how to clean dirt/yellowing from old document

[gimptime]

I am working on an old baptismal certificate. It has a white background. There is what looks like
dirt on some of the background, which I would like to remove. It is also yellowed to varying degrees
which I would like to fix. I have used the brush/pencil tool and painted some of those areas
with a lighter color from the background but its too slow. Any ideas would be greatly appreciated.

Thanks.

[denzjos]

Copy the layer to a new layer
On the new layer use 'Colours /Threshold' (left value 160, right value 255)
Set layer mode of the new layer on 'Pin Light' / Opacity on 50%
There is some lost of detail 
   

[PixLab]

Many possibilities, I'll give a quick one as well.

Go to menu Colors > Levels, a window opens

1. Click on the Auto Input Levels button, see if you are satisfied, white enough, etc, if yes go to step 4, if not continue to step 2
   
2. Then click on that pipette (the one at the right), it's for the white
   
3. Then take a sample on the image of something that should be white (you can sample multiple time to try different zone)
   
4. Restrain the slider of the black on the levels' histogram
   
5. Play with that middle slider right-left-right-and so until you got a good contrast
   
   

   

Another quick one...

Go to Colors > Desaturate > Desaturate... a window opens (Desaturate 2 times is not an error)

1. Put the Mode Value (HSV)
   
2. Blending option in Screen Mode
   

   

[Ofnuts]

(08-27-2022, 04:47 PM)gimptime Wrote: I am working on an old baptismal certificate. It has a white background. There is what looks like
dirt on some of the background, which I would like to remove. It is also yellowed to varying degrees
which I would like to fix. I have used the brush/pencil tool and painted some of those areas
with a lighter color from the background but its too slow. Any ideas would be greatly appreciated.

Thanks.

Some heavy JPG compression artifacts. Is this the original version or has it been recompressed?

[Mando8000]

Dang you guys are smart. Maybe you guys can answer my question I just posted lol.