In imsave, let pnginfo have precedence over metadata. by anntzer · Pull Request #15434 · matplotlib/matplotlib · GitHub
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In imsave, let pnginfo have precedence over metadata. - #15434

Merged
tacaswell merged 2 commits into
matplotlib:v3.2.xfrom
anntzer:imsave-priority
Oct 19, 2019
Merged

tacaswell merged 2 commits into
matplotlib:v3.2.xfrom
anntzer:imsave-priority

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@anntzer

@anntzer anntzer commented Oct 17, 2019

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This is consistent with the documented behavior ("If the 'pnginfo' key
is present, it completely overrides metadata, including the default
'Software' key.") and also with the behavior of
FigureCanvasAgg.print_png, cf

The feature came in in #13902 which is not in any released version so far, so it would be nice if this was fixed before the final 3.2 release. I will prepare a separate PR for master.

PR Summary

PR Checklist

  • Has Pytest style unit tests
  • Code is Flake 8 compliant
  • New features are documented, with examples if plot related
  • Documentation is sphinx and numpydoc compliant
  • Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
  • Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

This is consistent with the documented behavior ("If the 'pnginfo' key
is present, it completely overrides *metadata*, including the default
'Software' key.") and also with the behavior of
FigureCanvasAgg.print_png.
@anntzer anntzer added the Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions. label Oct 17, 2019
@anntzer anntzer added this to the v3.2.0 milestone Oct 17, 2019
@timhoffm

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Is #13092 really the relevant issue here?

Comment thread lib/matplotlib/image.py Outdated
"RGBA", pil_shape, rgba, "raw", "RGBA", 0, 1)
if format == "png" and metadata is not None:
if (format == "png"
and metadata is not None and "pnginfo" not in pil_kwargs):

@timhoffm timhoffm Oct 17, 2019

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Silently ignoring metadata if pnginfo is present does not feel right. Can we raise or warn in that case, or are there subsets of metadata that may still be needed?

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print_png (used by savefig("foo.png") has had this behavior ever since pil_kwargs is supported (which is 3.1), and no one has complained about it so far (it probably hasn't been too much used yet in the wild, though); I'd rather keep both places in sync.
Also a verb is missing in your sentence ("Can we ???").

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Fixed the missing verb. I'd be happy to warn in both places. Raising would now be a breaking change.

I wouldn't expect too much complaint. It's not widely used, it will only happen if you provide both parameters. It might actually have affect users without them realizing it.

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sure, added a warning in both places.

@anntzer

anntzer commented Oct 17, 2019

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edited: the correct original PR was #13902.

@tacaswell
tacaswell merged commit d687c21 into matplotlib:v3.2.x Oct 19, 2019
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@anntzer
anntzer deleted the imsave-priority branch October 20, 2019 08:19
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3 participants