Re: [Gimp-user] selection by value threshold

[Ofnuts <ofnuts gmx com>]

On 07/10/17 08:33, Mitti Mithai wrote:
> Gimp 2.9 loads by 16-bit astrophotography files either TIF or FITS just
> great.
>
> I've never had to to this with gimp yet, but I need to make a selection by
> value threshold (I want to "cut out" stars that are hitting saturation in
> my image with values of 64k)...I can't quite seem to figure out how to do
> it.  Does anyone have any advice?
> _______________________________________________
Quick and dirty:

- open the channels list
- drag any of the RGB channels down to the lsti to below to make a copy
- treshold the copy
- channel to selection

Slightly more accurate:

- Create grayscale copy of layer (Color>Desaturate (lightness)
- Threshold to your liking
- While it is visible, open the channel list, right click any R,G,B 
channel and "Channel to selection"