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. The searching algorithm makes use of multi-resolution Haar wavelet decomposition of the query and database images.
An open source server-side version of the same image similarity engine found on imgSeek is also available.
A rewrite of imgSeek is currently under planning using the Eclipse RCP framework and many other Java technologies.