Methods, Systems and Apparatus for Determining Orientation in a Document Image

• US 20140212047A1
• Filed: 01/29/2013
• Published: 07/31/2014
• Est. Priority Date: 01/29/2013
• 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
• Granted Patent: US 9,076,058 B2
• Time in Patent Office: Days
• US Class Current: 382/195
• CPC Class Codes: G06V 30/1478 of characters or characters lines
• CPC Class Codes: G06V 30/2445 Alphabet recognition, e.g. Latin, Kanji or Katakana

Abstract

Aspects of the present invention are related to systems, methods and apparatus for determining the orientation of a text line or a page in a document image. According to a first aspect of the present invention, an image of text blobs may be generated from a text mask associated with a document image. From the text-blob image, pixel-wise horizontal differences may be accumulated and compared to accumulated pixel-wise vertical differences. Text line orientation may be determined as horizontal when the accumulated pixel-wise horizontal differences are less than the accumulated pixel-wise vertical differences. According to a second aspect of the present invention, page orientation may be determined by reconciling an estimated text-line orientation with document language information.

Claims

1. A method for determining a line orientation in a document image, said method comprising:

receiving, in a processor, a text mask associated with a document image;

generating a text-blob image from said text mask;

accumulating pixel-wise horizontal differences in said text-blob image;

accumulating pixel-wise vertical differences in said text-blob image; and

selecting a line orientation based on a comparison of said accumulated pixel-wise horizontal differences and said accumulated pixel-wise vertical differences.

2. A method as described in claim 1, wherein said text mask is a lower resolution than said document image.

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

receiving said document image; and

generating said text mask from said document image.

4. A method as described in claim 3, wherein said generating said text mask comprises:

extracting a luminance image from said document image; and

generating said text mask from said luminance image.

5. A method as described in claim 3, wherein said generating said text mask comprises:

extracting a luminance image from said document image;

generating a first text mask from said luminance image; and

down-sampling said first text mask to form said text mask.

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

prior to said generating a text-blob image, said text mask is down-sampled; and

said text-blob image is generated from said down-sampled text mask.

7. A method as described in claim 1, wherein said line orientation is horizontal when said accumulated pixel-wise horizontal differences is less than said accumulated pixel-wise vertical differences.

8. A method as described in claim 7, wherein said line orientation is vertical when said accumulated pixel-wise horizontal differences is not less than said accumulated pixel-wise vertical differences.

9. A method as described in claim 1, wherein said generating a text-blob image comprises an operation selected from the group consisting of a smearing operation, a morphological closing operation and a morphological operation comprising a dilation operation followed by a hole filling operation.

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

receiving document language information; and

determining a page orientation by reconciling said document language information and said line orientation.

11. A non-transitory computer-readable medium encoded with a computer program code for implementing a method for determining a line orientation in a document image, said method comprising:

receiving, in a processor, a text mask associated with a document image;

generating a text-blob image from said text mask;

accumulating pixel-wise horizontal differences in said text-blob image;

accumulating pixel-wise vertical differences in said text-blob image; and

selecting a line orientation based on a comparison of said accumulated pixel-wise horizontal differences and said accumulated pixel-wise vertical differences.

12. A computer-readable medium as described in claim 11, said method further comprising:

receiving said document image; and

generating said text mask from said document image.

13. A computer-readable medium as described in claim 12, wherein, in said method, said generating said text mask comprises:

extracting a luminance image from said document image; and

generating said text mask from said luminance image.

14. A computer-readable medium as described in claim 12, wherein said generating said text mask comprises:

extracting a luminance image from said document image;

generating a first text mask from said luminance image; and

down-sampling said first text mask to form said text mask.

15. A computer-readable medium as described in claim 11, wherein, in said method:

prior to said generating a text-blob image, said text mask is down-sampled; and

said text-blob image is generated from said down-sampled text mask.

16. A computer-readable medium as described in claim 11, wherein, in said method, said line orientation is horizontal when said accumulated pixel-wise horizontal differences is less than said accumulated pixel-wise vertical differences.

17. A computer-readable medium as described in claim 16, wherein, in said method, said line orientation is vertical when said accumulated pixel-wise horizontal differences is not less than said accumulated pixel-wise vertical differences.

18. A computer-readable medium as described in claim 11, wherein, in said method, said generating a text-blob image comprises an operation selected from the group consisting of a smearing operation, a morphological closing operation and a morphological operation comprising a dilation operation followed by a hole filling operation.

19. A system for determining a line orientation in a document image, said system comprising:

a text-mask receiver for receiving a text mask associated with a document image;

a text-blob generator for generating a text-blob image from said text mask;

an accumulator for accumulating pixel-wise horizontal differences in said text-blob image and for accumulating pixel-wise vertical differences in said text-blob image;

a comparator for comparing said accumulated pixel-wise horizontal differences and said accumulated pixel-wise vertical differences; and

an orientation selector for selecting a line orientation based on said comparison of said accumulated pixel-wise horizontal differences and said accumulated pixel-wise vertical differences.

20. A method for determining a page orientation in a document image, said method comprising:

receiving, in a processor, a text mask associated with a document image;

generating a text-blob image from said text mask;

accumulating pixel-wise horizontal differences in said text-blob image;

accumulating pixel-wise vertical differences in said text-blob image;

selecting a line orientation based on a comparison of said accumulated pixel-wise horizontal differences and said accumulated pixel-wise vertical differences;

receiving a document language information; and

selecting a page orientation based on said line orientation and said document language information.