Give gain slider more flexibility #272
Description
There's currently one "gain" slider that ties the red and blue channels together, but low gain/exposure settings results in green images under fluorescent lighting. This is a problem if the target is lit green; the user has to use a much wider hue passband.
One solution to this would be separate red, green, and blue exposure sliders. A button could be added to autoselect the settings for them when the targeting LEDs are off (aka "auto white balance").
MATLAB's docs mention a few different algorithms that I imagine would be a starting point.
https://www.mathworks.com/help/images/comparison-of-auto-white-balance-algorithms.html
OpenCV has this, but idk if it's helpful: https://docs.opencv.org/4.5.2/d7/d71/classcv_1_1xphoto_1_1GrayworldWB.html
Another option is turning on auto white balance of the camera temporarily to get the values, then turn it back off.