Method and apparatus for repurposing binary images

• US 6,633,411 B1
• Filed: 07/06/1998
• Issued: 10/14/2003
• Est. Priority Date: 04/01/1998
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: International Business Machines Corporation
• Inventors: Rao, Ravishankar, Thompson, Gerhard Robert, Mintzer, Frederick Cole
• Primary Examiner(s): ROGERS, SCOTT A
• Application Number:
  US09/110,900
• Time in Patent Office: 1,926 Days
• Field of Search: 382/237, 382/176, 382/171, 382/173, 382/199, 382/270, 382/266, 358/1.9, 358/298, 358/462, 358/456, 358/458, 358/466, 358/2.1, 358/3.06, 358/3.07, 358/3.08, 358/3.27
• US Class Current: 358/2.1
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone
• CPC Class Codes: H04N 1/40075 Descreening, i.e. converting a halftone signal into a corresponding continuous-tone signal; Rescreening, i.e. combined descreening and halftoning

Abstract

A method, computer program product, and a program storage device readable by machine, for repurposing images includes classifying the pixels of a binary image as being either halftone image pixels or non-halftone image pixels, further processing the halftoned image pixels with halftone image pixel processing and combining the outputs of the halftone image pixel processing and non-halftone image pixel processing to prepare the images for a second purpose such as a second printer. The processing that classifies the binary pixels as being either halftone image pixels or non-halftone image pixels segments the image into regions of halftone image pixels and regions of non-halftone image pixels. The processing of regions of halftone image pixels first constructs an intermediate gray scale representation of the regions of halftone image pixels. The processing to construct the gray scale representation of the region of halftone image pixels estimates the primary periodicity of the values of the binary pixels within the region of halftone image pixels. The intermediate gray scale image is rehalftoned and combined with the non-halftone image to form the repurposed image.

Claims

1. A method for repurposing a bi-level image, comprised of an array of pixels, each pixel having one of two values, said method comprising:

(a) for each of at least selected ones of the pixels, identifying an area of the array around the pixel, determining gradient density activity in said area by determining the number of changes in pixel intensity values, per unit area, in said identified area, and segmenting the bi-level image into halftone area, with or without text, and non-halftone areas;

(b) rehalftoning the halftone areas; and

(c) combining the rehalftoned areas with the non-halftoned areas to form a repurposed image.

2. The method of claim 1 wherein step (a) includes classifying pixels of the bi-level image as halftone and non-halftone pixels based on a distribution of gradient information.

3. The method of claim 2 wherein the distribution of gradient information is determined by measuring a gradient activity per unit area of the bi-level image.

4. The method of claim 1 wherein step (a) includes clustering pixels of the bi-level image into clusters of halftone pixels and clusters of non-halftone pixels.

5. The method of claim 2 wherein step (a) includes further classifying the pixels into clusters of halftone pixels and clusters of non-halftone pixels.

6. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for repurposing a bi-level image comprised of an array of pixels, each pixel having one of two values, the computer readable program code means in said article of manufacture comprising computer readable program code means for causing a computer to effect the following steps:

(a) for each of at least selected ones of the pixels, identifying an area of the array around the pixel, determining gradient density activity in said area by determining the number of changes in pixel intensity values, per unit area, in said identified area, and segmenting the bi- image into halftone areas, with or without text, and non-halftone areas;

(b) rehalftoning the halftone areas; and

(c) combining the rehalftoned areas with the non-halftoned areas to form a repurposed image.

7. An article of manufacture as recited in claim 6, wherein step (a) includes classifying pixels of the bi-level image as halftone and non-halftone pixels based on a distribution of gradient information.

8. An article of manufacture as recited in claim 7, wherein the distribution of gradient information is determined by measuring a gradient activity per unit area of the bi-level image.

9. An article of manufacture as recited in claim 6, wherein step (a) includes clustering pixels of the bi-level image into clusters of halftone pixels and clusters of non-halftone pixels.

10. An article of manufacture as recited in claim 7, wherein step (a) includes further classifying the pixels into clusters of halftone pixels and clusters of non-halftone pixels.

11. A computer program product comprising a computer usable medium having computer readable program code means embodied therein for repurposing a bi-level image comprised of an array of pixels, each pixel having one of two values, the computer readable program code means in said computer program product comprising computer readable program code means for causing a computer to effect:

(a) for each of at least selected ones of the pixels, identifying an area of the array around the pixel, determining gradient density activity in said area by determining the number of changes in pixel intensity values, per unit area, in said identified area, and segmenting the bi-level image into halftone areas, with or without text, and non-halftone areas;

(b) rehalftoning the halftone areas; and

(c) combining the rehalftoned areas with the non-halftoned areas to form a repurposed image.

12. A computer program product as recited in claim 11, wherein step (a) includes classifying pixels of the bi-level image as halftone and non-halftone pixels based on a distribution of gradient information.

13. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for repurposing a bi-level image comprised of an array of pixels, each pixel having one of two values, said method steps comprising:

(a) for each of at least selected ones of the pixels, identifying an area of the array around the pixel, determining gradient density activity in said area by determining the number of changes in pixel intensity values, per unit area, in said identified area, and segmenting the bi-level image into halftone areas, with or without text, and non-halftone areas;

(b) rehalftoning the halftone areas; and

(c) combining the rehalftoned areas with the non-halftoned areas to form a repurposed image.

14. A method of segmenting a bi-level image into halftone areas, with or without text, and non-halftone areas, said image being comprised of an array of pixels, each pixel having one of two values, said method comprising:

for each of at least selected ones of the pixels, identifying an area of the array around the pixel, determining gradient density activity in said area by determining the number of changes in pixel intensity values, per unit area, in said identified area, , and classifying pixels of the bi-level image as halftone and non-halftone pixels based on said determined gradient density.

15. The method of claim 14, wherein the distribution of gradient information is determined by measuring a gradient activity per unit area of the bi-level image.

16. The method of claim 15, further comprising the step of clustering pixels of the bi-level image into clusters of halftone pixels and clusters of non-halftone pixels.

17. The method of claim 16, further comprising the step of classifying the pixels into clusters of halftone pixels and clusters of non-halftone pixels.

18. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for segmenting a bi-level image into halftone areas, with or without text, and non-halftone areas, said image being comprised of an array of pixels, each pixel having one of two values, said method steps comprising for each of at least selected ones of the pixels, identifying an area of the array around the pixel, determining gradient density activity in said area by determining the number of changes in pixel intensity values, per unit area, in said identified area, and classifying pixels of the bi-level image as halftone and non-halftone pixels based on said determined gradient density.

19. A program storage device readable by machine as recited in claim 18, wherein the distribution of gradient information is determined by measuring a gradient activity per unit area of the bi-level image.

20. A program storage device readable by machine as recited in claim 19, said method steps further comprising the step of clustering pixels of the bi-level image into clusters of halftone pixels and clusters of non-halftone pixels.

21. A program storage device readable by machine as recited in claim 20, said method steps further comprising the step of classifying the pixels into clusters of halftone pixels and clusters of non-halftone pixels.