[gthumb-list] embedded thumbnails

["Dr. Michael J. Chudobiak" <mjc avtechpulse com>]

Hi all,

We've moved the photo importer over to the gvfs-gphoto2 backend, instead 
of libgphoto2, which seems to work great - except that we lost the 
ability to rapidly generate previews for cameras mounted as mass storage 
devices under /media.

So, I've added code to extract exif previews quickly using exiv2 
instead, which speeds up the importer noticeably. This feature will stay.

More experimentally, the browser thumbnailer now uses the embedded 
thumbnails provided by exiv2. We'll have to see if that is reliable. 
Feedback is welcome!

In both cases, the embedded thumbnails are ignored if they are obviously 
rotated relative to the main image. But this certainly won't catch all 
discrepancies.


- Mike