How to use white balance card with specific RGB values in gimp

[Krikor]

(11-19-2021, 12:12 AM)Liese Wrote: Hello,
I have a white balance card that has specific RGB values, 219, 220, 220. I am trying to adjust my photo in gimp so that the area of the picture with that white balance card matches its actual numbers and thereby correcting all colors in the photo. I appreciate any help I can get on this! Thank you.

Good question.

I did a quick search and found almost nothing on the subject related to Gimp (most use PS or Lightroom).

A post that might shed some light on this question:
https://www.gimp-forum.net/Thread-Noob-q...20question% 20about%20white%20balance%20calibration,-New%20Reply