Method and apparatus for multi-color printing using a rosette or diamond halftone screen for one or more of the colors

1. A processor for generating composite image data representing a mono-color input separation, the processor being adapted to:

process the mono-color input separation data in accordance with a first halftone screen having a first screen angle to produce first halftone image data, wherein the first halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

process the mono-color input separation data in accordance with a second halftone screen having a second screen angle different from the first screen angles to produce second halftone image data, wherein the second halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel; and

combine the gray values of the first and second halftone image data to generate composite image data for the mono-color input separation such that the composite image data includes a first series of dot structures or line structures along lines at the first screen angle and a second series of dot structures or line structures along lines at the second screen angle, and the first and second series are present across the full tone scale, wherein the composite image data includes a plurality of gray values for corresponding pixel locations, each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel, and the gray values of corresponding pixel locations in the first and second halftone image data are combined to generate gray values of the composite image data for those locations.

2. The processor of claim 1 , wherein the processor is operative to process the mono-color input separation data in accordance with a dot structure dot growth pattern.

3. The processor of claim 2 , further including a printer responsive to the composite image data for printing a corresponding printed separation as a rosette pattern.

4. The processor of claim 3 , wherein the first and second screen angles are separated by 30°.

5. The processor of claim 3 , wherein the first and second screen angles are separated by 60°.

6. The processor of claim 2 , wherein the processor is further operative to process the mono-color input separation data in accordance with third halftone screen having a different screen angle than the first and second screen angles to provide third halftone image data including a plurality of gray values for corresponding pixel locations, and to combine the gray values of the first, second, and third halftone image data to generate composite image data.

7. The processor of claim 1 , wherein the processor is operative to process the mono-color input separation data in accordance with a line structure dot growth pattern, so that the composite image data for the mono-color separation has a diamond structure.

8. The processor of claim 7 , wherein the first and second screen angles are separated by 60°.

9. The processor of claim 7 , wherein the first and second screen angles are separated by an angle within the range of 53° to 64°.

10. An apparatus for generating combined image data representing a plurality of mono-color input separations for respective, different colors, comprising:

a screen generator responsive to the respective mono-color input separation data of each mono-color input separation for generating a respective halftone screen for each mono-color input separation, and adapted to:

select one of the mono-color input separations;

process the mono-color input separation data for the selected mono-color separation in accordance with a first halftone screen having a first screen angle to produce first halftone image data, wherein the first halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

process the mono-color input separation data for the selected mono-color separation in accordance with a second halftone screen having a second screen angle different from the first screen angles to produce second halftone image data, wherein the second halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel; and

combine the gray values of the first and second halftone image data to generate respective composite image data for the selected mono-color input separation such that the respective composite image data includes a first series of dot structures or line structures along lines at the first screen angle and a second series of dot structures or line structures along lines at the second screen angle, and the first and second series are present across the full tone scale, wherein the respective composite image data includes a plurality of gray values for corresponding pixel locations, each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel, and the gray values of corresponding pixel locations in the first and second halftone image data are combined to generate gray values of the respective composite image data for those locations;

process the respective mono-color input separation data for each non-selected mono-color input separation in accordance with the respective generated halftone screen to generate respective image data for the respective mono-color input separation; and

combine the composite image data for the selected mono-color input separation and the respective image data for the non-selected mono-color input separations to generate combined image data for output to a printer.

11. The apparatus of claim 10 , wherein the processor is operative to process the selected mono-color input separation data in accordance with a dot structure dot growth pattern processing.

12. The apparatus of claim 11 , further including a printer for printing the respective image data for the non-selected mono-color input separations as respective printed separations and for printing the respective composite image data for the selected mono-color input separation as a printed separation having a rosette pattern.

13. The apparatus of claim 12 , wherein the printer includes four printer components for printing printed separations in cyan, magenta, yellow, and black, respectively.

14. The apparatus of claim 13 , wherein the printer further includes hi-fi printer component for printing the respective composite image data for the selected mono-color input separation in a fifth color different from cyan, magenta, yellow, and black.

15. The apparatus of claim 10 , wherein the selected mono-color input separation data is processed in accordance with a line structure dot growth pattern.

16. The apparatus of claim 12 , wherein the printer is an electrostatographic printer.

17. The apparatus of claim 10 , further including a printer for printing the respective image data for the non-selected mono-color input separations as respective halftone color separation images and for printing the respective composite image data for the selected mono-color input separation as a diamond structure pattern.

18. The apparatus of claim 17 , wherein the printer includes four printer components for printing mono-color input separations in cyan, magenta, yellow, and black, respectively.

19. The apparatus of claim 18 , wherein the printer further includes a hi-fi printer component for printing the respective composite image data for the selected mono-color input separation in a fifth color different from cyan, magenta, yellow, and black.

20. The apparatus of claim 19 , wherein the printer is an electrostatographic printer.

21. A method for processing image data representing a mono-color input separation, the method comprising:

processing the mono-color input separation data in accordance with a first halftone screen having a first screen angle to produce first halftone image data, wherein the first halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

processing the mono-color input separation data in accordance with a second halftone screen having a second screen angle different from the first screen angles to produce second halftone image data, wherein the second halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

combining the gray values of the first and second halftone image data to generate composite image data for the mono-color input separation such that the composite image data includes a first series of dot structures or line structures along lines at the first screen angle and a second series of dot structures or line structures along lines at the second screen angle, and the first and second series are present across the full tone scale, wherein the composite image data includes a plurality of gray values for corresponding pixel locations, each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel, and the gray values of corresponding pixel locations in the first and second halftone image data are combined to generate gray values of the composite image data for those locations; and

printing the composite image data on a printer for generating a mono-color printed separation.

22. The method of claim 21 , wherein the mono-color input separation data is processed in accordance with a dot structure dot growth pattern.

23. The method of claim 22 , wherein the first and second screen angles are separated by 30°.

24. The method of claim 22 , wherein the first and second screen angles are separated by 60°.

25. The method of claim 22 , wherein the mono-color input separation data is further processed in accordance with a third halftone screen having a different screen angle than the first and second screen angles to provide third halftone image data including a plurality of gray values for corresponding pixel locations.

26. The method of claim 21 , wherein the mono-color input separation data is processed in accordance with a line structure dot growth pattern, so that the composite image data of the mono-color input separation has a diamond structure.

27. The method of claim 26 , wherein the first and second screen angles are separated by 60°.

28. The method of claim 26 , wherein the first and second screen angles are separated by an angle within the range of 53° to 64°.

29. A method for printing combined image data representing a plurality of mono-color input separations for respective, different colors, comprising:

selecting one of the mono-color input separations;

generating a respective halftone screen for each non-selected mono-color input separation;

processing the respective mono-color input separation data for each non-selected mono-color input separation in accordance with the respective halftone screen to generate respective image data;

processing the mono-color input separation data for the selected mono-color input separation in accordance with a first halftone screen having a first screen angle to produce first halftone image data, wherein the first halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

processing the mono-color input separation data for the selected mono-color input separation in accordance with a second halftone screen having a second screen angle different from the first screen angles to produce second halftone image data, wherein the second halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel; and

combining the gray values of the first and second halftone image data to generate respective composite image data for the selected mono-color input separation such that the respective composite image data includes a first series of dot structures or line structures along lines at the first screen angle and a second series of dot structures or line structures along lines at the second screen angle, and the first and second series are present across the full tone scale, wherein the respective composite image data includes a plurality of gray values for corresponding pixel locations, each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel, and the gray values of corresponding pixel locations in the first and second halftone image data are combined to generate gray values of the respective composite image data for those locations;

combining the composite image data for the selected mono-color input separation and the respective image data for the non-selected mono-color input separations to generate combined image data for output to a printer; and

printing the combined image data using a printer.

30. The method of claim 29 , wherein the mono-color input separation data of the selected color is processed in accordance with a dot structure dot growth pattern.

31. The method of claim 30 , wherein the respective image data for the non-selected mono-color input separations are printed in cyan, magenta, yellow, and black, respectively.

32. The method of claim 31 , further including printing the composite image data of the selected mono-color input separation in a fifth color different from cyan, magenta, yellow, and black.

33. The method of claim 32 , wherein the printing is performed using an electrophotographic printer.

34. The method of claim 29 , wherein the mono-color input separation data of the selected color is processed in accordance with a line structure dot growth pattern.

35. The method of claim 34 , further including printing the respective image data for the non-selected mono-color input separation as respective printed separations and printing the composite image data for the selected mono-color separation as a printed separation having a diamond structure pattern.

36. The method of claim 35 , wherein the printer includes four components for printing mono-color separations in cyan, magenta, yellow, and black, respectively.

37. The method of claim 36 , further including printing the composite image data of the selected mono-color input separation in a fifth color different from cyan, magenta, yellow, and black.

38. The method of claim 37 , wherein the printer is an electrophotographic printer.

39. The method of claim 29 , wherein the printer is an electrophotographic printer.

40. The apparatus of claim 14 , wherein

i) the selected mono-color input separation is a separation of a selected color, so that a complementary color of the selected color is defined;

ii) one of the non-selected mono-color input separations is a complementary mono-color input separation of the complementary color, and is processed according to the first and second screen angles to generate respective composite image data; and

iii) the respective composite image data for the selected mono-color input separation and for the complementary mono-color input separation are printed with the same rosette structure.

41. The apparatus of claim 40 , wherein the selected color is blue and the complementary color is yellow.

42. The apparatus of claim 40 , wherein the selected color is red and the complementary color is cyan.

43. The apparatus of claim 40 , wherein the selected color is green and the complementary color is magenta.

44. The apparatus of claim 19 , wherein

i) the selected mono-color input separation is a separation of a selected color, so that a complementary color of the selected color is defined;

ii) one of the non-selected mono-color input separations is a complementary mono-color input separation of the complementary color, and is processed according to the first and second screen angles to generate respective composite image data; and

iii) the respective composite image data for the selected mono-color input separation and for the complementary mono-color input separation are with the same diamond structure.

45. The method of claim 32 , wherein

i) the selected mono-color input separation is a separation of a selected color, so that a complementary color of the selected color is defined;

ii) one of the non-selected mono-color input separations is a complementary mono-color input separation of the complementary color; and

iii) the respective composite image data for the selected mono-color input separation and for the complementary mono-color input separation are printed with the same rosette structure.

46. The method of claim 45 , wherein the selected color is blue and the complementary color is yellow.

47. The method of claim 45 and wherein the selected color is red and the complementary color is cyan.

48. The method of claim 45 and wherein the selected color is green and the complementary color of the selected color is magenta.

49. The method of claim 37 , and wherein:

i) the selected mono-color input separation is a separation of a selected color, so that a complementary color of the selected color is defined;

ii) one of the non-selected mono-color input separations is a complementary mono-color input separation of the complementary color; and

iii) the respective composite image data for the selected mono-color input separation and for the complementary mono-color input separation are printed with the same diamond structure.

50. The method of claim 49 and wherein the selected color is blue and the complementary color is yellow.

51. The method of claim 49 and wherein the selected color is red and the complementary color is cyan.

52. The method of claim 49 and wherein the selected color is green and the complementary color is magenta.

53. The method of claim 30 , wherein

i) the selected mono-color input separation is a separation of a selected color, so that a complementary color of the selected color is defined;

ii) one of the non-selected mono-color input separations is a complementary mono-color input separation of the complementary color, and is processed according to the first and second screen angles to generate respective composite image data;

iii) the non-selected mono color input separation are separations of cyan, magenta and yellow; and

iv) the respective composite image data for the selected mono-color input separation and for the complementary mono-color input separation are printed with the same rosette structure.

54. The method of claim 53 and wherein the selected color is blue and the complementary color is yellow.

55. The method of claim 53 and wherein the selected color is red and the complementary at color is cyan.

56. The method of claim 53 and wherein the selected color is green and the complementary color is magenta.

57. The method of claim 35 , wherein

i) the selected mono-color input separation is a separation of a selected color, so that a complementary color of the selected color is defined;

ii) one of the non-selected mono-color input separations is a complementary mono-color input separation of the complementary color, and is processed according to the first and second screen angles to generate respective composite image data;

iii) the non-selected mono color input separation are separations of cyan, magenta, and yellow, and

iv) the respective composite image data for the selected mono-color input separation and for the complementary mono-color input separation are printed with the same diamond structure.

58. The method of claim 57 and wherein the selected color is blue and the complementary color is yellow.

59. A method for printing a multi-color image having first and second mono-color input separations for first and second different colors, respectively, the method comprising:

processing the respective mono-color input separation data of the first and second mono-color input separation images in accordance with a first halftone screen having a first screen angle to produce respective first halftone image data, wherein the first halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

processing the respective mono-color input separation data in accordance with a second halftone screen having a second screen angle different from the first screen angle to produce respective second halftone image data, wherein the second halftone image data includes a plurality of gray values for corresponding pixel locations, and each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel;

combining the gray values of the respective first halftone image data and respective second halftone image data to generate respective composite image data for the mono-color input separations such that each respective composite image data includes a first series of dot structures or line structures along lines at the first screen angle and a second series of dot structures or line structures along lines at the second screen angle, and the first and second series are present across the full tone scale, wherein each respective composite image data includes a plurality of gray values for corresponding pixel locations, each gray value represents a respective dot size, chosen from a plurality of different dot sizes, for the corresponding pixel, and the gray values of corresponding pixel locations in the first and second halftone image data are combined to generate gray values of the composite image data for those locations; and

printing the respective composite image data on a printer to generate respective printed separations of the first and second colors, respectively, so that similar rosette structures are printed for each of the two colors, wherein the two colors are complementary colors to each other.

60. The method of claim 59 , wherein the first color is blue and the second color is yellow.

61. The method of claim 59 , wherein the first color is red and the second color is cyan.

62. The method of claim 59 , wherein the first color is green and the second color is magenta.