG libjpeg 8 
ABI. I presume if you built if from source and linked it against GDAL, 
you'd get the same checksums.

We should try to minimize tests using JPEG for that reason, but in that 
instance, this test is really meant to check JPEG specific code paths in 
the COG driver. Or use some kind of perceptualdiff test for such test, 
but the "perceptualdiff" utility does consider "your" and "mine" image 
to be different, so that wouldn't help. We'd probably need something 
clever that tolerates pixel values differences that can be quite 
important (the max here is a difference of 19 units) but detects there's 
no spatial shift.

>
> On Wed, Apr 28, 2021 at 8:35 AM Even Rouault 
> <even.rouault at spatialys.com <mailto:even.rouault at spatialys.com>> wrote:
>
>     Andew,
>
>     visually the difference between your image and the one generated
>     on my PC are almost indistinguishable (no spatial shift at least).
>     Please submit a PR adding your checksums as alternate accepted
>     ones. You may just remove the "if sys.platform == 'darwin'" case.
>     Hopefully adding your checksums should fix the OSX CI too
>
>
> -- 
> Andrew Bell
> andrew.bell.ia at gmail.com <mailto:andrew.bell.ia at gmail.com>

-- 
http://www.spatialys.com
My software is free, but my time generally not.

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