Pretty straight forward question, say in Gimp I have an image with 2 layers in question, one is temporary, I want to use it as the mask for the other. How can I transfer a layer into the mask of another? I get as far as having a grey scale floating selection which I can't place on the mask. I know how to paint on a mask, or use a layer's grey scale as it's own mask, but not a layer's grey scale for a different layer's mask.

Hope that makes sense


2 Answers 2


Assuming you are using white for opacity and black for transparency and, when making the layer mask, you chose the second option, "Black (full transparency)":

Right click on the floating layer and select "Anchor Layer". The image contained in the floating layer will replace the solid black mask.


It might not be a smart method, but here’s how I do this:

  1. The “layer1” has a transparent background. pic 1

  2. Copy “layer1”, protect the transparent area, and fill it with pure black. pic 2 pic 3

  3. Go to channel dialog, and drag one RGB channel down to create a new channel. It doesn’t matter which one, R or G or B, you drag.
    Make sure to set “layer 1” invisible. The picture must be black and white for this step. pic 4

  4. Create the “layer2”. pic 5

  5. Go to channel dialog, right click on the new created channel and make selection out of it. pic 6

  6. While the selection is active, add a layer mask to “layer 2”. In the add mask dialog, choose use selection. pic 7 pic 8

  7. We are almost there. Now the mask of “layer 2” is the contrary of what we want.
    Choose “layer 2”’s mask and invert its color. pic 9

  8. And this is it, we’ve made “layer 2”’s mask according to “layer 1”’s content. pic 10

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