Z-downsampling metadata

[will-moore]

It's possible that we may generate multiple "datasets" for a given OME-Zarr Image, e.g. with and without down-sampling in Z. It could be useful to have a way to identify these.

See hms-dbmi/vizarr#71 (comment)
"will there be any way to distinguish between the downsampled-in-z version of a dataset and the non-downsampled version? The shape of the zarr array, I presume? But will there be any metadata about it? Just curious........."

@joshmoore "One thing we could do at the moment (pre-lightsheet changes) would be to have a naming convention for the multiscales themselves. Another option would be to use the metadata for the method of the downsampling, but we’d need something well-defined to say “in-z".

[ilan-gold]

Just out of curiosity @will-moore @joshmoore, what are the "lightsheet changes?"

[joshmoore]

Hi @ilan-gold. The next body of work is focused around having better support for large 3D volumes. We'll likely use the opportunity to make the first breaking changes to the metadata (0.1 --> 0.2) so if there's something that's needed (e.g. the way to detect the z-downsampled multiscale zgroup as you were asking in hms-dbmi/vizarr#71 (comment)) then it would be good to roll them into the "lightsheet changes".

[ilan-gold]

Gotcha @joshmoore, I know @will-moore and I talked on image.sc about scaling as well, derived from the reported physical size, so that would be great too in the next change. We are very interested in this 3D stuff as well so I'll keep my ear to the ground.

[constantinpape]

The downsamplling is now specified using coordinateTransformations:scale in v0.4; so the downsampling across all spatial dimensions is transparent.