imgSeek: sketch your search
“imgSeek is a photo collection manager and viewer with content-based search and many other features. The query is expressed either as a rough sketch painted by the user or as another image you supply (or an image in your collection). The searching algorithm makes use of multiresolution wavelet decomposition of the query and database images.” You draw a rough sketch of what you want to find and imgSeek returns thumbnail views of the best matches. Written in Python.