Source information can be lost when ROIs generated from one source are applied to another.

[jimfinnis]

ROIs controlling image operations can have sources which do not contribute to the source set!

For example:

• Create an RGB image
• Create a dqmod node to set a DQ bit when the R channel is >0.5
• Create an roidq node to generate an ROI from this DQ bit
• Create an expr node doing "a$G * 10".
• The output will be the green channel, but with parts where the corresponding value in the red channel is more than 0.5 multiplied up.

In that output, the sources should probably be R,G because the image was generated from data in those two bands (G for the pixel values, R for the multiplication mask). It is just G.

[jimfinnis]

For the time being I'm going to "fix" this by adding a warning to the roidq box. But this could potentially also happen with just error bits:

Error bits limit calculation. Suppose we set an error bit on ALL bands if ANY band has a dodgy pixel. That means that calculations on any band which involves those bad pixels will be using information generated from all bands.

I'd better add a comment to the dqmod node as well. And add that as a separate issue.