Line extraction in digital ink
AssigneeSilverbrook Research Pty Ltd
InventorsDimitrios Koubaroulis, Jonathon Leigh Napper, Paul Lapstun, Kia Silverbrook
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Abstract
A method of line extraction in a digital ink sequence of handwritten text data points, the method including the steps of: obtaining a stroke sequence comprised of a sequence of strokes; segmenting the strokes into a sequence of substrokes by applying a stroke segmentation algorithm; calculating angular differences between neighbouring groups of substrokes, in the sequence of substrokes; and, determining the positions of the extrema of the angular differences, thereby identifying the substrokes at line breaks and enabling line extraction. A system for line extraction also disclosed.
Claims14
A method of line extraction in a digital ink sequence of handwritten text, the method including the steps of:
- obtaining a stroke sequence comprised of a sequence of strokes;
- segmenting the strokes into a sequence of substrokes by applying a stroke segmentation algorithm;
- calculating angular differences between neighbouring groups of substrokes, in the sequence of substrokes;
- and,
- determining the positions of the extrema of the angular differences, thereby identifying the substrokes at line breaks and enabling line extraction.
The method as claimed in claim 4, wherein substrokes are grouped about a selected substroke into a preceding group of N substrokes and a subsequent group of N substrokes, the centroid of the preceding group and the following group used to calculate the angular difference at the selected substroke.
The method as claimed in claim 8, wherein pre-processing includes removing data points that are less than a threshold distance from a preceding data point in the digital ink sequence.
The method as claimed in claim 8, wherein pre-processing includes removing strokes that are less than a threshold length dimension compared to neighbouring strokes.
The method as claimed in claim 11, wherein post-processing includes removing any line breaks between substrokes of a parent stroke.
A method of line extraction in an on-line digital ink sequence of handwritten text data points, the method including the steps of:
- (1) obtaining a stroke sequence comprised of a sequence of strokes;
- (2) removing small strokes less than a threshold length;
- (3) segmenting the strokes into a sequence of substrokes by:
- (A) computing a relative angle for each line segment connecting successive stroke data points;
- and,
- (B) segmenting the stroke into substrokes if the difference between successive relative angles is greater than a preset threshold;
- and,
- (4) identifying the substrokes at line breaks, thereby facilitating line extraction, by:
- (A) computing N-neighbourhood centroids;
- (B) computing angular differences between N-neighbouring substrokes, or groups of substrokes;
- and,
- (C) computing local maxima of the angular differences in the sequence of substrokes.
A system for line extraction in a digital ink sequence of handwritten text data points, the system comprising:
- (1) an input device to obtain a stroke sequence comprised of a sequence of strokes;
- (2) a processor in communication with the input device and adapted to:
- (A) segment the strokes into a sequence of substrokes by applying a stroke segmentation algorithm;
- (B) calculate angular differences between neighbouring substrokes, or groups of substrokes, in the sequence of substrokes;
- and,
- (C) determine the positions of the extrema of the angular differences, thereby identifying the substrokes at line breaks enabling line extraction.
Dependencies are inferred from the claim text.