Method and apparatus for recognition of hand-printed characters represented as an electronic ink stream using a box filtering technique

• US 5,920,647 A
• Filed: 08/12/1997
• Issued: 07/06/1999
• Est. Priority Date: 08/12/1997
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Nowlan, Steven J., Monheit, Mark A., Demartines, Pierre, Panagrossi, Jerry
• Primary Examiner(s): Shalwala, Bipin H.
• Application Number:
  US08/909,500
• Time in Patent Office: 693 Days
• Field of Search: 382/187, 382/189, 382/191, 382/202, 382/190, 382/192, 382/194, 382/198, 382/226, 345/173, 345/179
• US Class Current: 382/187
• CPC Class Codes: G06V 30/1423 the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32
• CPC Class Codes: G06V 30/333 Preprocessing; Feature extraction
• CPC Class Codes: G06V 30/373 using a special pattern or subpattern alphabet

Abstract

A method and apparatus to recognize hand-printed characters represented as an electronic ink stream. A first filtering box (300) is defined around a center of a first output point (324) in the electronic ink stream and the first output point is added to a filtered ink stream. A second output point (328) is added to the filtered ink stream only when the electronic ink stream moves outside the filtering box (300). When the second output point (328) is added, the filtering box is re-centered on the second output point (328) only in a dimension that is exceeded after adding the second output point (328) to the filtered ink stream to create a second filtering box (310). Moreover, extraction points (630, 640, 650 and 660) are provided approximately equally spaced across a finite set of points of electronic ink to create a compact representation of a finite set of points of electronic ink.

Claims

1. A method for recognition of hand-painted characters represented as an electronic ink stream using a box filtering technique having at least two points, comprising the step of:

defining a filtering box centered on a first point in the electronic ink stream;

adding the first point to a filtered ink stream;

adding a new point to the filtered ink stream only when a next point of the electronic ink stream lies outside of the filtering box; and

when the new point is added, re-centering the filtering box on the new point in a first dimension only when the new point lies beyond the filtering box in the first dimension but re-centering the filtering box on the new point in a second dimension only when thenew point lies beyond the filtering box in the second dimension.

2. The method of claim 1 further comprising the step of providing, at an output, a pair of coordinates identifying the new point.

3. The method of claim 1 further comprising the step of re-sampling the at least two points when the electronic ink stream is moving in a consistent direction.

4. The method of claim 1 wherein the filtering box has equal height and width.

5. The method of claim 1 wherein the filtering box has sides of equal length.

6. The method of claim 1 wherein the filtering box has orthogonal dimensions.

7. A method for creating a compact representation of a finite set of points of electronic ink comprising:

filtering a set of electronic ink data points using a filtering technique to provide a first set having a number of filtered data points;

providing a second set having a number of extraction points approximately equally spaced across the first set of filtered data points, wherein the second set of extraction points has fewer data points than the first set of filtered data points, and wherein the step of providing the second set of extraction points comprises;

determining how many data points are In the first set of filtered data points; and

extracting the second set of extraction points along the first set of filtered data points dependent on a desired ratio of the number of filtered data points in the first set to the number of extraction points in the second set.

8. The method of claim 7 wherein the first set of filtered data points encompasses plurality of pen-up and pen-down segments.

9. An apparatus for recognition of hand-printed characters as an electronic ink stream using a box filtering technique comprising

a digitizer.

a microprocessor, coupled to the digitizer, having a box filter, a checkpoint extractor, a template comparator and a display processor, wherein the box filter defines a filtering box centered on a first point in the electronic ink stream, adds the first point to a filtered ink stream, adds a new point to the filtered ink stream only when a next point of the electronic stream lies outside of the filtering box, and when the new point is added, re-centering the filtering box on the new point in a selected dimension only, wherein the selected dimension is an x-dimension when the new point lies outside filtering box in the x-dimension but is a y-dimension when the new point lies outside the filtering box in the y-dimension;

a memory, coupled to the microprocessor, having a template and a character representation; and

a display coupled to the microprocessor.

10. A date medium comprising instruction and data which, when load into a microprocessor cause the microprocessor to comprise a filter, a checkpoint extractor, a template comparator and a display processor, wherein the box filter defines a filtering box centered on a first point in the electronic ink stream, adds the first point to a filtered ink stream, adds a new point the filtered ink stream only when a next point of electronic ink stream lies outside of the filtering box, and when the new point is added, re-centers the filtering box on the new point in only first dimension, when the new point lies beyond the filtering box in the first dimension but re-centers filtering box an the new point in only a second dimension, when the new point lies beyond the filtering box in the second dimension.

11. An apparatus for recognition of hand-printed characters as an electronic Ink stream comprising:

a digitizer;

a microprocessor, coupled to the digitizer, having a box filter and a check point extractor, wherein the box filter filters a set of electronic ink data points to provide a first set of filtered data points, and the check point extractor provides a second set of extraction points approximately equally spaced across the first set of filtered data points by determining how many data points are in the first set of filtered data points and extracting the second set of extraction points along the first set of filtered data points dependent on a desired ratio of the number of filtered date points in the first set to the number of extraction points in the second set such that the second set of extraction points has fewer data points than the first set of filtered data points.

12. A data storage medium comprising instructions and data which, when loaded into a microprocessor cause the microprocessor to comprise a box filter and a checkpoint extractor, wherein the box filter filters a set of electronic ink data points to provide a first set of filtered data points, and the checkpoint extractor provides a second set of extraction points approximately equally spaced across the first set of filtered data points by determining how many data points are in the first set of filtered data points and extracting the second set of extraction points along the first set of filtered data points dependent on a desired ratio of the number of filtered data points in the first set to the number of extraction points in the second set such that the second set of extraction points has fewer data points than the first set F filtered points.