JPH1175063A - Picture processing device and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a user to freely change a half tone processing method by inputting a parameter necessary for constituting a dot constituted of tetragonal grids, and overwriting a generated threshold matrix in a threshold store means. SOLUTION: A γ tables 1, γ table 4, and threshold value memory 3 use a RAM. A parameter inputting part 101 interacts with a user I/F under the flow control of a controlling part 100, and inputs a parameter necessary for constituting an arbitrary dot. A threshold value generating part 102 generates a threshold matrix based on the inputted parameter, and loads it in a threshold value memory 3. A γ table generating part 103 generates the data of the γtable based on the parameter inputted from the parameter inputting part 101, and loads it in the γ table 1. The threshold value of default is stored in a ROM 8, and the γ table of default is stored in a ROM 9, and at the time of power supply, the contents are respectively loaded to the threshold value memory 3 and the γtable 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method for performing pseudo halftone processing digitally.

[0002]

2. Description of the Related Art The operation of a conventional hard copy apparatus for performing pseudo halftone processing will be described with reference to FIG. Now, in the initial state, the counter value of the counter 7 is (H, V) = (0, 0)
And the size of the threshold matrix is set to M × N
(However, M and N are the sizes in the horizontal direction and the vertical direction, respectively). Since P comparators are placed in parallel in the comparison processing unit 2,
From the threshold memory 3 storing thresholds defined in the threshold matrix, P types of thresholds corresponding to the address (0, 0) are loaded into the comparison processing unit 2. Then, the printing unit 6
Input value is given to the γ table 1 for correcting the nonlinearity of
Sent to In the comparison processing unit 2, the comparison between the input value and the threshold value given earlier is performed in parallel by P comparators. Assuming that the comparator is set to output “True” when the input value is larger than the threshold value, the comparison processing unit 2 counts the number of “true” output, and counts from 0 to (P−1). To a number. The numerical value output from the comparison processing unit 2 is converted to an n-bit pixel modulation intensity signal based on the γ table 4 for obtaining the actual pixel modulation intensity, and sent to the pixel modulation unit 5.

On the other hand, a horizontal synchronizing signal and a vertical synchronizing signal are input to a counter 7 in synchronization with an input signal. The counter 7 counts the horizontal number H and the vertical number V of the processed pixels. That is, the horizontal synchronizing signal is generated every time one pixel is input, and the vertical synchronizing signal is generated every line break. Upon receiving the vertical synchronization signal, the counter 7 resets H to 0, and thereafter, is incremented every time a horizontal synchronization signal is input. Here, H is a cyclic counter having a cycle M which becomes 0 next to M-1. Also, V
Is a cyclic counter having a cycle N which is incremented each time a vertical synchronization signal is received. Therefore, the output (H, V) of the counter can be considered to represent the local coordinates of the pixel of interest in the threshold value matrix. When the processing for one page is completed, a print output of one page is obtained from the printing unit 6.

Next, a threshold matrix used in the processing will be described. FIG. 9 shows a relationship between a pixel group forming a halftone dot and a threshold matrix. Now, if the vector a is represented as a_, in FIG.

[0005]

A2 _ = (n, m) a1 _ = (m, −n) where n and m are integers.

Is a basic vector in a halftone dot coordinate system. That is, given a certain coordinate R _ = (X, Y),

[0007]

R ′ _ = R_ + p * a1_ + q * a2_ (1) where p and q are integers, and A * B represents multiplication of A and B.

The thresholds at arbitrary coordinates R'_ represented by the following are all equal to those at R_. When a square having a1_ and a2_ as two adjacent sides is considered, the square represents one halftone dot, and a pixel group inside the halftone dot is one pixel.
One halftone dot unit. Therefore, once the threshold value of the pixel in a certain halftone dot unit has been obtained, the threshold value of the pixel in the entire space can be obtained using Expression (1). However, since the actual processing system is a real-time processing system that requires sequential processing for each pixel as described above, there is no time to solve Equation (1) for each processing.

Therefore, usually, the periods in the X and Y directions are obtained from the equation (1), and a square area corresponding to one period is considered.
Having a threshold table inside that area is performed. The threshold table in this square area is called a threshold matrix. In FIG. 9, pixel numbers are assigned instead of threshold values. Referring to FIG. 9, it can be seen that the pixel numbers are repeated vertically and horizontally in one cycle of the threshold matrix.

[0010]

However, in the above-mentioned prior art, since the threshold matrix used for the halftone processing is fixed, it is necessary to change the processing method caused by the quality of the image, the user's preference, and the like. There was a problem that could not be met.

An object of the present invention is to provide an image processing apparatus and method which solve the above-mentioned problems and allow a user to freely change the halftone processing method.

[0012]

According to a first aspect of the present invention, there is provided a threshold value storing means for storing a threshold value matrix, a gamma table storing means for storing a gamma table for correcting non-linearity of an output device, and comparing means for comparing the input value converted based on the γ table stored in the γ table storing means with a threshold matrix stored in the threshold storing means, and a pixel corresponding to the comparison result of the comparing means In an image processing apparatus having a signal generation unit for generating a modulation intensity signal, an input unit for inputting a parameter necessary for forming a halftone dot composed of a square lattice, and an input unit for inputting a parameter based on the parameter input by the input unit Threshold matrix generation overwriting means for generating a threshold matrix by means of a threshold matrix and overwriting the generated threshold matrix with the threshold storage means; And a γ table preparation overwriting means for overwriting the γ table store means γ table prepared to create the γ table based on the parameters entered by means.

In the first aspect, the parameter may be a component of a grid vector forming a halftone dot.

In a preferred embodiment of the present invention, the threshold matrix generation overwriting means checks whether or not the grid vector component satisfies a screen angle constraint, and calculates the number of pixels constituting a unit halftone dot. And a pixel number calculating means for calculating the number of pixels.

According to a second aspect of the present invention, the gamma table creation overwriting means comprises: a gray scale number calculating means for calculating the gray scale number of the unit dot; an input value; and a gray scale calculated by the gray scale number calculating means. Gamma table data calculating means for calculating gamma table data from the numbers.

In the first aspect, the parameters can be the number of pixels forming the unit dot area and the screen angle.

According to a sixth aspect of the present invention, an input value converted based on a γ table for correcting non-linearity of an output device stored in a γ table storing means and a threshold value stored in a threshold storing means are provided. Compare with the matrix,
In an image processing method for generating a pixel modulation intensity signal according to the comparison result, a parameter input step of inputting parameters necessary for forming a halftone dot composed of a square grid,
A threshold matrix generation overwriting step of generating a threshold matrix based on the input parameters and overwriting the generated threshold matrix in the threshold storage means, and a γ table created by creating a γ table based on the input parameters Overwriting to the γ table storing means.

In the present invention, the parameter may be a component of a lattice vector forming a halftone dot.

According to a seventh aspect of the present invention, in the threshold matrix generation overwriting step, it is checked whether or not the components of the lattice vector satisfy the constraint condition of the screen angle, and the number of pixels constituting the unit halftone dot is calculated. And a step.

According to a seventh aspect of the present invention, the step of overwriting the γ table comprises the step of calculating the number of tones of the unit halftone, the input value and the number of tones calculated by the number of tones calculating means. Calculating table data.

In the present invention, the parameters can be the number of pixels forming the unit dot area and the screen angle.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> FIG. 1 shows a first embodiment of the present invention. This is an example of a hard copy device. 1, reference numerals 1 to 7 denote the same parts as in FIG. In the conventional example, the γ tables 1 and 4 and the threshold memory 3 are ROM (rea
d only memory), but in the present embodiment, the RAM
(random access memory). 8 is a ROM,
A default threshold table is stored, and its contents are loaded into the threshold memory 3 in an initialization process performed when the power is turned on. Reference numeral 9 denotes a ROM in which a default γ table is stored, and its contents are loaded into the γ table 1 in an initialization process performed when the power is turned on.

Reference numeral 10 denotes an arbitrary halftone dot generating unit which has a function of generating an arbitrary halftone dot and interacts with a user through a user I / F. , A threshold generation unit 102 and a control unit 100. The control unit 100 performs overall flow control. The parameter input unit 101 is for inputting parameters necessary for forming an arbitrary halftone dot. The threshold generator 102 generates a threshold matrix based on the input parameters and loads the threshold matrix into the threshold memory 3. The γ table generation unit 103 generates γ table data based on the parameters input from the parameter input unit 101, and loads the data into the γ table 1.

FIG. 2 is a flowchart showing an example of a control procedure by the control unit 100 shown in FIG. Step S0
At 01, it is selected whether or not to set a halftone dot. If not, at step S004, it is selected whether or not to set a γ table. If the setting of the γ table is not performed, the process is terminated and the default setting is used.

On the other hand, if the setting of a halftone dot is selected in step S001, the parameter input unit 101 is called in step S002 to input parameters. In step S003, the threshold generation unit 102 is called based on the obtained parameters, a threshold is created, and data is loaded into the threshold memory 3. In step S005, the γ table generation unit 103 is called to determine the data of the γ table 1.

On the other hand, if the setting of the γ table has been performed in step S004, the process proceeds to step S005.

FIG. 3 is a flowchart showing an example of a control procedure by the parameter input unit 101 of FIG. In step S101, parameters (n, m) of halftone dots are input. This represents a component of the halftone dot basic vector a2_ drawn on the coordinate system shown in FIG. That is,

[0028]

A1 _ = (m, -n) a2 _ = (n, m) Next, in step S102, it is checked whether or not the input parameter satisfies the screen angle constraint. The screen angle here is an angle θ between a1_ in FIG. 4 and the x-axis. However, the direction in FIG. 4 is negative. Now, assuming that the absolute value of the basic vector is fixed, as can be seen from FIG.
Invariant to 0 degree rotation. Therefore, it is necessary and sufficient for the setting range of θ to be 90 °.
The conditions examined at 102 are:

[0029]

-45 ° ≦ θ <45 ° (2)

If the condition of equation (2) is not satisfied, a warning is displayed in step S106 and
Return to 101. If the condition of Expression (2) is satisfied, the process proceeds to step S103, and in step S103, the number of pixels forming the unit halftone dot is obtained. The number of pixels W is equal to the area of the unit dot area and is represented by the following equation.

[0031]

W = n ＾ 2 + m ＾ 2 (3) where A ＾ B represents A raised to the Bth power.

In step S104, the size of the threshold value matrix is obtained. Assuming that the desired size is L,

[0033]

L = W / g (4) Here, g is the greatest common divisor of the absolute values of n and m. However, when n = 0, it is defined as g = m. In step S105, it is checked whether the size of the threshold value matrix is equal to or smaller than the capacity of the threshold value memory 3. If L exceeds the capacity of the threshold memory 3, a warning is displayed in step S107, and step S101 is performed.
When the capacity is exceeded, the control is returned to the control unit 100.

FIG. 5 is a flowchart showing an example of a control procedure performed by the threshold value generator 102 in FIG. Step S2
At 01, the coordinates of the pixels constituting the unit dot area are obtained,
In step S202, a threshold value is assigned to the corresponding pixel based on the obtained coordinates. As shown in FIG. 8, the assignment of the threshold value includes a circumscribed square area surrounding the unit dot area,

[0035]

8 ≦ 0 <x <n + m; −n ≦ y <m (when n ≧ 0) n ≦ x <m; 0 ≦ y <mn (when n <0) is indicated by an arrow in FIG. If the coordinates of interest are included in the coordinate list obtained in step S201 as a result of scanning in order, the numerical value is sequentially assigned to the corresponding pixels. The threshold value m given to the k-th found pixel is as follows, where the number of gradations per pixel is Pt.

[0036]

Th (k) = (W−k) * (Pt−1) (1 ≦ k ≦ W) (5) The obtained halftone dot becomes a spiral type growing from the center.

When the threshold value in the unit dot area is determined in this way, in step S203, the value is substituted into the threshold value matrix. The substitution work is performed in the threshold matrix area shown in FIG.

[0038]

This is performed by scanning the coordinates inside 0 ≦ x <L, 0 ≦ y <L, and comparing the coordinates with the coordinate list of the halftone dot area. For comparison, the coordinates of the pixel of interest are R'_, certain coordinates in the coordinate list are R_, and equation (1) is solved as a simultaneous equation for p and q,
This is performed by adopting a threshold value corresponding to the coordinates R_ when the obtained p and q are integers as a threshold value of R′_.

When the threshold matrix has been determined, loading to the threshold memory 3 is performed in step S204. The threshold memory 3 is configured to receive (Pt-1) thresholds per pixel. Now, between the pixel address (x, y) of the threshold matrix and the two-dimensional address (X, Y) of the threshold memory 3,

[0040]

X = (Pt-1) * x, Y = y, and when the value of the threshold matrix at the address (x, y) is given by T (x, y), the address of the threshold memory 3 The threshold value T '(X, Y) loaded to (X, Y)
Y) is

[0041]

T (X, Y) = T ([X / (Pt−1)], Y) + Mod (X / (Pt−1) (6) where [A] is A And Mod (A / B) represents the remainder of A / B.
The control ends, and the process returns to the control unit 100.

FIG. 6 is a flowchart showing in detail an example of the control procedure in step S201 shown in FIG.
In step S301, the vectors a1_ and a2_ shown in FIG.

[0043]

A1 ′ _ = a1_ / g = (m ′, − n ′) a2 ′ _ = a2_ / g = (n ′, m ′) From the above, the vector component, that is, the parameter (n ′,
m '). In step S302, it is checked whether the screen angle θ (FIG. 4) is 0 degrees. n '
Is 0, it is determined that θ is 0 degrees. If it is determined in step S302 that the screen angle θ (FIG. 4) is not 0 degrees, the process proceeds to step S303, and step S3 is performed.
03 to step S307, a1 'and a2'_
Is considered as a square having two adjacent sides, and pixel coordinates are obtained within a circumscribed square area surrounding the square. That is, the following method is used.

First, this area is further divided into five areas as shown in FIG. In this case, the range of the area 1 and the area 2 is defined by the following equation.

[0045]

Region 1: n'≤x≤m'-1, 0≤y≤m'-n'-1 (when n '> 0) 0≤x≤m' + n '+ 1, -n'≤ y ≦ m′−1 (when n ′ <0) (7) Area 2: 0 ≦ x ≦ m′−1, −n ′ ≦ y ≦ −1 (when n ′> 0) 0 ≦ x ≦ m′−1, 0 ≦ y ≦ −n′−1 (when n ′ <0) (8) Here, the coordinates of the pixel are represented by the coordinates of the upper left vertex of the pixel. In this case, as apparent from FIG. 7, all the pixels belonging to the area 1 are included in the square lattice. In step S303, the square area defined by equation (7) is scanned, and all appearing coordinates are stored.
In step S304, pixel coordinates in the area 2 are obtained. Here, among the pixels included in the region, the coordinates of the pixel whose portion larger than 1/2 of the area is included in the square lattice are determined coordinates. The necessary and sufficient conditions for the pixel at the coordinates (x, y) to satisfy the above conditions are:

[0046]

-1/2 * (1 + n '/ m')-n '/ m' * x ≤ y (9)

In steps S305 to S307, the coordinates of area 3 to area 5 are obtained by projecting the coordinates obtained in step S304 by rotation and translation. The general formula for projection from region 2 to another region is:

[0048]

X ′ = x * cos φ−y * sin φ + Ux y ′ = x * sin φ + y * cos φ + Uy (10) Where φ is a rotation parameter,
(Ux, Uy) is a parameter for the parallel movement. The parameters of equation (8) in each region are

[0049]

Area 3: φ = −π / 2, (Ux, Uy) = (n ′, m′−1) Area 4: φ = −π, (Ux, Uy) = (n ′ + m′−1) ,
m′−n′−1) Area 5: φ = −π / 2, (Ux, Uy) = (m′−1, −n ′) In step S308, it is determined whether or not all the pixel coordinates forming the square grid of FIG. 7 have been obtained.

In step S304, if there is a pixel whose area of the portion included in the square lattice is exactly equal to 1/2, the result of the determination in step S308 is false. This is because, in step S304, only the area having the area larger than 1/2 is selected. Here, FIG.
The number of pixels to be included in the square grid and the area are exactly 1
The relationship with the number of pixels equal to / 2 will be described. Now, assuming that the number of pixels to be included in the square lattice is W ′,

[0051]

W ′ = n ′ ＾ m ′ + m ′ ＾ 2 = (m′−abs (n ′)) ＾ 2 + 4 * (m ′ * abs (n ′) / 2) (11) Here, abs (A) represents the absolute value of A. As is clear from FIG. 7, the first term on the right side of the equation (11) is equal to the number of pixels included in the area 1, and the second term (m ′ * a
bs (n ′) / 2) is equal to the sum of the number of pixels included in the regions 2 to 5. Considering the symmetry of each area, the number of pixels included in each area should be equal to each other, so that the second term (m '* abs (n') / 2)
Can be considered as the number of pixels included in a certain area other than the area 1.

If one area has an odd number of 1/2 pixels, the second term (m '* abs)
(N ') / 2) is represented in the form of (integer + 0.5). However, in the process of obtaining W ', (m' * abs (n ') /
Since 2) is multiplied by 4, the sum of the number of pixels existing outside the area 1 appears as an integer. This fact indicates that W pixels cannot be obtained if half the area is removed. Actually, since it is impossible to obtain only 1/2 of the pixel, 1/2 pixels of the area are adopted in the areas 2 and 3 using the symmetry of the area described above, and they are discarded in the areas 4 and 5. That's why I decided to make it consistent.

Satisfying the condition that just 1/2 of a pixel is included in the square lattice of FIG. 7 means that the coordinates (x, y) of the pixel are

[0054]

## EQU18 ## n '* x + m' * y =-(n '+ m') / 2 (12) Examining equation (10), since the left-hand side is an integer and n 'and m' are relatively prime, both sets of (n ', m') satisfying equation (10) are odd. Limited to

In step S308, if at least one of n 'and m' is an even number, true is output. Therefore, in step S308, if it is false, that is, there is an area 1/2 pixel. If so, step S
At 310, a 1/2 pixel search is performed. That is, the range 2 is scanned to find coordinates satisfying the expression (10).
Furthermore, the coordinates of all 1/2 pixels are obtained by extending the coordinates to the area 3 by projection. On the other hand, if true in step S308, in step S309, the coordinates thus obtained are extended to the entire unit dot area using the following equation.

[0056]

R_ = r_p * a1 ′ _ + q * a2′_ (where 0 ≦ (p, q) <g) (13) where R_ is a coordinate to be obtained, and r_ is a pixel coordinate in the square grid of FIG. It is.

On the other hand, if the screen angle is 0 ° as a result of the judgment in step S302, the square grid shown in FIG. 4 and the circumscribed square area completely match, and all the pixels contained in the area are united. It becomes a pixel constituting a halftone dot. Therefore, in step S311, the region (0 ≦ x <m; 0
.Ltoreq.y <m) and records all the internal coordinates.

FIG. 10 is a flowchart showing an example of the control procedure of the γ table generator 103 in FIG. As described in the description of the conventional example, the γ table 1 is for compensating for the non-linearity of the output characteristics of the hard copy device including the pseudo halftone processing system. However, in a device having a function of setting an arbitrary halftone dot, the characteristic at the time when the halftone dot is set is not yet known, and therefore, it is necessary to obtain the characteristic by some means.

If automatic generation is selected in step S401, the characteristics are examined by the automatic generation processing in steps S402 to S403. That is, in step S402, the number of gradations Pa of the unit halftone dot is

[0060]

[Equation 20] It is determined by Pa = W * (Pt-1) +1. In step S403, table data D (n) when the input value is n is

[0061]

D (n) = [n / N * (Pa-1)] where 0 ≦ n ≦ N, N = 2 ＾ u−1, and u is the bit width of the input value.

[0062] In step S405, the data is loaded into the γ table 1, and then the process ends.

On the other hand, if it is determined to be false in step S401, data defined by the user is input in step S404, and the flow advances to step S405.

<Second Embodiment> This embodiment is a first embodiment.
In comparison with this embodiment, the types of parameters are different, and accordingly, the control procedure of the parameter input unit 101 is different.

FIG. 11 is a flowchart showing an example of a control procedure of the parameter input unit 101 according to the second embodiment. In step S501, the number of pixels of a unit halftone dot and the screen angle are input. In step S502, a set of integers (n, m) that best approximate these is obtained from the input number of pixels Wi and the screen angle θi. . That is, ta
If n θi = t, then n = m * t, so substituting this into equation (3) and solving

[0066]

Since m = (Wi / (t ＾ 2 + 1)) is obtained, the obtained m is rounded off and newly set to m. This m is expressed by the following equation:

[0067]

[Mathematical formula-see original document] n is obtained by substituting into n = m * t, and the obtained n is rounded off to obtain a new n.
far. Therefore, a set of integers (n, m) is obtained.

In step S503, a new screen angle θ = arctan (−n / m) and the number W of pixels are obtained from n and m. In step S504, the screen angle θ and the number of pixels W are displayed, and the user is asked for confirmation. When the user denies, the process returns to step S501, and when the user affirms, the process proceeds to step S505. Steps S505 to S508 are the same as steps S102 to S105 in FIG.
If the size of the threshold matrix does not satisfy the constraint condition in step S508, a warning is displayed in step S510, and the process returns to step S501.

[0069]

As described above, according to the present invention,
Since the halftone processing method can be freely changed only by the minimum parameter setting by the user, there is an effect that the user can easily create a desired image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing an example of a control procedure by a control unit 100 shown in FIG.

FIG. 3 is a flowchart illustrating an example of a control procedure performed by a parameter input unit 101 in FIG. 1;

FIG. 4 is a diagram illustrating an example of a relationship between a unit dot region and a lattice vector.

FIG. 5 is a flowchart illustrating an example of a control procedure by a threshold value generation unit 102 in FIG. 1;

6 is a flowchart showing an example of a control procedure in step S201 shown in FIG. 5 in detail.

FIG. 7 is a diagram illustrating an example of a relationship between a square grid and pixels in a divided area.

FIG. 8 is an explanatory diagram illustrating threshold value assignment.

FIG. 9 is a diagram illustrating an example of a relationship between a unit dot region and a threshold matrix.

FIG. 10 is a flowchart illustrating an example of a control procedure of the γ table generation unit 103 in FIG.

FIG. 11 is a flowchart illustrating an example of a control procedure of a parameter input unit according to the second embodiment.

FIG. 12 is a block diagram illustrating a conventional example of an image processing apparatus.

[Description of Signs] 100 control unit 101 parameter input unit 102 threshold value generation unit 103 γ table generation unit

Claims (10)

[Claims] 1. A threshold value storing means for storing a threshold value matrix, and γ for correcting non-linearity of an output device.
Γ table storing means for storing a table, and comparing means for comparing an input value converted based on the γ table stored in the γ table storing means with a threshold matrix stored in the threshold storing means. An image processing apparatus having a signal generation unit that generates a pixel modulation intensity signal in accordance with a comparison result of the comparison unit, wherein an input unit for inputting a parameter necessary for forming a halftone dot composed of a square grid; A threshold matrix generation overwriting means for generating a threshold matrix based on the parameters input by the input means and overwriting the generated threshold matrix on the threshold storage means; and γ based on the parameters input by the input means.
An image processing apparatus, comprising: a γ table creating and overwriting means for creating a table and overwriting the created γ table on the γ table storing means. 2. The method according to claim 1, wherein the parameter is:
An image processing apparatus characterized by being a component of a lattice vector forming a halftone dot. 3. The method according to claim 2, wherein the threshold matrix generation overwriting means includes: a checking means for checking whether a component of the grid vector satisfies a screen angle constraint, and a pixel forming a unit dot. An image processing apparatus comprising: a pixel number calculation unit for calculating the number. 4. The method according to claim 2, wherein the gamma table creation overwriting means includes: a gradation number calculating means for calculating a gradation number of a unit halftone dot; an input value; And a gamma table data calculating means for calculating gamma table data from the number of tones. 5. The method according to claim 1, wherein the parameter is:
An image processing apparatus comprising: the number of pixels forming a unit dot area; and a screen angle. 6. A comparison is made between an input value converted based on a γ table for correcting non-linearity of an output device stored in a γ table storing means and a threshold matrix stored in a threshold storing means. An image processing method for generating a pixel modulation intensity signal according to a comparison result, wherein a parameter input step of inputting parameters necessary for forming a halftone dot composed of a square grid; and a threshold matrix based on the input parameters. A threshold matrix generation overwrite step of overwriting the generated and generated threshold matrix in the threshold storage means, and a γ table for creating a γ table based on the input parameters and overwriting the created γ table in the γ table storage means An image processing method, comprising: a table creation overwriting step. 7. The method according to claim 6, wherein the parameter is:
An image processing method characterized by being a component of a lattice vector forming a halftone dot. 8. The method according to claim 7, wherein the step of overwriting the threshold matrix comprises the step of checking whether a component of the grid vector satisfies a screen angle constraint, and the number of pixels constituting a unit halftone dot. Calculating the image processing. 9. The method according to claim 7, wherein the step of overwriting the γ table comprises the steps of calculating the number of gradations of the unit halftone dot, an input value, and the number of gradations calculated by the gradation number calculating means. Calculating gamma table data from the image data. 10. The image processing method according to claim 6, wherein the parameters are a number of pixels forming a unit dot area and a screen angle.