System For Line Extraction In Digital Ink

Abstract

A system is provided having a database storing annotation digital ink representing handwritten annotations on a printed document and a processor configured to segment the annotation digital ink into lines by obtaining a stroke sequence comprised of a sequence of strokes, removing small strokes less than a threshold length, segmenting the strokes into a sequence of substrokes by computing a relative angle for each line segment connecting successive stroke data points and segmenting the stroke into substrokes if the difference between successive relative angles is greater than a preset threshold, and identifying the substrokes at line breaks, thereby facilitating line extraction, by computing N-neighbourhood centroids, computing angular differences between N-neighbouring substrokes, or groups of substrokes and computing local maxima of the angular differences in the sequence of substrokes.

1 . A system comprising a first database storing annotation digital ink representing handwritten annotations on a printed document and a processor configured to segment the annotation digital ink into lines by:
 obtaining a stroke sequence comprised of a sequence of strokes;   removing small strokes less than a threshold length;   segmenting the strokes into a sequence of substrokes by:
 computing a relative angle for each line segment connecting successive stroke data points; and 
 segmenting the stroke into substrokes if the difference between successive relative angles is greater than a preset threshold; and 
   identifying the substrokes at line breaks, thereby facilitating line extraction, by:
 computing N-neighbourhood centroids; 
 computing angular differences between N-neighbouring substrokes, or groups of substrokes; and 
   computing local maxima of the angular differences in the sequence of substrokes.   
   
   
       2 . A system as claimed in  claim 1  further comprising a handheld sensing device for generating the annotation digital ink during interaction with the printed document. 
   
   
       3 . A system as claimed in  claim 1  further comprising second database for storing a digital representation of the printed document. 
   
   
       4 . A system as claimed in  claim 3  wherein the processor matches an input digital ink query against the annotation digital ink in the first database to thereby identify a corresponding digital representation in the second database.