Stain removal suggestions needed

[Danbor]

Hello all. I've been looking all over and trying different things but haven't had much success so I'm looking for some ideas. As a photo restoration rookie I'm out of ideas.
   Does anyone know of a way to remove the stain from the attached photo? I'm thinking there should be a way to remove whatever color that is overlaying the actual various colors under the stain.

[Krikor]

(03-25-2024, 03:29 PM)Danbor Wrote: Hello all. I've been looking all over and trying different things but haven't had much success so I'm looking for some ideas. As a photo restoration rookie I'm out of ideas.
   Does anyone know of a way to remove the stain from the attached photo? I'm thinking there should be a way to remove whatever color that is overlaying the actual various colors under the stain.

At the moment I can only remember to suggest the following reading: 

Stain Removal by Pat David

https://patdavid.net/2014/07/wavelet-dec...in-removal

I hope it can be useful.

[Danbor]

(03-25-2024, 08:02 PM)Krikor Wrote: At the moment I can only remember to suggest the following reading: 

Stain Removal by Pat David

https://patdavid.net/2014/07/wavelet-dec...in-removal

I hope it can be useful.

Thanks. Interesting, but it didn't help in this application.

---

Update on my attempts and questions ...
I'm trying to remove the amber stain on this image. I've had some success in spots by using the free select tool to select an area, then adjusting the selection with the hue chroma tool mainly, among others, with varied results.
As I'm new to image editing as a whole as well as new to Gimp, I've a question that probably has already been asked, but here goes. Sorry for the length of the question but I don't know the terminology for the short version.
Ok, how can I pick a spot, say somewhere in the sky that is not stained. then pick a spot right beside it, IN the stain, compare the two, and convert the difference into a usable variable. Then remove that variable from selected areas? Not just areas of the sky, but everywhere that is stained regardless of the underlying color.
I can get the HTML notation for different colors, but that's not really what I need. I need to be able to remove the "stain element". For lack of a better term, turn the "stain element" into a layer that can be deleted, or at least masked.
I'm guessing the result would be akin to greyscale, that could then be colorized?

[denzjos]

I tried this : first 'Colours / Auto / White Balance'. Select the color left from the sky and paste the selection as a new layer. Flip the new layer and past it to the right side of the photo, scale the selection and erase the place where the tree is. Then use the brush and take a color from the dark place on the horse (pencil with CTRL key pressed) and set the paintbrush mode 'HSL Colour'. Paint over the stain on the horse. Try different place to take the color if not satisfied. Use the 'Healing Tool' and the 'Clone Tool' to optimise the rest. I've done a quick restoration (not fully done): 
     

[Danbor]

Thank you so much denzjos! I've been trying everything I can think of to fix this image. Of course, since I don't know what I'm doing I haven't had much success.
I don't fully understand what you've done here but I'm going to attempt to reproduce it. It make take a few days, but I'll report back my progress.
  On a positive note, I'm sure learning a lot!

Edit:
   Ok, right off the bat, I'm lost. I managed the Colours / Auto / White balance step. But, just how do I select the color left from the sky and paste it as a new layer? And of course I don't know how to flip the layer and paste it to the right side of the photo.

[denzjos]

(04-06-2024, 01:55 AM)Danbor Wrote: Thank you so much denzjos! I've been trying everything I can think of to fix this image. Of course, since I don't know what I'm doing I haven't had much success.
I don't fully understand what you've done here but I'm going to attempt to reproduce it. It make take a few days, but I'll report back my progress.
  On a positive note, I'm sure learning a lot!

Edit:
   Ok, right off the bat, I'm lost. I managed the Colours / Auto / White balance step. But, just how do I select the color left from the sky and paste it as a new layer? And of course I don't know how to flip the layer and paste it to the right side of the photo.

First of all, right-click on the photo in the layer dock (small image on the right of your screen) end set 'Add Alpha Channel'
Correct this area :
   
Select this area and use it to correct the richt side (use the 'Free Select Tool):
   
To flip : Tools /Transform Tools / Flip (use vertical)
Use the 'Erase Tool' to get the small tree back

[Krikor]

(04-05-2024, 05:53 PM)denzjos Wrote: I tried this : first 'Colours / Auto / White Balance'. Select the color left from the sky and paste the selection as a new layer. Flip the new layer and past it to the right side of the photo, scale the selection and erase the place where the tree is. Then use the brush and take a color from the dark place on the horse (pencil with CTRL key pressed) and set the paintbrush mode 'HSL Colour'. Paint over the stain on the horse. Try different place to take the color if not satisfied. Use the 'Healing Tool' and the 'Clone Tool' to optimise the rest. I've done a quick restoration (not fully done): 
 

denzjos, the solution you found is very good!

The tree part is really delicate and requires a lot of patience.

[denzjos]

After some boring time I got this (not pefect yet) :
   

[zeuspaul]

Looks good.  Try adding unsharp mask.  Attached is using the defaults.
   

[sallyanne]

There is no easy fix for this photo. Denzjos did a good job. It can be fixed but you would have to spend a lot of time on it.