Character contour correction

• US 20090046938A1
• Filed: 08/15/2007
• Published: 02/19/2009
• Est. Priority Date: 08/15/2007
• Status: Abandoned Application

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Yoder, Gabriel J.
• Application Number:
  US11/893,259
• Publication Number:
  US 20090046938A1
• Time in Patent Office: Days
• US Class Current: 382/242
• CPC Class Codes: G06T 9/20 Contour coding, e.g. using detection of edges

Abstract

Systems and methods are presented for correcting contours of alphanumeric characters. At least one string of numbers that characterizes a given contour of an alphanumeric character is generated. Each number within the string of numbers represents a direction of transition between consecutive pixels in the contour. Sets of consecutive numbers within the string that represent defects in the contour are identified. The identified sets of consecutive numbers are replaced with corrected sets of at least one consecutive number to produce a corrected at least one string of numbers.

Claims

1. A method for correcting contours of alphanumeric characters, comprising:

generating at least one string of numbers that characterizes a given contour of an alphanumeric character, each number within the string of numbers representing a direction of transition between consecutive pixels in the contour;

identifying sets of consecutive numbers within the string that represent defects in the contour; and

replacing the identified sets of consecutive numbers with corrected sets of at least one consecutive number to produce a corrected at least one string of numbers.

2. The method of claim 1, further comprising decoding the corrected at least one string of numbers to construct a corrected contour for the alphanumeric character.

3. The method of claim 1, wherein identifying sets of consecutive numbers within the string comprises identifying sets of numbers within the image that represent single pixel extensions to otherwise ninety-degree corners within the contour.

4. The method of claim 1, wherein identifying sets of consecutive numbers within the string comprises identifying sets of numbers within the image that represent pixel wide line segments that are connected to the alphanumeric character only at one end.

5. The method of claim 1, wherein identifying sets of consecutive numbers within the string comprises identifying sets of numbers within the image that represent short jogs within a longer, straight run of pixels.

6. The method of claim 1, wherein generating the at least one string of numbers comprises encoding the contour via Freeman chain coding.

7. An optical character recognition process, comprising:

scanning a plurality of alphanumeric characters as a respective plurality of digital images;

binarizing the plurality of digital images;

correcting the contours of the binarized plurality of images via the method of claim 1;

extracting respective sets of features from the corrected plurality of images; and

classifying each of the plurality of images as an alphanumeric character according to its associated set of extracted features.

8. The process of claim 7, wherein the scanned plurality of alphanumeric characters represent text on an envelope, and the process further comprises directing the processing of the envelope according to the classified plurality of images corresponding to the scanned plurality of alphanumeric characters.

9. A computer readable medium comprising computer executable instructions for correcting contours of alphanumeric characters, the computer executable instructions comprising:

a contour coder that generates at least one string of numbers that characterizes a given contour of an alphanumeric character, each number within the string of numbers representing a direction of transition between consecutive pixels in the contour;

a rule-based processor that identifies sets of consecutive numbers within the string that represent defects in the contour and replaces the identified sets of consecutive numbers with corrected sets of at least one consecutive number to produce a corrected at least one string of numbers; and

a character reconstruction element that reconstructs the alphanumeric character from the corrected at least one string of numbers.

10. The computer readable medium of claim 9, wherein the rule-based processor identifies sets of numbers within the image that represent single pixel extensions to otherwise ninety-degree corners within the contour.

11. The computer readable medium of claim 9, wherein the rule-based processor identifies sets of numbers within the image that represent pixel wide line segments that are connected to the alphanumeric character only at one end.

12. The computer readable medium of claim 9, wherein the rule-based processor identifies sets of numbers within the image that represent short jogs within a longer, straight run of pixels.

13. The computer readable medium of claim 9, the contour coder being operative to generate the at least one string of numbers via Freeman chain coding.

19. The system of claim 13, the contour coder being operative to generate the at least one string of numbers via Freeman chain coding.

14. An optical character recognition system that classifies a digital image, comprising:

a binarization element that binarizes the digital image;

a character preprocessor, comprising;

a contour coder that generates at least one string of numbers that characterizes a given contour of an alphanumeric character, each number within the string of numbers representing a direction of transition between consecutive pixels in the contour; and

a rule-based processor that identifies sets of consecutive numbers within the string that represent defects in the contour and replaces the identified sets of consecutive numbers with corrected sets of at least one consecutive number to produce a corrected at least one string of numbers;

a feature extractor that extracts respective sets of features from the corrected plurality of images; and

a pattern recognition classifier that classifies each of the plurality of images as an alphanumeric character according to its associated set of extracted features.

15. The system of claim 14, the character preprocessor further comprising a character reconstruction element that reconstructs the alphanumeric character from the corrected at least one string of numbers.

16. The system of claim 14, wherein the rule-based processor comprises a bump removal element that identifies sets of numbers within the image that represent single pixel extensions to otherwise ninety-degree corners within the contour and replaces these sets of numbers with corrected sets of numbers.

17. The system of claim 14, wherein the rule-based processor comprises a spike removal element that identifies sets of numbers within the image that represent pixel wide line segments that are connected to the alphanumeric character only at one end and replaces the identified sets of numbers with corrected sets of numbers.

18. The system of claim 14, wherein the rule-based processor comprises a jog removal element that identifies sets of numbers within the image that represent short jogs within a longer, straight run of pixels and replaces the identified sets of numbers with corrected sets of numbers.

20. A mail sorting system, comprising:

a region of interest identifier that locates regions containing alphanumeric characters on a scanned image of an envelope;

a candidate segmentation element that separates the scanned image of the envelope into digital images representing individual alphanumeric characters;

the optical character recognition system of claim 14; and

a post-processing element that directs the processing of the envelope according to the classified plurality of images corresponding to the plurality of alphanumeric characters associated with the envelope.