GIMP Version: 2.8.14
Operating System: Windows
GIMP Experience: New User

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I am using the latest version of GIMP with Win 10 Pro. I have 3 x 8.1 meg Tif files which are greyscale, Red, Green, Blue, filter images from 2M telescope observations.

I want to stack the 3 files and put a red green blue color mask onto each of the files according to the filter used to take the image from the telescope.

I want to stack the 3 files and merge the layers to output a single layer single RGB tiff file image of the telescope observation.

I cannot get it to work and it is driving me crazy.

I want to be able to show students how to process the telescope images like this and I cannot get it to work myself at the moment.

Please help.

Errol Simpson.

Try this.

1) Import all layers. Switch: Image > Mode to Gray Scale.
2) Click Colors > Components > Compose.

Use layer groups, each group having:

- your grayscale channel image at the bottom
- a color filter at the top.

Set the color filter layers to "Multiliply" mode and set the two top groups to "Addition" mode. Something like this:



You can change the opacity of layer masks to decrease saturation, and the opacity of each group. You can of course use any other color for the color masks.

If the initial images are grayscale, the image mode could be in grayscale which prevent adding colors. Chnage to RGB with Image>Mode>RGB.