Content-based image similarity search — determining the images in a database visually similar to a search image on the basis of pixel data alone — is a hot topic. Applications are numerous. Just recently, amazon.com has introduced a visual product similarity search for some products, and google has introduced a search-by-image feature.
In addition to hands-on applications, there is a lot of research on the topic. The abilities of university maintained image search engines grow constantly. Unfortunately, implementing current techniques requires a bunch of specialist knowledge and some mathematical sophistication. Fortunately, however, there are effective simple techniques for which there exist open source libraries.
One such library for JAVA is the LIRE API. In this short article, I demonstrate how to implement a basic linear content-based visual image similarity search using this library.