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Hello,

I have a finger print that needs to be on a white background.

I changed the background to white using Quick Mask, but the issue is that the finger print has crests / troughs, and the troughs color is that of the old background.

[attachment=6530]

1. Is there a way to resolve this?

2. Is there a way to make the crests a deeper red?

I haven't used gimp in quite a few years and have forgotten quite a bit of what I used to know.
Any help would be appreciated.

Thanks.

There are going to be a few ways:

You could try to desaturate using Colours -> Destaurate -> Mono Mixer https://i.imgur.com/cCC4xgQ.jpg
or
Tools -> GEGL Operation -> Color warp (from the drop down menu) Color pick (carefully) bump the weight up to a large value https://i.imgur.com/PgoYQrM.jpg

I have discovered that I can use  Colors/Levels to accomplish what I need.

I brought the high Input levels to about 170 which lightened the trough color, the Low input levels to 41 which darkened the crests, and moved the gama to 0.74 which further defined the finger print.

If you have other suggestions I'd like to hear them.

rich2005 - thanks for your input

Not an other suggestions, Levels are very fine to keep the color (and increase it) and remove the gray of your image, I have tendency to use curves, though, but it's same result (the Levels' window shows a button if you want to edit as curves, it's just to tell you how similar they are).

Levels
[attachment=6533]

just to let you know with Curves
[attachment=6534]

Advantages of both methods is you can play with the different colors' channel as well (for example in this image red and blue channel to adjust that orange to your liking (I would start with the blue channel because of the yellow in that orange))