Enhancing degraded document images via bitmap clustering and averaging

Proper display and accurate recognition of document im-ages are often hampered by degradations caused by poor scanning or transmission conditions. We propose a method to enhance such degraded document images for better dis-play quality and recognition accuracy. The essence of the method is in finding and averaging bitmaps of the same sym-bol that are scattered across a text page. Outline descriptions of the symbols are then obtained that can be rendered at arbi-trary resolution. The paper describes details of the algorithm and an experiment to demonstrate its capabilities using fax images.