[KPhotoAlbum] image persistency x checksums

[Tim McCormack]

Martin Jabůrek wrote:
> In my case I did 2 things: renamed file (changed to lowercase) and clear 
> the exif tag+rotate.

And that is the problem. KPA tracks files by two identifiers: Their filepath, 
and their checksum (MD5). If you only modify one of those between KPA sessions, 
KPA will resolve the discrepancy by updating its database. However, if you 
modify *both*, KPA has no way of identifying the file.

Note that KPA has to be *explicitly* told to recalculate the checksum of a file, 
even if it was a KIPI plugin that modified it.

One might suggest various enhancements, of course:
* Recalc checksum when plugin modifies file
* When a file disappears and displays as "not on disk", add a context menu 
option to allow "moving" the image's tags to another file that KPA thinks is new

In any case, for now you should only modify either the filename *or* the file 
data between any two KPA sessions, and always ask KPA to recalc the checksum on 
the file after you modify it.

  - Tim McCormack

P.S. Working from version 3.1.1