Storing only a label mask image

[tischi]

@joshmoore @constantinpape

With the current specs, is it possible to only store labels without an image?

└── image.zarr                 
    │
    └── labels
        │
        ├── .zgroup
        │
        ├── .zattrs        

[joshmoore]

I believe so though I don't think it's clearly stipulated. @DragaDoncila and @jni may already be doing this and can say more. I think the primary downside in the current spec is that if you do that, it would be difficult to add the image back into the same fileset at a later date. Of course, if you're going to use the (future) remote links (https://github.com/ome/ngff/issues/13) then it would be fine.

[DragaDoncila]

Sorry for the delayed reply on this! You can indeed store label files exclusively. We were doing this more than 6 months ago now, so the metadata structure may have changed, but we were storing a multiscale label image without the labels subdirectory, specifically:

└── label_image.zarr                 
    │
    └── 0
    │
    └── 1
    |
    └── ...
    │
    ├── .zgroup
    │
    ├── .zattrs 

With .zattrs specifiying the `"multiscales" and "image-label" members.

[tischi]

Thanks @DragaDoncila! @joshmoore so the labels sub-directory is not mandatory?

[joshmoore]

For an image to be a label, no. For an image to have labels, currently yes.