Update hemisphere slicing

[IgorTatarnikov]

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Description

What is this PR

• [x] Bug fix
• [ ] Addition of a new feature
• [ ] Other

Why is this PR needed? See the discussion in https://github.com/brainglobe/brainglobe-atlasapi/issues/330

What does this PR do? If the atlas is marked as symmetrical in the metadata the midpoint is now calculated by taking the mean of the root mesh bounds for each axis. If the atlas isn't marked as symmetrical the previous behaviour is maintained.

References

https://github.com/brainglobe/brainglobe-atlasapi/issues/330

How has this PR been tested?

Tested locally by visual inspection. For an asymmetric atlas:

scene = Scene(atlas_name="mpin_zfish_1um")
scene.add_brain_region("hindbrain", hemisphere="right")
scene.add_brain_region("forebrain", hemisphere="left")
scene.render()

For symmetric atlases:

scene = Scene(atlas_name="allen_cord_20um")
scene.add_brain_region("WM", hemisphere="left")
scene.render()

scene = Scene(atlas_name="allen_mouse_25um")
scene.add_brain_region("CTX", hemisphere="left")
scene.render()

Is this a breaking change?

No

Checklist:

• [x] The code has been tested locally
• [x] The code has been formatted with pre-commit

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.06%. Comparing base (9cd07c8) to head (89ffcaf). Report is 1 commits behind head on main.

Files	Patch %	Lines
brainrender/scene.py	80.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #375 +/- ## ========================================== - Coverage 88.13% 88.06% -0.08% ========================================== Files 27 27 Lines 1214 1215 +1 ========================================== Hits 1070 1070 - Misses 144 145 +1 ```

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[adamltyson]

Thanks @IgorTatarnikov! This looks good to me, but I won't review until it's marked as "ready for review".

I checked, and it also fixes this image.sc issue.

[IgorTatarnikov]

I unmarked it because this approach fails with the new axolotl atlas, so I was going to do some more investigating!

[IgorTatarnikov]

This fix works appropriately if the axolotl and other asymmetric atlases have the correct metadata tag. I've opened https://github.com/brainglobe/brainglobe-atlasapi/issues/359 to track this issue. However, I believe this PR is ready to go in.

[adamltyson]

Great, thanks @IgorTatarnikov. I'll merge this then release.