Method and apparatus for recognizing handwritten words

• US 5,615,285 A
• Filed: 06/06/1995
• Issued: 03/25/1997
• Est. Priority Date: 05/27/1992
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Beernink, Ernest H.
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Tadayon, Bijan
• Application Number:
  US08/478,728
• Time in Patent Office: 658 Days
• Field of Search: 382/173, 382/181, 382/187, 382/199, 382/203, 382/209, 382/218, 382/282, 382/155, 382/159, 382/160, 382/161, 382/177, 382/178, 382/179, 382/185, 382/186, 382/188, 382/189 , 382/190, 382/198, 382/200, 382/202, 382/217, 382/224, 382/229, 382/288, 382/286, 382/290, 382/292, 382/293, 382/296, 382/227, 382/315, 364/419.11, 364/920.4, 364/926.9, 364/927, 364/927.2, 364/925.6
• US Class Current: 382/189
• 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 for the angle-independent recognition of handwritten objects including: a) receiving a handwritten stroke; b) normalizing the stroke; c) matching the normalized stroke against a stroke database to obtain at least one character part interpretation; and d) recognizing a handwritten object using one or more of the character part interpretations. Preferably, the step of normalizing the stroke includes the step of normalizing an angle of the stroke by first determining a stroke angle and then rotating the stroke by the stroke angle until the stroke is at a normalized position. An apparatus for the angle independent recognition of handwritten objects includes: a) a central processing unit (CPU); b) a pointer mechanism coupled to the CPU for providing a handwritten stroke to the CPU; c) a mechanism for normalizing the strokes provided by the pointer mechanism; d) a mechanism for matching the normalized strokes against a stroke database to obtain a number of character part interpretations; and e) a mechanism for recognizing a handwritten object using the character part interpretations. Preferably, the mechanism for normalizing the strokes includes a mechanism for detecting stroke angles of the strokes, and a mechanism for rotating the strokes by the stroke angles to create normalized strokes. The mechanism for recognizing the handwritten object preferably includes a controller, a number of recognition domains coupled to the controller, and an arbiter coupled to the controller for resolving multiple interpretations of the object.

Claims

1. A method for the recognition of handwritten objects on a display screen of a computer system, the computer system also having a processor and a memory, the method comprising the steps of:

receiving a handwritten stroke written on the display screen of said computer system, said stroke defining a character part and being received in a form that can be manipulated by said processor;

normalizing the stroke by adjusting the aspect ratio of a bounding box surrounding the stroke when the aspect ratio is greater than a first predetermined value or less than a second predetermined value, said step of normalizing reducing recognition errors due to distortion;

normalizing said stroke by a process including the steps of;

(i) identifying the endpoints of the stroke,

(ii) identifying two of the stroke'"'"'s most widely spaced points, at least one of which is an endpoint of the stroke,

(iii) defining a line between these points,

(iv) determining an angle between a defined axis and the line defined in step (iii), and

(v) rotating the stroke in its entirety by the angle determined in step (iv) such that at least one of the stroke'"'"'s endpoints lies on said defined axis;

matching the normalized stroke against pre-rotated templates in a stroke database stored in memory to obtain at least one character part interpretation; and

using the processor to recognize a handwritten object using one or more of the character part interpretations.

2. A method as recited in claim 1 wherein the first predetermined value is about 3 and the second predetermined value is about one-third.

3. A method as recited in claim 1 wherein the step of normalizing said stroke further comprises rotating the stroke by a predefined angle.

4. A method for recognizing handwritten entries created by writing on a display screen of a computer system with a stylus, the computer system also having a processor and memory, the method comprising the following steps:

receiving a handwritten stroke written on the display screen of said computer system, said stroke substantially begins when said stylus engages said display screen and substantially ends when said stylus subsequently disengages therefrom, said stroke being received in a form that can be manipulated by said processor;

normalizing said stroke by a process including the steps of;

(i) identifying the endpoints of the stroke

(ii) identifying two of the stroke'"'"'s most widely spaced points, at least one of which is an endpoint of the stroke,

(iii) defining a line between these points,

(iv) determining an angle between a defined axis and the line defined in step (iii), and

(v) rotating the stroke in its entirety by the angle determined in step (iv) such that at least one of the stroke'"'"'s endpoints lies on said defined axis;

matching said normalized stroke against a stroke database stored in memory to obtain at least one character part interpretation; and

using said processor to recognize a handwritten object using one or more of said character part interpretations, wherein said step of normalizing reduces recognition errors due to handwriting written at various angles.

5. The method of claim 4 further comprising a step of identifying the center of said stroke.

6. The method of claim 5 wherein the step of rotating the stroke by said angle comprises rotating the stroke about said center of the stroke.