feature request: python version dependent reference images

hi! I have a project with a CI/CD pipeline that runs pytest across different python versions, and today ran into a rather annoying issue where the matplotlib images on py3.10 are slightly different from py3.13 (text being offset by a few pixels). Now, if I regenerate the reference images on 3.10, the tests on 3.13 will fail, and the other way around as well.

I was hoping to be able to add python-version dependent reference images. Something like

@pytest.mark.mpl_image_compare(baseline_dir="baselines/{py_version}")
def test_my_plot():
...

which would detect the python version. Then the user (me) could run

pytest --mpl-generate-path=baselines/3.10

and

pytest --mpl-generate-path=baselines/3.13

if i need version dependent reference images.

edit: matplotlib 3.11 introduced a new text renderer that causes the mismatching images. The release notes https://matplotlib.org/stable/release/prev_whats_new/whats_new_3.11.0.html#fonts-and-text highlight a few workarounds. Adding here in case someone stumbles on this issue.

Start by tracing the mpl_image_compare decorator and the --mpl-generate-path option mentioned in the issue. Determine how baseline paths are currently resolved, then define how Python-version-specific paths should be selected and generated; done means separate baselines such as baselines/3.10 and baselines/3.13 can be used without cross-version comparison failures.