"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:

> Steven, you can use GIMP to do what you proposed doing with PhotoShop, scripted
> or manually. Here's the manual method:
>
> 1. Open the first partial image in GIMP.
> 2. Use the Dialogs > Layers menu (F7 on Windows) to pull up a list of layers
> 3. Open the second partial image in GIMP and copy it.
> 4. Paste this partial image onto the first partial image
>    (this makes a separate layer for the pasted image).
> 5. User menu Layer > New Layer (Shift+Ctrl+N)
> 6. In the Layers dialog set the pasted layer to mode: Screen.
> 7. Repeat 3-6 for each partial image.
>
> This will ignore the black areas and make all the layers visible as a single
> image at each step.
>
> You can do the same thing in PhotoShop - experiment with the different layer
> merge modes (Multiply, Lighten, etc.).
>

Thanks Rob, that's indeed what I would do in Photoshop if only it would open the
files :-)
Actually, F7 is the Photoshop way to bring up the Layers menu, in GIMP it seems
to be Ctrl-L. Screening is also what you do in PS. And in your manual method
step 5 isn't necessary.

The thing is, this is a HUGE image (400 megapixels) and placing layer upon layer
asks a lot of computer resources, unless you flatten layers after every step 6.
Still takes a lot of time though.
And I guess I made a wrong choice about the size of the partial images; there's
too many of them to do the operation by hand.

Thanks again.
Steven

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