Image processing apparatus and image forming apparatus

Patent metadata

Field	Value
Publication number	US-11539859-B2
Application number	US-202217591909-A
Country	US
Kind code	B2
Filing date	Feb 3, 2022
Priority date	Feb 8, 2021
Publication date	Dec 27, 2022
Grant date	Dec 27, 2022

Abstract

An image processing apparatus includes a halftone processing unit and a multi-level gradation processing unit. The halftone processing unit is configured to perform a halftone process for a target image and generate a binary image corresponding to the target image. The multi-level gradation processing unit is configured to (a) set a target pixel as a dot pixel in the binary image, (b) determine whether a dot exists on plural first periphery pixels with a predetermined first distance from the target pixel and plural second periphery pixels with a predetermined second distance from the target pixel or not, (c) derive a gradation level of the target pixel among predetermined three or more gradation levels on the basis of a number of dots on the plural first periphery pixels and a number of dots on the plural second periphery pixels and thereby generate a multi-level gradation image.

First claim

What is claimed is:

1. An image processing apparatus, comprising:
a halftone processing unit configured to perform a halftone process for a target image and generate a binary image corresponding to the target image; and
a multi-level gradation processing unit configured to (a) set a target pixel as a dot pixel in the binary image, (b) determine whether a dot exists on plural first periphery pixels with a predetermined first distance from the target pixel and plural second periphery pixels with a predetermined second distance from the target pixel or not, (c) derive a gradation level of the target pixel among predetermined three or more gradation levels on the basis of a number of dots on the plural first periphery pixels and a number of dots on the plural second periphery pixels and thereby generate a multi-level gradation image.

2. The image processing apparatus according to claim 1 , wherein the multi-level gradation processing unit (a) determines whether a predetermined exception condition is satisfied on the target pixel or not, and (b) performs an offset process, if the exception condition is satisfied on the target pixel;
the offset process adjusts the derived gradation level; and
the exception condition is that the target pixel and dot pixels among peripheral pixels in a predetermined range from the target pixel appear in a straight line.

3. The image processing apparatus according to claim 2 , wherein if the exception condition is satisfied on the target pixel, the multi-level gradation processing unit determines that the target pixel is a character pixel that is a part of a character, and performs the offset process corresponding to the character pixel.

4. The image processing apparatus according to claim 1 , wherein the multi-level gradation processing unit (a) determines whether a predetermined exception condition is satisfied on the target pixel or not, and (b) performs an offset process, if the exception condition is satisfied on the target pixel;
the offset process adjusts the derived gradation level; and
the exception condition is that in a peripheral pixel area of a predetermined range from the target pixel, a number of parts in which a dot pixel and a non-dot pixel appear adjacent to each other excesses a predetermined threshold value.

5. The image processing apparatus according to claim 4 , wherein if the exception condition satisfies on the target pixel, the multi-level gradation processing unit determines that the target pixel corresponds to an intermediate gradation level pixel that is a part of a gradation image, and performs the offset process corresponding to the intermediate gradation level pixel.

6. The image processing apparatus according to claim 1 , wherein the first periphery pixels are outermost peripheral pixels in a pixel area of vertical 3 pixels by horizontal 3 pixels with a center set on the target pixel; and
the second periphery pixels are outermost peripheral pixels in a pixel area of vertical 5 pixels by horizontal 5 pixels with a center set on the target pixel.

7. An image forming apparatus, comprising:
an image processing apparatus; and
a printing device configured to print a multi-level gradation image;
wherein the image processing apparatus comprises:
a halftone processing unit configured to perform a halftone process for a target image and generate a binary image corresponding to the target image; and
a multi-level gradation processing unit configured to (a) set a target pixel as a dot pixel in the binary image, (b) determine whether a dot exists on plural first periphery pixels with a predetermined first distance from the target pixel and plural second periphery pixels with a predetermined second distance from the target pixel or not, (c) derive a gradation level of the target pixel among predetermined three or more gradation levels on the basis of a number of dots on the plural first periphery pixels and a number of dots on the plural second periphery pixels and thereby generate the multi-level gradation image.

Assignees

• Kyocera Document Solutions Inc

Inventors

• Nakatsuji Hiroomi
• Sakane Hiroki
• Kawashima Naoko
• Nakano Jun
• Usui Masato

Classifications

• H04N1/58

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

• H04N1/405 Primary

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

• H04N1/40087

  Multi-toning, i.e. converting a continuous-tone signal for reproduction with more than two discrete brightnesses or optical densities, e.g. dots of grey and black inks on white paper · CPC title

• G03G15/5041

  Detecting a toner image, e.g. density, toner coverage, using a test patch (G03G15/553 takes precedence) · CPC title

• H04N2201/0094

  Multifunctional device, i.e. a device capable of all of reading, reproducing, copying, facsimile transception, file transception · CPC title