One month ago, with Marcel, we have worked on a new sets of Search Tools in digiKam for KDE4, called Fuzzy Search
During my digiKam presentation at LGM2008 i have introduced the concept to be able to search duplicates items around the whole collection of photos. But the concept is not just limited to find the similars photos by using copy, it even allows user to drawn a sketch of photo what user memories and shows photos what has similar shapes and colors as on sketch.
This is a companion discussion topic for the original entry at https://www.digikam.org/news/2008-06-10_digikam_fuzzy_search_tools_under_construction/