METHOD OF INDEXING WORDS IN HANDWRITTEN DOCUMENT IMAGES USING IMAGE HASH TABLES

A method of locating handwritten words in handwritten text images under a variety of transformations including changes in document orientation, skew, noise, and changes in handwriting style of a single author which avoids a detailed search of the image for locating every word by pre-computing relevant information in a hash table and indexing the table for word localization. Both the hash table construction and indexing can be done as fast operations taking time quadratic in the number of basis points. Generally, the method involves four stages: (1) Pre-processing where features for word localization are extracted; (2) Image hash table construction; (3) Indexing where query word features are used to look up hash table for candidate locations; and (4) Verification, where the query word is projected and registered with the underlying word at the candidate locations. The method has applications in digital libraries, handwriting tokenization, document management and OCR systems.