Missing `pillow` dependency? [ngio 0.4.2]

[tcompa]

PIL is imported directly

ngio/src/ngio/images/_create_synt_container.py

Line 6 in 59d759a

import PIL.Image

but it is not available in pyproject.toml.

[observed at https://github.com/fractal-analytics-platform/fractal-task-tools/actions/runs/18781266951/job/53587799899]

[jluethi]

I've hit the same when running tests with ngio locally. The PIL imports don't appear to make an issue for any of the ways we typically use ngio when running tasks though.

@lorenzocerrone Are these synthetic Zarr containers are only meant to be used in tests (=> an optional dependency, we should figure out how to communicate this) or are they meant to be a library feature? If they are a library feature, we should add PIL to the dependencies :)

[jluethi]

@lorenzocerrone This is broader, because this module is loaded upon init of ngio.images (see https://github.com/BioVisionCenter/ngio/blob/59d759ae41bb85a5ccb20b615b2abcfd70dcea05/src/ngio/images/__init__.py)

=> we need to either make PIL a ngio dependency, handle the import better or not include create_synth_ome_zarr in the init

[lorenzocerrone]

For now, I suggest simply adding PIL as a dependency.

I think in the next major version we should start compartmentalizing dependencies better and add a few extras.