Ubuntu – Show me only picture thumbnails

There is also now an officially recommended way to manage which thumbnails are generated in Thunar by tumbler, the Xfce thumbnailing service. Using the method described below means nothing will need to be uninstalled from the gstreamer set of packages, and all other thumbnails (apart from video) will be generated.

However, it is important to note that this is only possible if you have tumbler 0.1.27, although this will be at least the version in Raring (13.04). If you are on Xubuntu 12.10, you only need to enable the Xfce 4.12 ppa to get the latest version of tumbler.

On the Xfce announce mailing lists for January 2013, it was noted that, regarding tumbler 0.1.27,

This release ships a config file installed in the xdg directory to control the various plugins (especially the priority). There is also a cover download plugin (dependency is libcurl), but this has been disabled by default.

How to enable and disable various plugins is explained on the Xfce official page, but briefly here's how it works. As noted in the explanation, if you want to customise the tumbler rc file, you can make a tumbler folder in your user-specific configuration folder and then copy tumbler.rc from /etc/xdg/tumbler to that folder:

cd ${XDG_CONFIG_HOME:-$HOME/.config}
mkdir -p tumbler
cd tumbler
cp /etc/xdg/tumbler/tumbler.rc .

Now, edit the file with your preferred text editor, e.g.

gedit tumbler.rc

and you will see something like this sample rc file, which has sections for video, image and other thumbnailer plugins.

As an example, you could find the section Video Thumbnailers in the file above and set Disabled=true in the sections for the ffmpegthumbnailer and the gstreamer plugins. Using this method you do not have to remove gstreamer0.10-plugins to stop video thumbnails being shown.

Excerpt from the Video Thumbnailers section of tumbler.rc:

# ffmpegthumbnailer plugin
[FfmegThumbnailer]
Disabled=true
Priority=2
Locations=
MaxFileSize=0

# GStreamer plugin
[GstThumbnailer]
Disabled=true
Priority=1
Locations=
MaxFileSize=0

If at some later point you find that you do not want to entirely disable the video plugins, you could instead use Disabled=false to re-enable them and set a value for the MaxFileSize, so that only files up to a certain size were shown. This would solve problems with high memory usage when thumbnails for very large files are being generated.

• Note: after making any changes to tumbler.rc , it is crucial that you log out and log in again. Video thumbnailing for those two plugins, for example, would not be disabled until you logged in again.

• Remember, this will only work if you have tumbler 0.1.27 or a later version installed.

Digging up further (and researching a LOT), I figured it out:

About image thumbnailers: It seems that Nautilus uses libgnome-desktop for thumbnail management, and the latter uses libgdk-pixbuf to handle file types that have no external handler in /usr/share/thumbnailers. So the "basic" image types are ultimately handled by GnomeDesktopThumbnailFactory and GdkPixbuf (references shown for versions shipped in Ubuntu 12.04). And the formats it handles can be inspected using the gdk-pixbuf-query-loaders tool. In my system this means:

The GdkPixdata format
['gdkp']
['image/x-gdkpixdata']

The Sun raster image format
['ras']
['image/x-cmu-raster', 'image/x-sun-raster']

The PNG image format
['png']
['image/png']

The WBMP image format
['wbmp']
['image/vnd.wap.wbmp']

The JPEG image format
['jpeg', 'jpe', 'jpg']
['image/jpeg']

The ANI image format
['ani']
['application/x-navi-animation']

The TIFF image format
['tiff', 'tif']
['image/tiff']

The XBM image format
['xbm']
['image/x-xbitmap']

The PCX image format
['pcx']
['image/x-pcx']

The Targa image format
['tga', 'targa']
['image/x-tga']

The PNM/PBM/PGM/PPM image format family
['pnm', 'pbm', 'pgm', 'ppm']
['image/x-portable-anymap', 'image/x-portable-bitmap',
 'image/x-portable-graymap', 'image/x-portable-pixmap']

The JPEG 2000 image format
['jp2', 'jpc', 'jpx', 'j2k', 'jpf']
['image/jp2', 'image/jpeg2000', 'image/jpx']

The ICNS image format
['icns']
['image/x-icns']

The BMP image format
['bmp']
['image/bmp', 'image/x-bmp', 'image/x-MS-bmp']

Windows Metafile
['wmf', 'apm']
['image/x-wmf']

The QTIF image format
['qtif', 'qif']
['image/x-quicktime', 'image/qtif']

Scalable Vector Graphics
['svg', 'svgz', 'svg.gz']
['image/svg+xml', 'image/svg', 'image/svg-xml', 'image/vnd.adobe.svg+xml',
 'text/xml-svg', 'image/svg+xml-compressed']

The ICO image format
['ico', 'cur']
['image/x-icon', 'image/x-ico', 'image/x-win-bitmap']

The XPM image format
['xpm']
['image/x-xpixmap']

The GIF image format
['gif']
['image/gif']

So these are the "internal" thumbnailers. And it does include xpm files. So something was wrong with my particular files instead.

And indeed the files were not standard, they had a copyright note prior to the /* XPM * header:

// This file is part of BOINC.
// http://boinc.berkeley.edu
//

/* XPM */
static const char *atiicon_xpm[] = {

Once comments were removed, thumbnails were generated just file.

It is curious that even with the "invalid" header the default Image Viewer in Gnome ("Eye of The Gnome", or eog) was able to display the files! So either files are not actually invalid, or kudos to eog for being able to open them! Anyway, since it is possible to open, and eog uses gdk-pixbuf too, I've filled a bug in libgnome-desktop requesting that thumbnailers be generated for such non-standard xpm files. Any help promoting the bug is appreciated!

Also, some notes about my research:

ThumbnailerSpec is mentioned in several places as the specification for "external thumbnailers". But it has nothing to do with this! It talks about using D-Bus for thumbnailers management, and nothing indicates that such spec is actually implemented in Gnome.

Actually, I was unable to find any official spec on the implemented behavior of "saving a .thumbnailer file with [Thumbnailer Entry] and .desktop-esque format to /usr/share/thumbnailers". Bug 636819 is cited a lot as a source, but it only describes that behavior was changed in Gnome2->Gnome3 transition, and it no longer uses gconf to store external thumbnailers.

It looks like there is no spec at all. This obsolete documentation is still the only official reference, for example, on what %i %o %u %s means.

And the only "official" place announcing the change from gconf to /usr/share/thumbnailers, other than hunting down the source code commit that did it, is this seemingly ordinary bug report.