An image comparison and retrieval system compares objects and object clusters, or images. User controlled or automatic filtering to enhance object features is performed, and object pixels are defined. An object characterization parameter is computed based on certain object pixel values that characterize one or more aspects of the defined object. Object characterization parameters are compared for objects in different images to produce a measure of object similarity in the same or different images. The query image may be substantially continuously displayed during the image filtering and object definition processes.