This paper describes the Decentralized Image Retrieval for Education (DIRECT) service for the National Science, Technology, Engineering, and Mathematics (STEM) Digital Library (NSDL). DIRECT augments NSDL by providing content-based image-retrieval (CBIR) functionality. CBIR allows the user to designate a query image so that the service can search the library for images of similar content. DIRECT matches images not by text metadata but by the color or texture of the image objects; the matching process does not depend on a match between the cataloger description and the user description. DIRECT is a peer-to-peer service built for decentralized digital libraries. The content-based image-retrieval service is available to all collections in NSDL without imposing new standards or protocols. With DIRECT, NSDL can support images that have yet to be cataloged or have incomplete metadata without adding overhead (expenditure of additional resources) to the collections.