Image processing apparatus and image processing method that can print an image in which a pattern or sweeping phenomenon specific to the error diffusion process does not appear

• US 8,736,865 B2
• Filed: 01/20/2012
• Issued: 05/27/2014
• Est. Priority Date: 01/25/2011
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Yamaguchi, Hiromitsu, Marumoto, Yoshitomo, Tsuboi, Hitoshi
• Primary Examiner(s): NGUYEN, NGON BINH
• Application Number:
  US13/354,859
• Publication Number:
  US 20120188582A1
• Time in Patent Office: 858 Days
• Field of Search: 358/1.14, 358/1.16, 358/1.18, 358/3.13, 358/3.02, 358/3.03, 358/3.04, 358/3.05, 358/3.06, 358/3.09, 358/3.1, 358/3.23, 358/3.3, 358/501, 358/515, 358/517, 358/522, 358/524, 358/534, 358/540, 345/581, 345/586, 345/591, 345/587, 345/601, 345/606, 345/612, 345/613, 345/614, 345/616, 345/626, 345/627, 345/629, 345/639, 345/640, 345/643, 345/672, 345/571, 345/596, 345/597, 345/89, 347/131, 399/80, 399/181, 399/182
• US Class Current: 358/1.14
• CPC Class Codes: H04N 1/4053 with threshold modulated relative to input image data or vice versa

Abstract

In order to vary a threshold value for performing an error diffusion process depending on a pixel position, a threshold value matrix configured to have pluralities of rows and columns is prepared. In this case, pieces of data in the threshold value matrix are arrayed such that average values in the respective rows and average values in the respective columns are almost the same value. If such a threshold value matrix is used to perform the error diffusion process, the dot sparseness and denseness do not occur with a period of the matrix, and therefore the pattern or sweeping phenomenon specific to the error diffusion can be suppressed.

Claims

1. An image processing method, executed by an image processing apparatus, for performing a quantization process of multivalued image data into a lower level N-value (N is an integer equal to or more than 2) by an error diffusion process, the image processing method comprising:

inputting multivalued image data of an image;

an obtaining step of adding an error from a peripheral pixel to the multivalued image data of a target pixel of an image to obtain a correction value;

a setting step of, from a threshold value matrix configured such that different values are arrayed in a row array and in a column array, selecting one value according to a pixel position of the target pixel in the image to set a threshold value for comparing with the correction value, the row consisting of pixels corresponding to values in the row array and the column consisting of pixels corresponding to values in the column array intersecting;

a quantization step of, according to a result of comparing the threshold value set in the setting step with the correction value obtained in the obtaining step, outputting N-value data;

a diffusion step of diffusing an error between the correction value and the N-value data, the error occurring in association with the quantization step, in a peripheral pixel position where the quantization step has not been performed; and

outputting a value indicating printing or non-printing of the target pixel,

wherein in the threshold value matrix, average values in respective rows or average values in respective columns are almost a same value.

2. The image processing method according to claim 1, wherein the threshold value matrix is configured such that different threshold values for comparing with the correction value are arrayed in the row and the column, and in the setting step, according to a pixel position of the multivalued image data, one of the threshold values is selected and set from the threshold value matrix.

3. The image processing method according to claim 1, wherein the threshold value matrix is configured such that different components for setting differences from a threshold value serving as a reference are arrayed in the row and in the column, and in the setting step, according to a pixel position of the multivalued image data, one of the components is selected from the threshold value matrix, and on a basis of the component and the threshold value serving as a reference, the threshold value for comparing with the correction value is set.

4. The image processing method according to claim 1, wherein the N-value is a 2-value.

5. The image processing method according to claim 1, wherein the N-value is a 3-value or more, the image processing method further comprising:

a step of, from a plurality of dot patterns each in which printing or non-printing of a dot is preliminarily set for each of m×

k areas, selecting one dot pattern according to the N-value data outputted by the quantization step, and thereby converting the N-value data to binary data,

wherein regarding the plurality of dot patterns, a plurality of dot patterns are prepared for each of one level value of the N-value data.

6. The image processing method according to claim 1,

wherein the image processing method is a method for printing an image by ejecting ink according to the N-value data output in the quantization step while relative movement of a nozzle array, in which a plurality of nozzles for ejecting ink are arrayed in a predetermined direction, in a direction crossing to the predetermined direction with respect to a print medium,

wherein the predetermined direction corresponds to the column and the crossing direction corresponds to the row.

7. The image processing method according to claim 6,

wherein a printing for a unit area of the print medium is performed by a plurality of the relative movements of the nozzle array, and

ink ejecting is allowed for every other column in each of the relative movements and the column which is allowed to print is changed for each of the relative movement.

8. The image processing method according to claim 1, wherein in the threshold value matrix, the average values in respective rows are almost the same value.

9. The image processing method according to claim 1, wherein in the threshold value matrix, the average values in respective columns are almost the same value.

10. The image processing method according to claim 1, wherein in the threshold value matrix, the average values in respective rows and the average values in respective columns are almost the same value.

11. An image processing method, executed by an image processing apparatus, for performing a quantization process of multivalued image data into a lower level N-value (N is an integer equal to or more than 2) by an error diffusion process, the image processing method comprising:

inputting multivalued image data of an image;

an obtaining step of adding an error from a peripheral pixel to the multivalued image data of a target pixel of an image to obtain a correction value;

a setting step of, from a threshold value matrix configured such that different values are arrayed in a row array and in a column array, selecting one value according to a pixel position of the target pixel in the image to set a threshold value for comparing with the correction value, the row consisting of pixels corresponding to values in the row array and the column consisting of pixels corresponding to values in the column array intersecting;

a quantization step of, according to a result of comparing the threshold value set in the setting step with the correction value obtained in the obtaining step, outputting N-value data;

a diffusion step of diffusing an error between the correction value and the N-value data, the error occurring in association with the quantization step, in a peripheral pixel position where the quantization step has not been performed; and

outputting a value indicating printing or non-printing of the target pixel,

wherein in the threshold value matrix, average values in respective rows or average values in respective columns are included in a range of ±

15% of an average value of them.

12. The image processing method according to claim 11, wherein in the threshold value matrix, the average values in the respective rows and the average values in the respective columns are included in a range of ±

10% of an average value of them.

13. The image processing method according to claim 11,

wherein the image processing method is a method for printing an image by ejecting ink according to the N-value data output in the quantization step while relative movement of a nozzle array, in which a plurality of nozzles for ejecting ink are arrayed in a predetermined direction, in a direction crossing to the predetermined direction with respect to a print medium,

wherein the predetermined direction corresponds to the column and the crossing direction corresponds to the row.

14. The image processing method according to claim 13,

wherein a printing for a unit area of the print medium is performed by a plurality of the relative movements of the nozzle array, and

ink ejecting is allowed for every other column in each of the relative movements and the column which is allowed to print is changed for each of the relative movements.

15. The image processing method according to claim 11, wherein in the threshold value matrix, the average values in respective rows are almost the same value.

16. The image processing method according to claim 11, wherein in the threshold value matrix, the average values in respective columns are almost the same value.

17. The image processing method according to claim 11, wherein in the threshold value matrix, the average values in respective rows and the average values in respective columns are almost the same value.

18. An image processing method, executed by an image processing apparatus, for performing a quantization process of multivalued image data into a lower level N-value (N is an integer equal to or more than 2) by an error diffusion process, the image processing method comprising:

inputting multivalued image data of an image;

an obtaining step of adding an error from a peripheral pixel to the multivalued image data of a target pixel of an image to obtain a correction value;

a setting step of, from a threshold value matrix configured such that different values are arrayed in a row array and in a column array, selecting one value according to a pixel position of the target pixel in the image to set a threshold value for comparing with the correction value, the row consisting of pixels corresponding to values in the row array and the column consisting of pixels corresponding to values in the column array intersecting;

a quantization step of, according to a result of comparing the threshold value set in the setting step with the correction value obtained in the obtaining step, outputting N-value data;

a diffusion step of diffusing an error between the correction value and the N-value data, the error occurring in association with the quantization step, in a peripheral pixel position where the quantization step has not been performed; and

outputting a value indicating printing or non-printing of the target pixel,

wherein in the threshold value matrix, a variation among average values in respective rows or a variation among average values in respective columns are kept low as compared with a case of generating random numbers to prepare the different values.

19. The image processing method according to claim 18,

wherein the image processing method is a method for printing an image by ejecting ink according to the N-value data output in the quantization step while relative movement of a nozzle array, in which a plurality of nozzles for ejecting ink are arrayed in a predetermined direction, in a direction crossing to the predetermined direction with respect to a print medium,

wherein the predetermined direction corresponds to the column and the crossing direction corresponds to the row.

20. The image processing method according to claim 19,

wherein a printing for a unit area of the print medium is performed by a plurality of the relative movements of the nozzle array, and

ink ejecting is allowed for every other column in each of the relative movements and the column which is allowed to print is changed for each of the relative movements.

21. The image processing method according to claim 18, wherein in the threshold value matrix, the average values in respective rows are almost the same value.

22. The image processing method according to claim 18, wherein in the threshold value matrix, the average values in respective columns are almost the same value.

23. The image processing method according to claim 18, wherein in the threshold value matrix, the average values in respective rows and the average values in respective columns are almost the same value.

24. An image processing apparatus for performing a quantization process of multivalued image data into a lower level N-value (N is an integer equal to or more than 2) by an error diffusion process, the image processing apparatus comprising:

a processor executing;

inputting multivalued image data of an image;

an obtaining step of adding an error from a peripheral pixel to the multivalued image data of a target pixel of an image to obtain a correction value;

a setting step of, from a threshold value matrix configured such that different values are arrayed in a row array and in a column array, selecting one value according to a pixel position of the target pixel in the image to set a threshold value for comparing with the correction value, the row consisting of pixels corresponding to values in the row array and the column consisting of pixels corresponding to values in the column array intersecting;

a quantization step of, according to a result of comparing the threshold value set by the setting step with the correction value obtained by the obtaining step, outputting N-value data;

a diffusion step of diffusing an error between the correction value and the N-value data, the error occurring in association with the quantization step, in a peripheral pixel position where the quantization step has not been performed; and

outputting a value indicating printing or non-printing of the target pixel,

wherein in the threshold value matrix, average values in respective rows or average values in respective columns are almost a same value.

25. The image processing apparatus according to claim 24,

wherein the image processing apparatus is for printing an image by ejecting ink according to the N-value data output in the quantization step while relative movement of a nozzle array, in which a plurality of nozzles for ejecting ink are arrayed in a predetermined direction, in a direction crossing to the predetermined direction with respect to a print medium,

wherein the predetermined direction corresponds to the column and the crossing direction corresponds to the row.

26. The image processing apparatus according to claim 25,

wherein a printing for a unit area of the print medium is performed by a plurality of the relative movements of the nozzle array, and

ink ejecting is allowed for every other column in each of the relative movements and the column which is allowed to print is changed for each of the relative movements.

27. The image processing apparatus according to claim 24, wherein in the threshold value matrix, the average values in respective rows are almost the same value.

28. The image processing apparatus according to claim 24, wherein in the threshold value matrix, the average values in respective columns are almost the same value.

29. The image processing apparatus according to claim 24, wherein in the threshold value matrix, the average values in respective rows and the average values in respective columns are almost the same value.