Laser print apparatus with dual halftones

• US 7,733,532 B2
• Filed: 10/27/2004
• Issued: 06/08/2010
• Est. Priority Date: 10/27/2004
• Status: Expired due to Fees

• Current Assignee: Marvell International Technology, Ltd. (Marvell Technology Group Limited)
• Original Assignee: Marvell International Technology, Ltd. (Marvell Technology Group Limited)
• Inventors: Shoen, Jay R., Keithley, Douglas Gene
• Primary Examiner(s): LEE, TOMMY D
• Application Number:
  US10/974,079
• Publication Number:
  US 20060087695A1
• Time in Patent Office: 2,050 Days
• Field of Search: 358/3.06, 358/3.27, 358/1.1, 358/1.2, 358/1.9, 358/3.01, 382/266, 382/173, 382/176, 382/254, 382/264
• US Class Current: 358/3.06
• CPC Class Codes: G06K 15/1881 Halftoning halftoning of still images in general H04N1/405, H04N1/52
• CPC Class Codes: H04N 1/40068 Modification of image resolution, i.e. determining the values of picture elements at new relative positions H04N1/3935 takes precedence
• CPC Class Codes: H04N 1/40081 Soft dot halftoning, i.e. producing halftone dots with gradual edges

Abstract

A printing system comprises a memory configured to store image data representing an image. The printing system comprises a processor configured to perform a first digital halftone process on a first portion of the image and a second digital halftone process on a second portion of the image.

Claims

1. A printing system comprising:

a memory configured to store image data representing an image; and

a processor configured to perform a first digital halftone process on a first portion of the image and a second digital halftone process on a second portion of the image, wherein the processor is configured to locate the first portion by comparing an intensity value of a first pixel and an intensity value of a second pixel, wherein the second pixel is adjacent to the first pixel,

wherein the first portion is an edge of the image and the second portion is not an edge of the image, and the first digital halftone process comprises a higher resolution than the second digital halftone process,

wherein the processor adjusts the intensity value of the first pixel if a difference between the intensity value of the first pixel and the intensity value of the second pixel is greater than a predetermined threshold, and

wherein the first digital halftone process determines edge pixel values by selecting one of two nonzero pixel values.

2. The printing system of claim 1, wherein the higher resolution comprises a higher lines per inch (lpi) halftone.

3. The printing system of claim 1, wherein the first digital halftone process comprises a halftone within a range of approximately 200 lines per inch (lpi) to approximately 300 lpi.

4. The printing system of claim 1, wherein the second digital halftone process comprises a halftone within a range of approximately 100 lines per inch (lpi) to approximately 150 lpi.

5. The printing system of claim 1, wherein the one of two nonzero pixel values are selected semi-randomly.

6. The printing system of claim 5, wherein the first halftone process alternates between the two nonzero pixel values such that one of the two nonzero pixel values is selected more often that the other of the two nonzero pixel values.

7. The printing system of claim 1, wherein the first portion is at least one pixel wide.

8. The printing system of claim 1, wherein the processor adjusts the intensity value of the first pixel by darkening the first pixel.

9. A printing system comprising:

a memory configured to store image data; and

a processor configured to locate image edges in the image data and apply a first halftone to image data that is located at an image edge and apply a second halftone to image data that is not located at an image edge, wherein the processor is configured to locate the image edge by comparing an intensity value of a first pixel and an intensity value of a second pixel, wherein the second pixel is adjacent to the first pixel,

wherein the first halftone comprises a higher resolution than the second halftone,

wherein the processor adjusts the intensity value of the first pixel if a difference between the intensity value of the first pixel and the intensity value of the second pixel is greater than a predetermined threshold, and

wherein the first halftone determines edge pixel values by selecting one of two nonzero pixel values.

10. The printing system of claim 9, further comprising:

a laser print engine to print the image data.

11. The printing system of claim 9, wherein the higher resolution comprises a higher lines per inch (lpi).

12. The printing system of claim 9, wherein the processor adjusts the intensity value of the first pixel by darkening the first pixel.

13. A method for printing an image, the method comprising:

receiving image data;

locating a first image portion comprising an edge and a second image portion not comprising an edge in the image data by comparing an intensity value of a first pixel and an intensity value of a second pixel, wherein the second pixel is adjacent to the first pixel;

applying a first halftone to the first image portion by selecting one of two nonzero pixel values to determine edge pixel values;

applying a second halftone to the second image portion;

printing the image data with the applied first halftone and the applied second halftone; and

adjusting the intensity value of the first pixel if a difference between the intensity value of the first pixel and the intensity value of the second pixel is greater than a predetermined threshold,

wherein applying the first halftone comprises applying a halftone having a higher resolution than the second halftone.

14. The method of claim 13, wherein applying comprises applying a halftone having a higher lines per inch (lpi) than the second halftone.

15. The method of claim 13, wherein the one of two nonzero pixel values is selected semi-randomly.

16. The method of claim 15, wherein one of the two nonzero pixel values is selected more often that the other of the two nonzero pixel values.

17. The method of claim 13, wherein applying the second halftone comprises applying a halftone within a range of approximately 100 lines per inch (lpi) to approximately 150 lpi.

18. The method of claim 13, wherein applying the first halftone comprises applying a halftone within a range of approximately 200 lines per inch (lpi) to approximately 300 lpi.

19. The method of claim 13, wherein receiving image data comprises receiving image data comprising text.

20. The method of claim 13, wherein receiving image data comprises receiving image data comprising graphics.

21. The method of claim 13, wherein adjusting the intensity value of the first pixel comprises darkening the first pixel.

22. A printing system comprising:

means for storing image data representing an image;

means for performing a first digital halftone process on a first portion of the image and a second digital halftone process on a second portion of the image, wherein the first portion is located by comparing an intensity value of a first pixel and an intensity value of a second pixel, wherein the second pixel is adjacent to the first pixel, and

means for adjusting intensity that adjusts the intensity value of the first pixel if a difference between the intensity value of the first pixel and the intensity value of the second pixel is greater than a predetermined threshold,

wherein the first portion is an edge of the image and the second portion is not an edge of the image, and the first digital halftone process comprises a higher resolution than the second digital halftone process, and

wherein the first digital halftone process determines edge pixel values by selecting one of two nonzero pixel values.

23. The printing system of claim 22, wherein the higher resolution comprises a higher lines per inch (lpi).

24. The printing system of claim 22, wherein the first digital halftone process comprises a halftone within a range of approximately 200 lines per inch (lpi) to approximately 300 lpi.

25. The printing system of claim 22, wherein the second digital halftone process comprises a halftone within a range of approximately 100 lines per inch (lpi) to approximately 150 lpi.

26. The printing system of claim 22, wherein the one of two nonzero pixel values are selected semi-randomly.

27. The printing system of claim 26, wherein the first halftone process alternates between the two nonzero pixel values such that one of the two nonzero pixel values is selected more often that the other of the two nonzero pixel values.

28. The printing system of claim 22, wherein the first portion is at least one pixel wide.

29. The printing system of claim 22, wherein the means for adjusting intensity darkens the first pixel.

30. A printing system comprising:

means for storing image data;

means for locating image edges in the image data and applying a first halftone to image data that is located at an image edge and applying a second halftone to image data that is not located at an image edge, wherein the image edge is located by comparing an intensity value of a first pixel and an intensity value of a second pixel, wherein the second pixel is adjacent to the first pixel, and

means for adjusting intensity that adjusts the intensity value of the first pixel if a difference between the intensity value of the first pixel and the intensity value of the second pixel is greater than a predetermined threshold,

wherein the first halftone comprises a higher resolution than the second halftone, and

wherein the first halftone determines edge pixel values by selecting one of two nonzero pixel values.

31. The printing system of claim 30, further comprising:

means for printing the image data.

32. The printing system of claim 30, wherein the higher resolution comprises a higher lines per inch (lpi).

33. The printing system of claim 30, wherein the means for adjusting intensity darkens the first pixel.

34. A computer-readable medium having computer-readable content to cause a computer to perform acts of:

receiving image data;

locating a first image portion comprising an edge and a second image portion not comprising an edge in the image data by comparing an intensity value of a first pixel and an intensity value of a second pixel, wherein the second pixel is adjacent to the first pixel;

applying a first halftone to the first image portion by selecting one of two nonzero pixel values to determine edge pixel values;

applying a second halftone to the second image portion;

adjusting the intensity value of the first pixel if a difference between the intensity value of the first pixel and the intensity value of the second pixel is greater than a predetermined threshold; and

printing the image data with the applied first halftone and the applied second halftone, wherein applying the first halftone comprises applying a higher resolution than the second halftone.

35. The computer-readable medium of claim 34, wherein the higher resolution comprises a higher lines per inch (lpi).

36. The computer-readable medium of claim 34, wherein the one of two nonzero pixel values is selected semi-randomly.

37. The method of claim 36, wherein one of the two nonzero pixel values is selected more often that the other of the two nonzero pixel values.

38. The computer-readable medium of claim 34, wherein applying the second halftone comprises applying a halftone within a range of approximately 100 lines per inch (lpi) to approximately 150 lpi.

39. The computer-readable medium of claim 34, wherein applying the first halftone comprises applying a halftone within a range of approximately 200 lines per inch (lpi) to approximately 300 lpi.

40. The computer-readable medium of claim 34, wherein receiving image data comprises receiving image data comprising text.

41. The computer-readable medium of claim 34, wherein receiving image data comprises receiving image data comprising graphics.

42. The computer-readable medium of claim 34, wherein adjusting the intensity value of the first pixel comprises darkening the first pixel.