Import RGB files

[arjunrajlab]

Would be great to import RGB histology files. It sounded like the easiest way to do this would be to create a multi-source JSON (I think, if I understood correctly) that would split up the file into channels (R, G, B). These channels would then be just imported as individual layers. which then could be put together as a grouped layer.

[manthey]

When the metadata for a WSI file returns a bandCount other than 1, then these can be used as multiple channels. For example, using one the TCGA svs files, the multi source yaml file might look like this:

---
  sources:
    - path: ./TCGA-02-0010-01Z-00-DX4.07de2e55-a8fe-40ee-9e98-bcb78050b9f7.svs
      style: {"bands": [{"band": 1}]}
      c: 0
      channel: "red"
    - path: ./TCGA-02-0010-01Z-00-DX4.07de2e55-a8fe-40ee-9e98-bcb78050b9f7.svs
      style: {"bands": [{"band": 2}]}
      c: 1
      channel: "green"
    - path: ./TCGA-02-0010-01Z-00-DX4.07de2e55-a8fe-40ee-9e98-bcb78050b9f7.svs
      style: {"bands": [{"band": 3}]}
      c: 2
      channel: "blue"

Note that bands are numbered starting at 1 (blame the geospatial community), but we start channels at 0.