09-13-2022, 05:31 PM
For that particular sample: The greyish background is actually dithering, the scan might have been indexed at one time or it might have been the scanner software.
You can get some improvement by
1) Apply Filters -> Generic -> Dilate (grows light areas and shrinks the dithering to nothing)
2) Apply Filters -> Generic -> Erode (grows darker areas to try and get most of the original back)
3) Play with the color curves tool to get a little darker.
A 30 second demo of that: https://i.imgur.com/9U8qJoy.mp4
You can get some improvement by
1) Apply Filters -> Generic -> Dilate (grows light areas and shrinks the dithering to nothing)
2) Apply Filters -> Generic -> Erode (grows darker areas to try and get most of the original back)
3) Play with the color curves tool to get a little darker.
A 30 second demo of that: https://i.imgur.com/9U8qJoy.mp4