Please allow me to invoke Gigapixel fom Lightroom and/or Photoshop

With the current version (v5) you can now use GigaPixel from Lightroom by creating your own External Editor Preset pointing to the folder with the executable, then in GigaPixel select Save with the following settings (NOTE: Save directory of Source is important because you can then Sync the folder you are working in to import into Lightroom)

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For 100% integration with Lightroom there needs to be a Module wrapper built and for PS there needs to be an automation (not filter) to be able to expand the canvas after processing. Even in PS you can create a script but it would be pointless because it would need to be run as a batch and you can do that from GigaPixel

You need to read the post I was answering, talking about the current version at that time.