JP2001189859A - Image processing method and image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing method and an imager processor that conduct processing of converting image data denoting values of a plurality of pixels configuring an image into image data representing a dot pattern of each dot for a dot image output and can reduce a tone jump. SOLUTION: The image processing method adopts a super cell that consists of combinations of a plurality of dot patterns in a way that adjacent dot patterns are not simultaneously in contact with each other in a dot percent but are gradually in contact with each other within a dot percent of a degree.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image data (pixel value data) representing pixel values of a plurality of pixels constituting an image, and image data representing a dot pattern of each dot for outputting a dot image. The present invention relates to an image processing method for performing a process of converting the data into halftone data, and an image processing apparatus used for executing the process.

[0002]

2. Description of the Related Art Conventionally, a halftone image based on halftone data is formed in a printing machine and some color printers.

[0003] Here, when generating halftone dot data on which a halftone dot image is formed, for example, image data (pixel value data) representing the pixel values of a plurality of pixels constituting the image is added to the image. When a halftone pattern consisting of an array of threshold values is superimposed, the pixel values of the pixels on the image, which are superimposed on each other, are compared with the threshold values of the halftone pattern, and the pixel values of the pixels on the image are multi-valued. (Typically binary), and image data (dot data) representing the dot pattern of each dot is generated by such conversion.

Hereinafter, the process of generating dot data will be further described with reference to an example in which a printing machine outputs a dot image.

FIG. 1 is a block diagram showing an example of a printing system.

In the color scanner 10, a document image is read, and CMY representing the read document image.
K4 color separation image data is generated. This CMYK
Is input to the workstation 20,
At this workstation 20, the operator
Electronic plate collection based on the input image is performed. When the electronic plate collection is completed, image data (pixel value data) representing the image after the plate collection is generated, and the pixel value data is converted into dot data for printing as described later. The halftone dot data is input to the film printer 30, and the film printer 30 creates a printing film original including CMYK plates corresponding to the input halftone data.

[0007] A printing plate is prepared from the printing film master, and the prepared printing plate is mounted on a printing machine 40. Ink is applied to a printing plate mounted on the printing press, and the applied ink is transferred onto a printing paper to form a dot image 41 on the printing paper.

Here, the conversion from the pixel value data to the halftone data in the workstation 20 is performed as follows.

FIG. 2 is an explanatory diagram of a conversion method for converting pixel value data into halftone dot data.

FIG. 2A is a diagram showing an example of a halftone pattern in which threshold values are two-dimensionally arranged. In this halftone pattern, thresholds of values 1 to 25 are arranged as shown.

FIG. 2B is a diagram showing a part of the image data (pixel value data) before conversion, in which a uniform image in which all pixels have a pixel value of 14 is shown. ing.

Here, the image of FIG. 2B is replaced with the image of FIG.
2A is superimposed on each area, and the pixel value of each pixel on the image, which is superimposed on each other, Are converted to '0' when the pixel value is smaller than the threshold value and to '1' when the pixel value is larger than or equal to the threshold value, and a binary image as shown in FIG. Is done. Here, ink is applied to the pixel of “1” in FIG. 2C (the pattern to which the ink is applied is referred to as a dot pattern), and no ink is applied to the pixel of “0”. That is, in FIG. 2C, a dot pattern of one halftone dot is formed for the same size as the halftone pattern of FIG. 2C.

As can be seen from the arrangement of the threshold values forming the halftone pattern in FIG. 2A, when the pixel value of each pixel forming the image shown in FIG. The dot pattern for each dot becomes a dot pattern having a small area. As the pixel value of each pixel increases, the area of the dot pattern for each dot increases, and the density of the dot image increases. When the pixel value of each pixel is further increased, dot patterns of adjacent halftone dots are connected to each other, and finally, a so-called solid image in which ink is applied to all pixels in all halftone dots is obtained.

Here, the halftone pattern shown in FIG. 2A is a halftone pattern forming one halftone dot as a whole.
A halftone pattern corresponding to this one halftone dot, or a portion corresponding to one halftone dot in the whole halftone pattern when one halftone pattern corresponds to a plurality of halftone dots as shown in FIG. Are referred to as dot cells here.

FIG. 3 is a diagram showing an example of a net pattern.

In the halftone pattern shown in FIG. 3, a plurality of dot cells are arranged diagonally, and the halftone pattern is scanned vertically and horizontally so as to be sequentially superimposed on each area of the image. A halftone image in which dots are arranged diagonally is formed. The reason why the halftone dots are arranged obliquely is to prevent occurrence of visually noticeable moiré by changing the angle of the arrangement for each color ink.

Here, this halftone pattern is composed of a combination of a plurality of dot cells. Such a halftone pattern in which a plurality of dot cells are arranged is called a supercell. The use of this supercell enables high-speed scanning.

[0018]

As described above, in the workstation 20 shown in FIG. 1, the image data (pixel value data) representing the pixel value of each pixel constituting the image is converted to a halftone dot pattern. The image data (halftone data) is converted into image data (halftone data). The image density represented by the area of the dot pattern on the converted image data (halftone data) and the actual printing are performed based on the halftone data. The density of the obtained halftone image does not match, for example,
When the pixel value of each pixel of the image is sequentially changed from a small value (corresponding to low density) to a large value (corresponding to high density), the image density calculated from the dot pattern on the halftone dot data is continuous. Despite the change, the image density changes discontinuously at a certain density on the printed halftone image when it is actually printed based on the halftone data (such a discontinuity of the image density). The change is called a tone jump), and there is a problem that the discontinuity of the density is visually recognized depending on a print image, and the image quality of the print image is deteriorated.

The present invention has been made in view of the above circumstances, and has as its object to provide an image processing method in which the above-described discontinuity in density has been eliminated or alleviated, and an image processing apparatus used for implementing the image processing method. Aim.

[0020]

According to the present invention, there is provided an image processing method comprising: a first image data representing a pixel value of a plurality of pixels constituting an image; a second image data representing a halftone dot pattern; In an image processing method for performing a halftone process for converting image data, a pixel value of each pixel on a uniform image composed of a plurality of pixels all having the same pixel value is uniformly determined from a low density side. When the halftoning process is repeated while sequentially changing toward the high density side, the first halftone% which is the halftone% when the mutually adjacent dot patterns first appear in the same direction on the image.
And a second halftone dot ratio, which is a halftone dot ratio when all dot patterns adjacent in the same direction are in contact with each other, are different from each other.

Here, the pixel value of each pixel on the uniform image having the same pixel value is uniformly
When the above process is repeated while sequentially changing from the low density side to the high density side, "is an expression for associating the pixel value with the first halftone% and the second halftone%. This does not mean that a uniform image is actually prepared and that the pixel value of each pixel on the uniform image is actually changed as such.

Here, in the image processing method of the present invention, the halftoning process is performed by superimposing a halftone pattern composed of an array of thresholds on the image represented by the first image data. Is a process of comparing a pixel value of a pixel on an image with a threshold value of a halftone pattern, and converting the pixel value of each pixel on the image into a multi-valued binary or more. When viewing the halftone pattern in units of dot cells corresponding to the points, at least a part of the thresholds arranged on the dot cells,
A halftone pattern in which a plurality of types of dot cells are arranged, which are relatively different from pixel values of an image area on which dot cells are superimposed, wherein the first halftone dot and the second halftone dot in the same direction on the image It is preferable to perform the halftoning process using a halftone pattern in which each threshold value is adjusted so as to be different from%.

Here, the above-mentioned "a plurality of types of dot cells which are relatively different from the pixel value of the image area where the dot cells are superimposed" is typically a threshold value between the plurality of types of dot cells. However, since the threshold value of the dot cell is relative to the pixel value, the threshold value of the dot cell is fixed and the pixel value compared with the threshold value of the dot cell is It means that the correction may be made.

The above-mentioned "halftone pattern in which a plurality of types of dot cells are arranged" means that a result using a halftone pattern in which a plurality of types of dot cells are arranged may be used. I have. Specifically, for example, before comparing the pixel value of the pixel on the image with the threshold value of the halftone pattern, a halftone pattern in which a plurality of types of dot cells are arranged (this is called a supercell) is created. It is possible to scan over the image with such a supercell, or to use multiple types of dot cells alternately (for two types) or cyclically (for three or more types) to display on the image. Scanning may result in using a halftone pattern in which a plurality of types of dot cells are arranged, or in the present invention, it is not necessary to perform scanning, and a plurality of types of dot cells are arranged, A halftone pattern having the same area as the image when represented by the number of pixels may be used.

The ratio of the area of a dot pattern in one halftone dot to the area of one halftone dot is called halftone percentage. The halftone percentage is sequentially increased (the pixel value of a uniform image is increased from a lower density side to a higher density). If the area of the dot pattern is gradually increased by sequentially changing the density toward the density side), the dot patterns of adjacent halftone dots come into contact with each other at a certain dot%. On the image,
The ink spreads over an area larger than the contact point between the contact points of the dot patterns, which results in a tone jump. In the case of a printing system for producing a film master, the tone jump also occurs due to the spread of an exposure beam for producing the film master. As the dot pattern of the halftone dot, a rectangular (square) halftone dot and an elliptical (ell) are determined according to the method of determining the threshold shown in FIG.
Although some halftone dot shapes such as an (iptical) halftone dot are known, depending on the halftone dot shape, for example, a rectangle (sq
ure) If it is a halftone dot, it is 1 when the dot% is sequentially increased.
The four dots of the two dot patterns simultaneously contact the dot patterns of the adjacent halftone dots to form an elliptical shape.
In the case of a halftone dot, when halftone% is sequentially increased, two points in the same direction of one dot pattern simultaneously contact the dot pattern of an adjacent halftone dot, and a tone jump occurs at the halftone dot where this contact occurs. appear. For the purpose of this solution, for square halftone dots, 2% instead of 4 points simultaneously
It has been proposed that two points are brought into contact with each other with the difference of the halftone dot (see Japanese Patent No. 2578947). However, even in this case, there is a strong possibility that a large number of halftone dots will be touched two by two at the same time and a tone jump will occur.

Therefore, according to the image processing method of the present invention,
Since the first halftone dot and the second halftone dot in the same direction are different from each other, a high-quality halftone image in which tone jump hardly occurs or in which tone jump is less conspicuous than in the related art can be obtained. .

In the image processing method of the present invention, the pixel values of each pixel on a uniform image composed of a plurality of pixels all having the same pixel value are uniformly changed from a low density side to a high density side. When the halftoning process is repeated while sequentially changing toward the side, in the same direction on the image, the first half% which is the half% when the mutually adjacent dot patterns first appear; The second dot%, which is the dot% when all the dot patterns adjacent in the same direction are in contact with each other, is different from the second dot%, and further, the first dot% in the mutually different directions and the second dot% in the mutually different directions. It is preferable to perform the halftoning process so that the halftone percentages of 2 are different from each other.

In this case, when the halftoning process superimposes a halftone pattern consisting of an array of thresholds on the image represented by the first image data, the pixel values of the superimposed pixels on the image are superimposed on each other. And converting the pixel value of each pixel on the image into a multi-valued binary or higher value by comparing the pixel value with the threshold value of the halftone pattern.
When the halftone pattern is viewed in units of dot cells corresponding to two halftone dots, at least a part of the threshold values arranged on the dot cells is relative to the pixel value of the image area where the dot cells are superimposed. Is a halftone pattern in which a plurality of types of dot cells are arranged, wherein the first halftone% and the second halftone% in the same direction on an image are different from each other, and are different from each other. The halftone processing may be performed by using a halftone pattern in which each threshold value is adjusted so that the first halftone percentages of the first halftone dot and the second halftone percentages of the different directions differ from each other. .

In this case, the first half% and the second half% in one direction are made different from each other, and further, the first half% and the second half% in different directions are different from each other. Are different from each other, the occurrence of tone jump is further suppressed, and a higher quality halftone image can be obtained.

Further, in the image processing method of the present invention, the halftoning process is repeated while uniformly changing the pixel values of the pixels on the uniform image sequentially from the low density side to the high density side. In this case, a net is formed by using a net pattern in which a plurality of types of dot cells are arranged which form the same dot-patterns having different growth degrees within at least part of the average half-tone% range. The dot processing may be performed, or when the dot processing is repeated while the pixel values of the pixels on the uniform image are uniformly changed sequentially from the low density side to the high density side, A mesh pattern in which a plurality of types of dot cells are arranged while growing while maintaining the same mesh% and forming dot patterns different in shape within at least a part of the mesh% range. It may be subjected to halftone processing using.

Here, in the image processing method of the present invention, the minimum half% of the first half% in different directions and the maximum half of the second half% in different directions. So that the difference from net% is 1% or more,
It is preferable to perform the halftoning process using a halftone pattern in which a plurality of types of dot cells in which threshold values adjusted relative to the pixel values of the image region to be superimposed are arranged.

The difference between the minimum screen% and the maximum screen% is 1%.
By using the halftone pattern adjusted as described above, tone jump can be effectively suppressed.

The image processing method of the present invention typically converts the pixel value of each pixel of an image into a binary value using the halftone pattern. It may be converted to a value.

Further, in the image processing method of the present invention, when detecting the first halftone% and the second halftone%,
By determining whether or not a dot pattern is in contact with the second image data, the first halftone% and the second halftone% may be detected. The first halftone% and the second halftone% may be detected by outputting a halftone image based on the halftone image and determining whether or not a dot pattern is in contact with the halftone image.

A first image processing apparatus of the image processing apparatus according to the present invention for achieving the above object converts first image data representing pixel values of a plurality of pixels constituting an image into each halftone dot. In an image processing apparatus for performing a process of converting to a second image data representing a dot pattern, the image processing apparatus performs a process of superimposing a halftone pattern composed of an array of thresholds on an image represented by the first image data. A second image representing the dot pattern of each halftone dot by comparing the pixel value of the pixel on the image with the threshold value of the halftone pattern, and converting the pixel value of each pixel on the image to a multi-valued binary or more. A data conversion unit for executing a data conversion process for generating data; and a halftone pattern arranged on the dot cells when the halftone pattern is viewed in units of dot cells corresponding to one halftone dot. A halftone pattern in which a plurality of types of dot cells are arranged, at least a part of which is different from the threshold value. The data conversion unit includes a plurality of pixels having the same pixel value using the halftone pattern. Pixel value of each pixel on the uniform image
When the above data conversion process is repeated while changing the density uniformly from the low density side to the high density side, the dot% when the mutually adjacent dot patterns first appear in the same direction on the image. A halftone pattern in which a threshold is adjusted so that a certain first halftone dot and a second halftone dot which is a halftone dot when all dot patterns adjacent in the same direction are in contact with each other is obtained is stored. The data conversion unit executes the data conversion process using the halftone pattern stored in the halftone pattern storage unit.

Here, in the first image processing apparatus of the present invention, when the halftone pattern storage unit views the halftone pattern as a unit of a dot cell corresponding to one halftone dot, the halftone pattern storage unit stores the halftone pattern on the dot cell. At least a part of the arranged thresholds is a halftone pattern in which a plurality of types of dot cells different from one another are arranged among the dot cells, and the data conversion unit uses the halftone pattern to display a uniform image. When the above data conversion process is repeated while changing the pixel value of each pixel uniformly from the low density side to the high density side, dot patterns that are in contact with each other in the same direction on the image first 1st which is net% when it appears
Is different from the second half%, which is the half% when all the dot patterns adjacent in the same direction are in contact with each other, and further, the first half% in the mutually different directions.
It is preferable that the halftone percentages and the second halftone percentages in mutually different directions store halftone patterns whose threshold values are adjusted so as to obtain mutually different dot patterns.

Further, the second of the image processing apparatuses of the present invention
Is an apparatus that employs a method of changing pixel values to a plurality of types of patterns instead of using a plurality of dot cells having different thresholds.

That is, the second image processing apparatus of the present invention converts the first image data representing the pixel values of a plurality of pixels constituting an image into the second image data representing the dot pattern of each halftone dot. In the image processing apparatus for performing a process, when a correction pattern composed of an array of correction values is superimposed on an image represented by the first image data, the pixel value of the pixel on the image and the correction pattern superimposed on each other are superimposed on each other. A data correction for generating third image data representing corrected pixel values of a plurality of pixels forming an image by performing an operation between the correction values and the pixel values of the respective pixels on the image A data correction unit for performing a process, and a halftone pattern composed of an array of thresholds is added to an image represented by the third image data generated by the data correction unit. By comparing the pixel values of the pixels on the image, which are superimposed upon each other, with the threshold value of the halftone pattern, and converting the pixel values of each pixel of the image into multi-valued binary or more, each halftone dot A data conversion unit for executing a data conversion process for generating second image data representing the dot pattern of
When the correction pattern is viewed with a correction cell corresponding to one halftone dot as a unit, a plurality of types of correction cells in which at least some of the correction values arranged on the correction cells are different between the correction cells. The pixel value of each pixel on the uniform image composed of a plurality of pixels having the same pixel value in the arranged correction pattern is uniformly changed sequentially from the low density side to the high density side. When the data correction process in the data correction unit and the data conversion process in the data conversion unit are repeated, a dot pattern in which the mutually adjacent dot patterns appear first in the same direction on the image. % So that a dot pattern that is different from the first dot% that is different from the second dot% that is the dot% when all dot patterns adjacent in the same direction are in contact with each other is obtained. Using integer been corrected pattern, it is characterized in that to perform the data correction processing.

In the second image processing apparatus, when the data correction unit views the correction pattern as a unit of a correction cell corresponding to one halftone dot, the data correction unit calculates a correction value of the correction value arranged on the correction cell. At least a part of the correction pattern is a correction pattern in which a plurality of types of correction cells different from one another are arranged among the correction cells, and the pixel value of each pixel on the uniform image is uniformly increased from the low density side to the high value. When the data correction process in the data correction unit and the data conversion process in the data conversion unit are repeated while sequentially changing the density toward the density side, dot patterns that are in contact with each other in the same direction on the image Is the net% when first appears
Is different from the second half%, which is the half% when all the dot patterns adjacent in the same direction are in contact with each other, and further, the first half% in the mutually different directions.
The data correction process is performed using a correction pattern in which correction values are adjusted so that dot patterns different from each other and the second dot% in mutually different directions obtain mutually different dot patterns. Preferably, there is.

According to the image processing apparatus of the present invention, the first image data representing the pixel value of each pixel of the image is the first image data representing the dot pattern of each halftone dot, having little or no noticeable tone jump. 2 image data.

[0041]

Embodiments of the present invention will be described below.

FIG. 4 is an external perspective view of a personal computer, and FIG. 5 is a hardware configuration diagram of the personal computer.

The personal computer 100 corresponds to the workstation 20 in the printing system shown in FIG. 1. In the personal computer 100, first image data (pixel value data) representing the pixel value of each pixel of the image is stored. It is converted into second image data (dot data) representing a dot pattern of each dot of the dot image.

The personal computer 100 has a main body device 110, an image display device 120 for displaying an image on a display screen 120a in response to an instruction from the main body device 110, and a main device 110 in response to key operations. A keyboard 130 for inputting various types of information, and a mouse 140 for designating an arbitrary position on the display screen 120a and inputting an instruction corresponding to, for example, an icon or the like displayed at that position. This main unit 11
0 is a floppy disk loading slot 110a for loading a floppy disk, and a CD-ROM
And a CD-ROM loading port 110b for loading a CD-ROM.

As shown in FIG. 5, a CPU 101 for executing various programs and a program stored in a hard disk device 103 are read out from a main memory 110 and loaded into a main memory 1 for execution by the CPU 101, as shown in FIG.
02, a hard disk device 103 in which various programs and data are stored, a floppy disk 201 is loaded, an FD driver 104 for accessing the loaded floppy disk 201, a CD-ROM 202 are loaded, and the loaded CD-ROM 202 is loaded. CD-ROM driver 105 and color scanner 10 for accessing
(See FIG. 1), an input interface 106 that receives image data from the color scanner 10, and an output interface 10 that is connected to the film printer 30 (see FIG. 1) and sends dot data to the film printer 30.
7 are built in, and these various elements and FIG.
The image display device 120, the keyboard 130, and the mouse 140 are connected to each other via the bus 108.

Here, an image processing program for operating the personal computer 100 as an image processing device is stored in the CD-ROM 202, and the CD-ROM 202 is loaded in the CD-ROM driver 105, -The image processing program stored in the ROM 202 is uploaded to the personal computer 100 and stored in the hard disk device 103. The image processing program stored in the hard disk device 103 is developed on the main memory 102,
The processing is executed in U101, whereby the personal computer 100 operates as an image processing apparatus.

Next, the personal computer 100
An image processing method using an image processing program executed in the computer will be described.

FIG. 6 is a flowchart showing an image processing method by the image processing program executed in the personal computer shown in FIGS. Here, first image data (pixel value data) representing a pixel value of each pixel of the image is converted to second image data (dot data) representing a dot pattern of a halftone dot.

Here, first, a halftone pattern is obtained (step a). FIGS. 2A and 3 show examples of the halftone pattern. In step a, as described later,
A halftone pattern composed of a plurality of types of dot cells at least partially different in threshold value is obtained. This halftone pattern is, for example, a basic pattern or an ellipse (ellip) which is a basis for creating dot cells for forming a square halftone dot.
(tical) A halftone pattern composed of a plurality of types of dot cells created from a plurality of types of basic patterns, such as a basic pattern for forming dot cells forming halftone dots, or a single type of basic pattern. It may be a halftone pattern composed of a plurality of types of dot cells created while changing the threshold.

In step b of FIG. 6, first image data is obtained. Here, the color scanner 1 shown in FIG.
0, the original image is read, and electronic plate collection is performed by the workstation 20 (personal computer 100). Then, the workstation 20 (personal computer 100) displays a pixel value of each pixel of the print image. One image data (pixel value) is generated. Alternatively, such first image data (pixel value data) may be created outside the personal computer 100, and the created first image data (pixel value data) may be input to the personal computer 100. .

In step c, the pixel value data (first
Is converted to halftone data (second image data). The conversion method itself has been described with reference to FIG. 2 and will not be described here.

In step d, halftone data (second image data) is output to the film printer 30 shown in FIG. As described above, the film printer 30 creates a printing film original based on the halftone data.

Next, the operation of the present embodiment will be described in comparison with the operation of the conventional example.

FIG. 7 is a diagram showing both the operation of the present embodiment and the operation of the comparative example.

In the figure, the hatched portions are dot patterns to which ink is applied during printing. In FIG. 7, the halftone dots are arranged vertically and horizontally in the figure.

Pixel values are uniformly calculated for the entire image.
As the value is gradually changed from a small value on the low density side to a large value on the high density side, the area of the dot pattern gradually expands, and the dot pattern is changed from ((a), (b)) in FIG.
(C) → ((d), (e)) → (f).

Here, (a) → (c) → (d) →
(F) shows the change of the dot pattern in the comparative example. From the state in which the dot patterns are discrete in an island shape as shown in (a), all the dot patterns adjacent in the vertical direction as shown in (c) are completely different. At the same time, the dot patterns are further expanded as shown in FIG.
, All dot patterns adjacent to each other in the left-right direction are connected simultaneously. The ink spreads over an area larger than the connection point at the time of connection between the adjacent dot patterns, and a tone jump occurs.

FIG. 7 (b) → (c) → (d) → (e) →
FIG. 7F shows a change in the dot pattern according to the present embodiment. When the area of the dot pattern is sequentially increased, first, as shown in FIG. After being connected to only one of the dot patterns and the area of the dot pattern is further expanded, as shown in FIG. 7C, it is connected to another vertically adjacent dot pattern. Here, an 8% halftone dot difference is provided between the state shown in FIG. 7B and the state shown in FIG. 7C.

When the dot pattern expands further, FIG.
As shown in FIG. 7E, each dot pattern is connected to one of the two dot patterns adjacent to each other in the left-right direction, and after further swelling, as shown in FIG. Connected to one dot pattern. Here, an 8% halftone dot difference is also provided between the state of FIG. 7E and the state of FIG. 7F.

In the case of this embodiment, (b) → (c) in FIG.
As shown in the flow of → (e) → (f), a mesh pattern composed of a plurality of types of basic patterns in which the number of connection points connected at the same time is reduced and the threshold is adjusted so as to be connected sequentially is adopted. Is converted to halftone data representing a halftone image in which tone jump is less noticeable.

In order to obtain a halftone dot image in which tone jumps are not conspicuous, all of the adjacent dot patterns come into contact with the dot% (for example, the state shown in FIG. 7B) where the contact between adjacent dot patterns first appears. Net% (for example, FIG.
(State (f)) preferably has a dot percentage difference of 1% or more. This is because, even when the contact between adjacent dot patterns occurs sequentially instead of simultaneously, if the halftone dot difference is within 1%, the tone jump may be conspicuous.

FIG. 8 is another diagram showing both the operation of the present embodiment and the operation of the comparative example. This FIG. 8 also
Similar to FIG. 7, a hatched portion is a dot pattern. This FIG.
In, the halftone dots are arranged diagonally.

Here, similarly to the case of FIG. 7, when the pixel value is changed from a small value (low-density side) to a large value (high-density side) sequentially for the entire image uniformly, the dot pattern of the dot pattern is changed. The area gradually increases, and the dot pattern is shown in FIG.
((A), (b)) → (c) → ((d), (e))
→ It changes as shown in (f).

Here, (a) → (c) → (d) →
(F) shows the change of the dot pattern in the comparative example. When the dot pattern swells from a state where each dot pattern is separated into an island shape as shown in (a), the upper right and lower left are changed as shown in (c). All dot patterns adjacent to each other in the connecting direction are connected at the same time, and then the dot patterns connected diagonally further expand as shown in (d), and this time, the upper left and lower right are connected as shown in (e). All are connected simultaneously in the connecting direction. When the adjacent dot patterns are connected, the ink spreads over an area larger than the connection point, and a tone jump occurs.

FIG. 8 (b) → (c) → (e) → (f)
FIG. 8 is an example showing a change in the dot pattern according to the present embodiment.
As shown in FIG. 8 (b), dot patterns arranged in the direction connecting the upper right and lower left are connected alternately in that direction, and after the dot pattern further expands, as shown in FIG. Are connected in all directions connecting. As the dot pattern expands further, FIG.
As shown in FIG. 8E, every other direction is connected in the direction connecting the upper left and lower right, and after expanding further, the direction connecting the upper left and lower right is also changed as shown in FIG. 8F. All dot patterns are connected. Here, in FIG. 8 as well as in the case of FIG. 7, between (b) and (c),
There is a halftone difference of 8% between (e) and (f). As described above, by adopting the basic patterns whose threshold values are adjusted so as to be sequentially connected and reducing the number of connected points that are simultaneously connected, it is possible to obtain a halftone dot image in which tone jumps are less noticeable.

As shown in FIG. 8, even in the case where the halftone dots are arranged diagonally, there is no difference from the case of FIG. A dot% at which the connection between dot patterns first appears
It is preferable that there is a halftone difference of 1% or more between the halftone dot (for example, the state shown in FIG. 8B) and the halftone dot (for example, the state shown in FIG. 8F) where all the adjacent dot patterns are in contact.

FIG. 9 is an explanatory diagram of a method of creating a plurality of types of dot cells whose threshold values have been adjusted from one type of basic pattern, and FIG. 10 is an explanatory diagram of the one-dimensional LUT shown in FIG.

Here, first, one type of basic pattern A (example
For example, as shown in FIG.
The UT (look-up table) is referenced and its basic
Turn A has a plurality of basic patterns (here, three types of
Basic pattern) A_a, A_b, A _cIs converted to

This one-dimensional LUT converts three thresholds along each of three curves (including straight lines) shown in FIG. 10 to create three new ones of basic patterns.
T, and in each one-dimensional LUT, the curves A _a ,
A _b, along the three curves shown in A _c, the basic pattern A, the basic pattern _{A a,} A _b, is converted to A _c.

That is, here, assuming that the original basic pattern A before conversion has a shape in which adjacent dot patterns come into contact with each other when the dot% is 50%, this one-dimensional LUT is Basic pattern A
Is a dot%, and when 50 + β%, 50%, and 50−β%, respectively, the basic patterns A _{a and} , the thresholds of which are adjusted so that adjacent dot patterns are in contact with each other.
A _b, is converted to A _c. Thus three basic patterns A _a which is generated, A _b, A _c is an image on the pixel values, uniformly, when is sequentially changed toward a low concentration side to the high density side, 50- Within the range of α% to 50 + α%, it is a basic pattern that forms a dot pattern that follows the same growth process in shape and has a different degree of growth.

[0071] Therefore, here, to configure these three kinds of basic patterns A _a, A _b, consists of a plurality of types of dot cells by combining A _c supercell. Using this supercell, when dot patterns are sequentially formed while sequentially changing the pixel values of the pixels of the entire image from a small value to a large value, when the dot pattern is formed with the original basic pattern before the above conversion, , In the area of the pixel value equal to or less than the pixel value when the dot% of the dot pattern (referred to as the original dot pattern) becomes 50-α%, the three basic patterns A _a ,
A _b, a dot pattern which has been converted using any A _c also follow the same growth process, and is always the same growth degree, three when the halftone% of the original dot pattern is larger than 50-alpha% The degree of growth differs depending on which of the basic patterns A _a , A _b , and A _c the dot pattern is converted. The dot pattern grows fastest when converted using the basic pattern A _c , A
_The result that the growth of the dot pattern when converted using a is the slowest. In the case of the original basic pattern A,
Since the halftone% is in contact dot patterns adjacent to each other at 50%, the dot pattern conversion using the basic pattern A _c is in contact dot patterns each other the dot% is adjacent to at 50-beta%, basic dot pattern converted by using the pattern a _b is the halftone% is in contact dot patterns adjacent to each other at 50%, the dot pattern conversion using the basic pattern a _a is the first time the halftone% is reached 50 + beta% , Adjacent dot patterns come into contact with each other.

When the pixel value is further increased and converted by using the original basic pattern A,
When the pixel value at which the dot pattern of α% is reached, the dot pattern converted using any of the three basic patterns A _a , A _b , and A _c has the same halftone dot (50 + α%).
In addition, when the pixel pattern has the same shape and the pixel value becomes larger thereafter, the dot pattern converted by using any of the basic patterns A _a , A _b , and A _c follows the same growth process while maintaining the same growth degree again.

As described above, in the predetermined halftone% range (range of 50-α% to 50 + α%), the same growth process is traced from one original basic pattern, but one halftone% (here, , Multiple types of basic patterns A
_a , A _b , and A _c ), generating a plurality of types (here, three types) of basic patterns having different degrees of growth in a plurality of dot patterns obtained by using the average dot% of the plurality of dot patterns. A supercell composed of a plurality of types of dot cells is generated by combining the types of basic patterns, and image data (pixel value data) representing a pixel value is represented by image data (dot value data) representing a dot pattern of a halftone dot using the supercell. By converting the dot data into dot data, it is possible to vary the dot% that the adjacent dot patterns contact. For example, in the examples shown in FIG. 9 and FIG.
(+ Β%) − (50−β%) = 2β%.

The curve A shown in FIG._aIs, for example, (5
0-α, 50-α), (50, 50 + β), (50+
α, 50 + α) quadratic curve defined to pass through three points
And the curve A shown in FIG._cIs, for example, (50
−α, 50−α), (50, 50−β), (50 + α,
50 + α) is a quadratic curve defined to pass through three points.
The original basic pattern along those quadratic curves.
A to basic pattern A _a, A_cFIG. 9 so that
The one-dimensional LUT shown in FIG. The basic pattern
A_bIs the original basic pattern A in this embodiment.
The one-dimensional LUT responsible for this conversion is:
Outputs the original itself, converting virtually nothing
LUT.

FIGS. 11 to 15 are diagrams showing the dot pattern distribution of each dot% when the pixel value is changed uniformly using the method described with reference to FIGS. It is.

In these figures, hatched portions represent each dot pattern. Here, when the process of converting the pixel value on the image into a dot pattern while sequentially changing the pixel value uniformly from the low density side to the high density side is repeated, the shape follows the same growth process and at least one A method is used in which a pixel value of each pixel of an image is converted using a supercell in which a plurality of types of basic patterns forming dot patterns having different growth degrees in the average halftone area range of a portion are arranged.

FIGS. 11 to 15 show the dot pattern distributions when the average dot% is 41%, 44%, 50%, 55%, and 59%, respectively.

As can be seen from these figures, when the pixel value changes from the low-density side to the high-density side, a plurality of dot patterns do not contact at many points at the same time, It is increasing. When such a supercell is employed, a high-quality halftone image with no or no noticeable tone jump can be obtained.

FIG. 16 is an explanatory diagram showing another example of the halftone pattern creating method according to the present invention.

Here, even if the same dot% is used, a plurality (three in this case) of basic patterns A, B, and C for forming dot patterns having mutually different shapes, such as a rectangular shape and an elliptical shape, for example. Is prepared, and a super cell including a plurality of types of dot cells is created by combining the plurality of types of basic patterns A, B, and C. Even if the dot patterns have the same dot%, if the dot patterns have different shapes, adjacent dot patterns come into contact with different dot%, and thus, by combining the originally different basic patterns, the adjacent dot patterns can be combined. It is possible to widen the range of halftone dot contact with each other and make contact little by little, and obtain a high-quality halftone image with no or no noticeable tone jump.

FIGS. 17 to 19 are diagrams showing the dot pattern distribution of each dot% when the pixel value is uniformly changed using the method described with reference to FIG.

Also in these figures, the hatched portions represent each dot pattern. Here, when the process of converting the pixel value into a dot pattern while repeatedly changing the pixel value of the pixel on the image uniformly from the low density side to the high density side repeatedly is repeated, %
A pixel value of each pixel of an image is converted using a supercell in which a plurality of basic patterns that form a dot pattern having a mutually different shape within at least a part of the dot% range while maintaining the same are maintained. Is used.

In FIGS. 17 to 19, the dot% represents
The distribution of the dot pattern at 41%, 51%, and 55% is shown.

As can be seen from these figures, as in the case of FIGS. 11 to 15, when the pixel value sequentially changes from the low density side to the high density side, a large number of dot patterns Instead of contacting at the same time, the number of contact points is gradually increasing.

FIG. 20 is a diagram showing a halftone image obtained by using a printer capable of outputting a multi-valued halftone image. Here, similarly to the above description, a change in the dot pattern when the pixel value of each pixel of the image is sequentially changed from the low density side to the high density side is shown.

FIG. 20 (a) shows a halftone image when an image in which certain pixel values are uniformly arranged is converted into a dot pattern, and is shown in FIGS. 20 (b), 20 (c) and 20 (c). 20 (d) represents a halftone image when an image having pixel values slightly larger in this order than the pixel value in FIG. 20 (a) is converted into a dot pattern.

In the above description of the embodiments, it has been described on the assumption that the inside of the dot pattern has a uniform density, but here the density of the density exists inside the dot pattern. Here, the inside of the dot pattern is represented by two values of “dark” and “light” of the density, and a ternary halftone image is formed in combination with the outside of the dot pattern.

First, when the pixel value changes to a slightly larger value from the stage of FIG. 20 (a), as shown in FIG. 20 (b), a low density outline appears around the dot pattern of FIG. When the value changes to a slightly larger value, the thin outline expands as shown in FIG. 20C, and when the pixel value changes to a slightly larger value, as shown in FIG.
As shown in (d), the density of the light outline is increased and the dot pattern is changed to a uniform dark density dot pattern. However, FIG.
In FIG. 20D, the dot percentage is larger even in the same dot pattern of only the dark density as compared to FIG.

In the case where such pixel value data is converted into halftone dot data representing a halftone image having three or more values, similarly to the case where the pixel value data is changed to the binary halftone data described above.
When the pixel value is gradually changed from a small value (low density side) to a large value (high density side), it is preferable to devise a halftone pattern so that the contact points between the dot patterns gradually increase. .

In the above description, a method of determining whether or not adjacent dot patterns are in contact with each other is not particularly described. However, it is determined whether or not dot patterns are in contact with each other on image data. Alternatively, it may be determined whether or not a contact is made on a halftone image printed using, for example, the printing press 40 shown in FIG.

FIG. 21 is a functional block diagram of the first embodiment of the image processing apparatus of the present invention.

This image processing apparatus is realized by combining the personal computer 100 shown in FIGS. 4 and 5 with a program executed by the personal computer.

The image processing apparatus shown in FIG. 21 includes a data conversion unit 301 and a halftone pattern storage unit 302. Here, the network pattern storage unit 302 is set inside the hard disk device 103. The feature of the present embodiment lies in the storage contents of the halftone pattern storage unit 302,
Here, the halftone pattern storage unit 302 stores FIGS.
, A supercell composed of a combination of a plurality of types of basic patterns originally derived from one type of basic pattern, or described with reference to FIG.
Originally, a supercell in which a plurality of types of basic patterns are combined is stored.

The data conversion unit 301 is provided by the CPU shown in FIG.
A supercell stored in the halftone pattern storage unit 30 and a first image representing a pixel value of each pixel of the image. Data (pixel value data) is input, and the first image data is converted into second image data (dot data) representing a dot pattern of each dot. The second image data obtained by this conversion is output to the film printer shown in FIG. 1, and finally a high quality halftone image having no tone jump or inconspicuous tone jump is obtained. Can be

FIG. 22 is a functional block diagram of a second embodiment of the image processing apparatus of the present invention.

In the case of the image processing apparatus shown in FIG.
As in the case of the image processing apparatus shown in FIG. 21, this is realized by combining the personal computer 100 shown in FIGS. 4 and 5 with a program executed by the personal computer.

The image processing apparatus shown in FIG. 22 has a configuration in which a data correction section 303 is added to a data conversion section 301 and a halftone pattern storage section 302 constituting the image processing apparatus shown in FIG. . However, FIG.
21 is different from the super cell stored in the network pattern storage unit of the image processing apparatus shown in FIG. 21 in that the super cell in which one type of basic pattern is simply arranged Is stored.

The operation of the data conversion unit 301 in the image processing apparatus of FIG. 22 is the same as the operation of the data conversion unit in the image processing apparatus of FIG. 21, but is stored in the halftone pattern storage unit 302 of the image processing apparatus of FIG. Is a supercell composed of a simple arrangement of only one type of dot cell.
Does not exist, a large number of contacts of dot patterns come into contact at the same time with a change in pixel value, and there is a possibility that a halftone dot image in which tone jump is conspicuous may be obtained.

Therefore, in the image processing apparatus of FIG. 22, a data correction section 303 is provided. In the data correction unit 303, the pixel value in each image area is corrected into a plurality of patterns for each unit, using the image area compared with one dot cell as one unit. That is, FIG.
In this image processing apparatus, the first image data (pixel value data) is corrected into a plurality of patterns, instead of preparing a super cell in which a plurality of types of dot cells are combined. In other words, since the comparison between the pixel value and the threshold value in the dot cell is relative, instead of preparing a plurality of types of dot cells in which the threshold value in the dot cell is changed, here, one type of dot cell is used. Then, the pixel value is corrected and then compared with the threshold value of the dot cell.

As described above, in the data correction unit 303, when the correction pattern composed of the array of correction values is superimposed on the image represented by the input first image data, By performing an operation between the pixel value of the pixel and the correction value of the correction pattern to correct the pixel value of each pixel on the image, a third value representing the corrected pixel value of a plurality of pixels constituting the image is obtained. A data correction process for generating image data is performed. In performing the data correction process, when the correction pattern is viewed in units of a correction cell corresponding to one halftone dot, the correction pattern is displayed on the correction cell. At least a part of the arranged correction values is a correction pattern in which a plurality of types of correction cells different from each other are arranged, and the data conversion unit 3 In 1, when the data conversion process is repeated while sequentially changing the pixel value of each pixel on the image from the low-density side to the high-density side, the pixels touch each other in the same direction on the image. It is possible to obtain a dot pattern in which the first dot% of the dot pattern when the dot pattern first appears and the second dot% of the dot pattern when all dot patterns adjacent in the same direction are in contact with each other. The correction pattern in which the correction value is adjusted is used. Further, the correction patterns used in this embodiment are such that mutually different dot patterns can be obtained for the first halftone dots in mutually different directions and for the second halftone% in mutually different directions. Is a correction pattern in which the correction value is adjusted.

In the data conversion section 301, the data correction section 3
03, when a supercell composed of an array of dot cells is superimposed on the image represented by the third image data generated in step 03, the pixel value of the pixel on the image and the threshold value of the supercell superimposed on each other And converting the pixel value of each pixel of the image into a binary value (or a multi-valued value of three or more values) to generate second image data representing a dot pattern of each halftone dot. Is executed.

Even when the image processing apparatus shown in FIG. 2 is employed, it is possible to obtain a high quality halftone image having no tone jump or inconspicuous tone jump.

The above-described various embodiments have been described with the printing system shown in FIG. 1 in mind. The printing system shown in FIG. 1 is an example using an image setter (film setter). Is not only imagesetter but also CTP
(Computer toplate), CTC (co
The present invention can be widely applied to printer to cylinder, on-demand printing, and the like.

In each of the above embodiments,
This is an example in which a halftoning process of generating a dot pattern of a halftone dot by comparing a pixel value on an image with a threshold value of the halftone pattern is employed. When the halftoning process is repeated while uniformly changing the pixel value of each pixel on the uniform image sequentially from the low density side to the high density side, With respect to the same direction on the image, the first dot% of the dot pattern when the mutually adjacent dot patterns first appear, and the second half of the dot pattern when all the dot patterns adjacent to each other in the same direction contact each other. What is necessary is just to perform a halftoning process for making the dot% different from the dot%.

[0105]

As described above, according to the present invention,
It is possible to obtain image data representing a high-quality halftone image having no tone jump or inconspicuous tone jump.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a printing system.

FIG. 2 is an explanatory diagram of a conversion method for converting pixel value data into halftone dot data.

FIG. 3 is a diagram illustrating an example of a halftone pattern.

FIG. 4 is an external perspective view of the personal computer.

FIG. 5 is a hardware configuration diagram of a personal computer.

FIG. 6 is a flowchart illustrating an image processing method using an image processing program executed in a personal computer.

FIG. 7 is another diagram showing both the operation of the present embodiment and the operation of the comparative example.

FIG. 8 is a diagram showing both the operation of the present embodiment and the operation of the comparative example.

FIG. 9 is an explanatory diagram of a method of creating a plurality of types of basic patterns with adjusted thresholds from one type of basic pattern.

FIG. 10 is an explanatory diagram of the one-dimensional LUT shown in FIG.

FIG. 11 is a diagram showing the distribution of dot patterns when the average dot percentage is 41% when the pixel values are uniformly changed using the method described with reference to FIGS. 9 and 10; It is.

FIG. 12 is a diagram showing a dot pattern distribution when the average dot percentage is 44% when pixel values are uniformly changed using the method described with reference to FIGS. 9 and 10; It is.

FIG. 13 is a diagram showing the distribution of dot patterns when the average dot% is 50% when the pixel values are uniformly changed using the method described with reference to FIGS. 9 and 10; It is.

FIG. 14 is a diagram showing a dot pattern distribution when the average dot percentage is 55% when pixel values are uniformly changed using the method described with reference to FIGS. 9 and 10; It is.

FIG. 15 is a diagram showing a dot pattern distribution when the average dot% is 59% when pixel values are uniformly changed by using the method described with reference to FIGS. 9 and 10; It is.

FIG. 16 shows another halftone pattern creation method according to the present invention.
It is explanatory drawing which shows two examples.

FIG. 17 shows a dot% of 41% when pixel values are uniformly changed using the method described with reference to FIG.
FIG. 9 is a diagram showing a distribution of dot patterns at the time of FIG.

FIG. 18 shows a case where halftone% is 50% when pixel values are uniformly changed using the method described with reference to FIG.
FIG. 9 is a diagram showing a distribution of dot patterns at the time of FIG.

FIG. 19 shows a case where the dot% is 55% when the pixel value is uniformly changed using the method described with reference to FIG.
FIG. 9 is a diagram showing a distribution of dot patterns at the time of FIG.

FIG. 20 is a diagram showing a halftone image obtained by using a printer capable of outputting a multi-valued halftone image.

FIG. 21 is a functional block diagram of the image processing apparatus according to the first embodiment of the present invention.

FIG. 22 is a functional block diagram of a second embodiment of the image processing apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Color scanner 20 Workstation 30 Film printer 40 Printing machine 41 Halftone image 100 Personal computer 101 CPU 102 Main memory 103 Hard disk drive 104 FD driver 105 CD-ROM driver 106 Input interface 107 Output interface 108 Bus 110 Main unit 110a Floppy disk loading Mouth 110b CD-ROM loading slot 120 Image display device 120a Display screen 130 Keyboard 140 Mouse 201 Floppy disk 202 CD-ROM 301 Data conversion unit 302 Network pattern storage unit 303 Data correction unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA24 AA29 AB07 AB13 AC04 BB01 BB06 BB14 BB19 BB22 BB25 BB27 5B057 CA01 CA02 CA08 CA12 CA16 CB01 CB02 CB07 CB12 CB16 CC01 CE13 CH07 5C077 LL04 NN1908 PQ22 PQ23 RR05 RR16 TT02 TT08

Claims (11)

[Claims] 1. An image processing method for performing a halftoning process for converting first image data representing pixel values of a plurality of pixels forming an image into second image data representing a dot pattern of halftone dots. The pixel value of each pixel on a uniform image composed of a plurality of pixels all having the same value,
In the case where the halftoning process is repeated while sequentially changing from the low density side to the high density side, in the same direction on the image, the halftone dot when the mutually adjacent dot patterns first appear is the first halftone dot. An image processing method, wherein a halftone percentage is different from a second half percentage which is a half percentage when all dot patterns adjacent in the same direction are in contact with each other. 2. The method according to claim 1, wherein the halftoning process is performed by superimposing a halftone pattern composed of an array of thresholds on an image represented by the first image data. This is a process of comparing a pixel value of each pixel on an image to a binary value or more by comparing with a threshold value of a halftone pattern. A dot cell corresponding to one halftone dot constituting the halftone pattern is defined as a unit. When looking at the halftone pattern, at least a part of the threshold values arranged on the dot cells is relatively different from the pixel value of the image area where the dot cells are superimposed, and a plurality of types of dot cells are provided. A net pattern that is arranged, wherein the first pattern is in the same direction on the image;
2. The image processing method according to claim 1, wherein the halftone processing is performed using a halftone pattern in which each threshold value is adjusted so that the halftone percentage of the second halftone dot differs from the second halftone percentage. 3. A network in which the pixel value of each pixel on a uniform image composed of a plurality of pixels having the same pixel value is sequentially changed from the low density side to the high density side in a uniform manner. When the dot processing is repeated, in the same direction on the image, the first half%, which is the half% when the mutually adjacent dot patterns first appear, and the dot patterns adjacent in the same direction are all different. Net% when touching
Is different from the second dot%, and further, the first dot% in different directions and the second dot% in different directions are different from each other. 2. The image processing method according to claim 1, wherein processing is performed. 4. The method according to claim 1, wherein the halftoning process is performed by superimposing a halftone pattern composed of an array of thresholds on an image represented by the first image data. This is a process of comparing a pixel value of each pixel on an image to a binary value or more by comparing with a threshold value of a halftone pattern. A dot cell corresponding to one halftone dot constituting the halftone pattern is defined as a unit. When looking at the halftone pattern, at least a part of the threshold values arranged on the dot cells is relatively different from the pixel value of the image area where the dot cells are superimposed, and a plurality of types of dot cells are provided. A halftone pattern that is arranged, wherein the first halftone% and the second halftone% in the same direction on the image are different, and further, the first halftone% in mutually different directions and The image processing method according to claim 3, wherein the performing halftone processing using what different the related direction second dot% and the net pattern in which each threshold as different from each other is formed by adjusting respectively. 5. The pixel value of a pixel on a uniform image is
In the case where the halftoning process is repeated while changing the density uniformly from the low density side to the high density side, the same growth process is traced on the shape and the growth of 3. The halftoning process is performed by using a halftone pattern in which a plurality of types of dot cells forming dot patterns of different degrees are arranged.
Or the image processing method according to 4. 6. The pixel value of a pixel on a uniform image is
In the case where the dot processing is repeated while changing the density from the low density side to the high density side uniformly, at least a part of the half% is grown while maintaining the same half%.
5. The image processing method according to claim 2, wherein the halftoning process is performed using a halftone pattern in which a plurality of types of dot cells forming different dot patterns within the range are arranged. 7. A difference between a minimum half% of the first half% in different directions and a maximum half% of the second half% in different directions is 1% or more. The halftoning process is performed using a halftone pattern in which a plurality of types of dot cells in which threshold values adjusted relative to pixel values of an image region to be superimposed are arranged. Item 5. The image processing method according to item 2 or 4. 8. An image processing apparatus for performing a process of converting first image data representing pixel values of a plurality of pixels constituting an image into second image data representing a dot pattern of each halftone dot, When a halftone pattern composed of an array of thresholds is superimposed on an image represented by one image data, pixel values of pixels on the image, which are superimposed on each other, are compared with a threshold value of the halftone pattern. A data conversion unit that executes a data conversion process for generating second image data representing a dot pattern of each halftone dot by converting a pixel value of a pixel into a binary value or more; When a dot cell corresponding to a point is viewed as a unit, at least some of the thresholds arranged on the dot cell are different, and a plurality of types of dot cells are arranged. The data conversion unit uses the halftone pattern to uniformly reduce the pixel value of each pixel on a uniform image composed of a plurality of pixels whose pixel values are all the same. When the data conversion process is repeated while sequentially changing from the side to the high density side, the first halftone%, which is the halftone dot when the mutually adjacent dot patterns first appear in the same direction on the image. A halftone pattern storage unit that stores a halftone pattern whose threshold value has been adjusted so that a dot pattern different from the second halftone%, which is the halftone percent when all dot patterns adjacent in the same direction are in contact with each other, is obtained. An image processing device, wherein the data conversion unit executes the data conversion process using a halftone pattern stored in the halftone pattern storage unit. . 9. When the halftone pattern storage unit views the halftone pattern as a unit of a dot cell corresponding to one halftone dot, at least a part of the threshold values arranged on the dot cell is a dot. A dot pattern in which a plurality of types of dot cells differing from one another among cells are arranged. In the data conversion unit, the pixel value of each pixel on a uniform image is uniformly reduced by using the dot pattern. When the data conversion process is repeated while sequentially changing the density from the density side to the high density side, a first halftone, which is a halftone% when a dot pattern that is mutually in contact in the same direction on the image first appears. % Is different from the dot% which is the dot% when all the dot patterns adjacent in the same direction are in contact with each other, and further, the first dot% in the mutually different directions is different from each other, and The second in mutually different directions
10. The image processing apparatus according to claim 9, wherein a halftone pattern in which a threshold value is adjusted so that dot patterns different from each other are obtained is stored. 10. An image processing apparatus for performing a process of converting first image data representing pixel values of a plurality of pixels forming an image into second image data representing a dot pattern of each halftone dot, When a correction pattern composed of an array of correction values is superimposed on an image represented by one image data, an operation is performed between a pixel value of a pixel on the image and a correction value of the correction pattern, which are superimposed on each other. A data correction unit that performs a data correction process of generating third image data representing corrected pixel values of a plurality of pixels forming the image by correcting a pixel value of each pixel on the image; When a halftone pattern composed of an array of thresholds is superimposed on an image represented by the third image data generated by the correction unit, The second image data representing the dot pattern of each halftone dot is obtained by comparing the pixel value of the pixel above and the threshold value of the halftone pattern, and converting the pixel value of each pixel of the image into a binary value or more. A data conversion unit that performs a data conversion process to generate the data, wherein the data correction unit is arranged on the correction cell when the correction pattern is viewed in units of a correction cell corresponding to one halftone dot. Is a correction pattern in which a plurality of types of correction cells in which at least some of the correction values differ among the correction cells are arranged, and each pixel on a uniform image including a plurality of pixels having the same pixel value. The data correction processing in the data correction unit and the data conversion processing in the data conversion unit are performed while uniformly changing the pixel value of the pixel sequentially from the low density side to the high density side. Is repeated in the same direction on the image, the first half% which is the half% when the mutually adjacent dot patterns first appear, and all the dot patterns adjacent in the same direction are in contact with each other. An image processing apparatus for executing the data correction process using a correction pattern whose correction value has been adjusted so as to obtain a dot pattern different from the second halftone% that is the halftone percentage. . 11. When the data correction unit views the correction pattern in units of correction cells corresponding to one halftone dot, at least a part of the correction values arranged on the correction cells A correction pattern in which a plurality of different types of correction cells are arranged among the correction cells, and the pixel value of each pixel on the uniform image is uniformly and sequentially reduced from the low density side to the high density side. When the data correction process in the data correction unit and the data conversion process in the data conversion unit are repeated while changing the dot pattern, the mutually adjacent dot patterns first appear in the same direction on the image. And a second half%, which is a half% when all dot patterns adjacent to each other in the same direction are in contact with each other. The data correction process is performed using a correction pattern whose correction value is adjusted so that the first halftone dots and the second halftone dots in mutually different directions obtain mutually different dot patterns. The image processing apparatus according to claim 10, wherein: