Re: Speeding up thumbnail generation (like multi threaded). Thoughts please.

[David Zeuthen <david fubar dk>]

On Wed, 2009-09-30 at 16:07 +0200, Alexander Larsson wrote:
> Another thumbnailing performance trick is to use thumbnails in EXIF
> data, which many cameras add, if availible. 

FWIW, we do this in the gphoto2:// GVfs backend. Browsing through a USB
connected camera in Nautilus is really fast these days; the thumbnails
are 20ish KB (vs. several MB for common consumer cameras). So this
matters _a lot_ when reading from a camera where you only get throughput
of a couple of MB/s at best. 

(Btw, this infrastructure is not specific to the gphoto2:// GVfs
backend; any GVfs backend can use it - say, a Flickr backend).

> This is slightly more
> dubious to do in gdk-pixbuf as the thumbnail is not 100% reliable (i.e.
> it may be out of date due to file modifications or whatnot). 

Another problem is that the embedded thumbnail may not be properly
rotated (on some cameras). This is not a huge problem, just an annoyance
and for gphoto2:// connected devices this tradeoff of quirky behavior vs
performance is justified. For browsing local filesystems it may or may
not be justified.

     David