Hybrid imaging system

• US 5,805,734 A
• Filed: 11/26/1996
• Issued: 09/08/1998
• Est. Priority Date: 04/01/1996
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Ebner, Fritz F.
• Primary Examiner(s): ROGERS, SCOTT A
• Application Number:
  US08/756,666
• Time in Patent Office: 651 Days
• Field of Search: 382/237, 382/252, 382/270, 358/456, 358/457, 358/458, 358/460, 358/466, 358/298, 358/534, 358/535, 358/536, 395/109
• US Class Current: 382/237
• CPC Class Codes: H04N 1/405 Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening

Abstract

A hybrid system for digitally screening black and white and/or color images using a number of imaging techniques is disclosed. A hybrid rendering system may be employed to improve image quality by rendering particular image areas according different halftoning schemes according to gray level.

Claims

1. A method of constructing a composite screen for halftoning a digitized color image having a predetermined number of color separations, comprising:

selecting a first halftoning system of a first type having a first set of pixel placement characteristics;

selecting a second halftoning system of a second type having a second set of pixel placement characteristics;

determining a gray scale transition region for transitioning from the first halftoning system to the second halftoning system;

merging the first halftoning system with the second halftoning system so as to provide a hybrid halftoning system in the gray scale transition region, said hybrid halftoning system including a hybrid set of pixel characteristics of said first set of pixel placement characteristics and said second set of pixel placement characteristics, and

rendering a first number of color separations of a color image using said hybrid halftoning system, the first number of color separations being equal to a value which is less the predetermined number of color separations.

2. The method of claim 1, wherein the gray scale includes 256 gray levels.

3. The method of claim 2, wherein an upper gray scale limit of the transition region is 65.

4. The method of claim 1, wherein the first halftoning system is a cluster dot halftoning system.

5. The method of claim 1, wherein the first halftoning system is a matrix dot halftoning system.

6. The method of claim 1, wherein the first halftoning system is a stochastic dot halftoning system.

7. The method of claim 1, wherein an upper gray scale limit of the transition region is equal to approximately one quarter of a total number of available grey levels.

8. A method of constructing a composite screen for halftoning a digitized image, comprising:

selecting a first halftoning system of a first type having a first set of pixel placement characteristics;

selecting a second halftoning system of a second type having a second set of pixel placement characteristics;

determining a gray scale transition region for transitioning from the first halftoning system to the second halftoning system; and

merging the first halftoning system with the second halftoning system so as to provide a hybrid halftoning system in the gray scale transition region, said hybrid halftoning system including a hybrid set of pixel characteristics of said first set of pixel placement characteristics and said second set of pixel placement characteristics;

selecting a third halftoning system of a second type having a third set of pixel placement characteristics;

determining a second gray scale transition region for transitioning from the second halftoning system to the third halftoning system; and

merging the second halftoning system with the third halftoning system so as to provide a hybrid halftoning system in the second gray scale transition region, said hybrid halftoning system including a second hybrid set of pixel characteristics of said second set of pixel placement characteristics and said third set of pixel placement characteristics.

9. The method of claim 8, wherein the first halftoning system is a matrix dot halftoning system.

10. The method of claim 8, wherein the first halftoning system is a stochastic dot halftoning system.

11. The method of claim 8, wherein the first halftoning system is a cluster dot halftoning system.

12. The method of claim 8, wherein an upper gray scale limit of the transition region is equal to approximately one quarter of a total number of available grey levels.