Re: [Tracker] fd.o compliant thumbnailing

[Erlend Davidson <E R M Davidson sms ed ac uk>]

Jamie McCracken wrote:
> Erlend Davidson wrote:
>   
> > Jon Phillips wrote:
> >     
> > > On Tue, 2006-11-28 at 18:57 +0000, Jamie McCracken wrote:
> > >   
> > >       
> > > > Edward Duffy wrote:
> > > >     
> > > >         
> > > > > I know this isn't a high priority item, but here's a patch that makes
> > > > > tracker's thumbnail support follow the fd.o spec.  It uses the
> > > > > $HOME/.thumbnails directory, so it'll work along side nautilus,
> > > > > thundar, and konq.  It will not overwrite up-to-date thumbnails, but
> > > > > the File.SmallThumbnailPath metadata item will be filled in correctly.
> > > > >
> > > > > Currently, it only works for "normal" size, or 128x128, thumbnails.
> > > > > This is because tracker defines "large" as 640x640 while fd.o spec
> > > > > defines it as only 256x256.  Maybe we could create a new directory,
> > > > > called "preview", for these extra-large thumbnails.
> > > > >
> > > > > The patch also removes the hard-coded disabling of thumbnails, so
> > > > > you'll be able to enable it via the EnableThumbnails key in
> > > > > tracker.cfg.  If everything is working right, nautilus should start
> > > > > showing thumbnails for your OO.o documents (currently the only
> > > > > thumbnail generator we have, that nautilus doesn't).
> > > > >
> > > > > Also, this puts a hard dependancy on libpng.  It's needed because the
> > > > > file's URI and MTime need to be embeded in the thumbnail file so it
> > > > > can be tested for validity.  I doubt this should be a problem though.
> > > > >
> > > > >
> > > > >       
> > > > >           
> > > > Great work!
> > > >
> > > > now added with a few minor changes.
> > > >
> > > > We only extract a 128x128 so I have disabled the big thumb for now
> > > >
> > > > Im not sure if we need a command line option for thumbnailing. I have 
> > > > not tested it fully as I cant seem to persuade it to thumbnail but then 
> > > > again maybe its because my thumbs are up to date!
> > > >
> > > > please check cvs (update with new directories from cvs) properly thumbnails
> > > >     
> > > >         
> > > This is great...so if you submit one more nice patch like this one, we
> > > will support you getting direct cvs access to this project.
> > >   
> > >       
> > What is tracker going to do about support for thumbnails?  The 
> > file-manager Thunar (http://thunar.xfce.org) handles thumbnailing in a 
> > freedesktop.org compliant way, could you just use its mechanism for 
> > generating thumbnails?  Thunar has built-in support for many common 
> > formats (this is as a part of thunar-vfs) like pdf, images supported by 
> > gdk-pixbuf and all the gconf thumbnailers.
> >
> > I am currently writing a host of thumbnailer plugins for thunar 
> > (http://goodies.xfce.org/projects/thunar-plugins/thunar-thumbnailers) - 
> > these are just short scripts that call external programs (usually 
> > "convert" from imagemagick).  They are written according to: 
> > http://thunar.xfce.org/documentation/C/customizing-thunar.html#thumbnailers.  
> > I think it would be quite easy to use the same thumbnailer scripts in 
> > tracker.
> >     
>
>
> scripts for thumbnails need to go in @prefix/share/tracker/thumbnailers
>
> I wish there was a freedesktop location for these scripts so that all 
> desktops and apps can share them - feel free to propose it on 
> freedesktop mailing list if you like.
>   
That would require a whole standard for thumbnailers... the thunar ones 
take three or four command-line arguments (input file, size, output file 
and optionally the URI of the file), this should be sufficient, but 
someone might want more and then the standard would break.

Incidently tracker uses the same command-line arguments as thunar for 
thumbnailers.  Coud you possibly change tracker to use the same 
directory as thunar?

Thunar places a .desktop file in /usr/local/share/thumbnailers (i.e. 
/usr/local/share/thumbnailers/eps-thumbnailer.desktop) that points 
towards a script or executable (which can actually be anywhere on the 
filesystem, but is generally in /usr/local/libexec) e.g. 
/usr/local/libexec/eps-thumbnailer.