When you save final mosaic using original images as a tiles (i.e. "use stored thumbs" option is off)
program will search every image file in the same location as it was at the moment of library creation. If
you deleted or moved your original images program will not find them. At this point the program will stop
and ask you:
Do you like to replace original tile picture with smaller thumbnail stored in the library?
Possible options are:
Replace: Replace this tile only.
Replace all rest: Replace all the rest with stored thumbs (don't even search for original).
Auto: Try to replay the rest with originals, if some not found - use thumbs.
Auto replace with source: Program will replace not founded cells with corresponded areas from your
original (source) image.
Cancel: Cancel saving.