Excessive color values in layer mask

[egrivel]

Hi,

I am using Gimp 3.0.8, which is the version my Linux distribution provides. When I inspect a layer mask I"m using, I'm seeing RGB color values wildly above 100% (see attachment).

Once this happens, the layer mask (which is supposed to be the the percentage of the background to shine through) gets "wonky": what shows is not related to either what is in the layer nor what is underneath. 

I'm think that I'm completely missing something important. The pink triangle in the color picker display seems to indicate something special is going on, but I have no idea what it stands for.

Note: I think this problem starts when I use Levels to force a lot of white (transparency) in the layer mask. It's like the levels create whiter-than-white colors...

I'd appreciate any help.

[rich2005]

(3 hours ago)egrivel Wrote: ....
Once this happens, the layer mask (which is supposed to be the the percentage of the background to shine through) gets "wonky": what shows is not related to either what is in the layer nor what is underneath. 

I'm think that I'm completely missing something important. The pink triangle in the color picker display seems to indicate something special is going on, but I have no idea what it stands for.

The (pink) magenta indicator shows when a color is out of gamut. Usually that is in a printing context and it means the colour cannot be printed. see: https://docs.gimp.org/3.0/en/gimp-view-s...gamut.html

Unusual for white to be marked out of gamut.

Check your image and is it high bit depth ? or a profile other than standard Gimp sRGB ?  I do not understand how you get that value in a layer mask, maybe you could give more detail.

You can usually correct by going out of Lch / 100 % mode to HSV / 255 mode and picking white from there.

   

Colour profiles are a big subject where some colours might show on specialist monitor (1) but not on a regular (RGB) monitor (2) and definitely not for a CMYK printer (3)

   

[rich2005]

hmm... Playing around and I got this 32 bit FP with a black layermask and selection filled (top) with white RGB(255,255,255) and bottom out-of-gammut white

...but I tried again and cannot reproduce that effect. Will try again tomorrow, Maybe if Ofnuts is around he might know.