Re: [Tracker] Are thumbnails from trackerd really useful?

[Jamie McCracken <jamiemcc blueyonder co uk>]

Laurent Aguerreche wrote:
> Le lundi 11 septembre 2006 Ã 14:15 +0100, Jamie McCracken a Ãcrit :
> > Laurent Aguerreche wrote:
> > > Le dimanche 10 septembre 2006 Ã 17:16 +0100, Jamie McCracken a Ãcrit :
> > > > Laurent Aguerreche wrote:
> > > > > Hello,
> > > > >
> > > > > currently trackerd generates thumbnails for PDF files. I just wonder
> > > > > whether it is useful!
> > > > >
> > > > > To have this feature, trackerd calls evince (which depends on many
> > > > > components of X and GNOME...) and those calls slowdown a little bit
> > > > > trackerd.
> > > > >
> > > > > Graphical shells, like Nautilus, Konqueror or Thunar, are supposed to
> > > > > know how to make thumbnails from files, and I have already many
> > > > > generated thumbnails in ~/.thumbnails. So I think that trackerd should
> > > > > not do thumbnails and let other programs do it by themselves.
> > > > >
> > > > > Am I missing something?
> > > > Yes.
> > > >
> > > > Doing it in tracker means you wont have to wait for file managers to 
> > > > thumbnail.
> > > Yes but I don't care about that! IMHO trackerd should be dedicated to
> > > extract datas from documents for research, and only for research.
> > >
> > > In future if trackerd does a thumbnail for each indexed file it will
> > > spend something like an equal, or greater, time for this task than for
> > > extracting datas.
> > > Furthermore I know that I have some documents that I won't never open
> > > because they are in archives, in big projects, etc. So while trackerd is
> > > losing its time with thumbnailing for documents that I won't never open,
> > > live queries aren't as responsives as they could be for instance.
> > >
> > > > However:
> > > >
> > > > 1) thumbnails should be optional so feel free to add an option to 
> > > > disable them.
> > > Ok. So I propose a patch.
> > thanks patch is good and now committed.
> > > (default is DoThumbnails=true...)
> > >
> > > > 2) They dont use the freedesktop spec for thumbnails yet. This is a bug 
> > > > and a fix would be nice
> > > > http://lists.freedesktop.org/archives/xdg/2004-October/005067.html
> > > But a fix doesn't seem to be so easy!
> > > Names in ~/.thumbnails/{normal,large,fail} are md5 hashes. I think it
> > > isn't a problem since there is a free (in public domain) implementation
> > > available in libgnomeui (it just takes time to compute uri). But
> > > problems come right after: thumbnails need to be resized and tagged. In
> > > libgnomeui, GDK is used. Since GDK is dependent to X, a replacement
> > > should be found...
> > MD5 hash does not require gnome. (mysql has a function for it built in 
> > but as md5's code is so small you could inline the source for it in 
> > tracker-utils.c)
>
> Yes I know. I just say that I found an implementation in public domain
> in libgnomeui. It is small and can be reused/copied. :-)
>
>
> > Its easy to fix and efficient too. Tracker would simply check the mtime 
> > of the existing thumbnail in ~./tumbnails before deciding whether to 
> > call a thumbnailer.
>
> You also need to resize thumbnails and tag them which requires a library
> that can handle many different picture format.

the gconf thumbnailers mostly do this (resize or they take size params). 
Im not sure what you mean by tag? (tags in the created thumbnail image?)

> Or other possibility: each thumbnailer produce a correctly sized and
> tagged PNG picture that can be copied. Problem is that many of them will
> require X... If someday you want a daemon that indexes documents
> in /usr/share/doc for all users (datas sharing), you will have to assume
> that it doesn't use X...

if X is not installed then thumbs wont get generated anyhow. Most of the 
thumbnailers are command line only (even if they have X dependencies)

> > Thumbnails are important for a tracker search gui and a possible tracker 
> > backed file manager which I plan to write some day!
>
> Look at GnomeThumbnail in libgnomeui, there is already all you need to
> manage tumbnailing! (perhaps this code is in GTK2.10 now)

libgnomeui will probably get deprecated at some point and in any event 
we dont want to depend on gnome specific stuff in case XFCE is 
interested in tracker.

> It is easy to use and any application that use it will fill
> ~/thumbnails/* automatically if necessary. :-)
>
> So I'm staying on my idea that thumnailing in trackerd isn't useful...
>
>
> And what is a "tracker backed file manager"?

one that uses tracker to get at files instead of doing a stat dance and 
a huge no of slow disk seeks. Eg with tracker getting all files in my 
home directory is a hell of a lot quicker than stat'ing around trying to 
read off all the data from disk (which nautilus does). Plus with mimes 
and thumbnails already generated it would make a super fast file manager.

Then of course is the integration of tags and metadata, more powerful 
search and the ability to sort data by say Image.Date so all photos are 
organised by when they were taken.

Also good for flat views of all files like all photos or all music which 
means the tracker filemanager would be able to act like a photo manager 
or music manager app.


--
Mr Jamie McCracken
http://jamiemcc.livejournal.com/