In this paper, we describe the architecture and implementation of a fr
amework to perform content-based search of an image database, where co
ntent is specified by the user at one or more of the following three a
bstraction levels: pixel, feature, and semantic. This framework incorp
orates a methodology that yields a computationally efficient implement
ation of image-processing algorithms, thus allowing the efficient extr
action and manipulation of user-specified features and content during
the execution of queries. The framework is well suited for searching s
cientific databases, such as satellite-image-, medical-, and seismic-d
ata repositories, where the volume and diversity of the information do
not allow the a priori generation of exhaustive indexes, but we have
successfully demonstrated its usefulness on still-image archives.