Add support to single channel images in visualization tool.
Add support to single channel images in visualization tool.

PiperOrigin-RevId: 190996725

tombstone/models,tombstone/models,cshallue/models,alexgorban/models,derekjchow/models,cshallue/models,alexgorban/models,alexgorban/models,tombstone/models,derekjchow/models,alexgorban/models,tombstone/models,tombstone/models,derekjchow/models,derekjchow/models,cshallue/models,cshallue/models,alexgorban/models,tombstone/models,cshallue/models,derekjchow/models