JPS61123273A - Method for processing color picture gradation - Google Patents

Abstract

PURPOSE:To improve the recording quality of gradation color recording by using a new coordinate obtained from a coordinate of picture element data to be processed through coordinate conversion in response to a screen angle to reference a threshold value matrix thereby setting an optional screen angle. CONSTITUTION:A scanner 100 reads information on an original at each three primary collors (R, G, B) and outputs digital multi-value data in response to the gradation level at each color. After prescribed processing is applied to the picture data by a controller cpu, recording processing is given to a color printer 500. Units 200, 300, 400 converting gradation data to a binary data are provided between the controller cpu and the color printer 500. Each conver sion unit stores a table where a prescribed threshold value is arranged on each element of a two-dimensional matrix, the coordinate of the picture element data to be processed is subjected to coordinate conversion in response to the screen angle based on the table to apply interpolation processing.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to color image gradation processing, for example, when recording gradation image data of multiple colors using a color printer, and particularly relates to color image gradation processing, such as when recording gradation image data of multiple colors using a color printer, and in particular, to Regarding the formation of a substantial screen angle when expressing.

[Prior Art] In a digital recording device, the unit recording pixel is
2I of “Record” and “Non-Record”! When using this type of digital recording device, which is often only capable of performing gradation recording, gradations cannot be expressed in pixel units, but by associating multiple recording pixels with one gradation information, it is possible to It is possible to perform gradation expression. As this type of gradation expression method, the dither method and the density pattern method are often used.

When converting gradation data into binary data, a certain threshold is used to determine whether it is "recorded: 1" or "non-recorded: 0". Can express the tone. That is, a threshold value having a different value is assigned to each element of a two-dimensional matrix of X rows and Y columns, and the threshold value of each element is compared with one or different gradation pixel data to determine the gradation. If the tone data is converted to 2(l! recording data), for each of the plurality of recording pixels corresponding to the two-dimensional matrix of threshold values, depending on the tone of the tone pixel data,
The number of pixels at the "record" level, that is, the recording density changes.

In the dither method, one threshold value in a matrix is assigned to one gradation pixel data.

Every time the position of gradation pixel data changes, the position of the selected threshold value in the matrix is updated. In addition, in the density pattern method, all elements of a matrix are associated with one gradation pixel data, and when one gradation pixel data is input, thresholds are sequentially selected to correspond to the number of matrix elements. The recorded pixel information is generated.

By the way, 1 For example, Y (yellow), 2 M (magenta), C
When performing color recording using inks of multiple colors such as (cyan), moiré may occur due to interference between recorded images of each color. Furthermore, since the threshold matrix used to convert gradation data into binary data is repeatedly used for each predetermined pixel, the threshold array pattern may stand out in the recorded image.

Furthermore, if there is a shift in the recording position of each color of ink due to mechanical positioning error, etc., the shift will appear in a fixed direction throughout the image, so the color shift in that case will be
For example, it appears as a continuous, large, conspicuous image in the form of a line.

Furthermore, depending on one pixel, these plurality of inks may be recorded overlappingly on one pixel. Theoretically, Y
, M and C are mixed together.

Can play any color. However, in reality, depending on the transparency of the ink, the colors reproduced will change depending on whether they overlap or not, and the order in which they overlap, resulting in cloudy reproduction. In the printing field, this problem has conventionally been solved to the extent that it is virtually invisible to the human eye by tilting a mesh-shaped plate by a predetermined amount for each color with respect to the recording paper. In this case, the slope is
Generally called the screen angle.

However, in digital image recording using the dot matrix method, such a screen angle cannot be set.

Therefore, a method has been proposed (Japanese Unexamined Patent Publication No. 173972/1983) in which the array of threshold values in a threshold matrix is given a slope to substantially form a screen angle.

However, in the conventional method, the scope of setting the screen angle is small, and in order to be able to set the screen angle in a box, a huge amount of memory must be prepared for the threshold matrix. .

[J! Ming’s purpose] The present invention does not require large capacity memory.

The purpose of this invention is to improve the recording quality in one-gradation color recording by making it possible to set an arbitrary screen angle.

[Structure of the Invention] In order to achieve the above object, one aspect of the present invention sets the screen angle by performing coordinate transformation calculations. For example, if the threshold matrix is arranged in the same way as before, and the coordinates of the pixel data to be processed are converted according to the screen angle and the threshold matrix is referred to as new coordinate values, then the screen angle is effectively is generated.

See Figure 3. Now, any cell Cx on the X+1 coordinate
Consider y @ X, a predetermined angle θ with respect to the 7 coordinate axis Axy
When the coordinate axis tilted by the angle Auv is assumed, if the cell Cxy is rotated by the angle θ so that it coincides with the coordinate axis A u V, the coordinates u and v on the coordinate axis Axy of the new cell Cuv generated thereby are respectively It will look like this:

u=S1・x g・Cosθ+S2・y o−5i
nθ= a 1 music xo+a2 ・yo ・・
・(1)v=S3・x O-5inθ+S4・yo
-Co5θ=a3 @xO+a4@yO@@′ (2) However, 51, 52, 53.54 are signs (+*) determined according to the angle θ.

That is, the above parameters a1.
Set a2*a3 and a4 and perform (1) above.

By performing the calculation of equation (2), the coordinate values after coordinate transformation are found, and by referring to the threshold matrix (table) using this, the screen angle is generated. Therefore, if the parameters a1 to a4 are set to different values for each color, the screen angle can be changed for each color, similar to what is done in the printing field, and the above-mentioned disadvantages can be solved. can.

By the way, when performing coordinate transformation operations, the result is usually
Although it cannot be obtained as an integer, the coordinate value is an integer. If only the integer part of the calculation result is used to refer to the threshold matrix, a relatively large error may occur. Therefore, in a preferred embodiment of the present invention, interpolation is performed to reduce the error.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows one type of image processing apparatus embodying the invention. This will be explained with reference to FIG. The control device 1CPU is
Microprocessor, RAM (read/write memory), R
OM (read-only memory: program memory), I
10 ports, J? ! It consists of a shaker, etc. scanner 10
0 and the I10 port of the control device 1 ICPU are connected via a predetermined signal line.

The scanner scans information on a given document in three primary colors (R, G).

B) is read for each color and outputs digital multi-value data according to the gradation level of each color. The control device CPU reads image data of each color from the scanner 100, performs predetermined processing on it, and then performs a recording processing operation on the color printer 500. Control unit CPU and color printer 5
00 are provided with conversion units 200, 300, and 400 for converting gradation data into binary data.

These conversion units 200, 300, and 400 process color information of Y (yellow), 9M (magenta), and C (cyan), respectively.

FIG. 2 shows the conversion unit 200 (300, 40
0 also indicates the same configuration). First, to give an overview,
In this example, the multipliers MPI, MP2° MP3 and MP4
Then, coordinate transformation is performed in a circuit consisting of adders AD5 and AD6. A memory ROM stores a table in which predetermined threshold data is arranged in each element of a two-dimensional matrix. In this example, the matrix is composed of 4×4.

Other circuit elements are provided for performing interpolation processing.

The principle of interpolation processing in this embodiment will be explained. In this example, interpolation is performed using the so-called area allocation method. See Figure 4a. The cell Cuv after coordinate transformation is the original x
, the coordinates (1,2) in the y coordinate.

A portion of each of the cells (1, 3), (2, 1), (2, 2), and (2, 3) is projected. The areas projected onto each of these cells are S2, 83. S4. S5
and S6, and the thresholds assigned to each cell are C(1,2), C(1,3), C(2,1), and C, respectively.
(2, 2) and c (2, 3), the threshold value C: (u, v) of the cell Cuv after coordinate transformation is expressed by the following equation.

C(u,v) = (52・C(1,2)+53・
C(1,3)+54・C(2,1) +55・C(2,
2) +56・C(2,3)) /(S2+53+34+
55+36)...(3) That is, in this interpolation method, the threshold values of all the cells (CX7) on which the cell Cuv is projected are weighted according to the projected area.

The value obtained by dividing the total sum by the number of cells, that is, the average value, is used as the interpolation result (threshold value).

However, such area calculations are extremely time-consuming when performed using software, and when performed using hardware, the equipment configuration becomes extremely complex. Perform seed distribution interpolation.

That is, as shown in No. 4b@, the cell Cu v is set to 1.
Divided into 6 equal parts, which cell (Cxy) is each divided microcell?
For example, in Figure 4b, the area Ca projected onto C(1,2) , the size of the area Cb projected onto C(2,3), and the area Cc projected onto C(2,2) (i.e., the number of minute cells) are 2. 1, and 13.

Therefore, the threshold value C(Ll, V) found in this case is C(u, S=(2・C(1,2)+C(2,3)+1
3-C(2,2))/L6.

Dividing into 16 in this way is actually equivalent to giving minute coordinate deviations (ΔX, Δy) of 1 or less corresponding to 16 divisions to the coordinate Cuv obtained by coordinate transformation, and , the above process can be executed by referring to the threshold value assigned to each integer coordinate in the integer part of the result and dividing the integrated value by 16.

Return to #2 @ and continue the explanation. In this example, 16 clock pulses are applied to the signal line CLK for each input gradation data (OAT^). CNT is a 4-bit counter that counts the clock pulses. Counter CN
The lower two bits of the T output are connected to the lower two bits of each input terminal B of the multipliers MPI and MP3, and the lower two bits of the counter C
The upper 2 bits of the NT output are multiplied 1i) MP2 and MP4
is connected to the lower two bits of each input terminal B of .

Note that in this example, the multipliers MPI, MP2 . MP3 and M
P4 performs multiplication of 4 bits (A) x 6 bits CB) and outputs 10 bits of data.

The coordinate values X and y that are updated each time each gradation data arrives are
These signals are applied to the upper four bits of each input terminal B of multipliers MPI, MP3, MP2 and MP4, respectively. Each multiplier MP
I, MP2. The 4 bits of input terminal A of MP3 and MP4 each have a constant alpa2+ corresponding to the screen angle.
Data a3 and a4 are given.

The output terminals of the multipliers MPI and MP2 are connected to the input terminals A and B of the adder AD5, respectively.
The output terminals of MP3 and MP4 are each connected to an adder AD6.
is connected to input terminals A and B of the.

Therefore, at the output terminals of addition @AD5 and AD6.

The following coordinate values U and V appear, respectively.

us+a1(x+ΔK)+a2(y+Δy)・
...(4) vwal(x+Δx)+a4(y+Δy)・
(5) ΔX and Δ are minute coordinate shifts given by the lower 2 bits and upper 2 bits of the counter CNT, respectively.

The lower two bits of additions @AD5 and AD6 are the decimal part in terms of coordinate values. Therefore, these lower two bits are discarded, and since the threshold matrix is 4x4 in this example,
Only the lower 2 bits above them (A u HA
v) and apply these 4 bits to the address lines of the memory ROM.

The memory ROM includes 16 4-bit memories corresponding to 4-bit addresses, and each memory stores predetermined threshold data. Memory R
The data output terminal of OM is connected to the lower 4 bits of input terminal A of adder AD7, and the upper 4 bits of input terminal A of adder AD7 are always set to zero.6 The output terminal of latch LT is Connected to input terminal B of adder @AD7. Latch pulse input terminal C of latch LT
A signal on a signal line CLK is applied to P via an inverter INV. Therefore.

The latch LT synchronizes with the clock pulse.
) and (5), that is, each time the address information applied to the memory ROM is updated, the output data of the adder AD7 is latched with a delay of half a clock period.

The data latched in the latch LT is applied to the input terminal B of the adder AD7, and this operation is performed once for each gradation data.
Since the operation is repeated 6 times, at the end of the 16 operations, 16
A value obtained by integrating the individual threshold data appears.

Of the 8-bit signal line output from the adder @AD7, the upper 4 bits are connected to the input terminal A of the digital comparator CMP. That is, by discarding the lower 4 bits of the data and extracting the higher order data, it is equivalent to shifting the data 4 bits lower, which means dividing the data by 16 in binary.

In other words, the 4-bit data (threshold value) applied to the input terminal A of the digital comparator CMP is applied to the coordinate values
, 1/4, 2/4, or 3/4 different minute coordinate shifts, and are determined by the above equations (4) and (5). This is the value obtained by dividing the sum of the values obtained by referring to 16. This is a threshold value obtained by interpolating the coordinate-transformed values by a method that can essentially be considered as an area allocation method.

Gradation data DATA consisting of 4 bits is input to input terminal B of the digital comparator CMP. Digital comparator commercial
P compares the threshold value applied to the input terminal A and the #ll level applied to the input terminal B, and if A<B, outputs a high level H (recording level) to the output terminal OUT, and otherwise If so, set the output terminal to low level L (non-recording level). Therefore, binary data is obtained at the output of the digital comparator CMP.

Referring to FIG. 1, in this example there are three conversion units 2
00, 300 and 400 are provided.

The coordinate information x, y of the input gradation data is commonly applied to the three conversion units. The control device CPU and the conversion unit 200 are connected by a 20-bit data line PSY consisting of 16-bit constant data (a1 to a4) corresponding to the yellow screen angle and 4-bit gradation data (DATA) of the yellow component. Control device CPU and conversion unit 3
00 is connected by a 20-bit data line PSM consisting of 16-bit constant data corresponding to the magenta screen angle and 4-bit gradation data of the magenta component, and the control device CPU and the conversion unit 400 are connected to the cyan screen angle. They are connected by a 20-bit data line PSC consisting of corresponding 16-bit constant data and 4-bit gradation data of the cyan component.

The clock pulse from the oscillating bone and the clear signal (CLR) from the I10 boat are sent to each conversion unit 200, 300,
400 in common. Each conversion unit 200,3
Output lines SY, SM and SC of 00 and 400 are connected to a color printer 500. Each signal line SY
, the timing signal indicating the validity of the signal levels of SM and SC (indicating that the integrated value of threshold data for 16 times appears at the output of addition @AD7) is connected to the control line C.
The signal is applied from the control device ficPU to the color printer 500 via ON2.

FIG. 5 shows a conversion unit implementing another embodiment of the invention. In this embodiment, similarly to the previous embodiment, there are four multipliers MPI, MP2, MP3 . MP4 and 2
(7) Addition aiAD1. Coordinate transformation is performed using AD2. In this example, all multipliers MPI-MP4 perform 4 bits x 4 bits operations and output 8 bits operation results.

In this embodiment, the integer coordinates closest to the coordinates after coordinate transformation are used as the coordinates when referring to the threshold matrix table. By finding the nearest integer coordinates, the coordinate error is at most 0.5 for each coordinate axis. This process can be executed by adding 0.5 to the value after coordinate transformation and extracting only the integer part of the result.

That is, 1, for example, as shown in FIG.
(0,1), C(0,0), C(1,1) and c(
i, o) should be selected to be the cell with the closest integer coordinates.

Assume arbitrary coordinate cells Pla, P2a, P3a, and P4a. If a shift of +0 and 5 is given to each of these arbitrary coordinate cells for each coordinate of X and y, the locus mcx of cells ptb, p2b, P3b and P4b after the shift
ey) are (0+α1. 1+βl) and (0+
α2,0+β2).

(1+α3, 1+β3) and (1+α4, 0+β4) (However, αl-α4.β1~β4<0.5)
.

If only the integer part of this result is extracted, the coordinates after the shift (x
, y) are (0, 1) and (0, O), respectively.

(1,l) and (110), and the cells to be selected are C(0,1), C(0,0), C(1,1) and C, respectively.
It can be seen that the coordinates match the coordinates of (1, 0).

Additions @ADI and AD2 shown in FIG. 5 are 1 multiplier MPI, which is a 9-bit + 9-bit adder.

MP2. Each 8-bit output line of MP3 and MP4 is connected to the upper 8 bits of each adder 11ADL and AD2. In adders ADI and AD2, the least digit (LSB) of input terminal A is fixed to zero (low level L), and input terminal B
The minimum digit of is fixed at 1 (high level H). That is, the input terminal BK of the adder ADI receives the value obtained by adding 0.5 to the output value of the 1 multiplier MP2, and the adder AD2
A value obtained by adding 0.5 to the output value of the 1 multiplier MP4 is input to the input terminal B of .

Since the minimum digit of the output of the adders ADI and AD2 is the decimal part, a predetermined lower digit (corresponding to the matrix arrangement) excluding one bit is connected to the address terminal of the memory ROM. In this example, the ROM directly stores as data the results of the comparison between the threshold value corresponding to the array coordinates output from the adders AD2 and A[)2 and each gradation data value.

For this reason.

In this example, gradation data is also applied to a predetermined address terminal of the memory ROM. Binary data is available at the data output terminal of the memory ROM.

FIG. 7 shows a conversion unit implementing the present invention in another embodiment. In this embodiment, as in the previous embodiment, there are four multipliers MPI, MP2° MP3 . MP4 and 2
Coordinate transformation is performed by two adders ADI and AD2,
In this example, both the integer part and the fractional part of the coordinate values obtained at the outputs of adders 1IIAD1 and AD2 are applied to the address terminals of the memory ROM. In the memory ROM, threshold data after interpolation at decimal coordinates is also stored in advance as a table at a predetermined address.

Therefore, just give the address to the memory ROM.

The interpolated threshold data is output from the data output terminal of the memory ROM. This threshold data is compared with one-tone data DATA by a digital comparator CMP, and binary data corresponding to the result is output from the output terminal of CMP.

In this case, a part of the table stored in the memory ROM is as shown in Table 1 below.

Table 1 Note: D8 and 09 (and others) are not in consecutive addresses. In Table 1, data is stored in units of 174 coordinates, and data located at integer coordinates is D 12. D1
6°D44 and D4B, and the other data are data generated by interpolation.

When the interpolated threshold values are stored as a table as in this embodiment, the stored threshold values may change depending on the method used to interpolate them. In other words, in this example configuration, any interpolation method may be used. For example, if the
Data interpolated by the area allocation method shown in equation 3) or the method shown in FIG. 5 may be stored as a table.

Here, cases using three other types of interpolation methods will be described.

As shown in FIG.
1゜y), Cb, y+1) and C(x+ l, y+
Consider 1). The decimal value of the coordinate in an arbitrary coordinate cell is Δ
X, Δy. Here, the threshold value in each integer coordinate cell is weighted by the product of the X-axis distance (complement) and the y-axis distance (complement) between that cell and the arbitrary coordinate cell, and the sum of these values is is the threshold value C(u,v) of the arbitrary coordinate cell Cu v, that is, the threshold value is determined by the following equation.

C(u,v)=C(x,y)・(1−Δx)・(1
-Δy)+C(x+1rV)・ΔX・(1
-Δy)+C(x ey + 1)・(1-ΔX)
・Δy+C(X+1.y+1)・Δx・Δy'' (6) For example, consider applying it to the data D22 when generating the data shown in Table 1 above.The decimal values ΔX and Δy of the coordinates in this case are: 1/4 and 2/4 respectively,
The data of integer coordinates of four points around data D22 are D12,
016. They are D44 and D48.

Therefore, from the above equation (6), D22=DL2・(1-1/4)・(1-2/4)+D
44・(1/4)・(1-2/4)+D16・(L-1
/4)・(2/4)+D48・(1/4)・(2/4) =D12・(3/8) + D 44・(1/8) +
It becomes 016・(3/8)+D48・(1/8). A specific numerical value is 1, for example D 12. D
44゜Substituting 5, 6.7 and 8 for D16 and D48 respectively, D22=5・(3/8) + 6・(1/8)+7・(
3/8) + 8・(1/8)= (ts, /a) +
(3/4) + (21/8) + 1=(15+6
+21+8)/8 km.

As shown in Figure 8, a cell Cuv with arbitrary coordinates and four integer coordinate cells surrounding it C(x,y), C(x+1°y), C(x,y+1) and C( x+1.y+1). Here, arbitrary coordinate cell Cuv and integer locus 1!1cx
The distance r from y is (Δx2+Δy')" (however, α is 1/2).

Each integer coordinate cell C(X, y), C(x+1.y), C(
x, y+1) and C(x+L, y+1) have an influence on the arbitrary coordinate cell Cuv that is inversely proportional to the distance, and let each distance be 'l+r2. If r3 and 4 are used, the threshold value C(u,v) of the arbitrary coordinate cell Cuv can be determined by the following equation.

C(u,v)=(C(x,y)/r1 +C(x+1
．． y)/r2+C(x,y+1)/rs+C(x+
1. y+1)/r4)/((1/r1)+(1/
r2 )+(1/r3)+(1/r4))...
(7) Here, let us consider again applying the data D22 in Table 1 above. In this case, the decimal values ΔX and Δy of the coordinates are 1/4 and 2/4, respectively. First, each distance r1 to r4 is determined.

r 1-((1/4)' + (2/4)')" = (
5/16)"r 2 = ((1-1/4)' + (2/
4)')" = (13/16) "ra" ((1/4
)"+(1-2/4)')"-(5/1e) crr
a = ((1-1/4)' + (1-2/14)')
"=(13/16)" Substituting these into equation (7) yields the following.

D22=(D12/(5/16)cf+044/(1
3/16)”+ o 16/ (5/16) cr+
D 48/ (13/16)σ〕X 2 / ((5)
’lr+ (13)”) Here, the specific value is 1
For example, D12. D44. Substituting 5.6.7 and 8 into D16 and D48, respectively, results in linear equations.

D 22= (5/ (5/16) “+6/(13/1
6) "+7/(5/16)C'+8/(13/16)]
X2/((5)+(13)σ) = [6・(5)“+7・(13)c′)/((5)
ct+(13)"] Ki 7 Cubic Convolution As shown in Figure 9, for an arbitrary coordinate cell Cuv, the cells Cxy of integer coordinates of 16 points around it are 5in7c
It is assumed that the effect is influenced according to d/πd (where d is the distance in each axis), and interpolation is performed by third-order polynomial approximation of Sinπd/πd.

That is, if each integer coordinate is represented by ipJ, and the threshold value at the integer coordinate is C(i, j), the threshold value to be obtained is as shown in the following equation.

C(u,v)=gΣC(i,j)・g(i−u)・
g (j-v) ・= (8) people, where g(d) is as follows g(d)=1-21d12+ldl':
O≦l d l <1g(d)=4-81dl+51d
12-ldl”: 1≦l d l <2g(d)
=O: 2≦ldl Here, for the case where U and V are l/4 and 2/4, respectively, the circumference g! Assuming that the threshold values of the coordinates corresponding to 16 points are as shown in Table 2 below, the threshold value C(u, v) will be determined.

The third table following the second table shows the distance 111i-ul between each coordinate of the 16 points and the arbitrary coordinate Cu v, and the fourth table shows the distance 1tlj-vl.

From the values in Tables 3 and 4, g(i-u) in equation (8)
and g (j - v), respectively, the following 5th
The results are as shown in Table and Table 6.

The influence Δcij due to the coordinate cell C1j in Table 5 and Table 6 is as follows.

ΔCaa: 2・(9/64)(-8/64)ΔCab
: 3・(-9/64)・(40/64)ΔCac:
11・(-9/64)・(40/64)ΔCad:
18・(-9/64)・(-8/64)ΔCba:
10(57/64)・(8/64)ΔCbb: 7
・(57/64) ・(40/64)ΔCbc:
14(57/64)・(40/64)ΔCbd: 2
6・(57/64)・(-8/64)ΔCca:17・
(19/64)l 8/64)ΔCab: 21(
19/64)・(40/64)ΔCcc: 29・(
19/64)・(40/64)ΔCcd: 33(1
9/64) (-8/64) ΔCda: 44 (3/6
4)l-8/64)ΔCdb: 48・(-3/64
)・(40/64)ΔCdc: 52(-3/64)
(40/64)ΔCdd:56・(−3/64)・(−
8/64) However, a = -1, b = 0, c
= 1, d = 2C (u, v) = ΔCa
a+ΔCab+ΔCac+ΔCad+ΔCha+Δcb
b+ΔCbc+ΔCbd+ΔCca+ΔCcb+ΔCc
c+ΔCcd+ΔCda+ΔCdb+ΔCdc+ΔCd
Effects] As described above, according to the present invention, it is possible to set an arbitrary screen angle by performing coordinate transformation calculations. By performing interpolation processing, errors caused by coordinate transformation can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one type of image processing apparatus implementing the present invention, and FIG. 2 is a block diagram showing a conversion unit 200 of FIG. 1. FIG. 3, FIG. 4a, and FIG. 4b are plan views showing coordinate conversion processing. 5 and 7 are block diagrams showing different layers of the conversion unit 200, respectively. FIG. 6, FIG. 8, and FIG. 9 are plan views showing interpolation processing. 100: Scanner 200. 300, 400: Conversion unit 500: Color printer CPU: Control device ROM: Memory also 6 A 8 ■ ff119 Direct o o o'o o o. to 1

Claims (6)

[Claims] (1) Color processing that processes each pixel data of at least two colors by referring to a threshold table formed by two-dimensionally arranging a plurality of components in which each component is assigned a predetermined threshold value. In the image gradation processing method; at least two types of slope values are set, two-dimensional coordinate data is sequentially generated, the coordinate data is subjected to a coordinate conversion operation according to the set slope, and the converted coordinate data is 1. A color image gradation processing method, comprising: referring to a threshold table based on the threshold value table. (2) Color image gradation according to claim (1), wherein the coordinate transformation calculation result is converted into an integer by extracting only the integer part of the result of adding 0.5 to the coordinate transformation calculation result. Processing method. (3) Sequentially give mutually different minute deviations with coordinate values of 1 or less to the coordinate transformation calculation results, refer to the threshold table for each coordinate value after the deviation, and average the referenced threshold values The color image gradation processing method according to claim 1, wherein: is set as a threshold value with which each pixel data is compared. (4) Weighting the values of the threshold table at four integer coordinates close to the coordinates of the coordinate transformation calculation result according to the distance between each integer coordinate and the coordinate of the coordinate transformation calculation result,
The color image gradation processing method according to claim 1, wherein a value obtained by adding these values is set as a threshold value with which each pixel data is compared. (5) The values of the threshold table at four integer coordinates close to the coordinates of the coordinate transformation calculation results are weighted by the results of multiplying the differences in each coordinate axis between the integer coordinates and the coordinates of the coordinate transformation calculation results, and 2. The color image gradation processing method according to claim 1, wherein a value obtained by adding the values is set as a threshold value with which each pixel data is compared. (6) Values of the threshold table at 16 integer coordinates close to the coordinates of the coordinate transformation calculation result, for the distance x between the coordinate of the coordinate transformation calculation result and each integer coordinate with respect to each coordinate axis,
The color image gradation processing method according to claim 1, wherein weighting is performed according to Sinπx/πx, and a value obtained by adding these values is set as a threshold value with which each pixel data is compared.