[Pkg-gmagick-im-team] Bug#1105051: imagemagick breaks xplanet autopkgtest: test_compare_images() returned non-zero return code

[Jochen Sprickerhof]

Hi,

* Paul Gevers <elbrus at debian.org> [2025-05-10 14:24]:
>With a recent upload of imagemagick the autopkgtest of xplanet fails 
>in testing when that autopkgtest is run with the binary packages of 
>imagemagick from unstable. It passes when run with only packages from 
>testing. In tabular form:
>
>                       pass            fail
>imagemagick            from testing    8:7.1.1.47+dfsg1-1
>xplanet                from testing    1.3.1-3
>all others             from testing    from testing
>
>I copied some of the output at the bottom of this report.
>
>Currently this regression is blocking the migration of imagemagick to 
>testing [1]. Due to the nature of this issue, I filed this bug report 
>against both packages. Can you please investigate the situation and 
>reassign the bug to the right package?

There are multiple problems:

1. imagemagick changed the output of compare in 7.1.1-44 (d85a7583f) 
    from some number <= 1 with 1 meaning the images are the same two two 
    numbers where the first is the distortion and the second one is the 
    old percentage in parenthesis. This breaks the test code in 
    https://sources.debian.org/src/xplanet/1.3.1-3/debian/tests/compare-create-image/#L32
    I assume that the new format will be kept so xplanet should adopt the 
    logic. Maybe something like:

    result_jpg="$( compare -metric ncc $AUTOPKGTEST_TMP/expected/$filename.jpeg $AUTOPKGTEST_TMP/$filename.jpeg $AUTOPKGTEST_TMP/diff.jpg 2>&1 | sed 's/.*(\(.*\))/\1/' )"

2. imagemagick in stable returns values below 0 for similar but 
    different images. I did not check if this was different in older 
    versions but I would expect so, given that the autopkgtest code 
    checks the value for >0.99. This has been corrected by multiple 
    patches in imagemagick git main.

3. imagemagick in unstable has a bug resulting in the same picture 
    getting a percentage of 0 and different images a value of > 1. This 
    has also been corrected in imagemagick git main (912b6a838).

4. The results of earth_markers.* in the compare-create-image 
    autopkgtest improved (not sure due to what) so the files in 
    debian/tests/expected/earth_markers.* need to be replaced.

I think we have to accept that the output of compare is not stable and 
adopt xplanet. I see two options what to do:

a. Adopt the xplanet to cope with any output of compare. This could be 
    either by just using the return value, hoping that the output on 
    different architectures is stable nowadays (I did not test this) or 
    by adding logic that only compares the number in case the return 
    value is not 0 (perfect match) and then try to interpret the 
    number(s).

b. Apply the imagemagick patches from git main and use the call from 1. 
    above.

Cheers Jochen
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