I'm migrating from Photoshop and everything I read says what I want to do in the GIMP should be easy, but here I am...

I have two images, A and B, which are black and white, from a proprietary program but saved as TIFFs. They open as RGB in the GIMP 2.2 on my Mac, with the image visible in all three channels.

I want to create a final image, C, consisting of image A in the red channel and image B in the blue channel, and no image in the green channel.

If there's a tutorial or plugin or previous mailing list post please give me a pointer and you have my thanks. I just can't find it myself.

If you need more info about my problem here's some. When I copy, cut or paste I can't seem to figure out how do so in a channel-specific manner. In other words, I deselect two layers from one image and copy, then similarly attempt to paste into one channel of the second image either through the Selection Editor Menu --> Save to Channel or by simple pasting after deselecting two layers. Neither has the desired effect of taking one channel's information from image A and copying into a single channel of image B. At best the paste goes into all three channels of the second image, overwriting the original information.

Thanks in advance for your help.

Bill Jackson

Ben's answer was exactly what I was looking for. Thanks!

For the sake of the archives I'll slightly modify his answer for other new users like myself to follow in the future:

PROBLEM:

I have two images, A and B, which are black and white, from a proprietary program but saved as TIFFs. They open as RGB in the GIMP 2.2 on my Mac, with the image visible in all three channels.

I want to create a final image, C, consisting of image A in the red channel and image B in the blue channel, and no image in the green channel.

SOLUTION:

1) Open the images representing each channel. 2) Convert these images to grayscale mode (as any given single channel
could be represented as a grayscale image.) (Image --> Mode --> Greyscale)
3) If necessary, open a third image/layer as a blank one, since you wanted nothing in the green channel. (A new blank image such as this must be
black and also in greyscale mode) To do this: File --> New, then OK. Then Edit --> Fill with FG Color (which should be black). Finally make it greyscale as in #2.
4) Perform the "compose" function found in Filters --> Colors --> Compose and
choose the layers for the appropriate channels.

The compose dialog is straightforward and easy to use, and generates a new file with the desired result.

Thanks again, Ben. This is very useful to scientists who have single channel images from microscopes.
This way those images are false colored and merged in one step.

Bill Jackson