Laser print apparatus with dual halftones

• US 8,098,405 B2
• Filed: 05/17/2010
• Issued: 01/17/2012
• Est. Priority Date: 10/27/2004
• Status: Expired due to Fees

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Technology, Ltd. (Marvell Technology Group Limited)
• Inventors: Keithley, Douglas Gene, Shoen, Jay R.
• Primary Examiner(s): Lee, Thomas D
• Application Number:
  US12/781,565
• Publication Number:
  US 20100225973A1
• Time in Patent Office: 610 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 printer controller for processing data representing an image, the printer controller comprising:

a first module configured to perform a first halftone process on an edge portion of the image, wherein the edge portion is located by comparing an intensity value of a first pixel and an intensity value of a second pixel and wherein the first halftone process comprises accessing two or more nonzero values based on the intensity value of the first pixel and alternating between the two or more nonzero values when multiple pixels comprise a same intensity value as the intensity value of the first pixel; and

a second module configured to perform a second halftone process on a non-edge portion of the image, wherein the first halftone process comprises a higher resolution than the second halftone process.

2. The printer controller of claim 1, wherein the first module 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 programmable threshold.

3. The printer controller of claim 2, wherein the programmable threshold is 25% of the intensity value of the first pixel.

4. The printer controller of claim 1, wherein the first halftone process involves semi-randomly alternating between the two or more nonzero values.

5. The printer controller of claim 1, wherein the two or more nonzero values include three nonzero values representing three amounts of toner.

6. The printing system of claim 1, further comprising:

a memory module operable to store the data representing the image.

7. The printing system of claim 1, wherein the first halftone process comprises a halftone within a range of approximately 200 lines per inch (lpi) to approximately 300 lpi and the second halftone process comprises a halftone within a range of approximately 100 lpi to approximately 150 lpi.

8. The printing system of claim 1, wherein the first module and the second module comprise hardware.

9. The printer controller of claim 1, wherein the first module and the second module comprise firmware.

10. A printer controller comprising:

first circuitry for identifying edge pixels and center pixels; and

second circuitry for applying a first halftone to at least some of the edge pixels of an image and a second halftone to at least some of the center pixels, wherein the first halftone comprises a higher resolution than the second halftone and the first halftone comprises accessing two or more nonzero values based on an intensity value of one of the edge pixels and alternating between the two or more nonzero values when additional edge pixels comprise the intensity value.

11. The printer controller of claim 10, wherein the first circuitry identifies the center pixels and the edge pixels by comparing intensity values of adjacent pixels.

12. The printer controller of claim 10, further comprising:

third circuitry for adjusting intensity values of the at least some of the edge pixels when a difference in values of adjacent pixels is above a programmable threshold.

13. The printer controller of claim 10, wherein the first halftone alternates between the two or more nonzero pixel values such that one of the two or more nonzero pixel values is selected more often than another of the two or more nonzero pixel values.

14. The printer controller of claim 10, wherein the first circuitry and the second circuitry comprise hardware.

15. The printer controller of claim 10, wherein the first circuitry and the second circuitry comprise firmware.

16. A method for halftoning an image, the method comprising:

receiving image data;

locating, in the image data, a first image portion including an edge and a second image portion lacking an edge by comparing an intensity value of a first pixel and an intensity value of a second pixel;

applying a first halftone to the first image portion by accessing two or more nonzero values based on the intensity value of the first pixel and alternating between two or more nonzero values corresponding as one or more subsequent pixels have the intensity value of the first pixel; and

applying a second halftone to the second image portion, wherein the second halftone has a lower resolution that the first halftone.

17. The method of claim 16, further comprising:

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 programmable proportion of the intensity value of the first pixel.

18. The method of claim 16, wherein the alternating between the two or more nonzero pixel values occurs semi-randomly.

19. The method of claim 16, wherein the second halftone results in a resolution in a range of approximately 100 lines per inch (lpi) to approximately 150 lpi and the first halftone results in a resolution in the range of approximately 200 lpi to approximately 300 lpi.

20. The method of claim 16, further comprising:

storing the image data in a memory.