Generally auto white balance (Colours > Auto > White balance) does a great job for me but in some circumstances it's pretty bad. Is it possible for me to intervene to make it behave without having to try do it entirely manually?
Here is the image (two different links to the same image; white background turns blue when auto white balance is used):
https://imgur.com/a/xtt4JbJ
https://www.dropbox.com/s/2qg7yc4o0gxjdx...2.jpg?dl=0
It would be handy if I could select an area that is supposed to be white, like some kind of semi-auto.
The auto white balance (
Colors ➤ Auto ➤ White balance is based on the "auto" levels
Colors ➤ Levels..., as a matter of fact
it is the auto button on the levels.
Try it and you will see it's the same result
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attachment=7704]
Before to give you the good news, this is what you could do after an "Auto"
Go inside the 3 different channels (Red Green Blue) and adjust the sliders, especially the one on each side to get back the full histogram
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attachment=7705]
(03-30-2022, 03:03 AM)THX 1138 4EB Wrote: [ -> ]It would be handy if I could select an area that is supposed to be white, like some kind of semi-auto.
Here it is 
In the end you can use those 3 button (below) to pick up your black point (left) or gray point (middle) or white point(on the right) directly on the picture
[
attachment=7706]
More about levels ➤
https://docs.gimp.org/2.10/en/gimp-tool-levels.html
Perfect, thanks very much!
(03-30-2022, 03:03 AM)THX 1138 4EB Wrote: [ -> ]Generally auto white balance (Colours > Auto > White balance) does a great job for me but in some circumstances it's pretty bad. Is it possible for me to intervene to make it behave without having to try do it entirely manually?
Here is the image (two different links to the same image; white background turns blue when auto white balance is used):
https://imgur.com/a/xtt4JbJ
https://www.dropbox.com/s/2qg7yc4o0gxjdx...2.jpg?dl=0
It would be handy if I could select an area that is supposed to be white, like some kind of semi-auto.
Auto white balance tries to make the image gray on average. If you start with gray and yellow, it its yellowish on average so the correction adds blue. AWB has its pitfalls, try shooting a nice sunset with your camera on AWB and say goodbye to all the nice colors (your smartphone likely has an algorithm to recognize sunsets and avoid AWB for these).
There is a
script that works quite well: sample the color of something that should be neutral gray and use the "Make foreground gray" function. It will apply a temperature correction that makes the foreground color a neutral gray.