JP2621856B2 - Digital color image reproduction processing method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image reproducing process, and in particular, obtains image data (density data) of each color component by separating an original image.
This is processed into recording color component density data, and for each recording color component, a halftone expression pattern is specified using the recording color component density data to record the pattern. Regarding processing.

2. Description of the Related Art In a conventional halftone image recording of one type, when performing halftone recording based on digital image data (density data) having a gradation range of 0 to M · N, M × N of 1 to M・ N
The threshold data indicating each of the above, a threshold matrix recordally or randomly distributed in an M × N matrix, and comparing each threshold of the digital image data with the digital image data, if the digital image data is equal to or greater than the threshold, A recording information bit is allocated to the position of the threshold value, and if the value is less than the threshold value, a non-recording information bit is allocated.
Printing is performed by allocating the above dots.

A threshold matrix is previously compared with each of the image data indicating 1 to M · N, and M · N recording / non-recording information bit matrices are generated when the image data is 1 to M · N. Then, this is stored in a memory, and at the time of image reading and recording, one of a storage and a non-recording information bit matrix is designated by image data obtained by image reading,
There is also a mode in which recording is performed in accordance with the bit matrix.

In the case of monochrome recording, a threshold matrix or M · N
The recorded and non-recorded information matrices may be one set. In the case of color printing, for example, in the case of three-color printing of Y (yellow), M (magenta) and C (cyan), color separation reading and read signal processing are assigned to printing of Y, M and C. Y image recording data, M image recording data and C
Image recording data is obtained, and the above-described halftone recording is performed for each of the image recording data.

However, when halftone recording of a plurality of colors is performed based on the same threshold matrix or the same set of recording and non-recording information bit matrices, moiré and the like appear in a reproduced color image and the image quality deteriorates. There is a problem that the vividness of colors is lost because all colors overlap on the same point.

Conventionally, in order to prevent moire or the like, a threshold matrix or a recorded / non-recorded information bit matrix is
By rotating by a predetermined angle, predetermined for each color, deformed into one having a screen angle different from that of many colors,
A threshold matrix having a screen angle peculiar to each color or a recorded / non-recorded information bit matrix is used. One example is disclosed in JP-A-58-182372.

However, in the related art, even in a low-density recording area, each color is overlapped and recorded at the same point, so that the improvement in color vividness is poor. Also, since the number of gradations is small, the halftone representation of the reproduced image is poor. To increase this, it is necessary to increase M × N. However, if M × N is increased, the image data (the original image That is, the recording area allocated to each of the reproduced image (the data indicating the density of the entire predetermined small area) becomes large, and the reproduced image is enlarged with respect to the original image. In order to prevent enlargement, it is necessary to set a large area to be read as one image data of the original image. This results in coarse image reading and ultimately impairs the fidelity of the reproduced image. As a result, even if the number of gradations is set to a wide range, the reproduction quality of an image is not substantially improved unless the area of one dot for recording is reduced. Therefore, conventionally, the halftone expression pattern (threshold matrix or recorded / non-recorded information bit matrix) cannot be so large.

Conventionally, the same halftone expression pattern (orthogonal threshold matrix or orthogonal recording or non-recording information bit matrix) is rotated by a predetermined angle for each color, so that the degree of freedom in setting the screen angle is low and the color vividness is low. Could not be set to improve the halftone expression pattern (threshold matrix or recorded / non-recorded information bit matrix). Conventionally, since the halftone expression pattern is relatively small as described above, there is a problem that this further limits the degree of freedom.

SUMMARY OF THE INVENTION It is an object of the present invention to simultaneously realize sharpness and wide gradation range of recording colors for color image reproduction and smoothness of gradation expression.

The present invention separates a color image into a plurality of colors, converts the image density into digital data for each color component, and processes the digital data into color component recording density data; The halftone expression pattern having several types of threshold data corresponding to one of the threshold data for the predetermined number of dots, or all of the threshold data are compared with the respective values of the recording density data in the predetermined range, and the predetermined number of the dots are compared. Converts color component recording density data into recording and non-recording bit information using a halftone expression pattern consisting of a set of bit distribution patterns corresponding to the range of recording density data, with corresponding recording and non-recording bit distributions Recording and non-recording bit information is associated with one dot of a recording medium for each color component, and a predetermined color is recorded in a dot to which recording information bits are associated; in digital color image reproduction processing: When a predetermined area is recorded by using the halftone expression pattern, the recording information bits have a recording information bit distribution that expands from a predetermined point of the X and Y coordinates as the recording density increases in correspondence with the recording density. The fixed point is a different position for each color. A halftone expression pattern addressed to each color in which one set is associated with each color component. The halftone expression patterns of all groups are centered on the predetermined point. When the halftone dot shape whose area increases as the expression density increases becomes the same, and when the color component recording density data is converted into recording and non-recording bit information, it is specified by the color component recording density data. From the halftone expression pattern, based on the coordinates of the pixels of the original image from which the color component recording density data was obtained, an area corresponding to a plurality of dots of a part of the halftone expression pattern is assigned to a child matrix corresponding to the pixel of the original image. And recording and non-recording bit information obtained from the child matrix pattern are output as image information corresponding to the color component recording density data.

According to this, on the halftone expression pattern, as the indicated density becomes higher, the recording area is set such that the image area becomes larger as the expression density becomes higher, starting from a different predetermined point for each color. Since they are spread and have the same halftone dot shape, the overlap of recording colors is minimized, and excellent color reproducibility and resolution can be obtained during color image reproduction.

Further, based on the halftone expression pattern specified by the color component recording density data, an area corresponding to a plurality of dots of a part of the halftone expression pattern is determined based on the coordinates of the pixels of the original image from which the color component recording density data was obtained. The sub-matrix method of regularly cutting out as a child matrix pattern corresponding to the pixel of the pixel is adopted, so that the smoothness of the halftone expression is not impaired, the sharpness of the recorded color and the wide gradation range, and the smoothness of the gradation expression Are realized at the same time. Also suitable for scaling output of images with smooth color expression.

The present invention will be described more specifically. For example, in yellow (Y) recording, magenta (M) recording, cyan (C) recording and black (BK) recording, respectively, FIG.
The halftone expression patterns (threshold matrices) shown in FIGS. 11b, 11c and 11d are assigned. In these drawings, the hatched cells indicate that the recording density data is 32 (10
(Base number)), the recording of one dot is assigned. In this example, the pattern shown in FIG. 11a is the basic pattern, and the center of the halftone dot is set at the center of 8 × 8 and the corner. The pattern shown in FIG. 11b is obtained by shifting the basic pattern by 4 dots (squares) only in the vertical direction, and the pattern shown in FIG. 11c is obtained by shifting the basic pattern by 2 dots in both the vertical and horizontal directions. The pattern shown in FIG. 11d is obtained by shifting the pattern shown in FIG. 11c by four dots in the vertical direction. As described above, when the recording of the density 16 for each color is performed based on the four types of halftone expression patterns forming halftone dots of the same shape,
As shown in FIG. 12, all of the four colors are recorded in the 8 × 8 matrix area with the same (16) number of dots and without any overlap. Therefore, up to the recording of the density 16, there is no weight of the recording color at all, and the color clarity is extremely high. As the recording instruction density gradually increases from 16, the number of different-color weight recording dots gradually increases, and accordingly, the color clarity decreases.

FIGS. 13a to 13d show the halftone expression pattern of FIG.
Another halftone dot setting example in the case of a × 8 matrix is shown.
FIG. 13a shows a halftone expression pattern used for Y recording,
This is a basic pattern in this example. The pattern in FIG. 13b is used for M recording, and is obtained by shifting the basic pattern by two dots both vertically and horizontally. The pattern shown in FIG. 13c is used for C recording, and is obtained by shifting the basic pattern by two dots only in the vertical direction. The pattern in Figure 13d is B
This is used for K recording, and is obtained by shifting the basic pattern by two dots only in the horizontal direction. Also in this example, when recording is performed at a density of 16 for each color, as shown in FIG.
In the matrix area, all four colors are recorded with the same (16) number of dots and without any overlap. Therefore, up to the recording of the density 16, there is no weight of the recording color at all, and the color clarity is extremely high. Recorded density is 16
, The number of dot recording dots of different colors gradually increases, and accordingly, the color clarity decreases.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

First, referring to FIG. 1, an original 1 is placed on a platen (contact glass) 2 and fluorescent lamps 3 ₁ and 3 ₂ for illuminating the original.
1st mirror which is illuminated by and whose reflected light can move
4 _1, is reflected by the second mirror 4, _second and third mirror 4 _3, through the imaging lens 5, dichroic enters the click prism 6, wherein three wavelengths of light, red (R), green (G) and blue It is split into (B). The split light enters the CCDs 7r, 7g, and 7b, which are solid-state imaging devices, respectively. That is, red light is incident on the CCD 7r, green light is incident on the CCD 7g, and blue light is incident on the CCD 7b.

Fluorescent lamp 3 _1, 3 ₂ and the first mirror 4 ₁ is mounted on the carriage 8, the second mirror 4 ₂ and the third mirror 4 ₃ is mounted on the second carriage 9, a second carriage 9 of the first carriage 8 1/2
, The optical path length from the document 1 to the CCD is kept constant, and the first and second carriages are scanned from right to left when reading the original image. Carriage drive pulley 11 fixed to the shaft of carriage drive motor 10
The first carriage 8 is connected to a carriage driving wire 12 wound around the second carriage 9, and the wire 12 is wound around a moving pulley (not shown) on the second carriage 9. As a result, the first carriage 8 and the second carriage move forward (scanning of the original image) and return (return) by the forward and reverse rotations of the motor 10, and the second carriage 9 is 1/2 of the first carriage 8. Move at speed.

When the first carriage 8 is at the home position shown in FIG. 1, the first carriage 8 is detected by a home position sensor 39 which is a reflection type photo sensor. That is, when the first carriage 8 is driven to the right by exposure scanning and deviates from the home position, the sensor 39 becomes non-light receiving (carriage non-detection). When the first carriage 8 returns to the home position by return, the sensor 39 returns to the home position. Numeral 39 indicates light reception (carriage detection), and when there is a change from non-light reception to light reception, the carriage 8 is stopped.

Referring now to FIG. 2, the outputs of the CCDs 7r, 7g, 7b are:
The image is subjected to analog / digital conversion and subjected to necessary processing by the image processing unit 100, so that recording color information of black (BK), yellow (Y), magenta (M) and cyan (C) is used for recording energization. Is converted into a binary signal. Each of the binarized signals is supplied to the laser driver 112bk, 11
The laser beams are input to 2y, 112m, and 112c, and the respective laser drivers energize the semiconductor lasers 113bk, 113y, 113m, and 113c, thereby emitting laser light modulated with a recording color signal (binary signal).

Referring to FIG. The emitted laser light is reflected by the rotating polygon mirrors 13bk, 13y, 13m, and 13c, respectively.
After passing through the f-θ lenses 14bk, 14y, 14m and 14c, they are reflected by the fourth mirrors 15bk, 15y, 15m and 15c and the fifth mirrors 16bk, 16y, 16m and 16c, and are polygon mirror mirror correction cylindrical lenses 17bk, 17y and 17m. And 17c, the photosensitive drum 18b
Image irradiation is performed on k, 18y, 18m and 18c.

The rotating polygon mirrors 13bk, 13y, 13m, and 13c are fixed to the rotating shafts of the polygon mirror driving motors 41bk, 41y, 41m, and 41c. Each motor rotates at a constant speed and drives the polygon mirror at a constant speed. By the rotation of the polygon mirror, the aforementioned laser light is
Scanning is performed in a direction perpendicular to the rotation direction (clockwise) of the photosensitive drum, that is, in a direction along the drum axis.

The laser scanning system of the color recording apparatus is disclosed in detail in Japanese Patent Application No. 60-37213 filed by the present applicant.
The same applies to the laser scanning system shown in the figure.

The surface of the photoreceptor drum is uniformly charged by charge scorotrons 19bk, 19y, 19m and 19c connected to a negative voltage high voltage generator (not shown). When the laser beam modulated by the recording signal is applied to the uniformly charged photoreceptor surface, the charge on the photoreceptor surface flows to the device ground of the drum main body due to a photoconductive phenomenon and disappears. Here, the laser is not turned on in a portion where the document density is high, and the laser is turned on in a portion where the document density is low. As a result, portions of the surface of the photosensitive drums 18bk, 18y, 18m, and 18c corresponding to portions where the document density is high have a potential of -800V, and portions corresponding to portions where the document density is low have a potential of about -100V. An electrostatic latent image is formed corresponding to the shading. This electrostatic latent image is developed by a black developing unit 20bk, a yellow developing unit 20y, a magenta phenomenon unit 20m, and a cyan developing unit 20c, respectively, and the surfaces of the photosensitive drums 18bk, 18y, 18m, and 18c are black, yellow, and magenta, respectively. And a cyan toner image. The toner in the developing unit is positively charged by agitation, and the developing unit is biased to about -200 V by a developing bias generator (not shown). A corresponding toner image is formed.

On the other hand, the recording paper 267 stored in the transfer paper cassette 22 is fed out by the feeding operation of the feed roller 259, and sent to the transfer belt 25 at a predetermined timing by the registration roller 24. The recording paper placed on the transfer belt 25 is a transfer belt.
25, the photosensitive drums 18bk, 18y, 18m and 18c
Of the black, yellow, magenta and cyan toners on the recording paper by the action of the transfer corotron at the lower part of the transfer belt while passing through the lower part of the transfer belt sequentially and passing through the photosensitive drums 18bk, 18y, 18m and 18c. Are sequentially transferred.
The transferred storage paper is then sent to a heat fixing unit 36, where the toner is fixed to the recording paper, and the recording paper is discharged to a tray 37.

On the other hand, the residual toner on the photoconductor surface after the transfer is removed by the cleaner units 21bk, 21y, 21m, and 21c.

The cleaner unit 21bk that collects black toner and the black developing unit 20bk are connected by a toner collecting pipe 42, and the black toner collected by the cleaner unit 21bk is collected by the developing unit 20bk. The yellow, magenta, and cyan toners collected by the cleaner units 21y, 21m, and 21c are transferred to the photosensitive drum 18y by reverse transfer of black toner from recording paper to a transfer station. Since the toner in the container is mixed, it is not collected for reuse.

A transfer belt 25 for feeding the recording paper in the direction from the photosensitive drums 18bk to 18c is stretched around an idle roller 26, a drive roller 27, an idle roller 28, and an idle roller 30, and is driven to rotate counterclockwise by the drive roller 27. Is done. Drive roller
27 is pivotally attached to the left end of a lever 31 pivotally attached to a shaft 32. A plunger 35 of a black mode setting solenoid (not shown) is pivotally attached to the right end of the lever 31. A compression coil spring 34 is disposed between the plunger 35 and the shaft 32,
The spring 34 applies a clockwise rotational force to the lever 31.

When the black mode setting solenoid is not energized (color mode), as shown in FIG. 1, the transfer belt 25 on which the recording paper is placed is in contact with the photosensitive drums 44bk, 44y, 44m and 44c. In this state, when the recording paper is placed on the transfer belt 25 and toner images are formed on all the drums, the toner images of the respective images are transferred onto the recording paper as the recording paper moves (color mode). When the black mode setting solenoid is energized (black mode), the lever 31 rotates counterclockwise against the repulsive force of the compression coil spring 34, the drive roller descends 5 mm, and the transfer belt 25
Are separated from the photosensitive drums 44y, 44m and 44c and remain in contact with the photosensitive drum 44bk. In this state, since the recording paper on the transfer belt 25 only comes into contact with the photosensitive drum 44bk, only the black toner image is transferred to the recording paper (black mode). Since the recording paper does not contact the photosensitive drums 44y, 44m and 44c, the recording paper
No attached toner (residual toner) of 4m and 44c is attached, and no stain such as yellow, magenta, and cyan appears.
That is, in copying in the black mode, a copy similar to that of a normal single-color black copying machine can be obtained.

The console board 30 has a copy start switch,
Color mode / black mode designation switch 302 (the switch key is turned off and color mode is set immediately after the power is turned on; when the switch is closed for the first time, the switch key is turned on and the black mode is set and the black mode setting solenoid is energized; the second time When the switch is closed, the switch key is turned off, the color mode is set and the black mode setting solenoid is turned off, and other input key switches, a character display, an indicator light, and the like are provided.

Next, the operation timing of the main part of the copying machine will be described. First
At substantially the same timing as the start of the exposure scanning of the carriage 8, the modulation bias of the laser 43bk based on the recording signal is started, and the lasers 43y, 42m, and 43c are respectively supplied to the photosensitive drums.
The modulation bias is started with a delay of the movement time Ty, Tm, and Tc of the transfer belt 25 by a distance of 44y, 44m, and 44c from 44bk. The transfer colonrons 29bk, 29y, 29m and 29c have a predetermined time from the start of modulation of the lasers 43bk, 43y, 43m and 43c, respectively (time until the laser irradiation position on the photosensitive drum reaches the transfer corotron). Triggered after a delay.

Please refer to FIG. The image processing unit 100 includes CCDs 7r and 7
The three color image signals read by g and 7b are converted into black (BK), yellow (Y), magenta (M), and cyan (C) recording signals required for recording. The BK recording signal is supplied to the laser driver 112bk as it is, but the Y, M and C recording signals are stored in buffer memories 108y, 108m and 108c, respectively. After a time delay of reading and converting to a recording signal after Tc and Tc, the laser driver 11
Feed 2y, 112m and 112c. The image processing unit 1
00 is supplied with the three-color signals from the CCDs 7r, 7g and 7b in the copying machine mode as described above. In the graphics mode, the three-color signals are supplied from the outside of the copying machine to the external interface 11.
Given through 7.

Shading correction circuit 101 of image processing unit 100
Reads the color gradation data obtained by A / D converting the output signals of CCD7r, 7g and 7b into 8 bits, by correcting for uneven optical illuminance, sensitivity variations of the internal unit elements of CCD7r, 7g and 7b, etc. Create color gradation data.

The multiplexer 102 is a multiplexer that selectively outputs one of the output gradation data of the correction circuit 101 and the output gradation data of the interface circuit 117.

The gamma correction circuit 103, which receives the output (color gradation data) of the multiplexer 102, changes the gradation (input gradation data) according to the characteristics of the photoreceptor. And further changes the input 8-bit data to the output 6-bit data. Since the output is 6 bits, data indicating one of the 64 gradations is output. The 6-bit three-color gradation data indicating the gradations of red (R), green (G), and blue (B) output from the γ correction circuit 103 are supplied to a complementary color generation / black separation circuit 104.

Complementary color generation and complementary color generation in the black separation circuit 104 are replacement of names of color reading signals with recording color signals, in which red (R) gradation data is cyan (C) gradation data and green (G) gradation data. The grayscale data is converted (read) by converting the grayscale data into magenta (M) grayscale data and the blue grayscale data (B) into yellow grayscale data (Y). The C, M, and Y gradation data are directly supplied to the averaged data compression circuit 105. If all of these gradation data indicate high density, black recording may be performed. Therefore, the digital comparator in the circuit 104 converts the C, M, and Y gradation data to respective threshold setting switches. Compare with the set reference value data. Each of the digital comparators compares 8-bit data with each other, and outputs data (input data) obtained by adding upper 2 bits of L level to 6 bits of gradation data, 1 bit of lowermost digit and 1 bit of upper digit. The 3 bits are set to the L level, and the lower 2nd to 4th bits are compared with 8-bit data (reference value data) set as reference value data set by the threshold setting switch, and if the input data is the reference value data When L is exceeded, H is given to the NAND gate. The NAND gate outputs L (black) when all the comparators are supplying the L signal, and outputs H (white) when any of the comparators is supplying the H signal.
To explain this in more detail, the gradation data input of the comparator is in the range of 0 to 3FH in hexadecimal 6-bit data. When the value is 0, black is output, as the value increases, white is output, and the output black At the time of insertion, L is black and H is white. Therefore, the MSB side 2 bits (Q6, 7) of the 8-bit input data are set to L
Then, the gray scale data 9 of C, M, and Y is input to the lower 6 bits (Q0 to Q5). The comparison data uses a rotary dip switch so that seven comparison levels can be set. Further, since the black level is set at 8 levels, if black is included including a very white color, halftone (gray) can be recorded as black to increase the resolving power. However, black is increased in color balance, which is not preferable. Therefore, the 5th and 6th bits are also set to L so that the intermediate level can be set in 7 steps. Also, since it is not necessary to set very finely, the LSB side 1 bit is set to L and the intermediate 3 bits (P1 to 3) are switched from the dip switch. Is entered. Now, if the setting of the dip switch is 010, the reference value is 0000010, and C, M,
When all the data of each Y is below this value, that is, between 0 and 3 of the decimal number, the output of the comparator is L and the black (BK) output is L (black). Here, the setting DIP switch is used for comparison of C, M and Y. However, by using three sets, each color can be set or the setting range width of each color can be set to the minimum and maximum setting. By setting using a switch, it is also possible to output the resolving power of a specific color in a black pattern.

The averaged data compression circuit 105 of the image processing unit 100
4 × 4 with 6-bit gradation data for one image
The image data is averaged and output as 6-bit gradation data. In the case of this embodiment, the processing mode in which the size of the input image and the size of the output image are the same is standardized, and the input data (read value from the CCD) is A / D converted to 8-bit data and converted to 6-bit data by gamma correction. But
Output data to the laser driver is laser on / off (1 bit) data. By input 6-bit data
It is possible to separate 64 levels of density. Accordingly, density data is obtained by averaging the density of 8 × 8 pixels of the input data. or,
By this averaging, the data amount and the processing speed are reduced to 1/64, and the data capacity for storage and the cost of the hardware are reduced.

Next, the masking processing circuit 106 and the UCR processing circuit 107 will be described. The formula for the masking process is generally Yi, Mi, Ci: unmasked _{data, Y 0, M 0, C} 0: the masking after data.

In addition, UOR processing is also a general formula: Can be represented by

Thus, in this embodiment, using these equations and using the product of both coefficients, Is calculated to find a new coefficient. Masking process and
The coefficient (a ₁₁ ″) of the above equation that performs both UCR processes simultaneously
) Are calculated in advance and substituted into the above-mentioned arithmetic expressions, and the calculated values (Y ₀ ′, etc.) of the UCR processing circuit 107 associated with the predetermined inputs Yi, Mi and Ci (each bit) of the masking processing circuit 106 The output is stored in the ROM in advance. Therefore, in this embodiment, the masking processing circuit 106 and the UCR processing circuit 107 are constituted by one set of ROM, and the data of the address specified by the inputs Y, M, and C to the masking processing circuit 106 is stored in the UCR processing circuit. Buffer memory 108 as output of 107
y, 108m, 108c and the gradation processing circuit 109. Generally speaking, the masking processing circuit 106 corrects the Y, M, and C signals in accordance with the spectral reflection wavelength characteristics of the recording image forming toner, and the UCR processing circuit 107 superimposes each color toner. The correction for color balance in the alignment is performed.

Next, the buffer memories 108y and 108m of the image processing unit 100
And 108c. These simply generate a time delay corresponding to the distance between the photosensitive drums.
Although the write timing of each memory is simultaneous, the read timing is such that the memory 108y is adjusted to the modulation energizing timing of the laser 43y, the memory 108m is adjusted to the modulation energizing timing of the laser 43m, and the memory 108c is adjusted to the laser 43c. This is performed in accordance with the modulation energizing timing, and differs for each. The capacity of each memory is when the maximum size is A3, and the memory 108y has a minimum of 24% of the maximum required size of A3 documents, and the memory 10
It suffices that 48% is used for 8 m, and about 72% is used for the memory 108. For example, assuming that the reading pixel density of the CCD is 400 dpi (dot per inch: 15.75 dots / mm), the memory 108y has approximately 87 Kbytes, the memory 108m has approximately 174 Kbytes, and the memory 108m has approximately 174 Kbytes.
8c should have a capacity of about 261 bytes. In this embodiment, since 64 gradations and 6 bit data are handled,
108y, 108m and 108c have capacity of 87K, 174K and 2 respectively
It is 61K bytes. When the memory address is calculated as a 6-bit unit from a byte unit (8 bits), a memory 108y: 116K × 6 bits, a memory 108m: 232 × 6 bits, and a memory 108c: 348K × 6 bits.

Next, the density pattern predetermined circuit 109 of the image processing unit 100
Will be described. This circuit 109 is a circuit for generating a pattern corresponding to the density from the recording density data of each of Y, M, C and BK, and includes a BK gradation processing circuit 109bk, a Y gradation processing circuit 109y, and a / M floor. Tone processing circuit 109m and C gradation processing circuit 109c
It is composed of

The 6-bit gradation data can represent density information of 64 gradations (65 gradations including 0 to which no pattern is assigned). Ideally, if the dot diameter of one dot can be varied to 64 steps, the resolution will not be reduced, but dot diameter modulation is only stable at most about 4 steps in the laser beam electrophotographic method. There are many combinations of density patterning and beam modulation. Here, a processing method of 64 gradation expression using an 8 × 8 matrix is used.

FIG. 3 shows the configuration of the Y gradation processing circuit 109y. The pattern memory 1012 is a ROM, and as shown in FIG.
From a halftone expression pattern (threshold distribution pattern) in which threshold data is distributed in 8 matrices, recording information bits are written only at one position of the threshold and non-recording information bits are written at other threshold positions. Density 1 pattern specified by density 1... Recording information bits are written at positions below the threshold value i and non-recording information bits are written at other threshold positions. And a total of 64 halftones of the recorded information bit representation of the pattern,... And the density 64 patterns specified by the density 64 in which the recorded information bits are written at positions (that is, the entirety) of those below the threshold value of 64 An expression pattern has been written. This Y allocation pattern has a center of an 8 × 8 matrix and a halftone dot center at four corners. The hatched cells in FIG. 11a indicate positions where recording information bits are allocated when the density data indicates 32.

The other tone processing circuits 109m, 109c, and 109bk have the same hardware configuration as the circuit 109y. However, the halftone pattern data 9 stored in the pattern memory is different.
In the pattern memory (not shown), 64 patterns created based on the original pattern shown in FIG.
A pattern memory (not shown) of 109bk stores 64 patterns created based on the original pattern shown in FIG. 11d.

Next, the halftone processing of one color Y will be described using the gradation processing circuit 109y as an example. The processing operations of the other gradation processing circuits are the same.

As described above, one halftone expression pattern (mother matrix pattern) in one group is specified by the recording density data, and information of a child matrix pattern forming a part of the mother matrix pattern is extracted. Image information is obtained in a form assigned to gradation data. According to this, since the gradation pattern is updated in the unit of the child matrix pattern, the resolution is increased, and thereby, the reproducibility of the edge portion of the face outline, line drawing, etc. of the photographic image is improved. For example, in the outline of the image, the corresponding child matrix pattern becomes a part of the high-density mother matrix pattern, so that the outline clearly appears, and in the low-density portion outside the outline, the corresponding child matrix pattern. Since the pattern becomes part of the low-density mother matrix pattern, a low-density image appears and the outline becomes clear. Further, since the large (mother) matrix pattern is specified by the recording density data, the smoothness is improved in the portion where the poorly changing gradation gradually changes. In other words, the number of child matrix patterns, each of which constitutes a mother matrix pattern corresponding to the recording density data, is arranged in an area corresponding to one mother matrix pattern of the reproduced image.

However, since the mother matrix pattern has similar patterns when the expression density is close, the number of child matrix patterns constituting one mother matrix pattern is small in the image portion where the density is gradually changing. Is similar to one specific mother matrix pattern, and the number of expressed gradations is about the same as the number of expressed gradations represented by the mother matrix pattern. Moreover, FIGS. 11a to 11d
As shown, any unique screen angle can be set for each color. As described later, the mother matrix pattern MM
P is m in the main scanning direction and n in the sub-scanning direction.
× n child matrix patterns CMP _{11 to} CMP _mn ,
The head of the script indicates the position in the main scanning direction of the child matrix pattern in the mother matrix pattern, and the latter half of the script indicates the position in the sub-scanning direction. And m × n pieces of grayscale data, which are also ICD ₁₁ to ICD _mn Assuming that the image information of one mother matrix pattern is obtained, the information of the child matrix pattern CMPij of the mother matrix pattern specified by the gradation data ICDij is obtained as the image information of the bit distribution corresponding to the gradation data ICDij. .
That is, the position of the child matrix pattern for obtaining the image information corresponding to each of the arrangement of one mother matrix pattern and the number m × n of gradation data corresponds to the position of the gradation data in the mother matrix pattern. Position. According to this, in the area corresponding to one mother matrix pattern of the reproduced image, the information is that of each mother matrix pattern corresponding to each gradation data, but the position is a predetermined number that constitutes one mother matrix pattern as a whole. It has a shape in which m × n child matrix patterns at positions are arranged. According to this, since the mother matrix pattern is similar when the expression density is close, in the image portion where the density is slowly changing, the reproduced image by the m × n child matrix patterns is specified. The similarity with one mother matrix pattern is further increased, the number of expressed gradations becomes equal to the number of expressed gradations represented by the mother matrix pattern, and the density is expressed by the conventional fixed density pattern method using the mother matrix pattern. Be equivalent. Further, for example, in the contour line of the image, the corresponding child matrix pattern becomes a part of the high-density mother matrix pattern, so that the contour line clearly appears, and in the low-density portion outside the contour line, it corresponds thereto. Since the child matrix pattern becomes a part of the low-density mother matrix pattern, a low-density image appears, and the outline becomes clearer.

The mother matrix pattern of one group has density No. 1 to 64
8 × 8-bit (pixel) configuration that expresses 64 gradations (no density 0 pattern, but 65 densities with 0 density included), each with one mother matrix pattern Is created based on the original mother pattern (FIG. 11a) having 64 threshold data, as described above.

When the mother matrix pattern is divided into two, A and B shown in FIG. 5A or 5B are child matrix patterns. In the child matrix pattern division shown in FIG. 5a, the odd-numbered one of the recording density data for one row is
Mother matrix pattern corresponding to density (1 out of 648 types)
) And extract the left half A as recorded data,
An even numbered mother matrix pattern corresponding to the density is specified, and the right half B thereof is extracted as recording data. In the child matrix pattern division shown in FIG. 5b, a mother matrix pattern (one of 64 types) corresponding to each density of the recording density data of the odd-numbered row is specified, and the upper half A
Is extracted as print data, a mother matrix pattern corresponding to the density is specified in each of the print density data of the odd-numbered rows, and the lower half B is extracted as print data.

FIG. 5c shows an example in which the mother matrix pattern is divided into four child matrices A to D. In this example, the mother matrix pattern (one of 64 types) is specified by the odd-numbered recording density data of the odd-numbered row, and the data of the upper left quarter (corresponding to A in FIG. 5c) is extracted. , The mother matrix pattern (one of the 64 types) is identified from the even-numbered recording density data in the odd-numbered row, and the data of the upper right quarter (corresponding to the B in FIG. 5c) is extracted. Identify the mother matrix pattern (one of 64 types) using the odd-numbered recording density data in the row, extract the data of the lower left quarter (corresponding to C in FIG. 5o), and extract the even-numbered row. The mother matrix pattern (one of 64 types) is specified by the number recording density data, and the data of the lower right quarter (corresponding to D in FIG. 5c) is extracted.

When the mother matrix pattern is divided into 16 matrix patterns A to P as shown in FIG.
Similarly, when dividing the mother matrix pattern into 64 child matrix patterns A, B, C,... As shown in FIG. The image information of the child matrix pattern at the position corresponding to the assignment position of the density data to the pattern is extracted.

Now, the recording density data shown in FIG. 7a has arrived, and the mother matrix pattern (recording information bit distribution) is
Assuming that there are 64 types corresponding to densities 1 to 64 shown in the figure, and when four divisions are specified, the gradation data is The reproduced image data is the distribution shown in Fig. 8a (the values in Fig. 8a correspond to the density values in Fig. 10;
5c shows the divided part). That is, the child matrix patterns are arranged as follows in accordance with the distribution of the incoming recording density data (FIG. 7a).

Note that the leading numeral indicates a mother matrix pattern of the mother matrix pattern 1 assigned to the density indicated by the numeral.

In the above, the rectangular range surrounded by the line is the size of one mother matrix pattern. In FIG. 8a, a rectangular area surrounded by a bold line is the size of one mother matrix pattern. The reproduced image has the form shown in FIG. 9a.

When gradation data is arranged as shown in FIG. 7b,
When the image information is reproduced in 16 divisions (as shown in FIG. 5d),
The arrangement of the child matrix pattern shown in FIG.

In FIG. 8b, the rectangular area surrounded by the thick line is the size of one mother matrix pattern. In FIG. 8a, the numbers are
It refers to the mother matrix pattern of the mother matrix pattern 4 assigned to the density indicated by the numeral.
The reproduced image has the form shown in FIG. 9b.

The child matrix pattern A shown in FIG.
The extraction of the child matrix patterns A and C shown in FIG.
4a, the 1-byte matrix pattern F0H shown in FIG.
This is performed by taking a logical product with the data of the line. When the logical product is obtained, the logical product is stored in a page memory or a buffer memory. This is performed for eight lines.

In the mask pattern shown in FIG. 4a, "1" (shown by oblique lines) is stored in a portion to be extracted, and "0" is stored in a portion not to be extracted. That is, the mask pattern F0H shown in FIG. 4a is data indicating F0H.

The child matrix pattern B shown in FIG.
The extraction of the child matrix patterns B and D shown in FIG.
This is performed by taking the logical product of the one-byte mask pattern 0FH shown in FIG. 4a and the data of one line in the main scanning direction of the mother matrix pattern to be extracted. When the logical product is calculated, the page memory or the buffer memory stores “0” of the non-extracted portion of the previous logical product memory. Therefore, the data in the memory target area of the page memory or the buffer memory is read, and the logic obtained just now is obtained. The logical sum with the product data is calculated, and the logical sum is updated and stored in the page memory or the buffer memory. This is done for the line. No.
The mask pattern OFH shown in FIG. 4a also stores “1” (shown by diagonal lines) in a portion to be extracted, and stores “0” in a portion not to be extracted. The mask pattern 0FH shown in FIG. 4a is data indicating 0FH.

Similarly, in the extraction of the pattern information in the child matrix pattern division shown in FIG. 5d, the extraction of the child matrix patterns A, E, I, and M uses the mask pattern C0H shown in FIG. For the extraction of F, J and N, a mask pattern of 30H is used, for the extraction of C, G, K and O, the mask pattern of 0CH is used, and for the extraction of D, H, L and P, 03H is used. A certain mask pattern is used.

Thus, the data (logical product) extracted from A, E, I, and M is written to the page memory or the buffer memory as it is, but A, E, I and M, C, G, K, and O, and D, H, The data (logical product) obtained by extracting L and P is ORed with data already written in the page memory or the buffer memory, and then updated in the page memory or the buffer memory.

In the child pattern division shown in FIG. 5e, information extraction of the child matrix pattern is similarly performed.

In the above description, the mother matrix pattern is one byte in the main scanning direction and is in byte units, and the child matrix patterns are all the same size. The number of bits in the sub-scanning direction of the mother matrix pattern and the child matrix pattern is arbitrary since there is no problem in terms of information processing whether it is a byte unit.

However, in the main scanning direction, it is preferable that both the mother matrix pattern and the child matrix pattern be byte units first, since information can be processed at a high speed in byte units. Therefore, in the above-described embodiment, the child matrix pattern is processed in byte units by the logical processing using the mask pattern. Therefore, according to this logical processing, all the child matrix patterns constituting one mother matrix pattern do not have to be the same size. When the mother matrix pattern is in units of bytes, the child matrix pattern can be easily processed in units of bytes as described above.

However, when both the number of bits in the main scanning direction of the mother matrix pattern and the number of bits in the main scanning direction are fractions of bytes, the processing becomes complicated.

Therefore, in such a case, focusing on the number of bits c in the main scanning direction of the child matrix pattern, c × d = e bytes,
Assuming that d and e are the minimum integers, a mask pattern in which one column of data in a child matrix pattern arranged in the main scanning direction is continuously written c times to e bytes, and then only one column of data is required in e bytes AND data is written to the page memory or the buffer memory. When the child matrix pattern is the leftmost one, the logical product data is written as it is to the page memory or the buffer memory, but in the case of the child matrix pattern at other positions, the data of the page memory or the buffer memory is further written. The logical sum is obtained and then written to the page memory or the buffer memory.

As described above, since a large mother matrix pattern is used, the number of gradations can be increased, and since the mother matrix pattern can be easily configured in bytes, information processing can be easily performed in bytes. Since the child matrix pattern is assigned to the gradation data, there is an advantage that the resolution is increased.

Further, there is an advantage that the magnification of the reproduced image can be changed. For example, one child matrix pattern is assigned to one gradation data, but in the child matrix pattern division shown in FIGS. 5a to 5e, the size (number of bits, that is, the number of dots) of each child matrix pattern is different. Therefore, the magnification of the reproduced image differs between the child matrix pattern divisions shown in FIGS. 5a to 5e.

That is, assuming that one piece of gradation data indicates the density of the entire area of four dots (corresponding to the child matrix shown in FIG. 5d) of the original image, the child matrix pattern division shown in FIG. In Fig. 5a, the reproduced image has a magnification of 1: 1 with respect to the original image. However, in the sub-matrix pattern division shown in Fig. 5a, the reproduced image is enlarged twice in the main scanning direction and quadrupled in the sub-scanning direction. In the child matrix pattern division shown in FIG. 5b, the reproduced image is enlarged four times in the main scanning direction and twice in the sub scanning direction. In the child matrix pattern division shown in FIG. In the sub-matrix pattern division shown in FIG. 5e, the reproduced image becomes twice as large in both the scanning direction and the reproduction image becomes 1/2.
The reproduced image is slightly reduced.

Therefore, for example, as shown in FIGS. 5c to 5e, a plurality of child matrix pattern divisions are set, and one division mode is specified in accordance with magnification instruction data M (M indicates the number of divisions). Then, the magnification of the reproduced image can be selected. In order to increase the selectable magnification, it is preferable to increase the size of the mother matrix pattern.

Here, the configuration and operation of the Y gradation processing circuit 109y shown in FIG. 3 will be described. The pattern memory 1012 is a ROM storing 64 types of mother matrix patterns created based on the original patterns shown in FIG. 11a. , One of the patterns is specified by the recording density data output from the memory 108y. Data of a specific portion (all rows: 8 bits) of the specified pattern is specified by the microprocessor 1010,
Read from the memory 1012 is supplied to the AND gate LG ₁ in. Andgate LG ₁ , microprocessor 1010
Gives the aforementioned mask pattern (1 byte). In logical processing by the AND gate LG _1, so that the data in the child matrix pattern is removed. Excised data is applied to the data selector G _3. Selectors G _3, and the OR gate LG ₂ is for processing the issued enemies data bit distribution of the recording surface corresponding, the control of Ki read out of the microprocessor, at least one row (8 dots width) or higher Extracted data is spread on a buffer memory having a memory capacity. The data expanded in the buffer memory is transferred to the laser driver 112y on a row-by-row basis.

6a and 6b show the data processing operation of the microprocessor 1010. To explain this, the computer
1010, when proceeding to gradation data processing for converting print density data received from the memory 108y into print data (data indicating print dot distribution), first, magnification instruction data M (M is the number of divisions of the mother matrix pattern = child matrix pattern) The number of divisions in the main scanning direction and sub-scanning direction,
That is, $ M is set in the register L (step 1:
Hereinafter, the word “step” is omitted in parentheses.) In this example, M is 4 (FIG. 5c), 16 (FIG. 5d) and 64
(Fig. 5e). Note that M = 16
(Extraction of the child matrix in FIG. 5d) is the standard, and the reproduced image is the same size as the original image.

Next, the microprocessor 1010 sets 1 (j = 1) to a counter V for grasping the position (j) of the sub matrix pattern to be processed in the sub-scanning direction (step 2),
The counter H for grasping the position (i) in the main scanning direction is set to 1 (i = 1) (step 3), and data from the memory 108y is read (step 4). If the input data is recording data, the contents of the line counter LC are
A value obtained by multiplying the content of the register L by a value obtained by subtracting 1 from the content of the counter V is set (8).

Next, the microprocessor 1010 specifies a mask pattern based on the magnification instruction data M and the contents of the counters V and H (9). That is, a child matrix pattern CMPij from which image data is to be extracted is specified based on the number of divisions M and the contents of the counters V and H (i is the contents of the counter H, j is the contents of the counter V, and M is FIG. The number of divisions that indicates which division mode in FIG. 5e), the matrix pattern to be assigned to this child matrix pattern (for example, FIGS. 4a and 4b
Figure).

Next, the microprocessor 1010 has a pattern memory 1012.
1 byte data of the line (aligned in the main scanning direction) indicated by the content of the line counter LC is stored in a buffer memory BUF (internal register) (10), and the data of the buffer memory BUF and the data of the mask pattern are ANDed. ANDs given to the gate LG _1, to update the memory of the logical data in the buffer memory BUF (11), the counter H
(12).

If the content of the counter H is 1, which indicates that the matrix turn for extracting information is the leftmost one in the mother matrix pattern, the buffer memory BUF
Is written to the buffer memory 1020 as is (1
Five).

If the content of the counter H is not 1, the data of the leftmost child matrix pattern has already been written in the memory 1020. By this writing, the data "0" of the mask pattern is written in the other child matrix pattern writing section. Since it is stored in memory, the LC line (LC is the contents of the counter LC) (1 byte) of the previously written pattern data is read from the memory 1020 and stored in the buffer memory MBUF (internal register). ORs giving data of the data and buffer memory BUF buffer memory MBUF to the OR gate LG _2, to update the memory of the logical sum data in the buffer memory BUF (14), and updates the memory data of the buffer memory BUF in the page memory 1020 (15 ).

Next, the microprocessor 1010 increments the line counter LC by one (16), and the contents of the line counter LC and the number of lines of the child matrix pattern (17), and the content of the line counter LC is equal to the number of lines. If not, the process proceeds to the next line of image extraction, but if it does, the counter H is incremented by one (18), and the contents of the counter H are compared with the contents of the register L (19). If the former is greater than the latter, image extraction has been completed for the child matrix pattern located at the leftmost position in the main scanning direction in the mother matrix pattern,
To advance the next process to the leftmost child matrix pattern, the content of the counter H is set to 1 (20), and the process proceeds to the next data reading (4).

When the data read in the data reading (4) indicates the end of the halftone processing, the microprocessor
1010 returns to the main routine. When the data is line feed "LF", the counter V is incremented by one (21), and the contents of the counter V are compared with the contents of the register L (22). If the former is larger than the latter, it means that the image processing for one mother matrix pattern has been completed, so 1 is set to the counter V (23) and the process returns to the data reading (4). When the data is the carriage return “CR”, it means that the image processing for the width of one mother matrix pattern in the main scanning direction has been completed.
Is set (3), and the process proceeds to data reading (4).

In the above description, a mother matrix pattern (halftone expression pattern) having 64 types as one group is formed using an original pattern having threshold data (FIG. 11a), and this is stored in the memory 1012 in advance. As described above, the memory 1012 stores the halftone expression pattern of the original pattern as a halftone expression pattern, compares the recording density data given from the memory 108y with each threshold of the original pattern, and A mother matrix pattern may be created, or the original pattern may be compared with each of the recording density gradation data (showing 1 to 64) before the gradation processing.
A mother matrix pattern of groups (64) may be created and stored in a memory such as a RAM. In this way, the data in the memory 1012 can be reduced.

With the same hardware configuration and control operation as the gradation processing circuit 109y described above, the gradation processing circuits 109m, 109c and 109bk
Generates recording image data of magenta M, cyan C and black BK, respectively. These are different in that the halftone dot centers of the mother matrix (halftone expression pattern) stored in the pattern memory are located at different positions based on the original patterns shown in FIGS. 11a to 11c, respectively. .

〔The invention's effect〕

According to the present invention, on the halftone expression pattern, as the indicated density increases, the recording area is set such that the area increases from the different predetermined point for each color, with the area increasing as the expression density increases. Since the spread and the halftone dot shape are the same, that is, the halftone dot center is different for each color and the halftone dot shape is the same, the overlap of the recording colors is minimized, and the color selected at the time of color image reproduction is minimized. Reproducibility and resolution can be obtained. Further, by adopting the above-described sub-matrix method, the smoothness of the halftone expression is not impaired, and the sharpness and wide gradation range of the recording color and the smoothness of the gradation expression are simultaneously realized. Also suitable for scaling output of images with smooth color expression.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a mechanical structure according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the electric system of the embodiment. FIG. 3 is a block diagram showing a configuration of the gradation processing circuit 109y shown in FIG. 4a and 4b are plan views showing mask patterns used for extracting a child matrix pattern. 5a, 5b, 5c, 5d and 5e show the number of modes in which the halftone expression pattern is divided into child patterns (partial patterns) A, B, C,. It is a top view which shows a seed. FIGS. 6a and 6b are flowcharts showing the recorded image data processing operation of the microprocessor 1010 shown in FIG. 7a and 7b are plan views showing the distribution of the recording density data corresponding to the recording surface, and the numbers in the figures indicate the densities (decimal numbers) indicated by the recording density data. 8a and 8b respectively correspond to the recording density data distributions shown in FIGS. 7a and 7b, respectively, and extract the recording data from the halftone expression pattern by dividing FIGS. 5c and 5d, respectively. FIG. 4 is a plan view showing a print data distribution when assigned to a print surface. 9a and 9b are plan views showing recording information distributions (shaded areas) when recording data is extracted from the halftone expression pattern shown in FIG. 10 in the mode shown in FIGS. 8a and 8b, respectively. It is. FIG. 10 is a plan view showing a halftone expression pattern of one group created based on the original data different from the original data shown in FIGS. 11a to 11d. FIG. 11a is a plan view showing a distribution pattern of original data used to create a halftone expression pattern for yellow Y print data processing according to an embodiment of the present invention, and FIG. 11b is an intermediate pattern for processing magenta M print data. 11c is a plan view showing a distribution pattern of original data used for creating a tone expression pattern, FIG. 11c is a plan view showing a distribution pattern of original data used for creating a halftone pattern during processing of cyan C print data, and FIG. FIG. 6 is a plan view showing a distribution pattern of original data used for creating a halftone pattern for BK recording dart processing. FIG. 12 is a plan view showing each color recording area distribution when each color recording density is 16, and A and a in FIG.
Based on the halftone expression pattern shown in the figure, B and b are based on the halftone expression pattern shown in FIG. 11b, and C and c are based on the halftone expression pattern shown in FIG. 11c.
D and d indicate areas recorded based on the halftone expression pattern shown in FIG. 11d. FIG. 13a is a plan view showing a distribution pattern of original data used for creating a halftone expression pattern for yellow Y recording data processing according to another embodiment of the present invention, and FIG. 13b is a magenta M
FIG. 13c is a plan view showing a distribution pattern of original data used for creating a halftone pattern for cyan C recording data processing, and FIG. 13c is a plan view showing a distribution pattern of original data used for creating a halftone expression pattern for recording data processing. FIG. 13d is a plan view showing a distribution pattern of original data used for creating a halftone pattern for black BK recording dart processing. FIG. 14 is a plan view showing the distribution of each color recording area when the recording density of each color is 16, and A and a in FIG.
Based on the halftone expression pattern shown in the figure, B and b are based on the halftone expression pattern shown in FIG. 13b, and C and c are based on the halftone expression pattern shown in FIG. 13c.
D and d indicate areas recorded based on the halftone expression pattern shown in FIG. 13d. 1: Original, 2: Platen 3 ₁ , 3 ₂ : Fluorescent light, 4 ₁ to 4 ₃ : Mirror 5: Variable lens unit 6: Dichroic prism 7r, 7g, 7b: CCD, 8: First carriage 9: Second Carriage 10: Carriage drive motor 11: Pulley, 12: Wire (1 to 12: Color image reading means) 13bk, 13y, 13m, 13c: Polygon mirror 14bk, 14y, 14m, 14c: f-θ lens 15bk, 15y, 15m , 15c, 16bk, 16y, 16m, 16c: Mirror 17bk, 17y, 17m, 17c: Cylindrical lens 18bk, 18y, 18m, 18c: Photosensitive drum 19bk, 19y, 19m, 19c: Charge scorotron 20bk, 20y, 20m, 20c: developing unit 21bk, 21y, 21m, 21c: cleaner 22: paper feed cassette, 23: paper feed roller 24: registration roller, 25: transfer belt 26, 28, 30; idle roller 27; drive roller 29 bk, 29y, 29m , 29c: Transfer corotron 31: Lever, 32: Shaft 33: Pin, 34: Compression coil spring 35: Plunger of solenoid for setting black copy mode 36: Fixer, 37: Tray (13 to 37, 41 to 46, 112: Recording means 39: Home Position Sensor 40: Carriage guide bar 41bk, 41y, 41m, 41c: Polygon mirror drive motor 42: Toner recovery pipe 43bk, 43y, 43m, 43c: Laser 44bk, 44y, 44m, 44c: Beam sensor 45: Photoconductor drum drive motor 46: motor driver 100: image processing unit 104y, 104m, 104c: digital comparator 104sh: rotary dip switch (101 to 107: color component data processing means) 109: gradation processing circuit, 109y: Y gradation processing circuit 109m: M gradation processing circuit, 109c: C gradation processing circuit 109bk: BK gradation processing circuit 1012: Pattern memory 1010: Microprocessor (pattern information reading means) 200: Microprocessor system 300: Console 301: Copy start key switch 302: Full color / monochrome black mode selection key switch

Claims (4)

(57) [Claims] 1. A color image is separated into a plurality of colors, the image density is converted into digital data for each color component, and the digital data is processed into color component recording density data; The halftone expression pattern having a plurality of threshold data corresponding to one of the threshold data for a predetermined number of dots, or all of the threshold data are compared with the respective values of the recording density data in the predetermined range, and The color component recording density data is converted into recording / non-recording bit information using a halftone expression pattern consisting of a set of bit distribution patterns corresponding to the range of recording density data, which is a recorded / non-recording bit distribution. Recording and non-recording bit information is associated with one bit of a recording medium for each color component, and a predetermined color is recorded in a dot to which recording information bits are associated; in digital color image reproduction processing: When a predetermined area is recorded by using the expression pattern, the recording information bits have a recording information bit distribution that expands from a predetermined point of the X and Y coordinates as the recording density increases in correspondence with the recording density, and the predetermined point is A halftone expression pattern destined for each color in which one set is associated with each color component, which is a position different from each other for each color, and the halftone expression patterns of all groups are centered on the predetermined point. When the halftone dot shape whose area increases as the expression density increases becomes the same, and the color component recording density data is converted into recording and non-recording bit information, the halftone specified by the color component recording density data is used. From the expression pattern, based on the coordinates of the pixels of the original image from which the color component recording density data was obtained, an area corresponding to a plurality of dots of a part of the halftone expression pattern is defined as a child matrix corresponding to the pixels of the original image. Regularly cut as a pattern, the child matrix pattern recording obtained from, and outputs the non-recording bit information as image information corresponding to the color component recording density data, wherein the digital color image reproduction processing method. 2. A halftone expression pattern having a size M · N
2. The digital color image reproduction processing method according to claim 1, wherein the gradation of the maximum number of dots M · N is determined by the following equation. 3. The halftone expression pattern MMF is divided into m × n child matrix patterns CMP _{11 to} CMP _mn by m in the main scanning direction and n in the sub scanning direction, and MMP
, The position of the child matrix pattern in the main scanning direction, and the latter half of the subscript indicate the position in the sub-scanning direction. And m × n pieces of recording density data, which similarly consist of ICD ₁₁ to ICD _mn Assuming that the image information of one halftone expression pattern is obtained, the information of the child matrix pattern CMPij of the halftone expression pattern specified by the recording density data ICDij is obtained as the recording information of the bit distribution for the recording density pattern ICDij. A digital color image reproduction processing method according to claim (1) or (2). 4. A color image reading means for separating a color image into a plurality of colors and converting image density into digital data for each color component; a color component data processing means for processing the digital data into color component recording density data; A plurality of sets of halftone expression pattern information consisting of a predetermined number of bits in which recording information bits and non-recording information bits are distributed corresponding to recording densities to be expressed as an entire area are grouped into one group. The halftone expression pattern information of each set in the same group, in which the groups are associated, is obtained by distributing the X, Y two-dimensional bits constituting the recording area, and as the recording density increases, the recording information increases as the recording density increases. Bits form a stored information bit distribution extending from predetermined points of the X and Y coordinates, and the predetermined points of each group are located at different positions. Memory means for storing halftone expression pattern information of a plurality of groups, wherein the halftone expression patterns of all groups have the same halftone dot shape whose area increases as the expression density increases with the predetermined point as the center; Means for identifying one group corresponding to the color component, identifying one set of halftone expression pattern information in the group based on the color component recording density data, and then identifying the source from which the color component recording density data was obtained. On the basis of the coordinates of the pixels of the image, an area corresponding to a plurality of dots of a part of the halftone expression pattern is regularly cut out as a child matrix pattern corresponding to the pixels of the original image. Outputting pattern information reading means; and in response to the output recording bit information, assigning the recording bit information of the recording medium. Digital color image reproducing apparatus comprising: recording means for dot recording predetermined color in the position to.