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Using GIMP 2.10

I have a colour photo and what to convert the background to greyscale but having trouble doing this. The current process I have followed is:
Duplicate image
Desaturate duplicate
Add layer mask (white opacity)

I am working on the greyscale image and have tried using the paintbrush and the easer to bring the colour of the background image through but it hasn't worked.

TIA

Did you add an alpha channel to the grayscale image? Right-click on the grayscale image layer in the layers dock, a pull-down menu appears and click on 'Add Alpha Channel'.
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(12-01-2021, 03:11 AM)Richard Wrote: [ -> ]Using GIMP 2.10

I have a colour photo and what to convert the background to greyscale but having trouble doing this. The current process I have followed is:
Duplicate image
Desaturate duplicate
Add layer mask (white opacity)

I am working on the greyscale image and have tried using the paintbrush and the easer to bring the colour of the background image through but it hasn't worked.

TIA

If you use the brush it has to be applied to the mask (black for transparency), so make sure you click on the mask thumbnail to make it the target "drawable". At the bottom of the screen, it should display "{layer name} mask" instead of just "{layer name}".

For a white layer mask, the colour image, with layer mask on top. Desaturated layer on the bottom.

Make sure the layer mask is active, click in the icon.

Paint in the canvas.

example 30 seconds so do not blink. https://i.imgur.com/SzhunnY.mp4