Method and apparatus for recording of electronic handwriting

• US 7,162,087 B2
• Filed: 12/27/2002
• Issued: 01/09/2007
• Est. Priority Date: 12/28/2001
• Status: Expired due to Fees

• Current Assignee: Anoto Group AB
• Original Assignee: Anoto Group AB
• Inventors: Bryborn, Mattias
• Primary Examiner(s): DESIRE, GREGORY M
• Application Number:
  US10/329,797
• Publication Number:
  US 20030122802A1
• Time in Patent Office: 1,474 Days
• Field of Search: 382/119, 382/186, 382/187, 382/198, 382/241, 345/173
• US Class Current: 382/187
• CPC Class Codes: G06V 10/19 by sensing codes defining pattern positions
• CPC Class Codes: G06V 30/1423 the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32

Abstract

According to a method for recording of electronic handwriting, a handwriting movement is digitized into a sequence of points along a writing curve that corresponds to the handwriting movement. The sequence of points is resampled by eliminating those points that are judged not to be necessary for being able to reconstruct the writing curve later with the required visual quality. A resampled representation of the writing curve is created from the points remaining—that is not eliminated—after the resampling. The resampling is carried out on successive and partially overlapping partial sequences of the points, the resampled representation of the writing curve being extended successively after resampling of a respective partial sequence.

Claims

1. A method for recording of electronic handwriting, in which a handwriting movement is digitized into a sequence of points along a writing curve that corresponds to the handwriting movement, the method comprising:

resampling the sequence of points by eliminating those points judged not to be necessary to reconstruct the writing curve later with a predetermined visual quality; and

creating a resampled representation of the writing curve from the non-eliminated points after the resampling, wherein

the resampling is carried out on successive and partially overlapping partial sequences of the sequence of points, and

the resampled representation of the writing curve is extended successively after resampling of a respective partial sequence.

2. The method as claimed in claim 1, wherein the resampling is carried out according to an algorithm for polygonal approximation of the writing curve, such that a curve segment between two consecutive non-eliminated points is represented by a straight line.

3. The method as claimed in claim 2, in which said algorithm is the Douglas-Peucker'"'"'s algorithm.

4. The method as claimed in claim 1, wherein:

a partial sequence of points includes n points, with an overlap between two consecutive partial sequences of w points, where 1<

w<

=n/2, and

an individual partial sequence is stored during the resampling in a memory buffer with room for n points, and the last w points in this individual partial sequence being left in the memory buffer and being included in the resampling of a next following partial sequence.

5. The method as claimed in claim 4, further comprising:

adding, after the resampling of said individual partial sequence, the non-eliminated points in the memory buffer to the resampled representation of the writing curve, with the exception of the non-eliminated points from a subset of said last w points in said individual partial sequence, the subset consisting of x points, which instead are included in the resampling of a next following partial sequence as regards addition to the resampled representation of the writing curve.

6. The method as claimed in claim 5, comprising the steps of

a) filling the memory buffer with points;

b) applying a line-generalization algorithm to the points in the memory buffer, wherein such remaining points are marked which are not eliminated by the algorithm;

c) letting the marked points from the points 1 to n−

x in the memory buffer be incorporated in the resampled representation of the writing curve;

d) deleting the first n−

w points in the memory buffer;

e) placing the remaining w points at the start of the memory buffer;

f) as long as points are available for resampling;

f1) filling up the memory buffer with n−

w new points;

f2) applying the line-generalization algorithm to the points in the memory buffer, in accordance with step b);

f3) letting the marked points from the points w−

x to n−

x in the memory buffer be incorporated in the resampled representation of the writing curve;

f4) deleting the first n−

w points in the memory buffer; and

f5) placing the remaining w points at the start of the memory buffer;

g) letting the marked points from the remaining points n−

1+x to n in the memory buffer be incorporated in the resampled representation of the writing curve.

7. A method as claimed in claim 6, wherein said line-generalization algorithm is the Douglas-Peucker'"'"'s algorithm.

8. The method as claimed in claim 5, in which x=w/2.

9. The method as claimed in claim 5, in which n=128 and w≈

n/10.

10. The method as claimed in claim 4, further comprising:

adding the non-eliminated points in the memory buffer after the resampling of said individual partial sequence to the resampled representation of the writing curve, such that the remaining points from the overlapping w points between two consecutive partial sequences are added to the resampled representation of the writing curve, if they are not eliminated during resampling of at least one of these two consecutive partial sequences.

11. The method according to claim 1, further comprising:

relative coding coordinates for the non-eliminated points corresponding to the resampled representation of the writing curve; and

compressing the relative-coded coordinates using statistical coding.

12. The method as claimed in claim 11, wherein relative coding the coordinates for an individual non-eliminated point comprises:

approximating a polynomial of order N to the N+1 preceding non-eliminated points;

determining a prediction of said individual non-eliminated point using said polynomial;

determining a deviation between said individual non-eliminated point and its prediction; and

using this deviation as a relative coding for said individual non-eliminated point.

13. The method as claimed in claim 1, further comprising:

storing the resampled representation of the writing curve as a data set in a memory.

14. The method as claimed in claim 1, in which the resampling is carried out as soon as the handwriting movement has been digitized into a predetermined number of points.

17. A computer program product that can be directly read into a computer readable memory associated with a processor, comprising program code for carrying out the steps according to claim 1.

15. An apparatus for recording of electronic handwriting, comprising:

a digitizer that digitizes a handwriting movement into a sequence of points along a writing curve corresponding to the handwriting movement; and

a resampling unit that eliminates those points in the sequence of points judged not to be necessary to reconstruct the writing curve later with a predefined visual quality, and creates a resampled representation of the writing curve from the non-eliminated points after the resampling, wherein

the resampling unit resamples points for successive and partially overlapping partial sequences of points, and extends the resampled representation of the writing curve successively after resampling of a respective partial sequence.

16. The apparatus as claimed in claim 15, wherein the apparatus is in the form of an electronic pen.