GIMP Version: 2.8.18
Operating System: Windows
OS Version: Windows 10 Home
GIMP Experience: New User

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I know there must be an easy solution to remove red casts in photos - or any other colour (have only seen red though).
I tried 'turn off red channel' Picture saved the same as it was originally.
So then I tried removing red altogether from the photo which removed red from other areas I would have liked it to remain and the whole photo turned green.
For future reference - what do you do?

did you try viewtopic.php?f=9&t=15079&hilit=white+balance ?

Thanks for replying dinasset.
Doesn't that filter affect the whole picture? No?
I was just talking about a red cast over an area. Like a strip down the middle.

Do you mean something that's described here?

http://retouchpro.com/tutorials/?m=show&id=304

I don't know a gimp tutorial. There is no quick filter for this (not yet). It is a lot of work. Succes.

I trick I accidentally concocted a few years back. Dup for a total of three layers, set top layer to Value and center layer to screen. This reduces red cast.

nonetheless it's worth a try, then you may judge the result

Sallyanne, as long as Gimpchat does not upload images, you can use Gimplearn to post there the image with the red cast and the result of using my filter (with your comments), or -if you do not want to try yourself- just post the source image and someone can try (myself using my filter, other people using other tools and/or a tested procedure, IDK)

You can always make a selection, then use Hue-Saturation filter..

This is the photo I am talking about
example by sallyanne,

I see.
Really difficult, outside my possibilities because the area where the red cast appears is also feathered.
Done some tries, but no outcome worth to be posted, sorry.

Not starting from a good base and is very much every-image-is-different.
Cloned the crosses out as they are a distraction.

You could try

1. Apply auto white balance, duplicate the image and select as best you can an area with suitable colours.
example: http://i.imgur.com/fo5B0mD.jpg That is the map for the next bit.

2. Back to the first image. Apply Colors -> Map -> Sample Colorise. Almost default settings, the input levels reduced a little to remove some red cast. http://i.imgur.com/B8YIKuY.jpg

3. That gets you to here: http://i.imgur.com/hId7ONQ.jpg

4. Then up to you how much time you spend on the image, the duplicate back under and with a layer mask, improve some areas, such as hands, remains of color cast which show up as colored speckles. Try cloning those out. You do need to get down to the pixel level. http://i.imgur.com/8rpyf1d.jpg



And that still needs work on the background, overdid the cloning on the trousers, all depends how much time you have.

Thank you rich. I did see that the background also needed some work. I am not going to do anything on this one at this time because other people have already presented their fixes. But for future reference I will book-mark this thread.

The crosses were not in the original. I didn't ask to share the photo so thought I would make the people unable to be recognised.

You may have a look also to my try at https://gimplearn.net/viewtopic.php?t=591&p=4670#4670

Very nice

I've only been using Gimp for about 3 weeks now, so don't yet know all of it's potential....

1) I used G'mic's "Channel to layers" (B'cause I don't know if gimp has a channel mixer).
2) I then deleted the red channel and switched the green channel blending mode to "Screen"
3) I then played with "Hues-Saturation" on the green channel to get this outcome.




Or PM me your original image and I'll see what I can do, if you like the outcome...........