[Digikam-users] What triggers digiKam to rebuild all the thumbnails?

[Marcel Wiesweg]

> So is a change of the file size what digiKam actually uses to decide
> that an image file has changed? Does it check anything else?

We check modification date and file size. These are readily available when 
stat'ing a directory.
Thumbnails are identified "by content" which means a hash over parts of the 
file and the file size.