Image processing apparatus, image forming apparatus, and image processing method which correct tone jump

Patent metadata

Field	Value
Publication number	US-10791250-B2
Application number	US-201715597867-A
Country	US
Kind code	B2
Filing date	May 17, 2017
Priority date	May 17, 2016
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

In an image processing apparatus gradation is represented by binary or multiple values. There is a memory to store correction information including a correction value corresponding to a position of image data. Correction circuitry corrects the image data according to the correction value. The number of bits representing the correction value for gradation is larger than the number of bits used to represent the image data.

First claim

What is claimed is:

1. An image processing apparatus, in which gradation is represented by binary or multiple values, comprising:
a memory to store correction information including correction value data corresponding to a position of image data;
correction circuitry configured to correct gradation of the image data according to the correction value data; and
a printer configured to form an image on a recording medium based on the corrected gradation of the image data, wherein
a number of bits used to represent the correction value data for the gradation is larger than a number of bits used to represent the image data,
the image data represents gradation by a half-tone cell that includes a set of pixels,
the correction circuitry is further configured to determine whether a particular half-tone cell is a correction target or not, and correct values of pixels in the particular half-tone cell, when determining that the particular half-tone cell is the correction target, and
the correction circuitry is further configured to determine that the particular half-tone cell is the correction target when determining that (1) a density value of the particular half-tone cell is a same value as a density value of a first half-tone cell adjacent in a sub scan direction, and (2) the density value of the particular half-tone cell is a same value as a density value of a second half-tone cell adjacent in a main scanning direction orthogonal to the sub scan direction.

2. The image processing apparatus according to claim 1 , wherein the correction circuitry is further configured to correct a value of a pixel within a group of pixels based on neighboring pixel values for pixels that are adjacent in the sub scan direction orthogonal to the main scan direction.

3. The image processing apparatus according to claim 1 , wherein the correction circuitry is further configured to increase a resolution of the half-tone cell and correct a value of a pixel of the resolution-increased half-tone cell.

4. An image processing apparatus, in which gradation is represented by binary or multiple values, comprising:
means for storing correction information including correction value data corresponding to a position of image data;
means for correcting gradation of the image data according to the correction value data; and
means for forming an image on a recording medium based on the corrected gradation of the image data, wherein
a number of bits used to represent the correction value data for the gradation is larger than a number of bits used to represent the image data,
the image data represents gradation by a half-tone cell that includes a set of pixels,
the means for correcting includes means for determining whether a particular half-tone cell is a correction target or not, and correcting values of pixels in the particular half-tone cell, when determining that the particular half-tone cell is the correction target, and
the means for determining determines that the particular half-tone cell is the correction target when determining that (1) a density value of the particular half-tone cell is a same value as a density value of a first half-tone cell adjacent in a sub scan direction, and (2) the density value of the particular half-tone cell is a same value as a density value of a second half-tone cell adjacent in a main scanning direction orthogonal to the sub scan direction.

5. The image processing apparatus according to claim 4 , wherein the means for correcting corrects a value of a pixel within a group of pixels based on neighboring pixel values for pixels that are adjacent in the sub scan direction orthogonal to the main scan direction.

6. The image processing apparatus according to claim 4 , wherein the means for correcting increases a resolution of the half-tone cell and corrects a value of a pixel of the resolution-increased half-tone cell.

7. An image processing method, in which gradation is represented by binary or multiple values, comprising:
reading, from a memory, correction information including correction value data corresponding to a position of image data,
correcting gradation of the image data according to the correction value data, and
forming an image on a recording medium based on the corrected gradation of the image data, wherein
a number of bits used to represent the correction value data for the gradation is larger than a number of bits used to represent the image data,
the image data represents gradation by a half-tone cell that includes a set of pixels,
the correcting step further includes determining whether a particular half-tone cell is a correction target or not, and correcting values of pixels in the particular half-tone cell, when determining that the particular half-tone cell is the correction target, and
the correcting step further includes determining that the particular half-tone cell is the correction target when determining that (1) a density value of the particular half-tone cell is a same value as a density value of a first half-tone cell adjacent in a sub scan direction, and (2) the density value of the particular half-tone cell is a same value as a density value of a second half-tone cell adjacent in a main scanning direction orthogonal to the sub scan direction.

8. The image processing apparatus of claim 1 , wherein the correction circuitry is further configured to set correction values of pixels in only those half-tone cells determined to be correction targets, based on corresponding correction value data of the correction value data stored in the memory.

9. The image processing apparatus of claim 8 , wherein the correction circuitry is further configured to calculate final correction value data based on the stored correction value data and a result of determining which of the half-tone cells are correction targets.

10. The image processing apparatus of claim 1 , wherein the correction circuitry is further configured to correct pixels in a half-tone cell adjacent to the particular half-tone cell in the sub scan direction, using a different correction value than used for the particular half-tone cell.

Assignees

• Watanabe Naoto
• Soma Takashi
• Ricoh Co Ltd

Inventors

• Watanabe Naoto
• Soma Takashi

Classifications

• H04N1/405

  Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels · CPC title

• H04N1/407

  Control or modification of tonal gradation or of extreme levels, e.g. background level · CPC title

• H04N1/6069 Primary

  spatially varying within the image · CPC title