IMAGE PROCESSING APPARATUS, IMAGE FORMING APPARATUS, IMAGE PROCESSING METHOD, AND STORAGE MEDIUM

• US 20150220824A1
• Filed: 01/31/2015
• Published: 08/06/2015
• Est. Priority Date: 02/06/2014
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kikuta, Kyohei
• Granted Patent: US 9,349,083 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B41J 2/2054 by the variation of dot disposition or characteristics, e.g. dot number density, dot shape
• CPC Class Codes: B41J 2/2132 Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding methods for local corrections by dot omission, image edge enhancement, or multi-pass mask selection G06K15/102; colour conversion H04N1/40
• CPC Class Codes: G06K 15/1872 Image enhancement
• CPC Class Codes: G06K 15/1876 Decreasing spatial resolution; Dithering
• CPC Class Codes: G06K 15/1878 Adjusting colours image colour correction or control for documents in general H04N1/60
• CPC Class Codes: G06K 15/1881 Halftoning halftoning of still images in general H04N1/405, H04N1/52
• CPC Class Codes: H04N 1/4051 producing a dispersed dots halftone pattern, the dots having substantially the same size different sizes H04N1/4057
• CPC Class Codes: H04N 1/4052 by error diffusion, i.e. transferring the binarising error to neighbouring dot decisions

Abstract

An image processing apparatus that generates image data for forming an image by performing printing a plurality of times on the same area of a printing medium. The image processing apparatus includes: a division unit configured to divide the image data into first image data and second image data by comparing a pixel value indicating a density of a pixel with a predetermined threshold value for each pixel constituting the image data so that the first image data includes pixels whose pixel value is equal to or greater than the predetermined threshold value and the second image data includes pixels whose pixel value is less than the threshold value; a first halftone processing unit configured to perform dither processing on the first image data; and a second halftone processing unit configured to perform error diffusion processing on the second image data.

Claims

1. An image processing apparatus that generates image data for forming an image by performing printing a plurality of times on the same area of a printing medium, the image processing apparatus comprising:

a division unit configured to divide the image data into first image data and second image data by comparing a pixel value indicating a density of a pixel with a predetermined threshold value for each pixel constituting the image data so that the first image data includes pixels whose pixel value is equal to or greater than the predetermined threshold value and the second image data includes pixels whose pixel value is less than the threshold value;

a first halftone processing unit configured to perform dither processing on the first image data; and

a second halftone processing unit configured to perform error diffusion processing on the second image data.

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

the plurality of times is N times,

the division unit further divides the image data including pixels whose pixel value is equal to or greater than the threshold value into image data corresponding to (N−

1) times by performing division in a predetermined ratio, and

the first halftone processing unit performs dither processing on each piece of the image data corresponding to the (N−

1) times.

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

the second halftone processing unit performs the second halftone processing based on the results of the first halftone processing by the first halftone processing unit.

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

the image data corresponding to the plurality of times of printing is subjected to processing by one of the first halftone processing unit and the second halftone processing unit.

5. The image processing apparatus according to claim 1, comprising:

a density setting unit configured to set a density range for halftone processing; and

a unit configured to set image data that is generated by one of the halftone processing units and which is to be used in each of the plurality of times of printing in accordance with a density range set by the density setting unit.

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

image data for predetermined preceding printing of the plurality of times of printing is generated by the first halftone processing unit, and

image data for printing that follows the predetermined preceding printing of the plurality of times of printing is generated by the second halftone processing unit.

11. The image processing apparatus according to claim 1, further comprising a printing density acquisition unit configured to read a density of an image printed on a printing medium, wherein

the second halftone processing unit performs halftone processing based on the density of the image printed on the printing medium, which is read by the printing density acquisition unit.

12. An image forming apparatus that comprises the image processing apparatus according to claim 1 and which forms an image by performing printing a plurality of times on the same area of a printing medium.

13. The image forming apparatus according to claim 12, wherein

the plurality of times of printing is performed by using the same color material.

14. The image forming apparatus according to claim 12, wherein

an image is formed by causing a print head having a plurality of printing elements to scan the same area of the printing medium a plurality of times.

15. The image forming apparatus according to claim 12, wherein

an image is formed by a plurality of printing element rows, each of which includes a plurality of printing elements put side by side in a main scan direction, performing printing, respectively, on an area in a sub scan direction of the recording medium.

19. A non-transitory computer readable storage medium storing a program for causing a computer to function as the image processing apparatus according to claim 1.

7. An image processing apparatus that generates image data for forming an image by performing printing a plurality of times on the same area of a printing medium, the image processing apparatus comprising:

a division unit configured to divide the image data into first image data and second image data by comparing a pixel value indicating a density of a pixel with a predetermined threshold value for each pixel constituting the image data so that the first image data includes pixels whose pixel value is equal to or greater than the predetermined threshold value and the second image data includes pixels whose pixel value is less than the threshold value;

a first halftone processing unit configured to perform dither processing on the first image data; and

a second halftone processing unit configured to perform, on the second image data, halftone processing to determine a value of a pixel of interest based on the pixel of interest and pixels adjacent to the pixel of interest.

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

the halftone processing by the second halftone processing unit is mean density approximation processing.

9. An image processing apparatus that generates image data for forming an image by performing printing N times on the same area of a printing medium, the image processing apparatus comprising:

a division unit configured to divide the image data into image data corresponding to the N times of printing by dividing the image data for each pixel constituting the image data;

a first halftone processing unit configured to generate first halftone image data corresponding to (N-a) times by performing dither processing on image data corresponding to (N-a) times of the image data corresponding to the N times of printing;

a second halftone processing unit configured to generate second halftone image data corresponding to a times by performing error diffusion processing on image data corresponding to a times of the image data corresponding to the N times of printing; and

a control unit configured to control printing based on the second halftone image data corresponding to the α and

the first halftone image data corresponding to the (N−

α

), wherein

the control unit causes the first halftone image data to be printed prior to the second halftone image data.

10. The image processing apparatus according to claim 9, comprising:

a detection unit configured to detect results of printing the first halftone image data; and

a correction unit configured to correct the second image data based on the results of the detection unit, wherein

the second halftone processing unit performs error diffusion processing on the second image data that is corrected by the correction unit.

16. An image processing method of generating image data for forming an image by performing printing a plurality of times on the same area of a printing medium, the image processing method comprising:

a step of dividing the image data into first image data and second image data by comparing a pixel value indicating a density of a pixel with a predetermined threshold value for each pixel constituting the image data so that the first image data includes pixels whose pixel value is equal to or greater than the predetermined threshold value and the second image data includes pixels whose pixel value is less than the threshold value;

a first halftone processing step of performing dither processing on the first image data; and

a second halftone processing step of performing error diffusion processing on the second image data.

17. An image processing method of generating image data for forming an image by performing printing a plurality of times on the same area of a printing medium, the image processing method comprising:

a step of dividing the image data into first image data and second image data by comparing a pixel value indicating a density of a pixel with a predetermined threshold value for each pixel constituting the image data so that the first image data includes pixels whose pixel value is equal to or greater than the predetermined threshold value and the second image data includes pixels whose pixel value is less than the threshold value;

a first halftone processing step of performing dither processing on the first image data; and

a second halftone processing step of performing, on the second image data, halftone processing to determine a value of a pixel of interest based on the pixel of interest and pixels adjacent to the pixel of interest.

18. An image processing method of generating image data for forming an image by performing printing N times on the same area of a printing medium, the image processing method comprising:

a step of dividing the image data into image data corresponding to the N times of printing by dividing the image data for each pixel constituting the image data;

a first halftone processing step of generating first halftone image data corresponding to (N−

α

) times by performing dither processing on image data corresponding to (N−

α

) times of the image data corresponding to the N times of printing;

a second halftone processing step of generating second halftone image data corresponding to a times by performing error diffusion processing on image data corresponding to a times of the image data corresponding to the N times of printing; and

a control step of controlling printing based on the second halftone image data corresponding to the α and

the first halftone image data corresponding to the (N−

α

), wherein

in the control step, the first halftone image data is printed prior to the second halftone image data.