Re: JPEG thumbnailing latency

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

Christian Kirbach wrote:
> > Thumbnailing is a slow process (especially for raw files) since it is 
> > compute and io intensive (i.e., lots of matrix algebra + large files).
>
> That is not neccessarily true. I know that  the Nikon RAW file format 
> also stores jpeg encoded preview images ('thumbnails')
...
> But I don't know whether ufraw is used by nautilus with this option

Yes, on my Fedora system, ufraw is called as a thumbnailer script with 
that option:

/usr/bin/ufraw-batch --embedded-image --out-type=png --size=%s %i 
--overwrite --silent

However, thumbnailing of ordinary jpeg and tiff images is still too slow 
and highly memory intensive, mostly because the gtk scaling routines 
don't work well for large scaling factors (typically required for 
digital photos). This will slow down the embedded thumbnail -> system 
thumbnail process too.

http://bugzilla.gnome.org/show_bug.cgi?id=80925
http://bugzilla.gnome.org/show_bug.cgi?id=142428
http://bugzilla.gnome.org/show_bug.cgi?id=522803

The gtk scaling routines really need some love from an algebra guru.

The tiff pixbuf loader could really use some optimization (e.g., 
skipping strips in strip-based images to speed up thumbnailing). Maybe 
the png loader could use similar tricks.

Side note: yes, some jpeg images also have embedded thumbnails. However, 
many apps forget to modify this thumbnail if the main image is modified, 
making the embedded thumbnail highly unreliable...

- Mike