Edge compaction in antialiased images

• US 6,381,035 B1
• Filed: 12/21/1998
• Issued: 04/30/2002
• Est. Priority Date: 12/21/1998
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Zhang, Yeqing, Banton, Martin E., Loce, Robert P.
• Primary Examiner(s): Lee, Thomas D.
• Assistant Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US09/217,035
• Time in Patent Office: 1,226 Days
• Field of Search: 358/1.9, 358/1.14, 382/239, 382/260-269
• US Class Current: 358/1.9
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/30 Erosion or dilatation, e.g. thinning
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening

Abstract

A method to compact a diffuse gray edge that is two pixels wide to a state where it is one pixel wide so that it may be well rendered with anti-alias rendering. The method identifies an observation window within continuous tone image data. The method then operates on the pixels within the observation window by: compacting horizontal features within the observation window; compacting vertical features within the observation window; and compacting corner features within the observation window.

Claims

1. A method for compacting a diffuse gray edge, comprising the steps of:

identifying an observation window within continuous tone image data, said observation window including a target pixel;

determining if said target pixel is within a diffuse horizontal edge; and

compacting horizontal features within said observation window,

wherein said step of compacting horizontal features comprises shifting gray from a first pixel (A) that is not adjacent to a saturated pixel to a second pixel (B) that is adjacent to a saturated pixel; and

updating a pixel value in response to said shifting step.

2. The method of claim 1 wherein said gray is shifted from said first pixel A to said second pixel B according to

3. The method according to claim 1, wherein said step of updating a pixel value comprises providing a modified value for said target pixel.

4. The method according to claim 1, wherein said step of updating a pixel value modifies the values of pixels within said observation window.

5. A method for compacting a diffuse gray edge, comprising the steps of

identifying an observation window within continuous tone image data, said observation window including a target pixel;

and

compacting vertical features within said observation window, wherein said step of compacting vertical features comprises

determining if said target pixel is within a diffuse vertical edge,

shifting gray from a first pixel (A) that is not adjacent to a saturated pixel to a second pixel (B) that is adjacent to a saturated pixel, and

updating a pixel value in response to said shifting step.

6. The method of claim 5 wherein said gray is shifted from said first pixel A to said second pixel B according to

7. A method for compacting a diffuse gray edge, comprising the steps of:

identifying an observation window within continuous tone image data, said observation window including a target pixel;

compacting horizontal features within said observation window;

compacting vertical features within said observation window; and

compacting corner features within said observation window, wherein;

said step of compacting horizontal features modifies said target pixel and a first pixel adjacent said target pixel by shifting gray between said target pixel and said first pixel when said target pixel is within a diffuse horizontal edge,

said step of compacting vertical features modifies said target pixel and a second pixel adjacent said target pixel by shifting gray between said target pixel and said second pixel when said target pixel is within a diffuse vertical edge, and

said step of compacting corner features modifies a pixel within said compaction window when said target pixel is within a diffuse corner.

8. The method according to claim 7, wherein said step of compacting horizontal features and said step of compacting vertical features are performed before said step of compacting corner features.

9. A method for compacting a diffuse gray edge, comprising the steps of:

identifying an observation window within continuous tone image data, said observation window including a target pixel;

determining if said target pixel is within a diffuse comer;

shifting gray from a first pixel (A) that is not adjacent to a saturated pixel to a second pixel (B) that is adjacent to a saturated pixel; and

updating a pixel value in response to said shifting step.

10. The method of claim 9 wherein said gray is shifted from said first pixel A to said second pixel B according to

11. The method of claim 9 further comprising the step of shifting gray from a third pixel (C) to said second pixel B.

12. The method of claim 11 wherein said gray is shifted from said third pixel C to said second pixel B according to

13. The method of claim 11 further comprising the step of shifting gray from a fourth pixel (D) to said second pixel B.

14. The method according to claim 9, wherein said step of updating a pixel value comprises providing a modified value for said target pixel.

15. The method according to claim 9, wherein said step of updating a pixel value modifies the values of pixels within said observation window.

16. In a printing system having a digital front end for processing image data to generate print ready data, a method for compacting a diffuse gray edge, comprising the steps of:

receiving continuous tone image data;

identifying a target pixel within said received continuous tone image data;

analyzing pixels neighboring said target pixel to determine if said target pixel is within a diffuse gray edge; and

compacting gray pixels within said diffuse gray edge.

17. The method of claim 16, wherein said step of compacting gray pixels within said diffuse gray edge comprises:

analyzing pixels neighboring said target pixel to determine if said target pixel is within a diffuse horizontal edge;

analyzing pixels neighboring said target pixel to determine if said target pixel is within a diffuse vertical edge; and

analyzing pixels neighboring said target pixel to determine if said target pixel is within a diffuse corner.

18. The method of claim 16, wherein said step of compacting gray pixels within said diffuse gray edge comprises:

shifting gray between pixels within a diffuse horizontal edge in response to a first edge condition;

shifting gray between pixels within a diffuse vertical edge in response to a second condition; and

shifting gray between pixels within a diffuse corner in response to a third condition.

19. The method of claim 18, wherein:

said step of shifting gray between pixels within a diffuse horizontal edge comprises shifting gray from a first pixel that is not adjacent to a saturated pixel to a second pixel that is adjacent to a saturated pixel;

said step of shifting gray between pixels within a diffuse vertical edge comprises shifting gray from a pixel that is not adjacent to a saturated pixel to a second pixel that is adjacent to a saturated pixel; and

said step of shifting gray between pixels within a diffuse corner comprises shifting gray from a pixel that is not adjacent to a saturated pixel to a second pixel that is adjacent to a saturated pixel.

20. The method of claim 16, wherein said step of compacting gray pixels within said diffuse gray edge comprises:

shifting gray from a first pixel that is not adjacent to a saturated pixel to a second pixel that is adjacent to a saturated pixel, and

updating a pixel value in response to said shifting step.