Image processing apparatus, image processing method, and program for generating a halftone image data

• US 10,547,762 B2
• Filed: 09/20/2018
• Issued: 01/28/2020
• Est. Priority Date: 09/27/2017
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takesue, Naoya
• Primary Examiner(s): Tran, Dung D
• Application Number:
  US16/137,242
• Publication Number:
  US 20190098172A1
• Time in Patent Office: 495 Days
• Field of Search: None
• CPC Class Codes: G06K 15/105 Multipass or interlaced printing
• CPC Class Codes: G06K 15/1876 Decreasing spatial resolution; Dithering
• CPC Class Codes: H04N 1/3872 Repositioning or masking
• 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 1/52 Circuits or arrangements for halftone screening

Abstract

An image processing apparatus for forming an image by superimposing n (n≥2) records on a same region in a recording medium includes: a holding unit configured to hold a threshold matrix characteristic representing a dispersity of a dot pattern of each tone obtained when dithering is performed using a threshold matrix; a setting unit configured to set recording data for n recording scans by dividing image data for the n recording scans based on the threshold matrix characteristic; and a halftoning unit configured to perform dithering using the threshold matrix on the recording data for each of the n records.

Claims

1. An image processing apparatus for generating halftone image data used for an image forming apparatus which forms an image based on the halftone image data by superimposing n (n≥

2) records on a same region in a recording medium, the image processing apparatus comprising;

a memory that holds threshold matrix characteristic information related to a threshold matrix characteristic representing a dispersity of a dot pattern of each tone value obtained when dithering is performed using a threshold matrix; and

one or more circuitry for causing the image processing apparatus to function as;

a setting unit configured to set recording data indicating an amount of recording for n recording scans by dividing values of respective pixels in an image indicated by image data for the n recording scans based on the threshold matrix characteristic information; and

a halftoning unit configured to perform dithering using the threshold matrix on the recording data for each of the n records to generate the halftone image data.

2. The image processing apparatus according to claim 1, wherein the setting unit equally divides pixel values of respective pixels in an image indicated by the image data into n values, and then updates at least one piece of recording data for the n recording scans based on the threshold matrix characteristic.

3. The image processing apparatus according to claim 2, wherein the setting unit sets a search area to recording data for a recording scan to be processed among the n recording scans, and determines whether a tone with a highest dispersity in the search area is present in the threshold matrix characteristic, and when the tone with the highest dispersity is present, the setting unit updates recording data for the recording scan to be processed with the tone with the highest dispersity.

4. The image processing apparatus according to claim 2, wherein the setting unit updates the recording data based on the threshold matrix characteristic for recording scans up to an (n−

1)th recording scan except an nth recording scan.

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

the holding unit holds, as the threshold matrix characteristic information, a dispersity evaluation value for each tone of the threshold matrix, and

the setting unit sets the recording data with reference to the dispersity evaluation value for each tone of the threshold matrix.

6. The image processing apparatus according to claim 1, wherein the threshold matrix is a matrix in which thresholds of different values are arranged to obtain a high-dispersion dot pattern for a plurality of tones set at predetermined intervals.

7. The image processing apparatus according to claim 1, wherein the threshold matrix includes a blue noise characteristic.

8. The image processing apparatus according to claim 2, wherein the setting unit does not update recording data corresponding to a last recording scan among the n recording scans.

9. The image processing apparatus according to claim 3, wherein the search area is set to 5% to 10% of a range of pixel values in the image data.

10. The image processing apparatus according to claim 1, wherein the threshold matrix is a matrix created by a Void-and-Cluster method.

11. The image processing apparatus according to claim 1, wherein the halftoning unit converts each piece of recording data into binary data.

12. The image processing apparatus according to claim 1, wherein the holding unit holds pieces of threshold matrix characteristic information respectively corresponding to a plurality of threshold matrices.

13. The image processing apparatus according to claim 1, wherein the halftoning unit selects any one of the plurality of threshold matrices for each of the pieces of recording data, and performs halftoning on the selected threshold matrix.

14. The image processing apparatus according to claim 1, wherein the halftoning unit generates constraint information based on half-tone image data obtained by performing halftoning on the recording data, and refers to the constraint information generated based on the half-tone image data corresponding to a recording scan preceding a target recording scan when halftoning is performed on the recording data for the target recording scan among the n recording scans.

15. The image processing apparatus according to claim 14, wherein the constraint information is information having a correlation with a possibility that a dot is already located at the same location in the preceding recording scan.

16. The image processing apparatus according to claim 14, wherein the halftoning unit determines, for a pixel of interest in the recording data corresponding to the target recording scan, a halftoning result for the pixel of interest based on the constraint information corresponding to the pixel of interest, a threshold corresponding to the pixel of interest in the threshold matrix, and the recording data corresponding to the pixel of interest.

17. The image processing apparatus according to claim 16, wherein the halftoning unit turns off a dot corresponding to the pixel of interest when the constraint information corresponding to the pixel of interest is greater than the threshold corresponding to the pixel of interest.

18. The image processing apparatus according to claim 17, wherein the halftoning unit compares the recording data corresponding to the pixel of interest with the threshold when the constraint information corresponding to the pixel of interest is smaller than the threshold corresponding to the pixel of interest, and the halftoning unit turns on the dot corresponding to the pixel of interest when the recording data corresponding to the pixel of interest is greater than the threshold corresponding to the pixel of interest.

19. A non-transitory computer-readable storage medium storing a program to cause a computer to perform an image processing method for generating halftone image data used for an image forming apparatus which forms an image based on the halftone image data by superimposing n (n≥

2) records on a same region in a recording medium, the method comprising;

holding threshold matrix characteristic information related to a threshold matrix characteristic representing a dispersity of a dot pattern of each tone obtained when dithering is performed using a threshold matrix;

setting recording data for n recording scans by dividing values of respective pixels in an image indicated by image data for the n recording scans based on the threshold matrix characteristic information; and

performing dithering using the threshold matrix on the recording data for each of the n records to generate the halftone image data.

20. An image processing method for forming an image, the method comprising:

holding threshold matrix characteristic information related to a threshold matrix characteristic representing a dispersity of a dot pattern of each tone obtained when dithering is performed using a threshold matrix;

setting recording data for n recording scans by dividing values of respective pixels in an image indicated by image data for the n recording scans based on the threshold matrix characteristic information; and

performing dithering using the threshold matrix on the recording data for each of the n records to generate halftone image data used by an image forming apparatus which forms an image based on the halftone image data by superimposing n (n≥

2) records on a same region in a recording medium.