System and method for smart color halftoning

• US 20060077468A1
• Filed: 10/12/2004
• Published: 04/13/2006
• Est. Priority Date: 10/12/2004
• Status: Abandoned Application

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Loce, Robert P., Xu, Beilei
• Application Number:
  US10/962,895
• Publication Number:
  US 20060077468A1
• Time in Patent Office: Days
• US Class Current: 358/3.60
• CPC Class Codes: H04N 1/4058 with details for producing a halftone screen at an oblique angle H04N1/4056 takes precedence

Abstract

A method for halftoning a color image, the color image including a plurality of color separations, includes parsing the color image into image objects; examining each image object to determine its color content; for each color separation: determining a dominant color of the image object, wherein a dominant color of an image object is determined in accordance with a predetermined relationship based on a desired output image characteristic; selecting a halftone screen property to optimize for the desired output image characteristic; and selecting a halftone screen having the halftone screen property that is optimized for the dominant image object color and the desired image output characteristic; and halftoning the image object using the selected halftone screens. Using this method, halftone screens can be optimized based on screen angle, screen offset, screen frequency and dot shape.

Claims

1. A method for halftoning a color image, the color image including a plurality of color separations, comprising:

parsing the color image into image objects;

examining each image object to determine its color content;

for each color object;

determining a dominant colorant of the image object, wherein a dominant colorant of an image object is determined in accordance with a predetermined relationship based on a desired output image characteristic;

selecting a halftone screen property to optimize for the desired output image characteristic; and

selecting a halftone screen having the halftone screen property that is optimized for the dominant image object colorant and the desired image output characteristic; and

halftoning the image object using the selected halftone screens.

2. The method of claim 1, wherein the color separations include cyan, magenta, yellow and black.

3. The method of claim 1, wherein the halftone screen property comprises halftone screen angle.

4. The method of claim 1, wherein the halftone screen property comprises halftone screen offset.

5. The method of claim 1, wherein the halftone screen property comprises halftone screen frequency.

6. The method of claim 1, wherein the halftone screen property comprises dot shape.

7. The method of claim 1, further comprising:

prior to selecting the halftone screen property, generating a tag based on image object color content; and

selecting a halftone screen based on the generated tag and having the halftone screen property that is optimized for the dominant image object color and the desired image output characteristic.

8. The method of claim 1, wherein the predetermined relationship is based on color content, desired output image characteristics and image object type.

9. The method of claim 1, wherein the predetermined relationship is based on color content and image features.

10. The method of claim 1, wherein the predetermined relationship is based on colorant density along image object edges.

16. The method of claim 6, wherein the selected halftone screen produces dots formed of non-touching circles.

17. The method of claim 6, wherein the selected halftone screen produces dots formed of touching circles.

11. A method for halftoning a color image, the color image including a plurality of color separations, comprising:

parsing the color image into image objects;

examining each image object to determine its color content;

for each color separation;

determining a dominant colorant of the image object; and

selecting an initial halftone screen having a halftone screen angle that is optimized for the dominant image object colorant;

determining a dot separation distance between dots printed in one colorant and dots printed in another colorant using the initial halftone screens;

if the dot separation distance is greater than a misregistration specification of an output device, selecting a halftone screen having a halftone screen angle and a halftone screen offset that compensates for the difference between the dot separation distance and the misregistration specification; and

halftoning the image object using the selected halftone screens.

12. The method of claim 11, wherein the selected halftone screens comprise rotated halftone screens offset from one another to provide a desired rosette structure.

13. The method of claim 12, wherein the desired rosette structure comprises a dot centered rosette.

14. The method of claim 12, wherein the desired rosette structure comprises a hole centered rosette.

15. The method of claim 11, further comprising:

selecting a lower frequency halftone screen that meets the dot-distance criterion.

18. A halftoning system, for use in a reproduction device printing a plurality of separations comprising:

a separation input, receiving said plurality of separations for printing, each separation representing a distinct printer colorant, and including a plurality of image signals described;

a parsing circuit for parsing the color image into image objects;

a memory storing a plurality of halftone screens;

a color analysis module for examining each image object to determine its color content;

for each color separation;

for determining a dominant colorant of the image object, wherein a dominant colorant of an image object is determined in accordance with a predetermined relationship based on a desired output image characteristic; and

for selecting a halftone screen property to optimize for the desired output image characteristic; and

a halftone selection module for selecting a halftone screen from memory having the halftone screen property that is optimized for the dominant image object colorant and the desired image output characteristic; and

a halftoner for halftoning the image object using the selected halftone screens.

19. The system of claim 18, further comprising:

a tag generator, responsive to the color analysis module, for generating a tag based on image object color content; and

wherein the halftone selection module is further responsive to the generated tag.

20. The system of claim 18, the halftone screen property comprises one of halftone screen angle, halftone screen offset, halftone screen frequency and dot shape.

21. A method for halftoning a color image, the color image including a plurality of color separations, comprising:

parsing the color image into image classes;

examining each image class to determine its color content;

for each image class;

determining a dominant colorant of the image class, wherein a dominant colorant of an image class is determined in accordance with a predetermined relationship based on a desired output image characteristic;

selecting a halftone screen property to optimize for the desired output image characteristic; and

selecting a halftone screen having the halftone screen property that is optimized for the dominant image object colorant and the desired image output characteristic; and

halftoning the image class using the selected halftone screens.

22. The method of claim 21, wherein the color separations include cyan, magenta, yellow and black.

23. The method of claim 21, wherein the color separations include orange, green and red.