Sunday, November 27, 2011

Reusing Shotwell thumbnails in Nautilus

As I have lots of photos on my machine, thumbnails start to consume considerable amount of space on the disk.

Another problem, is that gnome-raw-thumbnailer isn't enabled in Ubuntu (Natty, Oneiric) by default anymore, so my raw photos don't get thumbnailed in Nautilus. And, if I enable it manually, thumbnails of vertical photos don't show with the correct orientation.

So, I have researched a bit the freedesktop thumbnail spec, gnome thumbnailer spec and how Shotwell stores its thumbnails and came up with a shell script that reuses Shotwell thumbnails for Nautilus.

Save the script below as /usr/bin/shotwell-raw-thumbnailer


if [ -z $output ]; then
    echo "Usage: $0 input output"
    exit 1

file=`echo -n ${input##file://} | perl -pe 's/%([0-9a-f]{2})/sprintf("%s", pack("H2",$1))/eig'`
md5=`echo -n $input | md5sum | awk '{print $1}'`

shotwell_id=`sqlite3 ~/.shotwell/data/photo.db "select id from PhotoTable where filename = '$file'"`
if [ -z $shotwell_id ]; then
    gnome-raw-thumbnailer $input $output

thumb=`printf ~/.shotwell/thumbs/thumbs128/thumb%016x.jpg $shotwell_id`
if [ \! -e $thumb ]; then
    gnome-raw-thumbnailer $input $output

replaceWithLink() {
    sleep 1
    ln -sf $thumb ~/.thumbnails/normal/$md5.png

# gnome-thumbnail-factory doesn't support links
cp $thumb $output

# however, linked thumbnails work, so replace them after a delay
replaceWithLink &

In order to make it work, you then need to register it as a thumbnailer in Gnome, put this to /usr/share/thumbnailers/shotwell.thumbnailer
[Thumbnailer Entry]
Exec=/usr/bin/shotwell-raw-thumbnailer %u %o

So, what does this script do?
  • When Gnome (or Nautilus) needs a thumbnail, it runs this script
  • The script checks if the image has an entry in the Shotwell database (~/.shotwell/data/photo.db)
  • Then it checks if Shotwell has a thumbnail for it (in ~/.shotwell/thumbs)
  • If yes, the script returns the already generated thumbnail to Gnome - no generation needed, so it works much faster
  • If Shotwell doesn't have the thumbnail, the call is delegated to gnome-raw-thumbnailer that generates a new thumbnail, the old-fashioned way
  • If Shotwell's thumbnail was used, the script will asynchronously replace the thumbnail in ~/.thumbnails with the link to Shotwell's file, avoiding a copy on the disk

The last step is the one that saves disk space. Unfortunately, it is not possible to return a link right away to Gnome - it can't read it for some reason. However, by putting a link directly under ~/.thumbnails later works perfectly, even if we put a .jpg file under the name of .png (as required by a spec). Png is actually a worse choice for thumbnailing of photos due to its lossless compression, so the disk savings are more than twofold with this script.

The next step would be to rewrite this in C or Vala to make even faster and maybe even make Shotwell create these links right away when it generates the thumbnails.


Anonymous said...

Aw, this was an exceptionally nice post. Taking the time and
actual effort to generate a superb article… but what can
I say… I hesitate a lot and never seem to get nearly anything done.

Here is my website :: michael kors chain tote

Anonymous said...

I like the valuable information you supply on your articles.
I'll bookmark your blog and take a look at again right here regularly. I'm reasonably certain I'll be told a lot of new stuff right here! Good luck for the following!

Also visit my website; louis vuitton commercial
My web page: real louis vuitton purse

Anonymous said...

We stumbled over here coming from a different web page and thought I might check things out.
I like what I see so i am just following you. Look forward to exploring your web page

Also visit my website -

Anonymous said...

Have you ever thought about publishing an e-book or guest authoring on other websites?
I have a blog based on the same information you discuss and would love to have you share some stories/information.

I know my visitors would appreciate your work. If you are even remotely
interested, feel free to shoot me an email.

Here is my homepage ::