Re: [Gimp-user] removing tint from a picture

[Steve Kinney <admin pilobilus net>]

On 07/30/2015 04:46 AM, s.kortenweg wrote:
> You can use the restore filter.
>
> Go to www.gimpusers.com/news/00237-exeptional-plugin-photo-restore
>
> there you find the instructions to download and instal the filter.
> It works almost very fine.

Well heck.  That filter looks amazing, but on the first try here it
failed in a major way:  First it threw error messages and appeared
to exit, then it ate so much CPU and memory that I had to reboot the
machine to get rid of it.  I am using GIMP 2.8.10 on Linux Mint 17,
AMD 64.  Apparently the plugin was written for GIMP 2.6, and an
earlier version of Python than I have installed, so for now I will
blame the problem on compatibility issues with GIMP and/or Python.

What I usually do to remove tints from images is:

1)  Open the image and use the eyedropper to pick a sample of the
color I want to suppress.

2)  Open the color selection dialog and set the picked color to
maximum saturation/value.

3)  Make a new empty layer, fill it with the color in question and
set its mode to Color.

4)  Do Colors > Invert, to obtain a color that can cancel out the
unwanted tint.

5)  Set the transparency of the new layer to a low value, < 10%, and
adjust until the best looking results are found.

6)  Create a "new layer from visible" twice, set the mode of the new
top layer to Overlay, and adjust its transparency until the best
looking results are found.

That last step restores a lot of lost contrast and saturation to the
image.  Before this is done, the results look "foggy" because adding
the color from the layer to the tinted layer below it replaces the
unwanted color with unwanted gray.  Increasing the contrast of the
overlay layer may also be useful.

Results of this process are usually not as good as in the examples
of the restore.py plugin's results, but so far I don't have a better
way.  Any suggestions?

:o)

Steve