Fixed combination of rgb images not working and colorbounds not working for rgb images.

[CassandraAuri]

Hey Mike,

Just need to write tests and will do a pull request. eta week or 2. Selecting color bounds did nothing with rgb images and selecting only 'rg' returned nothing.

[mshumko]

Hi @CassandraAuri,

Thanks for pointing out this inconsistent behavior with the RGB images. Can you share the asilib version that you're using, and a minimal example that we can both run and compare resulting images?