Some of that wiki post is obviously old Gimp script save-layers-tiff-24 (For GIMP 2.4 and later) I think "later" is probably Gimp 2.6
As stated the most recent Gimp 2.10 will open multi-page tiff files and open as layers. I do not know if your versions open correctly or not. Regular multi-pages tiffs are no problem.
Can you provide an example tiff ? Maybe post one on dropbox if it is large.
Saving, again Gimp 2.10 will export to multiple pages. The only other way I know is Imagemagick command line. Where
convert file1 file2 file3 -type TrueColorAlpha multilayer.tif packs the files together.
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Edit: A quick test, I made a multilayer image, various layer sizes, one layer has 50% transparency, one layer has a layer mask.
Exporting using Gimp 2.10.22 looks like this: https://i.imgur.com/kC7ssMu.jpg If you use Windows make sure you turn save thumbnail off.
Importing back in: https://i.imgur.com/IBighMe.jpg The layer offsets are retained, the layermask has been applied, but the 50% transparency has been lost. That might be a killer.
Edit2: Just out of interest the save-layers-tiff-24.scm fixed as much as I can fix it. (attached, unzip it and put in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\scripts)
The only problem is the Gimp 2.10 multi-layer tiff procedure seems to break it, Makes a multi-layer tiff per layer. The script works fine in Gimp 2.8. Probably works OK in a pre Gimp 2.10.12 version.
As stated the most recent Gimp 2.10 will open multi-page tiff files and open as layers. I do not know if your versions open correctly or not. Regular multi-pages tiffs are no problem.
Can you provide an example tiff ? Maybe post one on dropbox if it is large.
Saving, again Gimp 2.10 will export to multiple pages. The only other way I know is Imagemagick command line. Where
convert file1 file2 file3 -type TrueColorAlpha multilayer.tif packs the files together.
----
Edit: A quick test, I made a multilayer image, various layer sizes, one layer has 50% transparency, one layer has a layer mask.
Exporting using Gimp 2.10.22 looks like this: https://i.imgur.com/kC7ssMu.jpg If you use Windows make sure you turn save thumbnail off.
Importing back in: https://i.imgur.com/IBighMe.jpg The layer offsets are retained, the layermask has been applied, but the 50% transparency has been lost. That might be a killer.
Edit2: Just out of interest the save-layers-tiff-24.scm fixed as much as I can fix it. (attached, unzip it and put in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\scripts)
The only problem is the Gimp 2.10 multi-layer tiff procedure seems to break it, Makes a multi-layer tiff per layer. The script works fine in Gimp 2.8. Probably works OK in a pre Gimp 2.10.12 version.