System For Line Extraction In Digital Ink

• US 20090238461A1
• Filed: 04/13/2009
• Published: 09/24/2009
• Est. Priority Date: 02/26/2003
• Status: Abandoned Application

• Current Assignee: Silverbrook Research Pty Limited
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Napper, Jonathon Leigh, Lapstun, Paul, Koubaroulis, Dimitrios
• Application Number:
  US12/422,866
• Publication Number:
  US 20090238461A1
• Time in Patent Office: Days
• US Class Current: 382/186
• CPC Class Codes: G06V 30/333 Preprocessing; Feature extraction

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.

Claims

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.