阅读说明：本技术 图像处理装置、记录装置、图像处理方法以及存储介质 (Image processing apparatus, recording apparatus, image processing method, and storage medium ) 是由 宇都宫光平 山崎乡志 伊藤伸朗 于 2021-06-25 设计创作，主要内容包括：本发明涉及一种形成二维平面以外的形状的图像的图像处理装置、记录装置、图像处理方法以及存储介质。该图像处理装置的特征在于,具备：取得部,其取得表示在于三维的第一空间内展示图像的情况下应当由第一空间内的多个像素中的每个像素所显示的图像的灰度值的第一图像数据；生成部,其通过使用具有与第一空间中的多个像素相对应的多个阈值的三维的第一抖动掩膜而对第一图像数据所表示的灰度值进行量化,从而生成第一显示数据,第一抖动掩膜在利用第一平面将第一空间切断时第一平面中的多个阈值在空间频率域内具有蓝噪声特性,在利用在与第一平面不同的方向上延伸的第二平面将第一空间切断时第二平面中的多个阈值在空间频率域内具有蓝噪声特性。(The present invention relates to an image processing apparatus, a recording apparatus, an image processing method, and a storage medium for forming an image of a shape other than a two-dimensional plane. The image processing apparatus is characterized by comprising: an acquisition unit that acquires first image data indicating a gradation value of an image to be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space; a generation section that generates first display data by quantizing a gradation value represented by first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in a first space, the first dither mask having a blue noise characteristic in a spatial frequency domain for a plurality of threshold values in a first plane when the first space is cut off by a first plane, and having a blue noise characteristic in a spatial frequency domain for a plurality of threshold values in a second plane when the first space is cut off by a second plane extending in a direction different from the first plane.)

1. An image processing apparatus is characterized by comprising:

an acquisition unit that acquires first image data representing a gradation value of an image that should be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space;

a generation section that generates first display data by quantizing a gradation value represented by the first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in the first space,

the three-dimensional first dither mask is set to,

when the first space is cut off by the first plane,

the plurality of thresholds in the first plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency,

and when the first space is cut off by a second plane not parallel to the first plane,

the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than the predetermined frequency is more than a low frequency component lower than the predetermined frequency.

2. The image processing apparatus according to claim 1,

the three-dimensional first dither mask is set to,

when the first space is cut off by a third plane parallel to the first plane,

the plurality of thresholds in the third plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency,

and when the first space is cut off by a fourth plane parallel to the second plane,

the plurality of thresholds in the fourth plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency in a spatial frequency domain.

3. The image processing apparatus according to claim 1 or 2,

the three-dimensional first dither mask is set to,

when the first space is cut off by an arbitrary plane parallel to the first plane,

the plurality of thresholds in the plane have a frequency characteristic in the spatial frequency domain in which high frequency components higher than a predetermined frequency are more frequent than low frequency components lower than the predetermined frequency,

and when the first space is cut by an arbitrary plane parallel to the second plane,

the plurality of thresholds in the plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency.

4. The image processing apparatus according to claim 1,

the three-dimensional first dither mask is set to,

when the first space is cut by a fifth plane extending in a direction different from the first plane and the second plane,

the plurality of thresholds in the fifth plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency in a spatial frequency domain.

5. The image processing apparatus according to claim 4,

the three-dimensional first dither mask is set to,

when the first space is cut off by a sixth plane parallel to the fifth plane,

the plurality of thresholds in the sixth plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency in a spatial frequency domain.

6. The image processing apparatus according to claim 4 or 5,

the three-dimensional first dither mask is set to,

when the first space is cut off by an arbitrary plane parallel to the fifth plane,

the plurality of thresholds in the plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than a predetermined frequency is more than a low frequency component lower than the predetermined frequency.

7. The image processing apparatus according to claim 1,

the plurality of pixels in the first space include:

two or more pixels arranged so as to extend in a first direction,

Two or more pixels arranged so as to extend in a second direction orthogonal to the first direction, an

Two or more pixels arranged so as to extend in a third direction orthogonal to the first direction and the second direction,

the first plane is a plane having a normal vector extending in a direction perpendicular to the first direction,

the second plane is a plane having a normal vector extending in a direction perpendicular to the second direction.

8. The image processing apparatus according to claim 7,

the first plane is a plane having a normal vector extending in a direction perpendicular to the second direction,

the second plane is a plane having a normal vector extending in a direction perpendicular to the third direction.

9. The image processing apparatus according to claim 1,

the plurality of thresholds in the first plane have a frequency characteristic in the spatial frequency domain different from a white noise characteristic,

the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain different from a white noise characteristic.

10. The image processing apparatus according to claim 1,

the plurality of thresholds in the first plane have a blue noise characteristic in the spatial frequency domain,

the plurality of thresholds in the second plane have a blue noise characteristic in a spatial frequency domain.

11. The image processing apparatus according to claim 1,

the acquisition unit acquires second image data representing a gradation value of an image to be displayed by each of a plurality of pixels in a three-dimensional second space adjacent to the first space when the image is displayed in the second space,

the generation section generates second display data by quantizing a gradation value represented by the second image data using a three-dimensional second dither mask having a plurality of threshold values corresponding to a plurality of pixels in the second space,

the first space is divided into a first partial space and a second partial space,

the three-dimensional second dither mask has a plurality of threshold values configured to reverse a relative positional relationship between a plurality of threshold values existing in the first partial space and a plurality of threshold values existing in the second partial space among a plurality of threshold values corresponding to a plurality of pixels in the first space, the plurality of threshold values being included in the three-dimensional first dither mask.

12. The image processing apparatus according to claim 11,

the plurality of pixels in a three-dimensional space including the first space and the second space include:

two or more pixels arranged so as to extend in a first direction,

Two or more pixels arranged so as to extend in a second direction orthogonal to the first direction,

Two or more pixels arranged so as to extend in a third direction orthogonal to the first direction and the second direction,

the second partial space is located in the first direction, the second direction, or the third direction when viewed from the first partial space.

13. The image processing apparatus according to claim 11 or 12,

the acquisition unit acquires third image data representing a gradation value of an image to be displayed by each of a plurality of pixels in a third space adjacent to the first space when the image is displayed in the third space,

the generation section generates third display data by quantizing a gradation value represented by the third image data using a three-dimensional third dither mask having a plurality of threshold values corresponding to a plurality of pixels in the third space,

the first space is divided into a third partial space and a fourth partial space,

the three-dimensional third dither mask has a plurality of threshold values configured to transpose relative positional relationships between a plurality of threshold values existing in the third partial space and a plurality of threshold values existing in the fourth partial space among a plurality of threshold values corresponding to a plurality of pixels in the first space, which the three-dimensional first dither mask has,

the second space is located in a different direction when viewed from the first space than the third space when viewed from the first space,

the second partial space is located in a different direction when viewed from the first partial space than the fourth partial space when viewed from the third partial space.

14. The image processing apparatus according to claim 1,

in the first space, the first and second spaces are arranged in parallel,

when a is a natural number of 2 or more,

arranged with 2 in a first direction^αA plurality of pixels, each of which is a pixel,

2 are arranged in a second direction orthogonal to the first direction^αA pixel, and

in a third direction orthogonal to the first direction and the second directionIs upwards arranged with 2^αAnd (4) a pixel.

15. The image processing apparatus according to claim 1,

the liquid ejecting apparatus includes a head unit that ejects liquid based on the first display data.

16. The image processing apparatus according to any one of claims 1 to 14,

the generating unit supplies the first display data to a recording device including a head unit that ejects liquid based on the first display data.

17. The image processing apparatus according to claim 1,

the acquisition unit acquires first color image data corresponding to a first color in the first image data and second color image data corresponding to a second color different from the first color in the first image data,

the generation section generates first color display data corresponding to the first color in the first display data by applying quantization processing to the first color image data using one three-dimensional first dither mask, and

applying quantization processing to the second color image data by using the other three-dimensional first dither mask to generate second color display data corresponding to the second color in the first display data,

the one three-dimensional first dither mask and the other three-dimensional first dither mask are different from each other.

18. A recording apparatus for forming an image of a three-dimensional object, comprising:

a head unit that ejects liquid;

a control section that controls ejection of liquid from the head unit to form the image for the target object through a plurality of dots formed by the liquid ejected from the head unit,

the control unit controls ejection of the liquid from the head unit such that, when the target object has a first surface, a distribution of the plurality of points on the first surface has, in a spatial frequency domain, a frequency characteristic in which a high-frequency component higher than a predetermined frequency is larger than a low-frequency component lower than the predetermined frequency,

and such that, in a case where the target object has a second plane extending in a direction different from the first plane, the distribution of the plurality of points on the second plane has, in a spatial frequency domain, a frequency characteristic in which a high-frequency component higher than a predetermined frequency is more frequent than a low-frequency component lower than the predetermined frequency.

19. The recording apparatus of claim 18,

the distribution of the plurality of points on the first face has a frequency characteristic different from a white noise characteristic in a spatial frequency domain,

the distribution of the plurality of points on the second plane has a frequency characteristic different from a white noise characteristic in a spatial frequency domain.

20. The recording apparatus according to claim 18 or 19,

the distribution of the plurality of points on the first face has a blue noise characteristic in a spatial frequency domain,

the distribution of the plurality of points on the second plane has a blue noise characteristic in a spatial frequency domain.

21. An image processing method is characterized by comprising:

an acquisition step of acquiring first image data representing a gradation value of an image to be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space;

a generation step of generating first display data by quantizing a gradation value represented by the first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in the first space,

the three-dimensional first dither mask is set to,

when the first space is cut off by a first plane, the plurality of threshold values in the first plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more frequent in a spatial frequency domain than a low frequency component lower than the predetermined frequency,

and when the first space is cut off by a second plane not parallel to the first plane,

the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than the predetermined frequency is more than a low frequency component lower than the predetermined frequency.

22. A storage medium storing a program for causing a computer to function as:

an acquisition unit that acquires first image data representing a gradation value of an image that should be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space;

a generation section that generates first display data by quantizing a gradation value represented by the first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in the first space,

the three-dimensional first dither mask is set to,

when the first space is cut off by a first plane, the plurality of threshold values in the first plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more frequent in a spatial frequency domain than a low frequency component lower than the predetermined frequency,

and when the first space is cut off by a second plane not parallel to the first plane,

the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than the predetermined frequency is more than a low frequency component lower than the predetermined frequency.

Technical Field

The invention relates to an image processing apparatus, a recording apparatus, an image processing method, and a program.

Background

Conventionally, as described in patent document 1, there is known a technique for forming an image on a two-dimensional plane by performing halftone processing using a two-dimensional dither mask.

However, the conventional technique has a problem that an image having a shape other than a two-dimensional plane cannot be formed.

Patent document 1: japanese laid-open patent publication No. 2010-214962

Disclosure of Invention

In order to solve the above problem, an image processing apparatus according to an aspect of the present invention includes: an acquisition unit that acquires first image data representing a gradation value of an image that should be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space; a generation unit that generates first display data by quantizing a gradation value represented by the first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in the first space, the three-dimensional first dither mask being set, when the first space is cut off by a first plane, the plurality of threshold values in the first plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more frequent in a spatial frequency domain than a low frequency component lower than the predetermined frequency, and when the first space is cut off by a second plane not parallel to the first plane, the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than the predetermined frequency is more than a low frequency component lower than the predetermined frequency.

A recording apparatus according to another aspect of the present invention is a recording apparatus for forming an image of a three-dimensional object, the recording apparatus including: a head unit that ejects liquid; a control section that controls ejection of liquid from the head unit so as to form the image with respect to the target object through a plurality of dots formed by the liquid ejected from the head unit, the control section controlling ejection of the liquid from the head unit, such that, in a case where the target object has a first surface, the distribution of the plurality of points on the first surface has, in a spatial frequency domain, a frequency characteristic in which a high-frequency component higher than a predetermined frequency is more numerous than a low-frequency component lower than the predetermined frequency, and such that in the case where the subject object has a second face extending in a different direction from the first face, the distribution of the plurality of points on the second surface has a frequency characteristic in which a high frequency component higher than a predetermined frequency is more frequent than a low frequency component lower than the predetermined frequency in a spatial frequency domain.

An image processing method according to an aspect of the present invention includes: an acquisition step of acquiring first image data representing a gradation value of an image to be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space; a generation step of generating first display data by quantizing a gradation value represented by the first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in the first space, when the first space is cut off by a first plane, the plurality of threshold values in the first plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more frequent in a spatial frequency domain than a low frequency component lower than the predetermined frequency, and when the first space is cut off by a second plane not parallel to the first plane, the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than the predetermined frequency is more than a low frequency component lower than the predetermined frequency.

A program according to an aspect of the present invention causes a computer to function as: an acquisition unit that acquires first image data representing a gradation value of an image that should be displayed by each of a plurality of pixels in a three-dimensional first space when the image is displayed in the first space; a generation unit that generates first display data by quantizing a gradation value represented by the first image data using a three-dimensional first dither mask having a plurality of threshold values corresponding to a plurality of pixels in the first space, when the first space is cut off by a first plane, the plurality of threshold values in the first plane have a frequency characteristic in which a high frequency component higher than a predetermined frequency is more frequent in a spatial frequency domain than a low frequency component lower than the predetermined frequency, and when the first space is cut off by a second plane not parallel to the first plane, the plurality of thresholds in the second plane have a frequency characteristic in the spatial frequency domain in which a high frequency component higher than the predetermined frequency is more than a low frequency component lower than the predetermined frequency.

Drawings

Fig. 1 is an explanatory diagram showing an example of a recording system Sys according to an embodiment of the present invention.

Fig. 2 is a functional block diagram showing an example of the configuration of the terminal device 1.

Fig. 3 is a functional block diagram showing an example of the configuration of the recording apparatus 5.

Fig. 4 is an explanatory diagram showing an example of the image forming space SP.

Fig. 5 is an explanatory diagram showing an example of the image data GD.

Fig. 6 is an explanatory diagram showing an example of the dither mask DZ.

Fig. 7 is an explanatory diagram showing an example of the curve FB 1.

Fig. 8 is a flowchart showing an example of the dither mask generation process.

Fig. 9 is a flowchart showing an example of the quantization process.

Fig. 10 is an explanatory diagram showing an example of the configuration of the threshold value Dd in the dither mask DZ.

Fig. 11 is an explanatory diagram showing an example of the configuration of the threshold value Dd in the dither mask DZ.

Fig. 12 is an explanatory diagram showing one example of the configuration of the threshold value Dd in the dither mask DZ.

Fig. 13 is an explanatory diagram showing an example of the dither mask DZ-A according to reference example 1.

Fig. 14 is an explanatory diagram showing an example of the dither mask DZ-A according to reference example 1.

Fig. 15 is an explanatory diagram showing an example of the dither mask DZ-A according to reference example 1.

Fig. 16 is an explanatory diagram showing an example of the dither mask DZ-B according to reference example 2.

Fig. 17 is an explanatory diagram showing an example of the dither mask DZ-B according to reference example 2.

Fig. 18 is an explanatory diagram showing an example of the dither mask DZ-B according to reference example 2.

Fig. 19 is an explanatory diagram showing an example of the dither mask DZ.

Fig. 20 is an explanatory diagram showing an example of the dither mask DZ.

Fig. 21 is an explanatory diagram showing an example of the dither mask DZ.

Fig. 22 is an explanatory diagram showing an example of the image forming space SP according to modification 1.

Fig. 23 is a functional block diagram showing an example of the configuration of the terminal device 1A.

Fig. 24 is an explanatory diagram showing an example of the dither mask DZ-X.

Fig. 25 is an explanatory diagram showing an example of the configuration of the threshold value Dd in the dither mask DZ-X.

Fig. 26 is an explanatory diagram showing an example of the dither mask DZ-Y.

Fig. 27 is an explanatory diagram showing an example of the dither mask DZ-Z.

Fig. 28 is a functional block diagram showing an example of the configuration of the terminal apparatus 1B according to modification 2.

Fig. 29 is a functional block diagram showing an example of the configuration of a terminal device 1C according to modification 6.

Fig. 30 is a flowchart showing an example of quantization processing according to modification 7.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the dimensions and scales of the respective portions in the drawings are appropriately different from those in the actual case. In addition, although various limitations that are technically preferable are added to the embodiments described below as preferable specific examples of the present invention, the scope of the present invention is not limited to these embodiments unless the present invention is specifically described as being limited to the following description.

A. Detailed description of the preferred embodiments

A recording system Sys according to the present embodiment will be described.

In the present embodiment, the recording system Sys is a system for forming an image G on the surface SF of the target object Obj having a three-dimensional shape. In addition, the recording system Sys can also form the image G for the target object Obj having a two-dimensional shape.

1. Overview of Sys of recording System

First, an example of the outline of the configuration of the recording system Sys according to the present embodiment will be described with reference to fig. 1 to 3.

Fig. 1 is an explanatory diagram showing an example of a recording system Sys.

As illustrated in fig. 1, the recording system Sys includes a terminal device 1 and a recording device 5.

The terminal apparatus 1 generates display data Img representing an image G formed on the surface SF of the target object Obj by the recording system Sys.

The recording device 5 forms an image G indicated by the display data Img for the surface SF of the target object Obj based on the display data Img generated by the terminal device 1.

As illustrated in fig. 1, the terminal device 1 sets a three-dimensional coordinate system having an X axis, a Y axis, and a Z axis in an image forming space SP which is a three-dimensional space where the target object Obj exists. Hereinafter, one direction along the X axis is referred to as + X direction, a direction opposite to the + X direction is referred to as-X direction, one direction along the Y axis is referred to as + Y direction, a direction opposite to the + Y direction is referred to as-Y direction, one direction along the Z axis is referred to as + Z direction, and a direction opposite to the + Z direction is referred to as-Z direction. Hereinafter, the + X direction and the-X direction are collectively referred to as an X-axis direction, the + Y direction and the-Y direction are collectively referred to as a Y-axis direction, and the + Z direction and the-Z direction are collectively referred to as a Z-axis direction. In the present embodiment, it is assumed that the terminal device 1 sets the X axis, the Y axis, and the Z axis to be orthogonal to each other, but the present invention is not limited to this configuration, and the X axis, the Y axis, and the Z axis may be defined to intersect with each other.

Fig. 2 is a functional block diagram showing an example of the configuration of the terminal device 1.

As illustrated in fig. 2, the terminal device 1 includes a terminal control unit 2 and a storage unit 3.

The storage unit 3 stores the image data GD, the dither mask DZ, and the control program Pgt of the terminal device 1.

The image data GD represents, for example, an image Gf that a user of the recording system Sys intends to form on the surface SF of the target object Obj using the recording system Sys. Specifically, the image data GD represents the gradation value of the image Gf corresponding to each of the plurality of pixels Px constituting the image forming space SP. Although details will be described later, the recording system Sys may not express the gradation value of the image Gf represented by the image data GD. Therefore, the recording system Sys forms the image G in which the image Gf is expressed with a gradation value that the recording system Sys can express. Specifically, the recording system Sys generates the display data Img by applying quantization processing to the image data GD using the dither mask DZ stored in the storage unit 3, and forms the image G indicated by the generated display data Img on the surface SF of the target object Obj. In the present embodiment, as will be described later, halftone processing (binarization processing) is performed to convert 256 values into binary values as quantization processing by setting image data GD to 8-bit 256 values and display data Img to 1-bit binary data.

As illustrated in fig. 2, the terminal control unit 2 is configured to include one or more CPUs, and controls each part of the terminal apparatus 1. Here, the CPU is an abbreviation of Central Processing Unit. The CPU or CPUs provided in the terminal control unit 2 can function as the image data acquisition unit 21, the dither mask generation unit 22, and the display data generation unit 23 by executing the control program Pgt stored in the storage unit 3 and operating in accordance with the control program Pgt.

The image data acquisition unit 21 acquires the image data GD stored in the storage unit 3. In the present embodiment, a case where the image data GD is stored in the storage section 3 is assumed as an example, but the present invention is not limited to this embodiment. The image data GD may be stored in an external device existing outside the terminal device 1, for example. In this case, the image data acquisition unit 21 may acquire the image data GD from the external apparatus.

The dither mask generator 22 generates the dither mask DZ, and causes the storage unit 3 to store the generated dither mask DZ.

The display data generation unit 23 generates the display data Img by applying quantization processing to the image data GD using the dither mask DZ.

Fig. 3 is a functional block diagram showing an example of the configuration of the recording apparatus 5.

As illustrated in fig. 3, the recording apparatus 5 includes a recording control unit 6, a head unit 7, an ink supply unit 8, and a robot arm 9.

The recording control unit 6 includes a processing circuit such as a CPU or FPGA, and a storage circuit such as a semiconductor memory, and controls each element of the recording device 5. Here, the FPGA is an abbreviation of Field Programmable Gate Array. The processing circuit provided in the recording control unit 6 can function as the head control unit 61 and the arm control unit 62.

The head control section 61 generates a drive control signal SI for controlling the driving of the head unit 7 based on the display data Img. The head control section 61 generates a drive signal Com for driving the head unit 7 and a control signal Ctr-L for controlling the ink supply unit 8.

The arm control unit 62 generates a control signal Ctr-R for controlling the position and posture of the robot arm 9 in the image forming space SP based on the display data Img.

The head unit 7 includes a drive signal supply unit 71 and a recording head 72.

The recording head 72 includes a plurality of discharge portions D. The ejection unit D is driven by the drive signal Com, and ejects the ink filled in the ejection unit D.

The drive signal supply unit 71 switches whether or not to supply the drive signal Com to each of the plurality of discharge units D based on the drive control signal SI.

In addition, in the present embodiment, a case where the head unit 7 is mounted at the tip end of the robot arm 9 is assumed as an example.

The ink supply unit 8 supplies the ink stored in the ink supply unit 8 to the head unit 7 based on the control signal Ctr-L.

The robot arm 9 changes the position and posture of the tip end of the robot arm 9 in the image forming space SP based on the control signal Ctr-R. Thus, the robot arm 9 changes the position and posture of the head unit 7 in the image forming space SP so that the head unit 7 attached to the tip end of the robot arm 9 is in a position and posture preferable for forming the image G on the surface SF of the target object Obj.

As described above, when the display data Img is supplied, the recording control unit 6 controls the ejection of the ink from the plurality of ejection portions D provided in the head unit 7 by the drive control signal SI generated based on the display data Img. Further, the recording control unit 6 controls the position and posture within the image forming space SP of the head unit 7 mounted at the tip end of the robot arm 9 by a control signal Ctr-R generated based on the display data Img. Therefore, the recording device 5 can form the image G corresponding to the display data Img on the surface SF of the target object Obj arranged in the image forming space SP. Hereinafter, the process of forming the image G corresponding to the display data Img on the surface SF of the target object Obj by the recording apparatus 5 may be referred to as a printing process.

2. Various data

Hereinafter, an example of various data stored in the recording system Sys according to the present embodiment will be described with reference to fig. 4 to 7.

First, in order to explain various data stored in the recording system Sys, a plurality of pixels Px arranged in the image forming space SP will be explained.

Fig. 4 is an explanatory diagram showing an example of a plurality of pixels Px arranged in the image forming space SP.

As illustrated in fig. 4, in the image forming space SP according to the present embodiment, Mx × My × Mz pixels Px are arranged in total so that Mx pixels Px extend in the X-axis direction, My pixels Px extend in the Y-axis direction, and Mz pixels Px extend in the Z-axis direction. Here, the value Mx is a natural number of 2 or more, the value My is a natural number of 2 or more, and the value Mz is a natural number of 2 or more. The values Mx, My, and Mz are preferably natural numbers of 128 or more.

In the present embodiment, a case where the value Mx, the value My, and the value Mz are natural numbers of 256 or more is assumed as an example. Hereinafter, a natural number M, which is "M × My × Mz", is defined. That is, in the present embodiment, M pixels Px are arranged in the image forming space SP.

Further, hereinafter, a variable Mx satisfying a natural number of 1. ltoreq. Mx. ltoreq. Mx, a variable My satisfying a natural number of 1. ltoreq. My. ltoreq.My, and a variable Mz satisfying a natural number of 1. ltoreq. Mz. ltoreq. Mz are introduced. As illustrated in fig. 4, among the M pixels Px existing in the image forming space SP, the pixel Px located at the mxth position from the-X side to the + X side in the X-axis direction, the my th position from the-Y side to the + Y side in the Y-axis direction, and the mzh position from the-Z side to the + Z side in the Z-axis direction may be referred to as a pixel Px (mx, my, mz). Further, hereinafter, the position in the X-axis direction of the pixel Px (mx, my, mz) in the image forming space SP is referred to as "X [ mx ]", the position in the Y-axis direction of the pixel Px (mx, my, mz) in the image forming space SP is referred to as "Y [ my ]", and the position in the Z-axis direction of the pixel Px (mx, my, mz) in the image forming space SP is referred to as "Z [ mz ]". That is, the position of the pixel Px (mx, my, mz) in the image forming space SP is represented as (X, Y, Z) ═ X [ mx ], Y [ my ], Z [ mz ]).

Fig. 5 is an explanatory diagram for explaining an example of the image data GD. In addition, in fig. 5, a case where the surface SF of the target object Obj includes a plane SF1, a plane SF2, and a plane SF3 is assumed as an example.

As described above, the image data GD is data representing the image Gf. Specifically, the image data GD represents a gradation value that should be displayed by each of the M pixels Px existing in the image forming space SP in order to display the image Gf in the image forming space SP. Hereinafter, as illustrated in fig. 5, the gradation value of the image Gf in the pixel Px (mx, my, mz) represented by the image data GD is referred to as a gradation value Gg (mx, my, mz).

In the present embodiment, a case is assumed where the gradation value Gg (mx, my, mz) is a natural number between the minimum gradation value Gg-min and the maximum gradation value Gg-max. Specifically, in the present embodiment, for example, a case is assumed where the gradation value Gg-min is "0" and the gradation value Gg-max is "255". In the present embodiment, a case is assumed where the gradation value Gg (mx, my, mz) is any of 256 values from "0" to "255".

In the present embodiment, the gradation value Gg (mx, my, mz) is set to the gradation value Gg-min for the pixel Px (mx, my, mz) on the surface SF of the object Obj in the image forming space SP. In the present embodiment, when the gradation value Gg (mx, my, mz) is the gradation value Gg-min, the pixel Px (mx, my, mz) is a pixel Px which does not display any content. That is, in the present embodiment, the image Gf does not exist in the pixel Px (mx, my, mz) having the gradation value Gg (mx, my, mz) of the pixel pg (mx, my, mz) of the gradation value Gg-min.

Fig. 6 is an explanatory diagram for explaining an example of the dither mask DZ.

As illustrated in fig. 6, the dither mask DZ has M threshold values Dd in one-to-one correspondence with the M pixels Px in the image forming space SP. Hereinafter, the threshold Dd corresponding to the pixel Px (mx, my, mz) is referred to as a threshold Dd (mx, my, mz).

In the present embodiment, the M thresholds Dd corresponding to the M pixels Px may be expressed as the thresholds Dd [1] to Dd [ M ] in view of the size of the threshold Dd. In the present embodiment, it is assumed that the threshold Dd [ M ] satisfies the following expressions (1) to (3) when the value M is a natural number satisfying "1. ltoreq. m.ltoreq.M".

Dd [1] ═ 1+ Gg-min … … formula (1)

Dd [ M ] ═ Gg-max … … formula (2)

Dd m +1 < Dd m > … … type (3)

However, the threshold Dd [1] may satisfy "Dd [1] ≧ 1+ Gg-min" instead of the above formula (1). In addition, the threshold Dd [ M ] may satisfy "Dd [ M ] ≦ Gg-max" in place of the above formula (2).

In the present embodiment, for convenience of explanation, the M thresholds Dd [1] to Dd [ M ] included in the dither mask DZ are grouped into one or a plurality of thresholds Dd [ M ] having equal values. That is, in the present embodiment, the M thresholds Dd [1] to Dd [ M ] included in the dither mask DZ are divided into a plurality of groups so that one or more thresholds Dd [ M ] belonging to each group have mutually equal values. In the present embodiment, the thresholds Dd [1] to Dd [ M ] are determined so that the number of thresholds Dd [ M ] belonging to each group is substantially equal to each other. In other words, in the present embodiment, the thresholds Dd [1] to Dd [ M ] are determined so that the number of thresholds Dd [ M ] to which one group belongs is substantially equal to the number of thresholds Dd [ M ] to which the other groups belong. This is because the gradation value Gg indicated by the image data GD can be appropriately reproduced by the display data Img described later, regardless of whether the gradation value Gg is any one of the gradation values Gg-min to Gg-max.

Further, hereinafter, the pixel Px corresponding to the threshold Dd [ m ] is sometimes expressed as the pixel Px [ m ].

The dither mask DZ used in the present embodiment arranges the thresholds Dd [1] to Dd [ M ] so that the dispersion of a plurality of thresholds Dd [ M ] equal to or smaller than the near-middle threshold Dd [ mh ] is high compared to the threshold Dd [ M ] larger than the threshold Dd [1 ]. When quantitatively evaluating the dispersion of the plurality of thresholds Dd [ m ] in the dither mask DZ, the spatial frequency characteristics, which are characteristics in the spatial frequency domain of the plurality of thresholds Dd [ m ], can be used by performing conversion from the spatial domain to the spatial frequency domain for the plurality of thresholds Dd [ m ] included in the dither mask DZ. In addition, fig. 10 to 12 are used to describe an example of the arrangement of the thresholds Dd [1] to Dd [ M ] in the spatial domain of the actual dither mask DZ, and the description thereof will be omitted.

Fig. 7 is an explanatory diagram for explaining the spatial frequency characteristics of the thresholds Dd [1] to Dd [ M ] when the dither mask DZ is cut off by the plane PL 1. Specifically, fig. 7 shows a curve FB1 showing the relationship between the spatial frequencies of the thresholds Dd [1] to Dd [ M ] and the power spectrum at each spatial frequency, that is, the amount of frequency components at each spatial frequency.

Hereinafter, an example of the generation method of the curve FB1 is explained. First, the image forming space SP is cut off by the plane PL 1. Second, of the plurality of thresholds Dd [ m ] corresponding to the plurality of pixels Px located ON the plane PL1, the pixel Px corresponding to the threshold Dd [ m ] for which the value equal to or less than the intermediate vicinity threshold Dd [ mh ] is determined is set as an ON pixel, and the pixel Px corresponding to the threshold Dd [ m ] for which the value larger than the intermediate vicinity threshold Dd [ mh ] is determined is set as an OFF pixel. Third, a two-dimensional fourier transform is applied to a plurality of ON pixels in the plane PL1, and the spatial frequency and the amount of frequency components of the arrangement of the plurality of ON pixels in the plane PL1 are obtained. A curve in which the spatial frequency thus obtained is plotted on the horizontal axis and the amount of each frequency component is plotted on the vertical axis is curve FB1 in fig. 7. In addition, please refer to t.mitsa and k.j.parker, "Digital halfning using a Blue Noise Mask", proc.spie 1452, pp.47-56(1991), regarding a method for replacing a plurality of thresholds Dd [ m ] located in a specific plane from among a plurality of thresholds Dd [ m ] of a three-dimensional dither Mask DZ from a spatial domain to a spatial frequency domain.

As illustrated in fig. 7, the curve FB1 according to the present embodiment has the following characteristics: the frequency component between the lowest frequency fmin, which is the lowest frequency, and the intermediate frequency fmid, among the spatial frequencies of the arrangement of the plurality of ON pixels located ON the plane PL1, is less than the frequency component between the highest frequency fmax, which is the highest frequency, and the intermediate frequency fmid, among the spatial frequencies of the arrangement of the plurality of ON pixels located ON the plane PL 1. In other words, in fig. 7, with respect to the curve FB1, the integrated value in the range of the spatial frequency from the lowest frequency fmin to the intermediate frequency fmid is smaller than the integrated value in the range of the spatial frequency from the intermediate frequency fmid to the highest frequency fmax. Here, the intermediate frequency fmid means a frequency intermediate between the intermediate frequency fmid and the highest frequency fmax. More specifically, the intermediate frequency fmid may be a frequency represented by "fmid ═ fmin + fmax } ÷ 2", for example.

Hereinafter, such a characteristic that the frequency components between the lowest frequency fmin and the intermediate frequency fmid are less than the frequency components between the intermediate frequency fmid and the highest frequency fmax in the spatial frequency domain is referred to as "predetermined spatial frequency characteristic".

Further, hereinafter, a curve representing a relationship between the spatial frequency of one plane and how many frequency components in the spatial frequency domain of the one plane are obtained by dividing, in the same manner as described above, a plurality of thresholds Dd that the dither mask DZ has, which correspond to a plurality of pixels Px located ON one plane that cuts OFF the image forming space SP, into ON pixels and OFF pixels and applying two-dimensional fourier transform to the plurality of ON pixels ON the one plane, among the plurality of thresholds Dd that the dither mask DZ has, is expressed as "the dither mask DZ has a predetermined spatial frequency characteristic within the one plane".

That is, the dither mask DZ used in the present embodiment has a predetermined spatial frequency characteristic in the plane PL 1.

In the present embodiment, the plane PL1 may be a plane parallel to the X-axis direction. In other words, the plane PL1 may be a plane having a normal vector extending in a direction orthogonal to the X-axis direction. Specifically, the plane PL1 may be a plane perpendicular to the YZ plane. The plane PL1 may be a plane parallel to the Y-axis direction. In other words, the plane PL1 may be a plane having a normal vector extending in a direction orthogonal to the Y-axis direction. Specifically, the plane PL1 may be a plane parallel to the XY plane. As an example of the plane PL1, the plane Z ═ Z [1 ].

The near-middle threshold Dd [ mh ] preferably satisfies the following expression (4).

(1-γ1)*Dd[1]+γ1*Dd[M]≤Dd[mh]

Less than or equal to (1-gamma 2) × Dd 1+ gamma 2 × Dd M … … type (4)

Here, the value γ 1 is, for example, a real number satisfying "0.2. ltoreq. γ 1. ltoreq.0.5", and the value γ 2 is, for example, a real number satisfying "0.5. ltoreq. γ 1. ltoreq.0.8". In the present embodiment, a case is assumed where the value γ 1 is "0.2" and the value γ 2 is "0.8".

As one example, in the case where the value γ 1 is "0.2" and the value γ 2 is "0.8" when the threshold value Dd [1] is "1" and the threshold value Dd [ M ] is "255", the middle vicinity threshold value Dd [ mh ] is "51. ltoreq. Dd [ mh ] ≦ 204". The near-middle threshold Dd [ mh ] is, for example, "64". When a plurality of thresholds Dd from the threshold Dd [1], i.e., "1", to the threshold Dd [ M ], i.e., "255", are arranged in order, it is the threshold Dd [ M ] located at about 1/4 th from the threshold Dd [1 ].

As illustrated in fig. 7, the curve FB1 according to the present embodiment has a peak on the highest frequency fmax side of the intermediate frequency fmid. Therefore, in the present embodiment, a curve showing a relationship between the spatial frequency of one plane and the number of frequency components in the spatial frequency domain of the one plane, which is obtained by dividing a plurality of thresholds Dd of the dither mask DZ corresponding to a plurality of pixels Px located ON one plane that cuts OFF the image forming space SP into ON pixels and OFF pixels and applying two-dimensional fourier transform to the plurality of ON pixels ON the one plane, among the plurality of thresholds Dd, may be referred to as "predetermined spatial frequency characteristic" when the peak is located ON the side of the highest frequency fmax than the intermediate frequency fmid.

More specifically, in the present embodiment, the predetermined spatial frequency characteristic is a blue noise characteristic. However, the present embodiment is not limited to the case where the predetermined spatial frequency characteristic is a blue noise characteristic. In the present embodiment, the predetermined spatial frequency characteristic may be a frequency characteristic having less frequency components on the lowest frequency fmin side than the intermediate frequency fmid in the spatial frequency domain than the white noise characteristic. That is, the predetermined spatial frequency characteristic only needs to be closer to the blue noise characteristic than the white noise characteristic. In other words, the predetermined spatial frequency characteristic only needs to be not closer to the red noise characteristic than the white noise characteristic. For example, in the present embodiment, the predetermined spatial frequency characteristic may be a purple noise characteristic.

As a method of generating the curve FB1, for example, the following method can be considered. That is, first, the image forming space SP is cut off by the plane PL 1. Second, the curved surface PC1 is generated in which the plurality of thresholds Dd corresponding to the plurality of pixels Px located on the plane PL1 are expressed as the height from the bottom surface when the plane PL1 is the bottom surface. Third, the number of frequency components in the spatial frequency domain of the curved surface PC1 is obtained by applying two-dimensional fourier analysis to the curved surface PC 1. Thereby, the curve FB1 indicating the relationship between the spatial frequency of the curved surface PC1 and the number of frequency components in the spatial frequency domain of the curved surface PC1 can be generated.

The dither mask DZ according to the present embodiment also has a predetermined spatial frequency characteristic in a plane PL2 different from the plane PL 1. Here, the plane PL2 refers to a plane extending in a different direction from the plane PL 1. In other words, the plane PL2 refers to a plane having a normal vector extending in a direction different from the normal vector of the plane PL 1. For example, the plane PL2 may be a plane orthogonal to the plane PL 1. In other words, the plane PL2 may be a plane having a normal vector extending in a direction orthogonal to the normal vector of the plane PL 1.

In the present embodiment, the plane PL2 may be a plane parallel to the Y-axis direction. In other words, the plane PL2 may be a plane having a normal vector extending in a direction orthogonal to the Y-axis direction. Specifically, the plane PL2 may be a plane perpendicular to the XZ plane. The plane PL2 may be a plane parallel to the Z-axis direction. In other words, the plane PL2 may be a plane having a normal vector extending in a direction orthogonal to the Z-axis direction. Specifically, the plane PL2 may be a plane parallel to the YZ plane. As an example of the plane PL2, the plane X ═ X [1 ].

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic in the plane PL3 different from the planes PL1 and PL 2. Here, the plane PL3 refers to a plane parallel to the plane PL 1. In other words, the plane PL3 refers to a plane having a normal vector extending in the same direction as the normal vector of the plane PL 1.

In the present embodiment, the plane PL3 may be a plane parallel to the X-axis direction. In other words, the plane PL3 may be a plane having a normal vector extending in a direction orthogonal to the X-axis direction. Specifically, the plane PL3 may be a plane perpendicular to the YZ plane. The plane PL3 may be a plane parallel to the Y-axis direction. In other words, the plane PL3 may be a plane having a normal vector extending in a direction orthogonal to the Y-axis direction. Specifically, the plane PL3 may be a plane parallel to the XY plane. As an example of the plane PL3, the plane Z ═ Z [2 ].

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic on a plane PL4 different from the planes PL1 to PL 3. Here, the plane PL4 refers to a plane parallel to the plane PL 2. In other words, the plane PL4 refers to a plane having a normal vector extending in the same direction as the normal vector of the plane PL 2.

In the present embodiment, the plane PL4 may be a plane parallel to the Y-axis direction. In other words, the plane PL4 may be a plane having a normal vector extending in a direction orthogonal to the Y-axis direction. Specifically, the plane PL4 may be a plane perpendicular to the XZ plane. The plane PL4 may be a plane parallel to the Z-axis direction. In other words, the plane PL4 may be a plane having a normal vector extending in a direction orthogonal to the Z-axis direction. Specifically, the plane PL4 may be a plane parallel to the YZ plane. As an example of the plane PL4, the plane X ═ X [2 ].

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic on a plane PL5 different from the planes PL1 to PL 4. Here, the plane PL5 is a plane extending in a different direction from the planes PL1 and PL 2. In other words, the plane PL5 is a plane having a normal vector extending in a direction different from the normal vector of the plane PL1 and extending in a direction different from the normal vector of the plane PL 2. For example, the plane PL5 may be a plane orthogonal to the planes PL1 and PL 2. In other words, the plane PL5 may be a plane having a normal vector extending in a direction orthogonal to the normal vector of the plane PL1 and extending in a direction orthogonal to the normal vector of the plane PL 2.

In the present embodiment, the plane PL5 may be a plane parallel to the Z-axis direction. In other words, the plane PL5 may be a plane having a normal vector extending in a direction orthogonal to the Z-axis direction. Specifically, the plane PL5 may be a plane perpendicular to the XY plane. The plane PL5 may be a plane parallel to the X-axis direction. In other words, the plane PL5 may be a plane having a normal vector extending in a direction orthogonal to the X-axis direction. Specifically, the plane PL5 may be a plane parallel to the XZ plane. As an example of the plane PL5, the plane Y ═ Y [1 ].

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic in a plane PL6 different from the planes PL1 to PL 5. Here, the plane PL6 refers to a plane parallel to the plane PL 5. In other words, the plane PL6 is a plane having a normal vector extending in the same direction as the normal vector of the plane PL 5.

In the present embodiment, the plane PL6 may be a plane parallel to the Z-axis direction. In other words, the plane PL6 may be a plane having a normal vector extending in a direction orthogonal to the Z-axis direction. Specifically, the plane PL6 may be a plane perpendicular to the XY plane. The plane PL6 may be a plane parallel to the X-axis direction. In other words, the plane PL6 may be a plane having a normal vector extending in a direction orthogonal to the X-axis direction. Specifically, the plane PL6 may be a plane parallel to the XZ plane. As an example of the plane PL6, the plane Y ═ Y [2 ].

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic in any plane parallel to the plane PL1, among the planes that cut the image forming space SP.

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic in any plane parallel to the plane PL2, among the planes that cut the image forming space SP.

The dither mask DZ according to the present embodiment may have a predetermined spatial frequency characteristic in any plane parallel to the plane PL5, among the planes that cut the image forming space SP.

For example, when the normal vector of one plane is expressed as a vector V1 ═ (V1x, V1y, V1z), and the normal vector of the other plane is expressed as a vector V2 having the same length as the vector V1 ═ V2x, V2y, V2z, "the one plane and the other plane extend in different directions" can be expressed as at least one of "| V1x | ≠ | V2x |", "| V1y | ≠ | V2y |", and "| V1z | ≠ | V2z |".

3. Operation of the recording system

Hereinafter, an example of the operation of the recording system Sys according to the present embodiment will be described with reference to fig. 8 and 9.

Fig. 8 is a flowchart showing an example of the operation of the recording system Sys when the recording system Sys executes the dither mask generation process. Here, the dither mask generation processing is processing for generating the dither mask DZ.

As illustrated in fig. 8, when the dither mask generating process is started, the dither mask generating unit 22 sets the variable m to "1" (S10).

Next, the dither mask generating section 22 selects a pixel Px [1] corresponding to the threshold Dd [1] from the M pixels Px in the image forming space SP (S11). Specifically, in step S11, the dither mask generating unit 22 may randomly select the pixel Px [1] from the M pixels Px, for example. In step S11, the dither mask generating unit 22 may select a predetermined pixel Px, which is determined in advance, from the M pixels Px, as the pixel Px [1 ].

Next, the dither mask generating unit 22 sets the threshold Dd (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected as the pixel Px [1] as the threshold Dd [1] (S12). Specifically, in step S12, the dither mask generating unit 22 sets the threshold Dd (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected as the pixel Px [1] to "1 + Gg-min". More specifically, since the gradation value Gg-min is "0" in the present embodiment, the dither mask generating unit 22 sets the threshold value Dd (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected as the pixel Px [1] to "1" in step S12.

Next, the dither mask generating unit 22 calculates the potential value Ep for each of the pixels Px other than the pixels Px [1] to Px [ m ] (S13). In addition, hereinafter, the pixels for which the threshold value Dd [ m ] is not determined are referred to as residual pixels PxZ. For example, in step S13, the residual pixel PxZ is a pixel Px other than the pixels Px [1] to Px [ m ].

Here, the potential value Ep is a value represented by the following formula (5) using the individual potential value Ek [ m ].

Ep ═ Ek [1] + Ek [2] + … + Ek [ m ] … … formula (5)

Note that the potential value Ep is represented by the following formula (6) in place of the formula (5) when "m" is 1, and is represented by the following formula (7) in place of the formula (5) when "m" is 2.

Ep ═ Ek [1] … … formula (6)

Ep ═ Ek [1] + Ek [2] … … formula (7)

Here, the individual potential value Ek [ m ] is a value represented by the following formula (8).

Ek [ m ] ═ Cs [ m ]/(R [ m ]) beta … … formula (8)

Here, the distance R [ m ] is a value indicating the distance between the pixel Px [ m ] and the residual pixel PxZ. Further, the value β is a real number of "1" or more and is preferably "2". Further, the coefficient Cs [ m ] is a positive real number. The coefficient Cs [ m ] may be, for example, a predetermined constant or a value determined based on the threshold value Dd [ m ].

Next, the dither mask generating unit 22 adds "1" to the variable m to calculate (S14). In the present embodiment, as described above, the threshold Dd [ m +1] is the same value as the threshold Dd [ m ] or a value "1" larger than the threshold Dd [ m ]. As described above, the thresholds Dd [1] to Dd [ M ] are divided into a plurality of groups according to the thresholds Dd having the same value. In the present embodiment, a case where the thresholds Dd [1] to Dd [ M ] are divided into "Gg-max-Gg-min + 1" groups is assumed as an example. In the present embodiment, a case where the threshold Dd of the predetermined number Q belongs to each group is assumed as an example. Here, the predetermined number Q is a value determined based on the value "Gg-max-Gg-min + 1" and the value M. For example, the predetermined number Q may be a value obtained by rounding a value calculated by dividing the value M by the value "Gg-max-Gg-min + 1", for example. For example, when M is "8 × 8 ═ 512", the gradation value Gg-min is "0", and the gradation value Gg-max is "255", the predetermined number Q is "512 ÷ 256 ═ 2". In this case, when a variable w is introduced to "1. ltoreq. w.ltoreq.255", the threshold value Dd [ 2. multidot. w-1] and the threshold value Dd [ 2. multidot. w ] belong to a group in which the gradation value Gg corresponds to "w".

Further, the dither mask generating section 22 selects the pixel Px [ m ] from the one or more residual pixels PxZ in the image forming space SP based on the potential value Ep determined corresponding to each residual pixel PxZ (S15). Specifically, in step S15, the dither mask generating section 22 selects the residual pixel PxZ, of which the potential value Ep becomes the smallest, as the pixel Px [ m ] from the one or more residual pixels PxZ.

Next, the dither mask generating unit 22 sets the threshold Dd (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected as the pixel Px [ m ] in step S15 as the threshold Dd [ m ] (S16).

Thereafter, the dither mask generating unit 22 determines whether or not the variable M is "M" (S17). If the result of this determination is negative, the dither mask generating unit 22 advances the process to step S13. On the other hand, if the result of this determination is affirmative, the dither mask generating unit 22 ends the dither mask generating process.

Fig. 9 is a flowchart showing an example of the operation of the recording system Sys when the recording system Sys executes the quantization processing. As described above, the quantization processing is processing for generating the display data Img based on the image data GD.

As illustrated in fig. 9, when the quantization processing is started, the display data generation section 23 selects a pixel Px (mx, my, mz) from the M pixels Px in the image formation space SP (S20).

Next, the display data generation unit 23 determines whether or not the gradation value Gg (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected in step S20, among the plurality of gradation values Gg indicated by the image data GD, is equal to or greater than the threshold Dd (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected in step S20, among the plurality of thresholds Dd indicated by the dither mask DZ (S3932) (S21).

In addition, in the present embodiment, the display data Img represents the gradation of the image G displayed by each of the M pixels Px present in the image forming space SP in order to form the image G on the surface SF of the target object Obj present in the image forming space SP. Specifically, in the present embodiment, the display data Img indicates that the image G displayed by each pixel Px existing in the image forming space SP has the highest gradation value Gg-1 or the lowest gradation value Gg-0. For example, in the present embodiment, the highest gradation value Gg-1 is "1" and the lowest gradation value Gg-0 is "0". That is, the display data Img is data indicating the gradation of the image G displayed by each of the M pixels Px by two values "1" and "0". The pixel Px displaying the image G having the highest gradation value Gg-1, i.e., the gradation value "1", is the pixel Px having dots formed by the ink discharged from the recording device 5. The pixel Px that displays the image G having the lowest gradation value Gg-0, i.e., the gradation value "0", is the pixel Px on which no dot is formed. Hereinafter, the pixel Px formed with a dot by displaying the image G having the highest gradation value Gg-1, i.e., the gradation value "1", will be referred to as a dot-formed pixel Px-1. The pixel Px in which no dot is formed by displaying the image G having the lowest gradation value Gg-0, i.e., the gradation value "0", is referred to as a non-dot forming pixel Px-0.

As illustrated in fig. 9, if the result of the determination in step S21 is affirmative, the display data generation unit 23 sets the gradation of the image G displayed by the pixel Px (mx, my, mz) to "1" which is the highest gradation value Gg-1 in the display data Img (S22).

On the other hand, if the result of the determination at step S21 is negative, the display data generation unit 23 sets the gradation of the image G displayed by the pixel Px (mx, my, mz) to "0" which is the lowest gradation value Gg-0 in the display data Img (S23).

Next, the display data generation unit 23 determines whether or not the highest gradation value Gg-1, that is, "1", or the lowest gradation value Gg-0, that is, "0", is set for all the M pixels Px in the image forming space SP in the display data Img (S24).

When the result of the determination at step S24 is negative, the display data generation unit 23 advances the process to step S20. On the other hand, if the result of the determination in step S24 is affirmative, the display data generation unit 23 ends the quantization processing.

Further, as described above, the recording device 5 forms the image G with respect to the surface SF of the target object Obj arranged in the image forming space SP based on the display data Img generated by the quantization processing.

Specifically, the head control unit 61 generates the drive control signal SI that instructs ink to be ejected and dots to be formed for the pixels Px whose display data Img indicates the highest gradation value Gg-1, i.e., "1", and that instructs ink to be not ejected and dots to be not formed for the pixels Px whose display data Img indicates the lowest gradation value Gg-0, i.e., "0". Then, the head unit 7 ejects ink to the pixels Px in the image forming space SP based on the drive control signal SI. Thus, the recording device 5 forms a dot at the pixel Px whose display data Img indicates the highest gradation value Gg-1, i.e., "1", and can form the image G on the surface SF of the target object Obj arranged in the image forming space SP.

4. Relationship of dither mask and display data

Hereinafter, an example of the dither mask DZ and an example of the generated display data Img according to the present embodiment will be described with reference to fig. 10 to 12.

Fig. 10 is an explanatory diagram showing a relationship between a plurality of threshold values Dd corresponding to a plurality of pixels Px located on the plane PL1, among the plurality of threshold values Dd provided in the dither mask DZ, and the display data Img. Fig. 11 is an explanatory diagram showing a relationship between a plurality of threshold values Dd corresponding to a plurality of pixels Px located on the plane PL2, among the plurality of threshold values Dd provided in the dither mask DZ, and the display data Img. Fig. 12 is an explanatory diagram showing a relationship between a plurality of threshold values Dd corresponding to a plurality of pixels Px located on the plane PL5, among the plurality of threshold values Dd provided in the dither mask DZ, and the display data Img. In fig. 10 to 12, each numerical value indicates a threshold Dd determined by the pixel Px. In fig. 10 to 12, a dot formation pixel Px-1 surrounded by a thick frame and having a dot added thereto represents the formation of a dot determined by the display data Img.

In the examples shown in fig. 10 to 12, a case is assumed where plane PL1 is a plane that becomes "Z ═ Z [1 ]", plane PL2 is a plane that becomes "X ═ X [1 ]", and plane PL5 is a plane that becomes "Y ═ Y [1 ]". Further, in the examples shown in fig. 10 to 12, a case is assumed where the surface SF of the target object Obj includes the plane PL1, the plane PL2, and the plane PL 5. In the examples shown in fig. 10 to 12, a case is assumed where "Mx ═ 8", "My ═ 8", "Mz ═ 8", "M ═ 8 ═ 512" exists and 512 pixels Px exist in the image forming space SP. In the examples shown in fig. 10 to 12, the gradation value Gg-min is "0", the gradation value Gg-max is "255", the threshold Dd [1] is "1", and the threshold Dd [ M ] is "255".

Further, hereinafter, the gradation value Gg-min and the gradation value near the middle of the gradation value Gg-max are referred to as middle-vicinity gradation value Gg-mid. Here, the near-middle gradation value Gg-mid is, for example, a gradation value satisfying the following expression (9).

(1-γ3)*Gg-min+γ3*Gg-max≤Gg-mid

Less than or equal to (1-gamma 4) × Gg-min + gamma 4 × Gg-max … … type (9)

Here, the value γ 3 is, for example, a real number satisfying "0.2. ltoreq. γ 3. ltoreq.0.5", and the value γ 4 is, for example, a real number satisfying "0.5. ltoreq. γ 4. ltoreq.0.8". In the present embodiment, a case is assumed where the value γ 3 is "0.2" and the value γ 4 is "0.8". That is, in the present embodiment, it is assumed that the near-middle gradation value Gg-mid is "51. ltoreq. Gg-mid. ltoreq.204". In the example shown in fig. 10 to 12, it is assumed that all of the gradation values Gg in the plurality of pixels Px represented by the image data GD are "64" which is the middle vicinity gradation value Gg-mid. This corresponds to 1/4 in the gradation value Gg of 256 levels. In the example shown in fig. 10 to 12, a case is assumed in which all of the gradation values Gg in the plurality of pixels Px included in the plane PL1, the plane PL2, and the plane PL5 in the image data GD are the near-middle gradation value Gg-mid.

As illustrated in fig. 10, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the plurality of dot formation pixels Px-1 of the plurality of pixels Px present on the plane PL1 are arranged so as to have high dispersibility, rather than being locally present in a specific region. In other words, the distribution of the plurality of dot formation pixels Px-1 among the plurality of pixels Px present on the plane PL1 has "predetermined spatial frequency characteristic" in the spatial frequency domain. In other words, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the distribution of the plurality of dots formed on the plane PL1 has "predetermined spatial frequency characteristic" within the spatial frequency domain. Here, the phrase "the distribution of a plurality of points in one plane has a predetermined spatial frequency characteristic" means that a curve indicating a relationship between the spatial frequency of one plane and how many frequency components in the spatial frequency domain of the one plane are obtained by applying a two-dimensional fourier transform to the point formation pixel Px-1 of the plurality of pixels Px has the predetermined spatial frequency characteristic described above. Further, "the distribution of a plurality of points in one plane has a predetermined spatial frequency characteristic" can also be grasped as a case where, when a curved surface is generated in which a value indicating whether or not a point is formed at each of a plurality of pixels Px located on one plane that cuts the image forming space SP indicates a height from the bottom surface when the one plane is taken as the bottom side, a curve indicating a relationship between a spatial frequency of the curved surface and how many frequency components in a spatial frequency domain of the curved surface have a predetermined spatial frequency characteristic.

Similarly, as illustrated in fig. 11, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the plurality of dot formation pixels Px-1 of the plurality of pixels Px present on the plane PL2 are arranged so as to have high dispersibility, rather than being locally present in a specific region. In other words, the distribution of the plurality of dot formation pixels Px-1 among the plurality of pixels Px present on the plane PL2 has "predetermined spatial frequency characteristic" in the spatial frequency domain. In other words, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the distribution of the plurality of dots formed on the plane PL2 has "predetermined spatial frequency characteristic" within the spatial frequency domain.

Similarly, as illustrated in fig. 12, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the plurality of dot formation pixels Px-1 of the plurality of pixels Px present on the plane PL5 are arranged so as to have high dispersibility, rather than being locally present in a specific region. In other words, the distribution of the plurality of dot formation pixels Px-1 among the plurality of pixels Px present on the plane PL5 has "predetermined spatial frequency characteristic" in the spatial frequency domain. In other words, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the distribution of the plurality of dots formed on the plane PL5 has "predetermined spatial frequency characteristic" within the spatial frequency domain.

As described above, according to the present embodiment, as illustrated in fig. 10 to 12, since the distribution of the threshold values of the dither mask DZ has the predetermined spatial frequency characteristic, the distribution of the plurality of points formed on the surface SF of the target object Obj located in the image forming space SP also has the predetermined spatial frequency characteristic in the case where the gradation value Gg indicated by the image data GD is the middle vicinity gradation value Gg-mid. In other words, according to the present embodiment, when the gradation value Gg indicated by the image data GD is the near-middle gradation value Gg-mid, the dispersibility of the plurality of points formed on the surface SF of the target object Obj can be improved.

5. Reference example and effects of the present embodiment compared with reference example

Hereinafter, the dither mask according to the reference example and the effect of the present embodiment compared to the reference example will be described while referring to fig. 13 to 21.

In the examples shown in fig. 13 to 21, a case is assumed where "Mx ═ 3", "My ═ 3", "Mz ═ 3", "M ═ 3 ═ 27" exists and 27 pixels Px exist in the image forming space SP. In the example shown in fig. 13 to 21, a case is assumed where the gradation value Gg-min is "0", the gradation value Gg-max is "9", the threshold Dd [1] is "1", and the threshold Dd [ M ] is "9". In addition, in the examples shown in FIGS. 13 to 21, a case is assumed where the near-middle gradation value Gg-mid is "2. ltoreq. Gg-mid. ltoreq.7". In the example shown in fig. 13 to 21, it is assumed that all of the gradation values Gg of the plurality of pixels Px represented by the image data GD are "4". That is, in the examples shown in fig. 13 to 21, a case is assumed in which all of the gradation values Gg in the plurality of pixels Px represented by the image data GD are the middle vicinity gradation value Gg-mid.

Fig. 13 to 15 are explanatory views for explaining reference example 1.

Reference example 1 usesA two-dimensional dither mask DZ-A for whichA plurality of threshold values corresponding toA plurality of pixels Px inA two-dimensional space are determined. The dither mask DZ-A extends inA direction parallel to the XY plane. The dither mask DZ-A is set to haveA predetermined spatial frequency characteristic inA spatial frequency domain so as to be able to arrange dots dispersively. In reference example 1, the same dither mask DZ-A is used for three planes, i.e., the plane Z ═ Z [1], the plane Z ═ Z [2], and the plane Z ═ Z [3 ]. In reference example 1,A two-dimensional quantization process is performed on each of the plane Z ═ Z [1], the plane Z ═ Z [2], and the plane Z ═ Z [3] using the dither mask DZ-A.

As illustrated in fig. 13, the dither mask DZ-A hasA plurality of threshold values Dd arranged to haveA predetermined spatial frequency characteristic in the plane Z ═ Z [1 ]. That is, the dither mask DZ-A can be arranged so that the plurality of dot formation pixels Px-1 haveA predetermined spatial frequency characteristic in the spatial frequency domain on the plane Z ═ Z [1 ]. Therefore, in reference example 1, when the surface SF of the target object Obj includes the plane Z ═ Z [1], the recording device 5 can arrange dots in a dispersed manner in the plane Z ═ Z [1 ].

The dither mask DZ-A hasA plurality of thresholds Dd in the same arrangement as the plane Z ═ Z [1] in the plane Z ═ Z [2 ]. Therefore, in reference example 1, when the surface SF of the target object Obj includes the plane Z ═ Z [2], the recording device 5 can arrange dots in a dispersed manner in the plane Z ═ Z [2 ].

The dither mask DZ-A hasA plurality of thresholds Dd in the same arrangement as the plane Z ═ Z [1] in the plane Z ═ Z [3 ]. Therefore, in reference example 1, when the surface SF of the target object Obj includes the plane Z ═ Z [3], the recording device 5 can arrange dots in a dispersed manner in the plane Z ═ Z [3 ].

On the other hand, the plane Y is Y [1], the plane Y is Y [2], the plane Y is Y [3], the plane X is X [1], the plane X is X [2], and the plane X is X [3], and the quantization process is performed by dividing the image by three two-dimensional dither masks DZ-A.

For example, as illustrated in fig. 14, of the nine pixels on the plane Y ═ Y [1], three pixels located on the plane Z ═ Z [1] are subjected to quantization processing by the two-dimensional dither mask DZ-A corresponding to the plane Z ═ Z [1], three pixels located on the plane Z ═ Z [2] are subjected to quantization processing by the two-dimensional dither mask DZ-A corresponding to the plane Z ═ Z [2], and three pixels located on the plane Z ═ Z [3] are subjected to quantization processing by the two-dimensional dither mask DZ-A corresponding to the plane Z ═ Z [3 ]. Since the three identical dither masks DZ-A are used in reference example 1 as described above, three pixels located on the plane Z ═ Z [1], three pixels located on the plane Z ═ Z [2], and three pixels located on the plane Z ═ Z [3] of the nine pixels of the plane Y ═ Y [1] are made to correspond to the same threshold values, respectively. Therefore, in reference example 1, as shown in fig. 14, dots are continuously formed at three pixels of the plane X ═ X [1] and three pixels of the plane X ═ X [3] on the plane Y ═ Y [1], while dots are not formed at three pixels of the plane X ═ X [2], on the other hand. Therefore, in reference example 1, when the surface SF of the target object Obj includes the plane Y ═ Y [1], the recording device 5 cannot distribute the dots in the plane Y ═ Y [1 ].

As considered in the same manner, in reference example 1, as shown in fig. 14, no dots are formed at none of the nine pixels on the plane Y ═ Y [2 ]. Therefore, in reference example 1, in the case where the surface SF of the target object Obj includes the plane Y ═ Y [2], the recording apparatus 5 cannot arrange points within the plane Y ═ Y [2] at all.

As can be seen from the same consideration, in reference example 1, as shown in fig. 14, dots are continuously formed at three pixels of the plane X ═ X [1] and three pixels of the plane X ═ X [3], while dots are not formed at three pixels of the plane X ═ X [2], on the other hand. Therefore, in reference example 1, when the surface SF of the target object Obj includes the plane Y ═ Y [3], the recording device 5 cannot distribute the dots in the plane Y ═ Y [3 ].

As can be seen from the consideration in the same manner, in reference example 1, as shown in fig. 15, dots are continuously formed at three pixels of the plane Y ═ Y [1] and three pixels of the plane Y ═ Y [3] on the plane X ═ X [1], while dots are not formed at three pixels of the plane Y ═ Y [2 ]. Therefore, in reference example 1, when the surface SF of the target object Obj includes the plane X ═ X [1], the recording device 5 cannot distribute the dots in the plane X ═ X [1 ].

As can be seen from consideration in the same manner, in reference example 1, as shown in fig. 15, no dots are formed at any of the nine pixels on the plane X ═ X [2 ]. Therefore, in reference example 1, in the case where the surface SF of the target object Obj includes the plane X ═ X [2], the recording apparatus 5 cannot arrange points within the plane X ═ X [2] at all.

As can be seen from the same consideration, as shown in fig. 15, dots are continuously formed at three pixels of the plane Y ═ Y [1] and three pixels of the plane Y ═ Y [3], while dots are not formed at three pixels of the plane Y ═ Y [2], on the other hand. In reference example 1, when the surface SF of the target object Obj includes the plane X ═ X [3], the recording device 5 cannot distribute the dots in the plane X ═ X [3 ].

As described above, in reference example 1, the same two-dimensional dither mask DZ-A extending in the direction parallel to the XY plane is applied to the plane Z ═ Z [1], the plane Z ═ Z [2], and the plane Z ═ Z [3], respectively, and display data is generated. Therefore, in reference example 1, in the case where the surface SF of the target object Obj is parallel to the XY plane, the recording apparatus 5 can dispersedly arrange the dots with respect to the surface SF, but in the case where the surface SF of the target object Obj is not parallel to the XY plane, the recording apparatus 5 cannot adjust the arrangement of the dots with respect to the surface SF, and as a result, the recording apparatus 5 cannot dispersedly arrange the dots, such as continuously arranging the dots, or the like. Therefore, in reference example 1, a granular feeling is generated in the image G formed on the surface SF of the target object Obj, and the image quality of the image G is degraded. In addition, on planes parallel to each other, a plane in which dots are collectively arranged (a plane X ═ X [1], a plane X ═ X [3], a plane Y ═ Y [1], and a plane Y ═ Y [3]) and a plane in which dots are not arranged (a plane X ═ X [2], and a plane Y ═ Y [2]) are mixed, and thus the image quality greatly differs depending on the surface SF of the target object Obj.

Fig. 16 to 18 are explanatory views for explaining reference example 2.

Reference example 2 uses a two-dimensional dither mask DZ-B1 for which a plurality of threshold values corresponding to a plurality of pixels Px in a two-dimensional space are determined, for a plane Z ═ Z [1 ]. The dither mask DZ-B1 extends in a direction parallel to the XY plane. The dither mask DZ-B1 is set so as to have a predetermined spatial frequency characteristic in the spatial frequency domain so that dots can be arranged in a dispersed manner.

Then, a dither mask DZ-B2 obtained by sliding the plurality of thresholds Dd of the dither mask DZ-B1 by one pixel in the + X direction is used for the plane Z ═ Z [2 ]. Specifically, the dither mask DZ-B2 is obtained by sliding the plurality of thresholds Dd in the plane X ═ X [1] of the dither mask DZ-B1 to the plane X ═ X [2], the plurality of thresholds Dd in the plane X ═ X [2] to the plane X ═ X [3], and the plurality of thresholds Dd in the plane X ═ X [3] to the plane X ═ X [1 ].

Further, a dither mask DZ-B3 obtained by sliding the plurality of thresholds Dd of the dither mask DZ-B1 by two pixels in the + X direction is used for the plane Z ═ Z [3 ]. Specifically, the dither mask DZ-B3 is a dither mask DZ-B3 obtained by sliding the plurality of thresholds Dd in the plane X ═ X [1] of the dither mask DZ-B1 to the plane X ═ X [3], the plurality of thresholds Dd in the plane X ═ X [2] to the plane X ═ X [1], and the plurality of thresholds Dd in the plane X ═ X [3] to the plane X ═ X [2 ].

In reference example 2, two-dimensional quantization processing is performed on the plane Z ═ Z [1] using the dither mask DZ-B1, two-dimensional quantization processing is performed on the plane Z ═ Z [2] using the dither mask DZ-B2, and two-dimensional quantization processing is performed on the plane Z ═ Z [3] using the dither mask DZ-B3.

As illustrated in fig. 16, the dither mask DZ-B1 has a plurality of threshold values Dd within the plane Z ═ Z [1], and the plurality of threshold values Dd are arranged so as to have a predetermined spatial frequency characteristic. That is, the dither mask DZ-B1 can be arranged so that the plurality of dot formation pixels Px-1 have a predetermined spatial frequency characteristic in the spatial frequency domain within the plane Z ═ Z [1 ]. Therefore, in reference example 2, when the surface SF of the target object Obj includes the plane Z ═ Z [1], the recording device 5 can arrange dots in a dispersed manner in the plane Z ═ Z [1 ].

On the other hand, the dither mask DZ-B2 is a dither mask obtained by sliding the plurality of thresholds Dd that the dither mask DZ-B1 has in the above-described manner. As a result, the dither mask DZ-B2 does not have predetermined spatial frequency characteristics in the spatial frequency domain. Therefore, in reference example 2, in the case where the surface SF of the target object Obj includes the plane Z ═ Z [2], the dispersibility of the dots formed by the recording device 5 in the plane Z ═ Z [2] is lower than the dispersibility of the dots formed by the recording device 5 in the plane Z ═ Z [1 ].

The dither mask DZ-B3 is obtained by sliding the plurality of thresholds Dd of the dither mask DZ-B1 in the above-described manner. As a result, the dither mask DZ-B3 does not have predetermined spatial frequency characteristics in the spatial frequency domain. Therefore, in reference example 2, in the case where the surface SF of the target object Obj includes the plane Z ═ Z [3], the dispersibility of the dots formed by the recording device 5 in the plane Z ═ Z [3] is lower than the dispersibility of the dots formed by the recording device 5 in the plane Z ═ Z [1 ].

On the other hand, the quantization process is performed by dividing the plane Y ═ Y [1], the plane Y ═ Y [2], the plane Y ═ Y [3], the plane X ═ X [1], the plane X ═ X [2], and the plane X ═ X [3] by three two-dimensional dither masks DZ-B1, DZ-B2, and DZ-B3, as in reference example 1.

For example, as illustrated in fig. 17, among the nine pixels in the plane Y ═ Y [1], three pixels located on the plane Z ═ Z [1] are subjected to quantization processing by the two-dimensional dither mask DZ-B1 corresponding to the plane Z ═ Z [1], three pixels located on the plane Z ═ Z [2] are subjected to quantization processing by the two-dimensional dither mask DZ-B2 corresponding to the plane Z ═ Z [2], and three pixels located on the plane Z ═ Z [3] are subjected to quantization processing by the two-dimensional dither mask DZ-B3 corresponding to the plane Z ═ Z [3 ]. Here, three pixels located on the plane Y ═ Y [1] and located on the plane Z ═ Z [1] correspond to the threshold values Dd of "1", "6", and "4" included in the dither mask DZ-B1 in order from the-X direction toward the + X direction. Further, three pixels located on the plane Y-Y [1] and located on the plane Z-Z [2] correspond to the threshold values Dd of "4", "1", and "6" included in the dither mask DZ-B2 in order from the-X direction toward the + X direction. Further, three pixels located on the plane Y-Y [1] and located on the plane Z-Z [3] correspond to the thresholds Dd of "6", "4", and "1" included in the dither mask DZ-B3 in order from the-X direction toward the + X direction. Therefore, in reference example 2, as shown in fig. 17, if compared with the plane Y ═ Y [1] in fig. 14, the dot dispersibility in the plane Y ═ Y [1] is high. However, if compared with the plane Y ═ Y [1] in fig. 20 described later, the number of dots arranged on the plane Y ═ Y [1] in fig. 17 is large, and the dot dispersibility is low. That is, the plane Y ═ Y [1] in fig. 17 does not achieve the preferable dispersibility as the plane Y ═ Y [1] in fig. 20 described later.

As considered in the same manner, in reference example 2, as shown in fig. 17, no dots are formed at nine pixels in the plane Y ═ Y [2 ]. Therefore, in reference example 2, in the case where the surface SF of the target object Obj includes the plane Y ═ Y [2], the recording apparatus 5 cannot arrange points within the plane Y ═ Y [2] at all.

As can be seen from the same consideration, in reference example 2, as shown in fig. 17, the dot dispersibility in the plane Y ═ Y [3] can be improved as compared with the plane Y ═ Y [3] in fig. 14, but the dot dispersibility in the plane Y ═ Y [3] is lower as compared with the plane Y ═ Y [3] in fig. 20 described later. Therefore, in reference example 2, when the surface SF of the target object Obj includes the plane Y-Y [3], the recording device 5 cannot sufficiently disperse and arrange the dots in the plane Y-Y [3 ].

As can be seen from the same consideration, in reference example 2, as illustrated in fig. 18, the dot dispersibility in the plane X ═ X [1] can be improved as compared with the plane X ═ X [1] in fig. 15, but the dot dispersibility in the plane X ═ X [1] is lower as compared with the plane X ═ X [1] in fig. 21 described later. Therefore, in reference example 2, when the surface SF of the target object Obj includes the plane X ═ X [1], the recording device 5 cannot sufficiently arrange dots in a dispersed manner in the plane X ═ X [1 ].

As can be seen from the same consideration, in reference example 2, as illustrated in fig. 18, the dot dispersibility in the plane X ═ X [2] can be improved as compared with the plane X ═ X [2] in fig. 15, but the dot dispersibility in the plane X ═ X [2] is lower as compared with the plane X ═ X [2] in fig. 21 described later. Therefore, in reference example 2, when the surface SF of the target object Obj includes the plane X ═ X [2], the recording device 5 cannot sufficiently arrange dots in a dispersed manner in the plane X ═ X [2 ].

In reference example 2, as illustrated in fig. 18, the dot dispersibility can be improved in the plane X ═ X [3 ]. Therefore, in reference example 2, when the surface SF of the target object Obj includes the plane X ═ X [3], the recording device 5 can arrange the dots in a dispersed manner on the plane X ═ X [3 ]. However, in reference example 2, the dispersibility of the points is low in the planes other than the plane X ═ X [3] and the plane Z ═ Z [1], so that the possibility that the points are arranged with sufficient dispersion on the surface SF of the object Obj is low.

As described above, in reference example 2, the two-dimensional dither mask DZ-B1 extending in the direction parallel to the XY plane is applied to the plane Z ═ Z [1], the two-dimensional dither mask DZ-B2 having the thresholds obtained by sliding the plurality of thresholds Dd of the dither mask DZ-B1 is applied to the plane Z ═ Z [2], and the two-dimensional dither mask DZ-B3 having the thresholds obtained by sliding the plurality of thresholds Dd of the dither mask DZ-B1 is applied to the plane Z ═ Z [3], thereby generating display data. Therefore, in reference example 2, the recording device 5 may not be able to sufficiently arrange dots in a dispersed manner with respect to the surface SF. Therefore, in reference example 2, a granular feeling is generated in the image G formed on the surface SF of the target object Obj, and the image quality of the image G is degraded.

Fig. 19 to 21 are explanatory diagrams for explaining the dither mask DZ according to the present embodiment. As described above, in the present embodiment, the three-dimensional dither mask DZ is applied, unlike the reference examples 1 and 2 to which the two-dimensional dither mask is applied.

As illustrated in fig. 19 to 21, the dither mask DZ has a plurality of thresholds Dd arranged so as to have a predetermined spatial frequency characteristic in any one of a plane Z ═ Z [1], a plane Z ═ Z [2], a plane Z ═ Z [3], a plane Y ═ Y [1], a plane Y ═ Y [2], a plane Y ═ Y [3], a plane X ═ X [1], a plane X ═ X [2], and a plane X ═ X [3 ]. That is, the dither mask DZ can be arranged so that a pixel Px-1 can be formed at a plurality of points in each of the planes Z [1], Z [2], Z [3], Y [1], Y [2], Y [3], X [1], X [2], and X [3] to have a predetermined spatial frequency characteristic in a spatial frequency domain. Therefore, in the present embodiment, when the surface SF of the target object Obj includes each of the planes Z ═ Z [1], Z ═ Z [2], Z ═ Z [3], Y ═ Y [1], Y ═ Y [2], Y ═ Y [3], X ═ X [1], X ═ X [2], and X ═ X [3], the recording device 5 can arrange dots in a dispersed manner in the plane. Therefore, in the present embodiment, compared to the above-described reference examples 1 and 2, the granular sensation in the image G formed on the surface SF of the target object Obj can be reduced, and the degradation of the image quality of the image G can be suppressed.

6. Summary of the embodiments

As described above, the terminal device 1 according to the present embodiment includes: an image data acquisition unit 21 that acquires image data GD that indicates a gradation value Gg of an image Gf that should be displayed by each of M pixels Px in a three-dimensional image formation space SP when the image Gf is displayed in the image formation space SP; a display data generation unit 23 that generates display data Img by quantizing a gradation value Gg indicated by image data GD using a three-dimensional dither mask DZ having M threshold values Dd corresponding to M pixels Px in the image forming space SP, when image forming space SP is cut off by plane PL1, the plurality of thresholds Dd in plane PL1 have a predetermined spatial frequency characteristic in the spatial frequency domain in which the high frequency component higher than intermediate frequency fmid is larger than the low frequency component lower than intermediate frequency fmid, and when the image forming space SP is cut off by the plane PL2 extending in a direction different from the plane PL1, the plurality of thresholds Dd in the plane PL2 have a predetermined spatial frequency characteristic in the spatial frequency domain in which high frequency components higher than the intermediate frequency fmid are more abundant than low frequency components lower than the intermediate frequency fmid.

That is, in the terminal device 1 according to the present embodiment, the display data generation unit 23 quantizes the gradation value Gg indicated by the image data GD by using the dither mask DZ having a predetermined spatial frequency characteristic in the plane PL1 and a predetermined spatial frequency characteristic in the plane PL2 extending in a direction different from the plane PL1, thereby generating the display data Img. Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as the plane PL1 and the plane PL2, it is possible to suppress the occurrence of a granular sensation in the image G. That is, according to the present embodiment, when forming the image G having the three-dimensional shape such as the plane PL1 and the plane PL2, it is possible to suppress the deterioration in the image quality of the image G due to the granular sensation generated in the image G.

In the present embodiment, the terminal device 1 is an example of an "image processing apparatus", the image data acquisition unit 21 is an example of an "acquisition unit", the display data generation unit 23 is an example of a "generation unit", the image formation space SP is an example of a "first space", the image data GD is an example of "first image data", the dither mask DZ is an example of a "first dither mask", the display data Img is an example of "first display data", the intermediate frequency fmid is an example of a "predetermined frequency", the plane PL1 is an example of a "first plane", and the plane PL2 is an example of a "second plane".

In the terminal apparatus 1 according to the present embodiment, the dither mask DZ may be characterized in that when the image forming space SP is cut by the plane PL3 parallel to the plane PL1, the plurality of thresholds Dd in the plane PL3 have a predetermined spatial frequency characteristic in which the high frequency component higher than the intermediate frequency fmid is larger than the low frequency component lower than the intermediate frequency fmid in the spatial frequency domain, and when the image forming space SP is cut by the plane PL4 parallel to the plane PL2, the plurality of thresholds Dd in the plane PL4 have a predetermined spatial frequency characteristic in which the high frequency component higher than the intermediate frequency fmid is larger than the low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as the plane PL1, the plane PL2, the plane PL3, and the plane PL4, it is possible to suppress the generation of a granular sensation in the image G.

In the present embodiment, the plane PL3 is an example of a "third plane", and the plane PL4 is an example of a "fourth plane".

In the terminal apparatus 1 according to the present embodiment, the dither mask DZ may be characterized in that when the image forming space SP is cut by an arbitrary plane parallel to the plane PL1, the plurality of thresholds Dd in the plane have a predetermined spatial frequency characteristic in which the high frequency component higher than the intermediate frequency fmid is larger than the low frequency component lower than the intermediate frequency fmid in the spatial frequency domain, and when the image forming space SP is cut by an arbitrary plane parallel to the plane PL2, the plurality of thresholds Dd in the plane have a predetermined spatial frequency characteristic in which the high frequency component higher than the intermediate frequency fmid is larger than the low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as a plane parallel to the plane PL1 and a plane parallel to the plane PL2, it is possible to suppress the occurrence of a granular sensation in the image G.

In the terminal apparatus 1 according to the present embodiment, the dither mask DZ may be characterized such that, when the image forming space SP is cut off by the plane PL5 extending in a direction different from the planes PL1 and PL2, the plurality of thresholds Dd in the plane PL5 have a predetermined spatial frequency characteristic in which the high frequency component higher than the intermediate frequency fmid is larger than the low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when forming the image G having a three-dimensional shape such as the plane PL1, the plane PL2, and the plane PL5, it is possible to suppress the occurrence of granular sensation in the image G.

In the present embodiment, the plane PL5 is an example of a "fifth plane".

In the terminal apparatus 1 according to the present embodiment, the dither mask DZ may be characterized in that, when the image forming space SP is cut off by a plane PL6 parallel to the plane PL5, the plurality of thresholds Dd on the plane PL6 have a predetermined spatial frequency characteristic in which a high frequency component higher than the intermediate frequency fmid is larger than a low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as the plane PL1, the plane PL2, the plane PL5, and the plane PL6, it is possible to suppress the generation of a granular sensation in the image G.

In the present embodiment, the plane PL6 is an example of a "sixth plane".

In the terminal device 1 according to the present embodiment, the dither mask DZ may be characterized in that, when the image forming space SP is cut off by an arbitrary plane parallel to the plane PL5, the plurality of thresholds Dd in the plane have a predetermined spatial frequency characteristic in which a high frequency component higher than the intermediate frequency fmid is larger than a low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when forming the image G having such a three-dimensional shape as to have a plane parallel to the plane PL1, a plane parallel to the plane PL2, and a plane parallel to the plane PL5, it is possible to suppress the occurrence of granular sensation in the image G.

In addition, in the terminal device 1 according to the present embodiment, the M pixels Px in the image forming space SP may be characterized by including: mx pixels Px arranged to extend in the + X direction; my pixels Px arranged to extend in a + Y direction orthogonal to the + X direction; mz pixels Px arranged to extend in the + Z direction orthogonal to the + X direction and the + Y direction, a plane PL1 is a plane having a normal vector extending in a direction perpendicular to the + X direction, and a plane PL2 is a plane having a normal vector extending in a direction perpendicular to the + Y direction.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as a plane parallel to the + X direction and a plane parallel to the + Y direction, it is possible to suppress the generation of a granular sensation in the image G.

In the present embodiment, the + X direction is an example of a "first direction", the + Y direction is an example of a "second direction", and the + Z direction is an example of a "third direction".

In the terminal device 1 according to the present embodiment, the plane PL1 may be a plane having a normal vector extending in a direction perpendicular to the + Y direction, and the plane PL2 may be a plane having a normal vector extending in a direction perpendicular to the + Z direction.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as a plane parallel to the XY plane and a plane parallel to the YZ plane, it is possible to suppress the generation of a granular sensation in the image G.

In the terminal apparatus 1 according to the present embodiment, the plurality of thresholds Dd in the plane PL1 may have a frequency characteristic different from a white noise characteristic in the spatial frequency domain, and the plurality of thresholds Dd in the plane PL2 may have a frequency characteristic different from a white noise characteristic in the spatial frequency domain.

Specifically, in the terminal apparatus 1 according to the present embodiment, the plurality of thresholds Dd in the plane PL1 may have blue noise characteristics in the spatial frequency domain, and the plurality of thresholds Dd in the plane PL2 may have blue noise characteristics in the spatial frequency domain.

Therefore, according to the present embodiment, when forming the three-dimensional image G, it is possible to suppress the generation of granular sensation in the image G.

In the terminal device 1 according to the present embodiment, the display data generating unit 23 may supply the display data Img to the recording device 5 including the head unit 7 that ejects the ink based on the display data Img.

The recording device 5 according to the present embodiment is a recording device that forms an image G of a three-dimensional object Obj and includes: a head unit 7 that ejects ink; a recording control unit 6 that controls ejection of ink from the head unit 7 so as to form an image G for the target object Obj through a plurality of dots formed by the ink ejected from the head unit 7, the recording control unit 6 controlling ejection of ink from the head unit 7, such that, in the case where the target object Obj has a first face, the distribution of the plurality of points on the first face has, in the spatial frequency domain, a predetermined spatial frequency characteristic in which a high frequency component higher than the intermediate frequency fmid is larger than a low frequency component lower than the intermediate frequency fmid, and such that in the case where the target object Obj has a second face extending in a different direction from the first face, the distribution of the plurality of points on the second plane has a predetermined spatial frequency characteristic in which a high frequency component higher than the intermediate frequency fmid is larger than a low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when the image G is formed for the object Obj having a three-dimensional shape such as having the first surface and the second surface, it is possible to suppress the generation of the granular sensation in the image G. That is, according to the present embodiment, when forming the three-dimensional image G having the first surface and the second surface, it is possible to suppress the deterioration of the image quality of the image G due to the granular feeling generated in the image G.

In the present embodiment, the recording control unit 6 is an example of a "control unit", and the ink is an example of a "liquid".

In the recording device 5 according to the present embodiment, the distribution of the plurality of dots on the first surface may have a frequency characteristic different from the white noise characteristic in the spatial frequency domain, and the distribution of the plurality of dots on the second surface may have a frequency characteristic different from the white noise characteristic in the spatial frequency domain.

Specifically, in the recording apparatus 5 according to the present embodiment, the distribution of the plurality of dots on the first surface may have a blue noise characteristic in the spatial frequency domain, and the distribution of the plurality of dots on the second surface may have a blue noise characteristic in the spatial frequency domain.

Therefore, according to the present embodiment, when the image G is formed for the object Obj having a three-dimensional shape such as having the first surface and the second surface, it is possible to suppress the generation of the granular sensation in the image G.

Further, an image processing method according to the present embodiment includes: a step of acquiring image data GD that indicates a gradation value Gg of an image Gf that should be displayed by each of M pixels Px in a three-dimensional image forming space SP when the image Gf is displayed in the image forming space SP; and a step of quantizing the gradation value Gg indicated by the image data GD by using a three-dimensional dither mask DZ having M threshold values Dd corresponding to the M pixels Px in the image forming space SP, to generate the display data Img, the dither mask DZ being such that, when the image forming space SP is cut off by using the plane PL1, the plurality of threshold values Dd in the plane PL1 have a predetermined spatial frequency characteristic in which a high frequency component higher than the intermediate frequency fmid is larger than a low frequency component lower than the intermediate frequency fmid in a spatial frequency domain, and when the image forming space SP is cut off by using the plane PL2 extending in a direction different from that of the plane PL1, the plurality of threshold values Dd in the plane PL2 have a predetermined spatial frequency characteristic in which a high frequency component higher than the intermediate frequency fmid is larger than a low frequency component lower than the intermediate frequency fmid in the spatial frequency domain.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as the plane PL1 and the plane PL2, it is possible to suppress the occurrence of a granular sensation in the image G.

The control program Pgt according to the present embodiment is characterized by causing one or more CPUs provided in the terminal device 1 to function as: an image data acquisition unit 21 that acquires image data GD that indicates a gradation value Gg of an image Gf that should be displayed by each of M pixels Px in a three-dimensional image formation space SP when the image Gf is displayed in the image formation space SP; a display data generation unit 23 for generating display data Img by quantizing a gradation value Gg indicated by image data GD using a three-dimensional dither mask DZ having M threshold values Dd corresponding to M pixels Px in the image forming space SP, when image forming space SP is cut off by plane PL1, the plurality of thresholds Dd in plane PL1 have a predetermined spatial frequency characteristic in the spatial frequency domain in which the high frequency component higher than intermediate frequency fmid is larger than the low frequency component lower than intermediate frequency fmid, and when the image forming space SP is cut off by the plane PL2 extending in a direction different from the plane PL1, the plurality of thresholds Dd in the plane PL2 have a predetermined spatial frequency characteristic in the spatial frequency domain in which high frequency components higher than the intermediate frequency fmid are more abundant than low frequency components lower than the intermediate frequency fmid.

Therefore, according to the present embodiment, when forming an image G having a three-dimensional shape such as the plane PL1 and the plane PL2, it is possible to suppress the occurrence of a granular sensation in the image G.

B. Modification example

The above-described embodiments can be variously modified. Hereinafter, specific modifications will be exemplified. Two or more modes arbitrarily selected from the following examples can be appropriately combined within a range not contradictory to each other.

Modification example 1

Although the above-described embodiment has exemplified the case where the quantization process is performed using the dither mask DZ having the same size as the image forming space SP, the present invention is not limited to this embodiment. For example, the quantization process may be performed using a plurality of dither masks having a size smaller than the image forming space SP.

Fig. 22 is an explanatory diagram for explaining the image forming space SP in the present modification.

As illustrated in fig. 22, in the present modification, the image forming space SP includes a plurality of unit spaces SS. In FIG. 22, for example, a case is illustrated where image forming space SP includes unit space SS-0, unit space SS-X adjacent in the + X direction when viewed from unit space SS-0, unit space SS-Y adjacent in the + Y direction when viewed from unit space SS-0, and unit space SS-Z adjacent in the + Z direction when viewed from unit space SS-0. In the present modification, a total of Mx × My × Mz ═ M pixels Px including Mx pixels Px extending in the X axis direction, My pixels Px extending in the Y axis direction, and Mz pixels Px extending in the Z axis direction are arranged in each unit space SS.

In the present modification, a plurality of dither masks are provided in one-to-one correspondence with a plurality of unit spaces SS included in the image forming space SP. Specifically, in the present modification, a case is assumed in which, as illustrated in fig. 22, a dither mask DZ corresponding to the unit space SS-0, a dither mask DZ-X corresponding to the unit space SS-X, a dither mask DZ-Y corresponding to the unit space SS-Y, and a dither mask DZ-Z corresponding to the unit space SS-X are provided. Each dither mask has M threshold values Dd corresponding one-to-one to the M pixels Px included in the unit space SS corresponding to the dither mask.

In addition, in the present modification, a case is assumed where the image data GD includes unit image data GS-0 indicating a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-0 in order to form the image Gf on the surface SF of the target object Obj, unit image data GS-X indicating a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-X in order to form the image Gf on the surface SF of the target object Obj, unit image data GS-Y indicating a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-Y in order to form the image Gf on the surface SF of the target object Obj, and unit image data GS-Z indicating a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-Y in order to form the image Gf on the surface SF of the target object Obj, the unit image data GS-Z represents a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-Z in order to form the image Gf on the surface SF of the target object Obj.

Further, in the present modification, it is assumed that the display data Img includes unit display data Img-0 representing a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-0 in order to form the image G on the surface SF of the target object Obj, unit display data Img-Y representing a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-X in order to form the image G on the surface SF of the target object Obj, and unit display data Img-Z representing a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-Y in order to form the image G on the surface SF of the target object Obj, the unit display data Img-Z indicates a gradation value that should be displayed by each of the M pixels Px included in the unit space SS-Z in order to form the image G on the surface SF of the target object Obj.

Fig. 23 is a functional block diagram showing an example of the configuration of a terminal device 1A provided in the recording system according to the present modification. The recording system according to the present modification is configured in the same manner as the recording system Sys according to the embodiment, except that the terminal device 1A is provided instead of the terminal device 1.

As illustrated in fig. 23, the terminal device 1A is different from the terminal device 1 according to the embodiment in that the terminal control unit 2 is provided instead of the terminal control unit 2A, and the storage unit 3 is provided instead of the storage unit 3.

The terminal control unit 2A is different from the terminal control unit 2 according to the embodiment in that the dither mask generating unit 22A is provided instead of the dither mask generating unit 22, and the display data generating unit 23A is provided instead of the display data generating unit 23.

The storage unit 3A is different from the storage unit 3 according to the embodiment in that the dither mask DZ-X, the dither mask DZ-Y, and the dither mask DZ-Z are stored in addition to the dither mask DZ, and the control program Pgt-a is stored instead of the control program Pgt. The terminal control unit 2A is capable of functioning as the image data acquisition unit 21, the dither mask generation unit 22A, and the display data generation unit 23A by operating in accordance with the control program Pgt-a by executing the control program Pgt-a stored in the storage unit 3A by one or more CPUs provided in the terminal control unit 2A.

The dither mask generator 22A generates a dither mask DZ-X, a dither mask DZ-Y, and a dither mask DZ-Z in addition to the dither mask DZ.

The display data generation unit 23A generates unit display data Img-0 by applying quantization processing to the unit image data GS-0 using the dither mask DZ, generates unit display data Img-X by applying quantization processing to the unit image data GS-X using the dither mask DZ-X, generates unit display data Img-Y by applying quantization processing to the unit image data GS-Y using the dither mask DZ-Y, and generates unit display data Img-Z by applying quantization processing to the unit image data GS-Z using the dither mask DZ-Z.

Fig. 24 is an explanatory diagram for explaining the dither mask DZ-X.

As illustrated in fig. 24, the dither mask generator 22A according to the present modification generates the dither mask DZ-X based on the dither mask DZ.

Specifically, first, the dither mask generating unit 22A generates the dither mask DZ by the dither mask generating process described above.

Next, the dither mask generator 22A divides the unit space SS-0 corresponding to the dither mask DZ into the partial space SB-X1 and the partial space SB-X2. Here, the partial space SB-X1 is a space located on the-X side of the division plane LX in the unit space SS-0 when the unit space SS-0 is divided by the division plane LX parallel to the YZ plane. The partial space SB-X2 is a space located on the + X side of the dividing plane LX in the unit space SS-0.

Next, the dither mask generator 22A slides the partial dither mask DZ-X1, which is composed of the plurality of thresholds Dd included in the dither mask DZ and corresponding to the plurality of pixels Px included in the partial space SB-X1, in the + X direction, and slides the partial dither mask DZ-X2, which is composed of the plurality of thresholds Dd included in the dither mask DZ and corresponding to the plurality of pixels Px included in the partial space SB-X2, in the-X direction.

Then, the dither mask generating section 22A generates the dither mask DZ-X by connecting the partial dither mask DZ-X1 at the + X side of the partial dither mask DZ-X2.

Fig. 25 is an explanatory diagram for explaining an example of the relationship between a plurality of thresholds Dd corresponding to a plurality of pixels Px located on the plane Z ═ Z [1] among a plurality of thresholds Dd provided to the dither mask DZ, and a plurality of thresholds Dd corresponding to a plurality of pixels Px located on the plane Z ═ Z [1] among a plurality of thresholds Dd provided to the dither mask DZ-X.

In the example shown in fig. 25, similarly to the examples shown in fig. 10 to 12, a case is assumed where "Mx" 8 "," My "8", "Mz" 8 "," M "8" 512 "is present in the image forming space SP, and there are 512 pixels Px in the image forming space SP. In the example shown in fig. 25, similarly to the examples shown in fig. 10 to 12, a case is assumed where the gradation value Gg-min is "0", the gradation value Gg-max is "255", the threshold value Dd [1] is "1", and the threshold value Dd [ M ] is "255".

As illustrated in FIG. 25, the dither mask DZ is comprised of a partial dither mask DZ-X1, and a partial dither mask DZ-X2 disposed at the + X side of the partial dither mask DZ-X1.

In contrast, the dither mask DZ-X is comprised of a partial dither mask DZ-X2, and a partial dither mask DZ-X1 disposed at the + X side of the partial dither mask DZ-X2. That is, the dither mask DZ-X is obtained by replacing the relative positional relationship in the X axis direction of the partial dither mask DZ-X1 and the partial dither mask DZ-X2 included in the dither mask DZ.

Fig. 26 is an explanatory diagram for explaining the dither mask DZ-Y.

As illustrated in fig. 26, the dither mask generating unit 22A according to the present modification generates the dither mask DZ-Y based on the dither mask DZ.

Specifically, first, the dither mask generating unit 22A generates the dither mask DZ by the dither mask generating process described above.

Next, the dither mask generator 22A divides the unit space SS-0 corresponding to the dither mask DZ into the partial space SB-Y1 and the partial space SB-Y2. Here, the partial space SB-Y1 is a space located on the-Y side of the division plane LY in the unit space SS-0 when the unit space SS-0 is divided by the division plane LY parallel to the XZ plane. The partial space SB-Y2 is a space located on the + Y side of the division plane LY in the unit space SS-0.

Next, the dither mask generator 22A slides the partial dither mask DZ-Y1, which is composed of the plurality of thresholds Dd included in the dither mask DZ and corresponding to the plurality of pixels Px included in the partial space SB-Y1, in the + Y direction, and slides the partial dither mask DZ-Y2, which is composed of the plurality of thresholds Dd included in the dither mask DZ and corresponding to the plurality of pixels Px included in the partial space SB-Y2, in the-Y direction.

Then, the dither mask generating section 22A generates the dither mask DZ-Y by connecting the partial dither mask DZ-Y1 at the + Y side of the partial dither mask DZ-Y2.

Fig. 27 is an explanatory diagram for explaining the dither mask DZ-Z.

As illustrated in fig. 27, the dither mask generating unit 22A according to the present modification generates the dither mask DZ-Z based on the dither mask DZ.

Specifically, first, the dither mask generating unit 22A generates the dither mask DZ by the dither mask generating process described above.

Next, the dither mask generator 22A divides the unit space SS-0 corresponding to the dither mask DZ into the partial space SB-Z1 and the partial space SB-Z2. Here, the partial space SB-Z1 is a space located on the-Z side of the division plane LZ in the unit space SS-0 when the unit space SS-0 is divided by the division plane LZ parallel to the XY plane. The partial space SB-Z2 is a space located on the + Z side of the division plane LZ in the unit space SS-0.

Next, the dither mask generator 22A slides the partial dither mask DZ-Z1, which is composed of the plurality of thresholds Dd included in the dither mask DZ and corresponding to the plurality of pixels Px included in the partial space SB-Z1, in the + Z direction, and slides the partial dither mask DZ-Z2, which is composed of the plurality of thresholds Dd included in the dither mask DZ and corresponding to the plurality of pixels Px included in the partial space SB-Z2, in the-Z direction.

Then, the dither mask generating section 22A generates the dither mask DZ-Z by connecting the partial dither mask DZ-Z1 at the + Z side of the partial dither mask DZ-Z2.

As described above, according to the present modification, the same dither mask DZ is not uniformly applied to a plurality of unit spaces SS, but a plurality of types of dither masks are applied thereto. Therefore, according to the present modification, when the image G is formed over a plurality of unit spaces SS, it is possible to prevent the same pattern from being repeatedly formed in a cycle of the unit spaces SS.

Further, according to the present modification, the dither mask generating unit 22A generates the dither masks DZ-X, DZ-Y, and DZ-Z based on the dither mask DZ without performing the dither mask generating process. Therefore, according to the present modification, the processing load associated with the generation of the dither masks DZ-X, DZ-Y, and DZ-Z can be reduced as compared with the generation of the dither masks DZ-X, DZ-Y, and DZ-Z by the dither mask generation processing.

As described above, the terminal device 1A according to the present modification is characterized by including: an image data obtaining unit 21 that obtains unit image data GS-0 and unit image data GS-X, the unit image data GS-0 indicating a gradation value Gg of an image Gf to be displayed by each of M pixels Px in a unit space SS-0 when the image Gf is displayed in the three-dimensional unit space SS-0, the unit image data GS-X indicating a gradation value Gg of the image Gf to be displayed by each of M pixels Px in the unit space SS-X when the image Gf is displayed in the three-dimensional unit space SS-X adjacent to the unit space SS-0; a display data generation unit 23A for generating unit display data Img-0 by quantizing a gradation value represented by unit image data GS-0 using a three-dimensional dither mask DZ having M thresholds Dd corresponding to M pixels Px in a unit space SS-0, and generating unit display data Img-X by quantizing a gradation value represented by unit image data GS-X using a three-dimensional dither mask DZ-X having M thresholds Dd corresponding to M pixels Px in a unit space SS-X, the dither mask DZ being such that, when the unit space SS-0 is cut off by using a plane PL1, a plurality of thresholds Dd in a plane PL1 have a predetermined spatial frequency characteristic in which a high frequency component higher than a median frequency fmid is larger than a low frequency component lower than the median frequency fmid in a spatial frequency domain, and when the unit space SS-0 is cut off by a plane PL2 extending in a direction different from the plane PL1, the plurality of thresholds Dd in the plane PL2 have a predetermined spatial frequency characteristic in which high frequency components higher than the intermediate frequency fmid are more abundant than low frequency components lower than the intermediate frequency fmid within the spatial frequency domain, the unit space SS-0 is divided into a partial space SB-X1 and a partial space SB-X2, and the dither mask DZ-X has a plurality of thresholds Dd arranged so as to exchange the relative positional relationship of the plurality of thresholds Dd existing in the partial space SB-X1 and the plurality of thresholds Dd existing in the partial space SB-X2, of the M thresholds Dd that the dither mask DZ has corresponding to the M pixels Px within the unit space SS-0.

Therefore, according to this modification, when forming an image G having a three-dimensional shape such as a plane PL1 and a plane PL2, which is an image G existing over the unit spaces SS-0 and SS-X, it is possible to suppress the occurrence of granular sensation in the image G. That is, according to the present embodiment, when forming an image G having a three-dimensional shape such as a plane PL1 and a plane PL2, which is an image G existing across the unit spaces SS-0 and SS-X, it is possible to suppress a decrease in the image quality of the image G due to the granular sensation generated in the image G.

In the present embodiment, the terminal device 1A is an example of an "image processing apparatus", the image data acquisition unit 21 is an example of an "acquisition unit", the display data generation unit 23A is an example of a "generation unit", the unit space SS-0 is an example of a "first space", the unit space SS-X is an example of a "second space", the unit image data GS-0 is an example of a "first image data", the unit image data GS-X is an example of a "second image data", the dither mask DZ is an example of a "first dither mask", the dither mask DZ-X is an example of a "second dither mask", the unit display data Img-0 is an example of a "first display data", and the unit display data Img-X is an example of a "second display data", plane PL1 is an example of a "first plane", plane PL2 is an example of a "second plane", intermediate frequency fmid is an example of a "predetermined frequency", partial space SB-X1 is an example of a "first partial space", and partial space SB-X2 is an example of a "second partial space".

In the terminal device 1A according to the present modification, the plurality of pixels Px in the image forming space SP, including the unit space SS-0 and the unit space SS-X, may be characterized by including: the display device includes two or more pixels Px arranged to extend in the + X direction, two or more pixels Px arranged to extend in the + Y direction orthogonal to the + X direction, and two or more pixels Px arranged to extend in the + Z direction orthogonal to the + X direction and the + Y direction, wherein the unit space SS-X is located in the + X direction when viewed from the unit space SS-0.

In the terminal device 1A according to the present modification, the image data obtaining unit 21 may obtain unit image data GS-Y indicating a gradation value Gg of an image Gf to be displayed by each of M pixels Px in the unit space SS-Y when the image Gf is displayed in a three-dimensional unit space SS-Y adjacent to the unit space SS-0, the display data generating unit 23A may generate the unit display data Img-Y by quantizing the gradation value indicated by the unit image data GS-Y using a three-dimensional dither mask DZ-Y having M thresholds Dd corresponding to the M pixels Px in the unit space SS-Y, the unit space SS-0 may be divided into a partial space SB-Y1 and a partial space SB-Y2, the dither mask DZ-Y has a plurality of thresholds Dd configured to reverse the relative positional relationship of the plurality of thresholds Dd present in the partial space SB-Y1 and the plurality of thresholds Dd present in the partial space SB-Y2, of the M thresholds Dd the dither mask DZ has corresponding to the M pixels Px within the unit space SS-0, the direction in which the unit space SS-X is located when viewed from the unit space SS-0 is different from the direction in which the unit space SS-Y is located when viewed from the unit space SS-0, and the direction in which the partial space SB-X2 is located when viewed from the partial space SB-X1 is different from the direction in which the partial space SB-Y2 is located when viewed from the partial space SB-Y1.

Therefore, according to this modification, when forming an image G that extends over the unit space SS-0, the unit space SS-X, and the unit space SS-Y and has a three-dimensional shape such as the plane PL1 and the plane PL2, it is possible to suppress the occurrence of a granular sensation in the image G.

In the present embodiment, the unit space SS-Y is an example of "third space", the unit image data GS-Y is an example of "third image data", the dither mask DZ-Y is an example of "third dither mask", the unit display data Img-Y is an example of "third display data", the partial space SB-Y1 is an example of "third partial space", and the partial space SB-Y2 is an example of "fourth partial space".

Modification 2

In the above-described embodiment and modification 1, the image Gf represented by the image data GD and the image G represented by the display data Img may include a plurality of colors. In this case, a plurality of dither masks may be provided so as to correspond one-to-one to a plurality of colors of the image Gf represented by the image data GD and the image G represented by the display data Img.

Fig. 28 is a functional block diagram showing an example of the configuration of the terminal device 1B provided in the recording system according to the present modification. The recording system according to the present modification is configured in the same manner as the recording system Sys according to the embodiment, except that the terminal device 1B is provided instead of the terminal device 1.

As illustrated in fig. 28, the terminal device 1B is different from the terminal device 1 according to the embodiment in that the terminal control unit 2 is provided instead of the terminal control unit 2, and the storage unit 3B is provided instead of the storage unit 3.

The terminal control unit 2B is different from the terminal control unit 2 according to the embodiment in that the dither mask generating unit 22B is provided instead of the dither mask generating unit 22, and the display data generating unit 23B is provided instead of the display data generating unit 23.

In the present modification, it is assumed that the image Gf represented by the image data GD and the image G represented by the display data Img are represented by four colors, cyan, magenta, yellow, and black.

Further, in the present modification, it is assumed that the image data GD includes image data GD-Cy representing a gradation value of cyan color to be displayed by each of the M pixels Px included in the image forming space SP in order to form the image Gf on the surface SF of the target object Obj, image data GD-Mg representing a gradation value of magenta color to be displayed by each of the M pixels Px included in the image forming space SP in order to form the image Gf on the surface SF of the target object Obj, image data GD-Yl representing a gradation value of yellow color to be displayed by each of the M pixels Px included in the image forming space SP in order to form the image Gf on the surface SF of the target object Obj, and image data GD-Bk representing a gradation value of cyan color to be displayed by each of the M pixels Px included in the image forming space SP in order to form the image Gf on the surface SF of the target object Obj, the image data GD-Bk represents the gradation value of black that should be displayed by each of the M pixels Px included in the image forming space SP in order to form the image Gf on the surface SF of the target object Obj.

Further, in the present modification, a case is assumed where the display data Img includes display data Img-Cy representing a gradation value of cyan color that should be displayed by each of the M pixels Px included in the image forming space SP in order to form the image G on the surface SF of the target object Obj, display data Img-Yl representing a gradation value of magenta color that should be displayed by each of the M pixels Px included in the image forming space SP in order to form the image G on the surface SF of the target object Obj, and display data Img-Yl representing a gradation value of yellow color that should be displayed by each of the M pixels Px included in the image forming space SP in order to form the image G on the surface SF of the target object Obj, the display data Img-Bk represents the gradation value of black that should be displayed by each of the M pixels Px included in the image forming space SP in order to form the image G on the surface SF of the target object Obj.

The storage unit 3B stores image data GD including image data GD-Cy, image data GD-Mg, image data GD-Yl, and image data GD-Bk, a dither mask DZ-Cy, a dither mask DZ-Mg, a dither mask DZ-Yl, and a dither mask DZ-Bk, and a control program Pgt-B.

Here, the dither mask DZ-Cy is a dither mask used when quantization processing is applied to the image data GD-Cy. The dither mask DZ-Cy has, for example, M threshold values Dd corresponding one-to-one to M pixels Px in the image forming space SP. The dither mask DZ-Cy has predetermined spatial frequency characteristics at least in the plane PL1 and the plane PL2, and may have predetermined spatial frequency characteristics in a part or all of the planes PL3 to PL 6.

The dither mask DZ-Mg is a dither mask used when quantization processing is applied to the image data GD-Mg. The dither mask DZ-Mg has, for example, M threshold values Dd in one-to-one correspondence with M pixels Px in the image forming space SP. The dither mask DZ — Mg has predetermined spatial frequency characteristics at least in the plane PL1 and the plane PL2, and may have predetermined spatial frequency characteristics in a part or all of the planes PL3 to PL 6.

The dither mask DZ-Yl is a dither mask used when quantization processing is applied to the image data GD-Yl. The dither mask DZ-Yl has, for example, M threshold values Dd in one-to-one correspondence with M pixels Px in the image forming space SP. The dither mask DZ-Yl has predetermined spatial frequency characteristics at least in the plane PL1 and the plane PL2, and may also have predetermined spatial frequency characteristics in a part or all of the planes PL3 to PL 6.

The dither mask DZ-Bk is a dither mask used when quantization processing is applied to the image data GD-Bk. The dither mask DZ-Bk has, for example, M threshold values Dd in one-to-one correspondence with M pixels Px in the image forming space SP. The dither mask DZ-Bk may have predetermined spatial frequency characteristics at least in the plane PL1 and the plane PL2, and may have predetermined spatial frequency characteristics in a part or all of the planes PL3 to PL 6.

The dither masks DZ-Cy, DZ-Mg, DZ-Yl, and DZ-Bk may have the same threshold value Dd or may have different threshold values Dd.

The terminal control unit 2B is capable of functioning as the image data acquisition unit 21, the dither mask generation unit 22B, and the display data generation unit 23B by one or more CPUs provided in the terminal control unit 2B executing the control program Pgt-B stored in the storage unit 3B and operating in accordance with the control program Pgt-B.

The dither mask generating unit 22B generates the dither masks DZ to Cy, DZ to Mg, DZ to Yl, and DZ to Bk by the dither mask generating process described above.

The display data generation unit 23B generates display data Img-Cy by applying quantization processing to the image data GD-Cy using the dither mask DZ-Cy, generates display data Img-Mg by applying quantization processing to the image data GD-Mg using the dither mask DZ-Mg, generates display data Img-Yl by applying quantization processing to the image data GD-Yl using the dither mask DZ-Yl, and generates display data Img-Bk by applying quantization processing to the image data GD-Bk using the dither mask DZ-Bk.

As described above, according to the present modification, since the plurality of dither masks are provided so as to correspond one-to-one to the plurality of colors of the image Gf represented by the image data GD and the image G represented by the display data Img, it is possible to suppress the generation of a granular sensation in the image G when the image Gf represented by the image data GD and the image G represented by the display data Img are color images.

As described above, the terminal device 1B according to the present modification is characterized by including: an image data acquisition unit 21 that acquires image data GD-Cy indicating a gradation value of a cyan image to be displayed by each of M pixels Px in the image forming space SP when a cyan image is displayed in the three-dimensional image forming space SP, and image data GD-Mg indicating a gradation value of a magenta image to be displayed by each of M pixels Px in the image forming space SP when a magenta image is displayed in the image forming space SP; a display data generation unit 23B for generating display data Img-Cy corresponding to cyan in the display data Img by quantizing a gradation value indicated by the image data GD-Cy using a three-dimensional dither mask DZ-Cy having M thresholds Dd corresponding to M pixels Px in the image forming space SP, and for generating display data Img-Mg corresponding to magenta in the display data Img by quantizing a gradation value indicated by the image data GD-Mg using a three-dimensional dither mask DZ-Mg having M thresholds Dd corresponding to M pixels Px in the image forming space SP, wherein the dither mask DZ-Cy is set such that, when the image forming space SP is cut off by a plane PL1, a plurality of the thresholds Dd in the plane PL1 have a predetermined frequency in a spatial frequency domain in which a high frequency component higher than a middle frequency fMID is compared with a low frequency component lower than the middle frequency fMID, and the plurality of the thresholds Dd in the plane PL1 have a predetermined frequency in the spatial frequency domain Rate characteristics, and when the image forming space SP is cut by the plane PL2 extending in a direction different from the plane PL1, the plurality of thresholds Dd in the plane PL2 have a predetermined spatial frequency characteristic in the spatial frequency domain in which the high frequency component higher than the intermediate frequency fmid is more abundant than the low frequency component lower than the intermediate frequency fmid, the dither mask DZ-Mg is set to, when image forming space SP is cut off by plane PL1, the plurality of thresholds Dd in plane PL1 have a predetermined spatial frequency characteristic in the spatial frequency domain in which the high frequency component higher than intermediate frequency fmid is larger than the low frequency component lower than intermediate frequency fmid, and when the image forming space SP is cut by the plane PL2 extending in a direction different from the plane PL1, the plurality of thresholds Dd in the plane PL2 have a predetermined spatial frequency characteristic in the spatial frequency domain in which high frequency components higher than the intermediate frequency fmid are more abundant than low frequency components lower than the intermediate frequency fmid.

That is, in the image processing apparatus according to the present modification, the first image data includes: first color image data representing a grayscale value of an image of a first color that should be displayed by each of a plurality of pixels within the first space if the image of the first color is exhibited within the first space; second color image data representing gradation values of an image of a second color that should be displayed by each of a plurality of pixels within the first space in a case where the image of the second color is exhibited within the first space, the generation section generating first color display data corresponding to the first color in the first display data by quantizing the gradation values represented by the first color image data using a three-dimensional first color dither mask having a plurality of threshold values corresponding to the plurality of pixels in the first space, and generating second color display data corresponding to the second color in the first display data by quantizing the gradation values represented by the second color image data using a three-dimensional second color dither mask having a plurality of threshold values corresponding to the plurality of pixels in the first space, the first color dither mask and the second color dither mask are different from each other, the first color dither mask is configured such that, when the first space is cut off by the first plane, the plurality of threshold values in the first plane have frequency characteristics in which a high frequency component higher than a predetermined frequency is more in a spatial frequency domain than a low frequency component lower than the predetermined frequency, and when the first space is cut off by the second plane, the plurality of threshold values in the second plane have frequency characteristics in which a high frequency component higher than the predetermined frequency is more in a spatial frequency domain than a low frequency component lower than the predetermined frequency, and the second color dither mask is configured such that, when the first space is cut off by the first plane, the plurality of threshold values in the first plane have a high frequency component higher than the predetermined frequency in a spatial frequency domain than a low frequency component lower than the predetermined frequency And a plurality of threshold values in the second plane have a frequency characteristic in which a high frequency component higher than the predetermined frequency is more frequent than a low frequency component lower than the predetermined frequency in a spatial frequency domain when the first space is cut off by the second plane.

That is, in the terminal apparatus 1 according to the present modification, the display data generation unit 23B generates the display data Img-Mg by quantizing the gradation value indicated by the image data GD-Cy using the dither mask DZ-Cy having a predetermined spatial frequency characteristic in the plane PL1 and a predetermined spatial frequency characteristic in the plane PL2 extending in a direction different from the plane PL1, and by quantizing the gradation value indicated by the image data GD-Mg using the dither mask DZ-Mg having a predetermined spatial frequency characteristic in the plane PL1 and a predetermined spatial frequency characteristic in the plane PL2 extending in a direction different from the plane PL 1. Therefore, according to the present modification, when forming an image G having a three-dimensional shape such as the plane PL1 and the plane PL2 and composed of a plurality of colors, it is possible to suppress the generation of a granular sensation in the image G. That is, according to the present modification, when forming an image G having a three-dimensional shape such as the plane PL1 and the plane PL2 and composed of a plurality of colors, it is possible to suppress a decrease in the image quality of the image G due to the granular sensation generated in the image G.

In the present modification, the terminal device 1B is an example of an "image processing apparatus", the image data acquisition unit 21 is an example of an "acquisition unit", the display data generation unit 23B is an example of a "generation unit", the image formation space SP is an example of a "first space", cyan is an example of a "first color", magenta is an example of a "second color", the image of cyan is an example of an "image of a first color", the image of magenta is an example of an "image of a second color", the image data GD-Cy is an example of "image data of a first color", the image data GD-Mg is an example of "image data of a second color", the dither mask DZ-Cy is an example of a "dither mask of a first color", the dither mask DZ-Mg is an example of a "dither mask of a second color", display data Img-Cy is an example of "first color display data", display data Img-Mg is an example of "second color display data", intermediate frequency fmid is an example of "predetermined frequency", plane PL1 is an example of "first plane", and plane PL2 is an example of "second plane".

In the terminal device 1B according to the present modification, the image data acquisition unit 21 may acquire image data GD-Cy corresponding to cyan in the image data GD and image data GD-Mg corresponding to magenta in the image data GD, and the display data generation unit 23B may generate display data Img-Cy corresponding to cyan in the display data Img by performing quantization processing on the image data GD-Cy using one dither mask DZ, and may generate display data Img-Mg corresponding to magenta in the display data Img by performing quantization processing on the image data GD-Mg using another dither mask DZ, the one dither mask DZ and the other dither mask DZ being different from each other.

Modification 3

In the above-described embodiment and modifications 1 and 2, the value Mx, the value My, and the value Mz may be values satisfying the following expression (10). In the following formula (10), α is a natural number of 2 or more.

Mx ═ My ═ Mz ═ 2 α … … formula (10)

Modification example 4

In the above-described embodiment and modifications 1 to 3, the terminal control unit 2A or the terminal control unit 2B, and the storage unit 3, the storage unit 3A or the storage unit 3B may be mounted on the recording device 5.

In the above-described embodiment and modifications 1 to 3, the terminal device 1A, or the terminal device 1B may include the recording control unit 6, the head unit 7, the ink supply unit 8, and the robot arm 9.

Modification example 5

Although the robot arm 9 changes the position and posture of the head unit 7 in the image forming space SP in the above-described embodiment and modifications 1 to 4, the present invention is not limited to this embodiment. The robot arm 9 may be configured to be able to change the position and posture of the target object Obj in the image forming space SP. In this case, the position and posture of the head unit 7 may be fixed in the image forming space SP.

Modification example 6

Although the terminal control unit 2, the terminal control unit 2A, and the terminal control unit 2B are provided with the dither mask generating unit 22, the dither mask generating unit 22A, or the dither mask generating unit 22B in the above-described embodiment and modifications 1 to 5, the present invention is not limited to this embodiment.

Fig. 29 is a functional block diagram showing an example of the configuration of a terminal device 1C provided in the recording system according to the present modification. The recording system according to the present modification is configured in the same manner as the recording system Sys according to the embodiment, except that the terminal device 1C is provided instead of the terminal device 1.

As illustrated in fig. 29, the terminal device 1C is different from the terminal device 1 according to the embodiment in that the terminal control unit 2 is provided instead of the terminal control unit 2C, and that the storage unit 3 is provided instead of the storage unit 3C. The termination control unit 2C is configured in the same manner as the termination control unit 2 according to the embodiment, except that it does not include the dither mask generating unit 22. The storage unit 3C is configured in the same manner as the storage unit 3 according to the embodiment, except that the control program Pgt-C is stored instead of the control program Pgt. The terminal control unit 2C is capable of functioning as the image data acquisition unit 21 and the display data generation unit 23 by one or more CPUs provided in the terminal control unit 2C executing the control programs Pgt-C stored in the storage unit 3C and operating in accordance with the control programs Pgt-C. In the present modification, the image data acquisition unit 21 may acquire the dither mask DZ from an external device existing outside the terminal device 1C and store the acquired dither mask DZ in the storage unit 3.

Modification example 7

Although the above-described embodiment and modifications 1 to 5 perform so-called halftone processing for generating binary display data Img from multi-valued image data GD as quantization processing, the present invention is not limited to this embodiment. In modification 7, when θ and Φ are integers satisfying 2 < θ < Φ, display data Img of a Φ value is generated from image data GD of a θ value. Hereinafter, a case where Φ is 5, that is, the display data Img of five values is generated will be described in detail as an example. In addition, θ is 256 for the image data GD.

Fig. 30 is a flowchart showing an example of the operation of the recording system Sys when the recording system Sys executes the quantization processing in modification 7.

As illustrated in fig. 30, when the quantization processing is started, the display data generation section 23 selects a pixel Px (mx, my, mz) from the M pixels Px in the image formation space SP (S30).

Next, the display data generation unit 23 divides the gradation value Gg (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected in step S30, among the plurality of gradation values Gg indicated by the image data GD, by a predetermined value determined in advance, thereby obtaining a quotient GgA (mx, my, mz) and a remainder GgB (mx, my, mz) (S31).

Here, the predetermined value is a quotient calculated by dividing the number of gradations θ of the image data GD by a number obtained by subtracting 1 from the number of gradations Φ of the display data Img. In modification 7, θ is 256 and Φ is 5 as described above. Therefore, the predetermined value is θ/(Φ -1) ═ 64.

For example, when the gradation value Gg (mx, my, mz) is 128, the quotient GgA (mx, my, mz) is 2, and the remainder GgB (mx, my, mz) is 0. For example, when the gradation value Gg (mx, my, mz) is 32, the quotient GgA (mx, my, mz) is 0, and the remainder GgB (mx, my, mz) is 32. For example, when the gradation value Gg (mx, my, mz) is 96, the quotient GgA (mx, my, mz) is 1, and the remainder GgB (mx, my, mz) is 32.

Next, the display data generation unit 23 determines whether or not the remainder GgB (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected in step S30 is equal to or greater than the threshold Dd (mx, my, mz) corresponding to the pixel Px (mx, my, mz) selected in step S30, among the plurality of thresholds Dd (mx, my, mz) indicated by the dither mask DZ (S32).

Here, the dither mask DZ to be used is determined in the same manner as in the above-described embodiment. However, the threshold Dd [ M ] satisfies the following expression (11) instead of the expression (2) shown in the embodiment.

Dd [ M ] ═ GgB-max … … formula (11)

GgB-max in the formula (11) is the maximum value of the above-mentioned remainder GgB (mx, my, mz). That is, it is a value obtained by subtracting 1 from a predetermined value. In modification 7, as described above, GgB-max is the predetermined value-1 is 63.

As illustrated in fig. 30, when the determination result in step S32 is affirmative, the display data generation unit 23 sets the gradation represented by the pixel Px (mx, my, mz) to a value obtained by adding 1 to the quotient GgA (mx, my, mz) in the display data Img (S33).

On the other hand, if the result of the determination at step S32 is negative, the display data generation unit 23 sets the gradation indicated by the pixel Px (mx, my, mz) as the quotient GgA (mx, my, mz) in the display data Img (S34).

For example, in the case where the gray value Gg (mx, my, mz) is 128 in the pixel Px (mx, my, mz) selected in step S30, the remainder GgB (mx, my, mz) is 0 in the above manner. On the other hand, "GgB (mx, my, mz) < Dd (mx, my, mz)" is determined by equation (1) so that the threshold Dd (mx, my, mz) ≧ 1 in any pixel Px (mx, my, mz). Thus, in step S34, the gradation of the display data Img in the pixel Px (mx, my, mz) is set to quotient GgA (mx, my, mz) of 2.

Further, for example, in the case where the gray value Gg (mx, my, mz) is 32 in the pixel Px (mx, my, mz) selected in step S30, the remainder GgB (mx, my, mz) is 32 as obtained in the above manner. Therefore, when the threshold Dd (mx, my, mz) of the pixel Px (mx, my, mz) selected in step S30 in the dither mask DZ is greater than 32, the gradation of the display data Img in the pixel Px (mx, my, mz) is set to the quotient GgA (mx, my, mz) of 0 in step S34. On the other hand, when the threshold Dd (mx, my, mz) of the pixel Px (mx, my, mz) selected in step S30 in the dither mask DZ is 32 or less, the gradation of the display data Img in the pixel Px (mx, my, mz) is set to "1" which is the value obtained by adding "1" to the quotient GgA (mx, my, mz) in step S33.

Further, for example, in the case where the gray value Gg (mx, my, mz) is 96 in the pixel Px (mx, my, mz) selected in step S30, the remainder GgB (mx, my, mz) is 32 as obtained in the above manner. Therefore, when the threshold Dd (mx, my, mz) of the pixel Px (mx, my, mz) selected in step S30 in the dither mask DZ is greater than 32, the gradation of the display data Img in the pixel Px (mx, my, mz) is set to the quotient GgA (mx, my, mz) of 1 in step S34. On the other hand, when the threshold Dd (mx, my, mz) of the pixel Px (mx, my, mz) selected in step S30 in the dither mask DZ is 32 or less, the gradation of the display data Img in the pixel Px (mx, my, mz) is set to "2" which is the value obtained by adding "1" to the quotient GgA (mx, my, mz) in step S33.

Thereby, the gradation of the display data Img in the pixel Px (mx, my, mz) is set to any one of "0" to "4".

Next, the display data generation unit 23 determines whether or not the gradation of the display data is set for all of the M pixels Px in the image forming space SP in the display data Img (S35).

When the result of the determination at step S35 is negative, the display data generation unit 23 advances the process to step S30. On the other hand, if the result of the determination in step S35 is affirmative, the display data generation unit 23 ends the quantization processing.

The five-valued display data Img generated as described above can be used in various ways. For example, the applied drive waveform may be different by the display data Img of five values. For example, it may be set such that ink is not ejected when the display data Img is "0", ink of approximately 1pl is ejected when the display data Img is "1", ink of approximately 2pl is ejected when the display data Img is "2", ink of approximately 3pl is ejected when the display data Img is "3", and ink of approximately 4pl is ejected when the display data Img is "4". The number of times of ink ejection for 1 pixel may be varied by the display data Img of five values. For example, the ink may be set so that the ink is not ejected when the display data Img is "0", the ink is ejected once when the display data Img is "1", the ink is ejected twice when the display data Img is "2", the ink is ejected three times when the display data Img is "3", and the ink is ejected four times when the display data Img is "4".

Description of the symbols

1 … terminal device; 2 … terminal control unit; 3 … storage unit; 5 … recording means; 6 … recording control unit; 7 … head unit; 8 … ink supply unit; 9 … mechanical arm; 21 … an image data acquisition unit; 22 … dither mask generating part; 23 … display data generating part; 61 … head control part; 62 … arm control; 71 … driving signal supply part; 72 … recording head; a D … discharge part; DZ … dither mask; sys … recording system.