[jdotc1]

ImageOps.contain() returns a newly created image when the result has zero width or height. For palette images this loses both palette state and transparency, so pad() can fill a very thin image with opaque black instead of the selected palette color.

Use a zero-area crop in the three empty-return branches. This preserves the existing output dimensions while carrying the source palette and metadata through the established copy path. Add synthetic regressions for P/PA images, RGB/RGBA palettes, transparent indices, full-palette allocation, and lazy PNG/GIF input, plus a release note.

Validation on Python 3.12 with the native core built from this source revision:

• The new regression selection produces 11 expected failures and one passing control before the fix.
• python selftest.py: 59 passed.
• python -m pytest -q Tests/test_imageops.py: 72 passed.
• Crop, palette, PNG and GIF modules: 219 passed.
• Applicable pinned pre-commit hooks pass on all three changed files; mypy passes for the production and test modules.
• The complete patch applies to a clean source checkout and the ImageOps tests pass there.

The empty paths now call load() through crop(), including for non-paletted sources. Lazy images can therefore incur decoding work or raise decoder errors that the previous empty shortcut bypassed. The full optional-codec/platform matrix was not executed locally.

CI follow-up: correct the release-note heading underline and move the MinGW job to MSYS2 UCRT64, including all dependency prefixes. The MINGW64 repository no longer supplies python-pyqt6; UCRT64 supplies it and all 18 other dependencies used by this job. This retains Qt test coverage. The changed release-note section builds with Sphinx warnings treated as errors, sphinx-lint passes, and the workflow passes GitHub Actions schema validation. Windows runtime validation remains with hosted CI.

[radarhere]

This PR is a sequel to #9673. Your concerns about ImageOps.contain() also apply to fit() and cover(), so I've pushed fixes for them as well.

I don't think this needs release notes. Creating an empty image in ImageOps contain() is pretty niche, and doing anything afterwards that would use palettes or transparency is even more niche.

[radarhere]

I appreciate the attempt to fix MinGW, but it's a bit out of scope for this PR.

[radarhere]

I cherry-picked your MinGW commit into #10300