Image processing method and apparatus, and printing apparatus, with dither result application level control

• US 10,462,331 B2
• Filed: 01/14/2019
• Issued: 10/29/2019
• Est. Priority Date: 01/16/2018
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kakutani, Toshiaki
• Primary Examiner(s): Rogers, Scott A
• Application Number:
  US16/246,585
• Publication Number:
  US 20190220714A1
• Time in Patent Office: 288 Days
• CPC Class Codes: G06K 15/1877 with provisions for treating some of the print data differently
• CPC Class Codes: G06K 15/1881 Halftoning halftoning of still images in general H04N1/405, H04N1/52
• CPC Class Codes: H04N 1/4053 with threshold modulated relative to input image data or vice versa
• CPC Class Codes: H04N 1/409 Edge or detail enhancement; Noise or error suppression
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence

Abstract

An image processing apparatus that prints an image includes a preliminary halftone processing unit configured to determine whether a preliminary dot through a dithering method is to be formed, a final halftone processing unit configured to determine whether a dot to be printed through an error diffusion method is to be formed, and a dither result application level control unit configured to control a dither result application level which is a level at which probability that the dot to be printed will be formed is raised with the final halftone processing unit when the preliminary dot is to be formed in the preliminary halftone processing unit. The dither result application level control unit reduces the dither result application level during printing in a case of copying a reflected document or a case where the image data contains many high-frequency components, compared to other instances of printing.

Claims

1. An image processing apparatus configured to print an image, the image processing apparatus comprising:

a preliminary halftone processing unit configured to determine whether a preliminary dot through a dithering method is to be formed on the basis of a data gradation value in image data;

a final halftone processing unit configured to determine whether a dot to be printed through an error diffusion method is to be formed on the basis of the data gradation value; and

a dither result application level control unit configured to control a dither result application level, the dither result application level being a level at which probability that the dot to be printed will be formed is raised when the preliminary dot is formed, wherein

the final halftone processing unit applies the dither result application level, and

the dither result application level control unit reduces the dither result application level during printing in a case where copy data from a reflected document is used as the image data or a case where the image data contains many high-frequency components, compared to other instances of printing.

2. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method when the preliminary dot is to be formed than when the preliminary dot is not to be formed, and reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is to be formed, and the error diffusion method threshold used in the case where he preliminary dot is not to be formed.

3. The image processing apparatus according to claim 1, wherein

the dither result application level control unit, in a case where the dither result application level is set to a maximum, sets a pixel, in which the preliminary dot is to be formed, to be formed with the dot to be printed with the final halftone processing unit.

4. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method when the preliminary dot is to be formed than when the preliminary dot is not to be formed, and reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is to be formed, and the error diffusion method threshold used in the case where the preliminary dot is not to be formed, and in the case where the dither result application level is set to a maximum, sets a pixel, in which the preliminary dot is to be formed, to be formed with the dot to be printed in the final halftone processing unit.

5. The image processing apparatus according to claim 1, wherein

the dither result application level control unit controls a percentage of the preliminary dots to be formed, and when the dither result application level is reduced, reduces a percentage of pixels determined, by the preliminary halftone processing unit, to have the preliminary dot to be formed.

6. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method, when the preliminary dot is to be formed than when the preliminary dot is not to be formed, reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is to be formed, and the error diffusion method threshold used in the case where the preliminary dot is not to be formed, and controls a percentage of the preliminary dots to be formed, and when the dither result application level is reduced, reduces a percentage of pixels determined, by the preliminary halftone processing unit, to have the preliminary dot to be formed.

7. The image processing apparatus according to claim 1, wherein

the final halftone processing unit applies the error diffusion method using a low-level threshold, the low-level threshold being the error diffusion method threshold in the case where the preliminary dot is to be formed, for a pixel in which the preliminary dot is to be formed with the preliminary halftone processing unit, and using a high-level threshold, the high-level threshold being the error diffusion method threshold in the case where the preliminary dot is not to be formed, for a pixel in which the preliminary dot is not to be formed with the preliminary halftone processing unit.

8. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method when the preliminary dot is to be formed than when the preliminary dot is not to be formed, and reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is to be formed, and the error diffusion method threshold used in the case where the preliminary dot is not to be formed, and

the final halftone processing unit applies the error diffusion method using a low-level threshold, the low-level threshold being the error diffusion method threshold in the case where the preliminary dot is to be formed, for a pixel in which the preliminary dot is to be formed with the preliminary halftone processing unit, and using a high-level threshold, the high-level threshold being the error diffusion method threshold in the case where the preliminary dot is not to be formed, for a pixel in which the preliminary dot is not to be formed with the preliminary halftone processing unit.

9. The image processing apparatus according to claim 1, wherein

the dither result application level control unit, in the case where the dither result application level is set to a maximum, sets a pixel, in which the preliminary dot is to be formed, to be formed with the dot to be printed with the final halftone processing unit, and

the final halftone processing unit applies the error diffusion method using a low-level threshold, the low-level threshold being the error diffusion method threshold in the case where the preliminary dot is to be formed, for a pixel in which the preliminary dot is to be formed with the preliminary halftone processing unit, and using a high-level threshold, the high-level threshold being the error diffusion method threshold in the case where the preliminary dot is not to be formed, for a pixel in which the preliminary dot is not to be formed with the preliminary halftone processing unit.

10. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a high-frequency component determination unit configured to determine an amount of high-frequency components in the image data, and in the case where the high-frequency component determination unit has determined that an amount of the high-frequency components in the image data is greater than or equal to a set amount, the dither result application level is reduced compared to cases where a different determination is made.

11. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method when the preliminary dot is to be formed than when the formation of the preliminary dot is not to be formed, and reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is to be formed, and the error diffusion method threshold used in the case where the preliminary dot is not to be formed,

the dither result application level control unit further includes a high-frequency component determination unit configured to determine an amount of high-frequency components in the image data, and in the case where the high-frequency component determination unit has determined that an amount of the high-frequency components in the image data is greater than or equal to a set amount, reduces the dither result application level compared to a case where a different determination is made.

12. The image processing apparatus according to claim 1, wherein

the dither result application level control unit, in the case where the dither result application level is set to a maximum, sets a pixel, in which the preliminary dot is to be formed, to be formed with the dot to be printed with the final halftone processing unit, and

the dither result application level control unit includes a high-frequency component determination unit configured to determine an amount of high-frequency components in the image data, and in the case where the high-frequency component determination unit has determined that an amount of the high-frequency components in the image data is greater than or equal to a set amount, reduces the dither result application level compared to a case where a different determination is made.

13. The image processing apparatus according to claim 1, wherein

the low-level threshold of the error diffusion method threshold, during printing that is neither a case where copy data from the reflected document is used as the image data nor a case where the image data contains many high-frequency components, is a value lower than a minimum value of a gradation range of the data gradation value in all gradation ranges of the data gradation value, or a pixel in which the preliminary dot is to be formed is set to be formed with the dot to be printed with the final halftone processing unit.

14. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method when the preliminary dot is to be formed than when the preliminary dot is not formed, and reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is formed, and the error diffusion method threshold used in the case where the preliminary dot is not to be formed, and

the low-level threshold of the error diffusion method threshold, during printing that is neither a case where copy data from the reflected document is used as the image data nor a case where the image data contains many high-frequency components, is a value lower than a minimum value of a gradation range of the data gradation value in all gradation ranges of the data gradation value, or a pixel in which the preliminary dot is to be formed is set to be formed with the dot to be printed with the final halftone processing unit.

15. The image processing apparatus according to claim 1, wherein

the dither result application level control unit, in the case where the dither result application level is set to a maximum, sets a pixel, in which the preliminary dot is formed, to be formed with the dot to be printed with the final halftone processing unit, and

the low-level threshold of the error diffusion method threshold, during printing that is neither a case where copy data from the reflected document is used as the image data nor a case where the image data contains many high-frequency components, is a value lower than a minimum value of a gradation range of the data gradation value in all gradation ranges of the data gradation value, or a pixel in which the preliminary dot is to be formed is set to be formed with the dot to be printed with the final halftone processing unit.

16. The image processing apparatus according to claim 1, wherein

the low-level threshold of the error diffusion method threshold, during printing in a case where copy data from the reflected document is used as the image data or a case where the image data contains many high-frequency components, is the same value as the high-level threshold when the data gradation value is less than a predetermined value, and is a lower value than the high-level threshold when the data gradation value is greater than or equal to the predetermined value.

17. The image processing apparatus according to claim 1, wherein

the dither result application level control unit includes a mechanism of using a lower error diffusion method threshold used in the error diffusion method when the preliminary dot is to be formed than when the formation of the preliminary dot is not to be formed, and reduces the dither result application level by reducing a difference between the error diffusion method threshold used in the case where the preliminary dot is to be formed, and the error diffusion method threshold used in the case where the formation of the preliminary dot is not to be formed, and

the low-level threshold of the error diffusion method threshold, during printing in a case where copy data from the reflected document is used as the image data or a case where the image data contains many high-frequency components, is the same value as the high-level threshold when the data gradation value is less than a predetermined value, and is a lower value than the high-level threshold when the data gradation value is greater than or equal to the predetermined value.

18. The image processing apparatus according to claim 1, wherein

the dither result application level control unit, in the case where the dither result application level is set to a maximum, sets a pixel, in which the preliminary dot is formed, to be formed with the dot to be printed with the final halftone processing unit, and

the low-level threshold of the error diffusion method threshold, during printing in a case where copy data from the reflected document is used as the image data or a case where the image data contains many high-frequency components, is the same value as the high-level threshold when the data gradation value is less than a predetermined value, and is a lower value than the high-level threshold when the data gradation value is greater than or equal to the predetermined value.

19. A method of controlling an image processing apparatus configured to print an image, by using a computer, the method comprising:

carrying out preliminary halftone processing of determining whether a preliminary dot through a dithering method is to be formed on the basis of a data gradation value in image data;

carrying out final halftone processing of determining whether a dot to be printed through an error diffusion method is to be formed on the basis of the data gradation value; and

controlling a dither result application level, the dither result application level being a level at which probability that the dot to be printed will be formed is raised when the preliminary dot is to be formed, wherein

the final halftone processing applies the dither result application level, and

the dither result application level control unit reduces the dither result application level during printing in a case where copy data from the reflected document is used as the image data or a case where the image data contains many high-frequency components, compared to other instances of printing.

20. A printing apparatus including a printing mode for printing an image and a reflective document copying mode for copying a reflected document, the printing apparatus comprising:

a preliminary halftone processing unit configured to determine whether a preliminary dot through a dithering method is to be formed on the basis of a data gradation value in image data;

a final halftone processing unit configured to determine whether a dot to be printed through an error diffusion method is formed on the basis of the data gradation value; and

a dither result application level control unit configured to control a dither result application level, the dither result application level being a level at which probability that the dot to be printed will be formed is raised when the preliminary dot is formed, wherein

the final halftone processing unit applies the dither result application level, and

the dither result application level control unit reduces the dither result application level during printing in the case of the reflective document copying mode, compared to other instances of printing.