This bug has been filled here:

https://bugs.launchpad.net/ubuntu/+source/gthumb/+bug/54764

"I own a Canon PowerShot A85 camera and am using gthumb on Dapper.

I have taken some photos in "Stitched" mode. This keeps a bit of the previous picture on the screen so that one can take multiple photos that line up into one long photo.

If I use the proprietary software in Windows, the following happens:
1) The photos are imported
2) The fact that I have taken photos in this mode is detected by the software and I am taken into a "Stitching" programme. This may be done off filenames as I cannot immediately see any tags about it.
3) The software automatically attempts to overlay the photos in the correct places and produces a chain of photos.
4) A square is drawn around the photos to give the biggest possible connected photo (when using this mode, one often slips up or down and this cuts off the bits either side).

For most photos, this is all automatic and merely requires the user to confirm things.

I would love to see this feature implemented in gthumb - it would give the feature to all cameras, not just mine. I realise that it is a lot of work and suggest that perhaps it could be done as follows:

1) Create a sub-programme to work with the photos manually. This would probably need the ability to manually move the photos around and the ability to draw a square to create one photo from them.
2) Create an option to select some photos and open the programme in (1). This would mean that the user could manually select photos to be stitched and somehow select "Stitch these Photos".
3) Try to automate the process of lining the photos up by matching similar regions and the process of drawing a square around the combined picture.
4) Try to detect sets of stitched photos - this is likely camera specific. If all the above is done, this could be implemented camera-by-camera with the owners of unsupported cameras keeping to the manual method.
5) Perhaps a dialogue could be displayed after importing asking whether or not the user would like to enter the stitching programme. The detected "sets" could be displayed as a list of small pictures on one side."