I want to fuse three monochorme images into one RGB image. I was told I should use the function color>components>compose...

When I load the images separately, the other images never appear as options for the "compose" function. When I load the images as layers of a single image, none of them appear as an option.

GIMP help says absolutely nothing about this. It only assumes all of them would be available to chose and attribute to a color channel.

What am I doing wrong?

What version of Gimp? 2.8 has a message bottom of the image window tell you only possible on an image that has been decomposed. https://i.imgur.com/YEiBuSB.jpg Gimp 2.10 has a big pop-up message.

However, 2.8 or 2.10 you can re-assemble like this:

Open the greyscale images https://i.imgur.com/YEiBuSB.jpg (detached the layers dialogue for better visibility)

Make a new RGB image like this: black background + 3 layers filled Red Green & Blue, each with a white layer mask https://i.imgur.com/pTMSJ3Z.jpg

see: https://docs.gimp.org/2.10/en/gimp-layer-mask-add.html

Copy in turn each greyscale image to the appropriate **layer mask** https://i.imgur.com/YZiVXlT.jpg

Put each layer (R, G & B) into Lighten only mode https://i.imgur.com/MPt6bOV.jpg

rich: www.gimp-forum.net

Appologies: Correction for screenshot: should be:

Open the greyscale images https://i.imgur.com/RzZCJxI.jpg (detached the layers dialogue for better visibility)

rich www.gimp-forum.net