[Gimp-user] alpha from image

[Michael J. Hammel]

On Mon, 2008-11-24 at 16:07 +0000, erniew at comcast.net wrote:
> I have an RGB image and a grayscale image of the same size.  I'd like
> to use the grayscale image as the alpha channel of the RGB image.  How
> can I do that?

Open RGB image.
Add an alpha channel (Layers->Transparency->Add Alpha Channel)
Add a layer mask (Layers->Mask->Add Layer Mask)
Open grayscale image - copy into layer mask you just created (Edit->Copy
in grayscale image, Edit Paste with Layer Mask active in the RGB image)
Optionally, apply the layer mask (Layer->Mask->Apply Layer Mask).

-- 
Michael J. Hammel <mjhammel at graphics-muse.org>