I found an awesome tutorial on fixing color cast in photos at gimp.pixtuts.com I searched the web for pics to use, and found a good one used in a photoshop tut. I tried it in GIMP, following the Photoshop instructions, which were quite different, and I couldn't complete it. I then followed the GIMP tut, and I was quite excited about the conclusion.

GIMP Tut: http://gimp.pixtuts.com/gimp-tutorials/ ... correction

Results below:

Hello Steven,

Here is my try, I used G'MIC "HSL adjustment" , "Specific saturation" (both from Garagecoder) and curves. My monitor isn't calibrated. Maybe it can be improved. Colors are always a matter of taste.

With more saturation:

I like it, but the colors seem a little muted. Not enough saturation. Made me want to try this G'MIC HSL adjustment, though. I just used it. with tweaks, and I prefer the result over my original repair. What do you think?

I tried calibrating my monitor once. I have no idea if it did anything.

Ha! We were both saturating at the same time. Both better results!!

I prefer your last result above your first. I gave you my examples to give you an idea of what is possible with those G'MIC filters. So you can use them and experiment with them to your own taste. The color balance of GIMP is also useful. Another great filter of G'MIC is "Color grading" (for colors only use color grade sliders) from John Lakkas. There is also a GIMP filter with the same name from him, but that doesn't work with GIMP 2.9

Anything that doesn't make the stove pure gray isn't really working correctly. Iarga's results are the closest...
This script does just that...

For some color cast images "HSL adjustment" works better than "Specific saturation". For others "Specific saturation" works better. In some cases you can use them in sequence. I like these filters, because you can have a decent result very quick. (In cases with wrong camera adjustment for light: candel light, tungsten, day light and vice versa, these filters are very useful)

You can always start with curves and color balance (GIMP: shadows, midtones and highlights). Also you can try curves in different color spaces (G'MIC "Curves interactive").

Also take a look to the G'MIC filters "RGB tone" and "CMYK -tone" from Iain Fergusson. This will take some time, but excellent for fine-tuning.

You can use al different kinds of color correction, also the one you mentioned with the inverted colors.

The nice thing is that you can afterwards combine them to get an optimal result to your taste.

The color corrected image with the script Ofnuts mentioned (Luca de Alfaro), the ligter grays/whites then become a little bit green/yellow, but you can correct that afterwards. (I took the stove color, just under handle as gray foreground gray, sliders 100,100, 0.... with different settings perhaps better results):

You can also use G'MIC "Color temperature" from Tom Keil. Without automatic color balance. Turn the slider to the left. After this refine with (GIMP and/or G'MIC) curves, (GIMP) color balance etc.

Other color temperature filters perhaps do the same.

There are many ways to skin a (color) ca(s)t.

The following classic method is almost the same as you mentioned in your first post:

1. Duplicate layer,
2. remove transparency (Layer>Transparency>Remove Alpha Channel),
3. Filters>Blur>Pixalise, with maximum width and hight. (with your image 900*600)
4. Now you have the avarage color of the image.
5. Invert color of this layer (Colours>invert).
6. Set this color-inverted layer to Overlay (above the Original). Adjust opacity of this overlay.
....[you can also make an duplicate of the inverted layer and set it to Colour. Now you can combine different
....opacities from this two layers (Overlay and Colour)]
7. New layer from visible, duplicate this layer.
8. Possibly desaturate to taste.

After this: curves, color balance etc. etc. (now I didn't take this last step, so you can compare)

Your final take looks to be the most natural of all. Thank you so much for all of your tips, iarga. They are greatly appreciated!

Thank you. It's all about personal taste. I think I would combine the last one with the (more saturated) second. I prefer the colors of the second one, but appreciate the light values of the last. So I would layer those images and then try to get a nice result with blend modes. The most important thing is that you can try all these filters and methods and find a result you like.

Sometimes automatic color balance gives a nice result, but a lot of times you have to find a nice result yourself. Color casts differ from photo to photo. So you everytime have to search what's the best method to correct the colors.

I most of the times use curves first.

Very good tutorials by Pat David:

Basic Color Curves
Getting around in gimp color correction
Color curves matching

Sometimes it doesn't work with curves first, then I try methods I mentioned earlier. Afterwards I use curves and color balance etc. etc.

I would love if someone else has something to "teach" here about this subject. I also like to learn new methods and like to know about other (unknown) Open Source tools and filters to work with colors, color correction and color grading. I think it's fascinating.