Greetings all,
I wonder does somebody have a technique for correcting/minimising the effect of mirroring in old photos.
This shows up in one photo in particular similar to water staining when it is scanned. If you look at the photo and tilt it to change the viewing angle the effect becomes a lot less noticeable.
Any thoughts?

I didn't know what "mirroring" was, so I Googled "mirroring in old photos" and got this result: http://www.retouchpro.com/forums/photo- ... -help.html which has a few methods, including isolating out the mirrored areas and processing them separately, leaving the rest of the image untouched.

Also there's a suggestion that fits with what you say about changing the viewing angle to minimise the effect - photograph the photo from that angle, then correct the perspective distortion in GIMP.

Kevin

where is the photo, HarryB?
just to understand the problem

I was toying with this a little, using one of the images from Kevin's link, and wrote the following script:

http://chiselapp.com/user/saulgoode/rep ... d17d85a073

The script generates six layers each to remove a particular hue (red, blue, green, cyan, magenta, yellow) from the image. These layers are all initially hidden, and can be made visible one-at-a-time to see if the result is an improvement. If one of the hue layers improves the image, its opacity can be adjusted to tweak the result.

The following image shows a before and after



The full XCF is available from http://barn.kerosenecow.net/u/saul/m/de-mirroring-xcf/

I actually processed the image twice. I first removed a lot of the BLUE-HUES from the image; and then created a new layer from the result ("Layer->New From Visible"), ran the script again, and removed some of the GREEN-HUES.

Though the result in this case was noticeably improved, I am not especially happy with the technique -- it seems rather crude. Nonetheless, there might be some hope to fine tune the hue removal by decomposing the image to produce a more customized "mask".

Thank you, Saulgoode.
Just made a trial, with appropriate selection I get really an improvement.
I have to play more, for better tuning.
Let us (gimp-chatters) know whether you will enrich the script in the future, I'm interested

Very interesting technique, I looked at the .xcf and played around with the settings. The result brought an improvement no doubt.
Thx Saulgoode