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Delayed Stroke Processor for Handwriting Recognition

IP.com Disclosure Number: IPCOM000042555D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Tappert, CC: AUTHOR

Abstract

An earlier article [*] describes a recognition system for cursive writing based on elastic matching of the unknown word against a set of letter prototypes. The input to the system is point data produced by the dynamic trace of a stylus on an electronic tablet. Processing is performed on a word-by-word basis after the writing is separated into words. Using prototypes for each letter, the matching procedure allows any letter to follow any letter and finds the letter sequence which best fits the unknown word. Because the unknown word is matched with a direct concatenation of letter prototypes, it must be possible to partition the time sequence of strokes into letters.

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Delayed Stroke Processor for Handwriting Recognition

An earlier article [*] describes a recognition system for cursive writing based on elastic matching of the unknown word against a set of letter prototypes. The input to the system is point data produced by the dynamic trace of a stylus on an electronic tablet. Processing is performed on a word-by-word basis after the writing is separated into words. Using prototypes for each letter, the matching procedure allows any letter to follow any letter and finds the letter sequence which best fits the unknown word. Because the unknown word is matched with a direct concatenation of letter prototypes, it must be possible to partition the time sequence of strokes into letters. Therefore, although this system gave excellent results, it was somewhat cumbersome to use because the writer had to complete each letter before beginning the next and could not use delayed strokes. A delayed stroke is one used to complete a character but which does not immediately follow the first portion of that character. For example, the word city is generally written with three strokes -- the first is the main portion of the word, the second the dot of the i and the third the cross of the t . Here, the second and third strokes are delayed. The procedure to be described herein solves the problem of having to complete each letter before beginning the next by moving delayed strokes to their appropriate places within a word. Basically, each stroke of a word is examined (beginning with the last) and if it is a dot or cross, the underlying stroke is cut (if necessary) into two strokes and the dot or cross moved by reordering the strokes so that it immediately follows the main part of the character i, j, t, or x . The resulting stroke sequence corresponds to that which would be obtained from writing in a manner such that each letter is completed before beginning the next. The procedure uses the following subroutines: REORDER uses bubble sort to reorder the delayed dots and crosses of a word by increasing the minimum x-value. This normalizes the sequence of dots and crosses to appear as though written from left to right. This order is necessary for obtaining the correct stroke order sequence in CUTSTROKE. STRAIGHTLINE is given a stroke and returns TRUE if the stroke is a straight line. A stroke is said to be a straight line if the variance of the direction angles from point to point is below a specified threshold. This is true of any line which is essentially straight. This routine is used to detect potential crosses. Thus, t crossings from left to right or vice versa, and x crossings in either direction are detected. A stroke considered a straight line which intersects a previous stroke is taken to be a cross. Therefore, this routine should be used only in cursive writing or where straight line strokes other than crosses do not intersect earlier writing. CUSP is given a stroke (dot). It examines the earlier strokes of a...