feat: reverse-populate OMEZarrMultiscale class with omero metadata on read

[jo-mueller]

Small PR to make sure that we can extract OMERO Metadata via the OMEZarrMultiscale classes. For context:

In the write direction, we can pass contrast_limits, channel_names, channel_colors arguments to the OMEZarrMultiscale class, which are translated into appropriate omero metadata entries. On read, this isn't possible, though. This PR adds minimal translation to the reader path of the OMEZarrMultiscale class.

TODO:

• testing

[codecov]

Codecov Report

❌ Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.49%. Comparing base (e65666e) to head (56d484e).

Files with missing lines	Patch %	Lines
ome_zarr/classes/image.py	89.47%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #607      +/-   ##
==========================================
+ Coverage   86.46%   86.49%   +0.02%     
==========================================
  Files          16       16              
  Lines        2365     2384      +19     
==========================================
+ Hits         2045     2062      +17     
- Misses        320      322       +2     

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[will-moore]

Might be nicer to use np.iinfo to get the min/max as these will distinguish e.g. unit8 from int8 etc:

>>> a = np.array([1,2,3], dtype="int8")
>>> np.iinfo(a.dtype).min
-128
>>> np.iinfo(a.dtype).max
127
>>> a.dtype.itemsize * 255
255

But we need different handling for floats, using np.finfo and cast np value to float:

>>> a = np.array([1,2,3], dtype="float64")
>>> np.finfo(a.dtype).min
np.float64(-1.7976931348623157e+308)
>>> float(np.finfo(a.dtype).min)
-1.7976931348623157e+308
>>> float(np.finfo(a.dtype).max)
1.7976931348623157e+308

The other possibility here, which is used in e.g. vizarr and ome-zarr.js is to use the actual min and max values of the smallest resolution array to provide the start and end values if they're missing.

[jo-mueller]

The other possibility here, which is used in e.g. vizarr and ome-zarr.js is to use the actual min and max values of the smallest resolution array to provide the start and end values if they're missing.

That's a neat idea 👍