(07-19-2022, 04:07 PM)PixLab Wrote: Other than the usual channel mixer, color balance, curves (my favorite), and so...



There is an extremely simple way that I already spoke in one of your thread...
Sample something supposed to be white or even "light" gray, then see the screenshot below



Once your colored layer is set, just play with opacity and hue-saturation to fine tune.

(07-19-2022, 04:52 PM)Stephen Liu Wrote: Thanks for your advice.

Performed following steps;

Select "Color Picker" -> click the wall

Pls refer to screenshot_image-1

But I couldn't start the "Symmetry Painting" screen ?

Regards

(07-20-2022, 02:01 AM)PixLab Wrote:

(07-19-2022, 04:52 PM)Stephen Liu Wrote: Thanks for your advice.

Performed following steps;

Select "Color Picker" -> click the wall

Pls refer to screenshot_image-1

But I couldn't start the "Symmetry Painting" screen ?

Regards

 I don't use nor speak about the Symmetry Painting in this example (just look at the active tab/dialog in my screenshot which are the layers' dialog and the tool options)

Let's try a step by step:
In the layer's stack/dialog you have only your picture ➤ No other layers at this stage.

➤ Click on the Color picker tool(NO window/dialog will open, that's normal)
➤ In the tool options of the color picker, set it to Set foreground color (first screenshot below)
➤ then pick the color on the wall (NO window/dialog will open, this action will ONLY set the foreground color of the FG/BG icon just below the tools ➤ see second screenshot)


➤ your new foreground color is set (see screenshot just below)
➤ now create a new layer (be sure it is selected)
➤ then use that new foreground color to fill the new layer (by directly drag n drop that FG icon on the new layer, or use the bucket fill tool, or in the menu Edit/Fill with FG color),


➤ then put that new colored layer in grain extract mode... basically that's all you have to do


Optional: once it's done, fine tune as explained at the bottom of my previous post

(07-20-2022, 03:56 AM)Stephen Liu Wrote: Something strange on the GIMP running here.  I couldn't reproduce what you have advised.

Clicking the wall with Color Picker tool is without response.

Pls refer to images upload

(07-20-2022, 03:56 AM)Stephen Liu Wrote: What I meant "Symmetry Painting" is the screen of the image upload on your post #2.  Pls refer to the image upload. 

I have spent more than half hour without result.

Regards

(07-19-2022, 06:10 PM)david Wrote: An alternative approach: Duplicate layer. On this layer go to Filters/Blur/Pixelize. Pixelize to the maximum dimension of the image. Colour/Invert and change the mode to Overlay.

(07-20-2022, 04:14 AM)PixLab Wrote: OM....
With all the explanations, me, myself I would have tried, at least, blindly the step by step EVEN if I see nothing happening, up to the very end to see if the method is working or to validate it, and NOT STOPPING at the first step because I don't understand the tool yet... (although I thought I gave you some explanations in the "step by step" on my previous post, but anyway and in case of... ➤ more about the color picker ➤ https://docs.gimp.org/2.10/en/gimp-tool-color-picker.html )

(07-20-2022, 03:56 AM)Stephen Liu Wrote: Something strange on the GIMP running here.  I couldn't reproduce what you have advised.

Clicking the wall with Color Picker tool is without response.

Pls refer to images upload

You did got a response ➤ Color Picker did change the FG on your GIMP see the screenshot of your screenshot. But you did not pay attention...

➤ now use this color to fill the new layer

(07-20-2022, 06:18 AM)denzjos Wrote: A one-click solution for this : G'Mic-Qt / Colors / Auto Balance (or 'Color Balance')