GIMP Version: 2.8.18
Operating System: Windows
OS Version: 10
GIMP Experience: Basic Level

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Hello GIMP friends.

How can I keep only one color in the image ?
All other colors in the image will be gray-white (Saturation -100).
The effect in the attached picture I've made with the application "Camera 360" in my Android phone.

Thanks
Doron.

There is a tutorial here:
https://www.gimp.org/tutorials/Selective_Color/

You mean 1 colour in a black and white picture
That can be acheived with a mask
I'll post the link to a tutorial on it in a minute
I see blighty beat me to it
Here is Molly's tutorial viewtopic.php?f=23&t=2888&hilit=mask+tutorial&start=60

I'm looking for the effect to work in the following way:
The user will select a color to keep in the image, for example: red, green, yellow .....
After selecting the color the user will start the effect.
the effect will make all other colors in the image to become gray and white without further action by the user.
the user will not need to select area or mask area.
this is the way the effect work in the application "Camera 360" in Android phone.

Thanks
Doron.

Just tried it a different way in Gimp. select all the red parts with the fuzzy selector, threshhold on 24. Invert your selection then desaturate (luminosity). Depending, it may take longer than the other way - took me about an hour.

This will require a script to do all the steps in one of the tutorials. Results will vary greatly, depending on the image. Can work well on one image, and on another image the result will not be good at all.

There is another way
With your picture in gimp open Hue/Saturation. With this one i just moved yellow and green saturation all the way to the left.

You could do mostly the same for any image. Just don't move your colour you want to keep to the left.

Doron,
I wrote a script to give a try.
This is my result, not exactly the same as what you show but close.
If you like, I can post it (after some cleaning)

Very overlooked: in the "By color" selector you can use various selection criteria, and here "Hue" is an obvious choice.

Excellent suggestion, Ofnuts, it's easy to select by hue, reverse, desaturate.
Great!
Use Ofnuts' rec, Doron.

Thanks

I like this method.
I will test as soon as possible.

Doron.

Hello

I test the HUE color after color.
And it works fine.

thanks
Doron.

I always over look tool options features and get to learn something new from you

Thank you for your help Dinasset.
Yes i like . can post your script here ?

thanks
Doron.

Here it is.
It makes use of the "Hue" technique suggested by Ofnuts.

Thank You dinasset for the script.
Can you please change the color select pop up windows
from photo number 1 to photo number 2 ?

Photo number 2 have more option to select the color.

Thanks
Doron.

Well, I don't know how to change the panel which appears on a python color-select parameter, maybe Ofnuts can help

edit: I have to leave now, when back I'll see what Ofnuts (or someone else) suggests to change

I think I'm of the opinion that you're better treating each image individually rather than having a button-press-preset mentality, so in this case using masks to select the parts you want as it gives more flexibility to do this sort of thing:

Kevin

When you do a script, you just tell Gimp that your script needs a color as one of the parameters, and Gimp creates the dialog on the fly using built-in sub-dialogs where necessary (colors, fonts, files/directories...). So either you accept the standard stuff and your script is written in 10 minutes or your write your own stuff and it takes days or weeks (the standard color dialog in Gimp (which is 4-5 dialogs in tabs actually) in a rather complex animal).

A better venue would be to file a bug/improvement request on bugzilla.gnome.org and suggest that the dialog used to pick color in scripts be augmented to match the standard color dialog. Then all the scripts will benefit from this.

The curious thing is that in GIMP 2.6, the script colour chooser dialog is the same as the standard colour dialog, so this is something that has changed with 2.8 and may indeed be a bug.

And it's the Python script colour chooser that's the problem as the script-fu dialog is the standard one.