Image processing apparatus, image processing method, printing medium and storage medium

Patent metadata

Field	Value
Publication number	US-10043118-B2
Application number	US-201514750128-A
Country	US
Kind code	B2
Filing date	Jun 25, 2015
Priority date	Jul 1, 2014
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

An image processing apparatus that generates a halftone image by quantizing an input image includes: a holding unit configured to hold a threshold value matrix in which different threshold values are arranged; a pixel position determination unit configured to determine a candidate of a pixel position whose threshold value is to be rewritten based on each pixel value of a plurality of pixels included in a predetermined area for the predetermined area in the input image; and a threshold value determination unit configured to determine a threshold value of the pixel position determined to be the candidate by using at least one threshold value of a plurality of threshold values corresponding to the predetermined area.

First claim

What is claimed is:

1. An image processing apparatus that generates a halftone image of an input image by performing quantization, comprising:
a processor; and
a memory having stored thereon instructions that, when executed by the processor, cause the processor to:
hold a threshold value matrix in which threshold values, corresponding to a plurality of pixels in the input image, are arranged;
determine a candidate of a pixel position whose threshold value is to be rewritten based on each pixel value of a plurality of pixels included in a predetermined area of the input image;
determine the threshold value of the pixel position determined to be the candidate by using at least one threshold value of a plurality of threshold values corresponding to the plurality pixels in the predetermined area; and
generate the halftone image of the input image based on the determined threshold value.

2. The image processing apparatus according to claim 1 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
rewrite the threshold value of the pixel position determined to be the candidate in the threshold value matrix using a threshold value corresponding to a pixel other than the pixel position determined to be the candidate.

3. The image processing apparatus according to claim 1 , wherein the candidate of the pixel position whose threshold value is to be rewritten is chosen from among pixels, in the predetermined area, having a pixel value greater than a predetermined value.

4. The image processing apparatus according to claim 1 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
determine whether each pixel in the predetermined area is a pixel that can provide a threshold value to be allocated to another pixel based on the pixel value of each pixel in the predetermined area.

5. The image processing apparatus according to claim 4 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
determine a pixel whose pixel value is equal to 0.

6. The image processing apparatus according to claim 1 , wherein the threshold value of the pixel position determined to be the candidate is determined using a threshold value of a pixel determined to be a pixel that can provide a threshold value to be the threshold value of the pixel position determined to be the candidate, in a case where the threshold value of the pixel determined to be a pixel that can provide a threshold value is smaller than the threshold value of the pixel position determined to be the candidate.

7. The image processing apparatus according to claim 1 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
determine a threshold value of a pixel determined to be a pixel that can provide a threshold value; and
multiply the threshold value of the pixel determined to be a pixel that can provide a threshold value by a coefficient to create a new threshold value,
wherein the threshold value of the pixel position determined to be the candidate, in a case where the threshold value of the pixel determined to be a pixel that can provide a threshold value is smaller than the threshold value of the pixel position determined to be the candidate, and is determined to be the new threshold value.

8. The image processing apparatus according to claim 1 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
determine a new threshold value of the pixel position determined to be the candidate in a case where the pixel of the pixel position determined to be the candidate is a pixel constituting a line within the input image.

9. The image processing apparatus according to claim 8 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to acquire information indicating whether or not each pixel of the input image is a pixel constituting at least a portion of a line,
wherein the candidate of the pixel position whose threshold value is to be rewritten is determined to be a pixel constituting at least a portion of a line.

10. The image processing apparatus according to claim 1 , the memory further has stored thereon instructions that, when executed by the processor, cause the processor to:
set an arbitrary value from among multiple quantization output values; and
determine the threshold value of the pixel position determined to be the candidate to be a new threshold value in a case where the pixel of the pixel position determined to be the candidate is a pixel whose value is equal to or less than the set arbitrary value.

11. The image processing apparatus according to claim 1 , wherein
the threshold value matrix is a threshold value matrix created by using a sub matrix smaller than the threshold value matrix.

12. The image processing apparatus according to claim 11 , wherein
a size of the sub matrix is the same as a size of the predetermined area.

13. The image processing apparatus according to claim 1 , wherein
the predetermined area is set so that pixels do not belong to a plurality of predetermined areas.

14. The image processing apparatus according to claim 1 , wherein
the threshold value matrix has blue noise characteristics.

15. The image processing apparatus according to claim 1 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
determine the candidate of the pixel position whose threshold value is to be rewritten from among non-white pixels in the predetermined area based on a corresponding threshold value;
extract a minimum threshold value from a threshold value corresponding to a white pixel in the predetermined area; and
compare the minimum threshold value corresponding to the white pixel within the predetermined area with the threshold value corresponding to the candidate of the pixel position and rewrite the threshold value corresponding to the candidate of the pixel position based on the minimum threshold value in accordance with the comparison results.

16. The image processing apparatus according to claim 15 , the memory further having stored thereon instructions that, when executed by the processor, cause the processor to:
rewrite the threshold value corresponding to the candidate of the pixel position into 0 in accordance with the comparison results.

17. An image processing method in an image processing apparatus that includes a holding unit configured to hold a threshold value matrix, in which threshold values, corresponding to a plurality of pixels in the input image, are arranged, and generates a halftone image by quantizing an input image, the method comprising:
determining a candidate of a pixel position whose threshold value is to be rewritten based on each pixel value of a plurality of pixels including in a predetermined area for the predetermined area in the input image;
determining a threshold value of the pixel position determined to be the candidate in the pixel position determination step by using at least one threshold value among a plurality of threshold values corresponding to the predetermined area; and
generate the halftone image of the input image based on the determined threshold value.

18. A non-transitory computer readable storage medium storing a program for causing a computer to perform an image processing method in an image processing a

Assignees

• Canon Kk

Inventors

• Sumi Naoki
• Yamada Akitoshi
• Miyazaki Shinichi
• Kato Masao
• Ishikawa Hisashi
• Fujimoto Akihiro
• Yamamoto Yusuke
• Hara Yuji

Classifications

• H04N1/58

  Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction (H04N1/62 takes precedence) · CPC title

• G06K15/1881 Primary

  Halftoning (halftoning of still images in general H04N1/405, H04N1/52) · CPC title

• H04N1/6008

  with primary colour signals, e.g. RGB or CMY(K) · CPC title

• H04N1/605

  for controlling ink amount, strike-through, bleeding soakage or the like · CPC title

• G06K15/1877

  with provisions for treating some of the print data differently · CPC title