Expanding a sky into transparent areas of an image

I frequently have an issue when making panoramas where I am missing parts of sky due to changes in landscape elevation, perspective, etc. I should remember to also shoot images of the sky to incorporate, but often don’t remember.
Are there any reasonably pleasing methods for extending existing sky into transparent areas?
I was hoping gimp’s liquid rescale would work, but I cannot get that to happen.
I tried rescaling individual images larger before stitching, but I had problems there – despite masks to prevent modification, some of the areas marked to preserve were still enlarged (probably due to the large extent of expansion necessary compared to the source material), which messes up panorama generation.
I also tried enhance/heal transparency but the result does not well impersonate the “character” of the existing sky – in this case a sky composed of long horizontal clouds generates a mass of cottonballs tightly packed.

Hah, I answered on the GIMP mailing list already but forgot to check if you’d posted here! :slight_smile:

Liquid rescale might not be the best solution here. One option might be Resynthesizer for GIMP or one of the G’MIC inpainting algorithms.

I’ve personally had luck just manually building a sky to fill in the sections, but this is highly dependent on the source material and how much repair needs to happen. Is there any chance you would be willing to share your image for us to see what might be a good approach?

I’m happy to give it a try and document my thought process and perhaps provide some ideas for approaching this in the future as well. (You can just drag-and-drop the image into a response here and it will automatically get uploaded.)

Thanks, I saw the gimp list reply and apologize for cross-posting. Wasn’t sure I would be reaching the same audience. The png is the result of stitching; jpg is the result of transparency heal (resynthesizer).
I’ve had luck manually building in some cases as well, but the problem I run into here is on the far left there is not much image to start with. When I tried that with this image I ended up with something that seemed pretty unlikely to result in much beyond a big smear by the time I was done.

I also tried copying in some sky from another image thinking I could blend it as well, but wasn’t sure how to do some kind of tone mapping to get the blues a reasonable hue.

I’m sure most of my problems are inadequate skills on my part, so any and all tips are much appreciated.

That image (lower one) is too small to work with. I tried deleting it and uploading a higher res one that was only the left half on the sky with little else (1MB) but got permission denied.

What was the message? Try again: sometimes the forum undergoes maintenance, etc.