Hi,
Channel mixing is very basic and important technique in color adjustment. I think camera matrix in raw processors is for it. However traditional channel mixer UI is simply reflected color mixing matrix as below and IMHO difficult for using. Because it is not intuitive for human.
To solve this problem, Alberto implemented new UI to channel mixer in ART, primaries correction mode, and I highly appreciate it.
However, I think another simple solution may exist. Therefor I made simple CTL script to implement this idea.
In this implementation, first user decides level of R, G, B. After that user decides relative mixing ratio of RGB in each channel. This means user decides first column sum of color changing matrix value, and next decides RGB ratio in each column.
The problem of traditional UI is when user moves the sliders user has difficulty to infer the changing direction of color. In this implementation, user can more easily infer the changing direction than traditional UI.
Maybe primaries correction mode is much intuitive than this implementation, however this idea is more reflected of the structure of color changing matrix.