Methods and systems for detecting numerals in a digital image

• US 8,406,530 B2
• Filed: 08/18/2011
• Issued: 03/26/2013
• Est. Priority Date: 05/23/2008
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ferman, Ahmet Mufit, Campbell, Richard John
• Primary Examiner(s): Wu, Jingge
• Application Number:
  US13/212,241
• Publication Number:
  US 20110299779A1
• Time in Patent Office: 586 Days
• Field of Search: 382199-201
• US Class Current: 382/200
• CPC Class Codes: G06V 20/62 Text, e.g. of license plates, overlay texts or captions on TV images
• CPC Class Codes: G06V 30/10 Character recognition

Abstract

Aspects of the present invention are related to systems and methods for determining the location of numerals in an electronic document image.

Claims

1. A method for detecting a numeral connected component in a digital image, said method comprising:

receiving a text-line component, wherein said text-line component comprises a plurality of connected components in a digital image;

calculating an aspect ratio for each of said connected components in said plurality of connected components, thereby producing a plurality of aspect ratios;

calculating a first characteristic of said plurality of aspect ratios;

determining a component bounding box for each of said plurality of connected components, wherein each component bounding box comprises a first-side coordinate, a second-side coordinate, a third-side coordinate and a fourth-side coordinate, wherein said first-side coordinate and said second-side coordinate are associated with a first axis of said bounding box and said third-side coordinate and said fourth-side coordinate are associated with a second axis of said bounding box;

determining a first variability measure associated with said first-side coordinates;

determining a second variability measure associated with said second-side coordinates;

determining a third variability measure associated with said third-side coordinates;

determining a fourth variability measure associated with said fourth-side coordinates;

determining a first accumulation of said first variability measure and said second variability measure;

determining a second accumulation of said third variability measure and said fourth variability measure;

when said first accumulation and said second accumulation meet a first accumulation criterion;

setting a first variability characteristic equal to said first variability measure; and

setting a second variability characteristic equal to said second variability measure;

when said first accumulation and said second accumulation do not meet said first accumulation criterion;

setting said first variability characteristic equal to said third variability measure; and

setting said second variability characteristic equal to said fourth variability measure;

classifying said text-line component as a numeral component when a first criterion comprising said first characteristic meeting a second criterion and said first variability characteristic meeting a third criterion and said second variability characteristic meeting a fourth criterion is met; and

classifying said text-line component as a non-numeral component when said first criterion is not met.

2. A method as described in claim 1, wherein said first characteristic is an average of said plurality of aspect ratios.

3. A method as described in claim 1, wherein said first characteristic is a standard deviation of said plurality of aspect ratios.

4. A method as described in claim 1 further comprising:

calculating a second characteristic of said plurality of aspect ratios; and

wherein, said first criterion further comprises said second characteristic meeting a fifth criterion.

5. A method as described in claim 4, wherein said second characteristic is selected from the group consisting of mean and variance.

6. A method as described in claim 1, further comprising:

determining the number of connected components in said plurality of connected components;

calculating a second characteristic of said plurality of aspect ratios; and

wherein, said first criterion further comprises said second characteristic meeting a fifth criterion and said number of connected components meeting a quantity criterion.

7. A method as described in claim 6, wherein:

said determining a first variability measure comprises;

calculating a first representative value of said first-side components; and

calculating a first error measure between said first representative value and said first-side components;

said determining a second variability measure comprises;

calculating a second representative value of said second-side components; and

calculating a second error measure between said second representative value and said second-side components;

said determining a third variability measure comprises;

calculating a third representative value of said third-side components; and

calculating a third error measure between said third representative value and said third-side components; and

said determining a fourth variability measure comprises;

calculating a fourth representative value of said fourth-side components; and

calculating a fourth error measure between said fourth representative value and said fourth-side components.

8. A method as described in claim 1, wherein:

said determining a first variability measure comprises;

calculating a first representative value of said first-side components; and

calculating a first error measure between said first representative value and said first-side components;

said determining a second variability measure comprises;

calculating a second representative value of said second-side components; and

calculating a second error measure between said second representative value and said second-side components;

said determining a third variability measure comprises;

calculating a third representative value of said third-side components; and

calculating a third error measure between said third representative value and said third-side components; and

said determining a fourth variability measure comprises;

calculating a fourth representative value of said fourth-side components; and

calculating a fourth error measure between said fourth representative value and said fourth-side components.