Tumbler is a D-Bus service for applications to request thumbnails for
various URI schemes and MIME types. It is an implementation of the
thumbnail management D-Bus specification described on
http://live.gnome.org/ThumbnailerSpec written in an object-oriented
fashion using GLib and GObject. Its modular architecture makes it very
flexible and useful in many situations. It provides plugin interfaces
for extending the URI schemes and MIME types for which thumbnails can be
generated as well as for replacing the storage backend that is used to
store the thumbnails on disk. Tumbler's functionality can also be
extended via specialized thumbnailer services implemented in accordance
to the thumbnail management D-Bus specification.

Homepage:
https://docs.xfce.org/xfce/tumbler/start
