Adding Contrast

[bcripps]

Hi Gimpsters
My problem is contrast between white foreground and white background.
The line between foreground is indistinct against the background for adding a Layer Mask. I need more contrast. Easily done Colors>Desaturate>Color to Grey. But after applying the Layer Mask how do I get my original colors back? Or, as usual, am I going about this all wrong?
I'm using 2.10 in Zorin.
Much thanks,
Bry

[rich2005]

Two layers
On the top layer the layer mask should be just black (for transparency) and white (for opaque)

   

You can get that using fuzzy select with a low (4 or 5) threshold value on the background. (or any other way you prefer)
The resulting selection creates the mask Layer -> Mask from selection (inverted)
Then adjust the top layer as required.

example: https://i.imgur.com/UOjWPhj.mp4

[bcripps]

Thanks, Rich... let me give that a try and I'll let you know how I made out.
Bry

[Ofnuts]

Rich gave you a solution but the important idea to remember is that the selection applies to the image, not to a specific layer.  So you can create a selection using a layer, and use that selection on some other item of the image (other layer, mask, channel...).

[bcripps]

Hey Rich,
Just wanted to say thanks again for your advice. You did a lot of work and I appreciate it. The Fuzzy Select Tool method worked well and I was pleased to find I could also touch up the mask after, by opening a brush.
And a special hello to Ofnuts, thank you for your comments.
All best,
Bry