One of the nicest things about digiKam is how easily its functionality can be extended, by using plugins:
Kipi Plugins: the Kde Image Plugins Interface project (Kipi) (manual) is an effort to develop a common plugin structure for digiKam, KPhotoAlbum, Showimg and Gwenview. Its aim is to share image plugins among graphical applications. Kipi-Plugins setup is described in this section.
Plugins can manipulate images in almost any way that users can. Their advantage is, that it is much easier to add a capability to digiKam by writing a small plugin than by modifying the digiKam core.