JP2000341547A - Device and method for image processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an image processor which performs optimum black generation and ground color elimination processing, even when image quality can be improved in such a manner a printing means uses a different binary pattern in each color and also improves image quality by performing density correction processing which corresponds to the printing means after generation of black color and the ground color elimination processing. SOLUTION: A binary processing part 7 binarizes CMY data after ROP processing, by the use of a prescribed binary pattern for each color. A data correcting part 9 performs black color generation and ground color elimination processing of the binarized CMY data and generates CMYK color print data. When the CMYK color print data is generated, the CMYK color print data is generated according to a binary pattern in a binary processing mode for each color. A density correction processing part 10 performs density correction processings to the characteristic of a printing part 3 of the binary CMYK color print data after the black color generation with respect to the ground color elimination processing and outputs corrected binary CMYK color print data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and an image processing method, and more particularly, to binary CMYK color print data from multi-value CMY color data and binary CMYK color data according to the characteristics of printing means. The present invention relates to an image processing apparatus and an image processing method for generating color print data.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, drawing data received from a host computer is converted into cyan (C), yellow (Y), magenta (M), and black (K). Convert to CMYK data corresponding to toner color and output to printer engine,
There is one that obtains a color image.

FIG. 10 is a block diagram showing an example of a conventional color image forming apparatus. In the figure, 1 is a host computer, 2 is an image processing unit, 3 is a printing unit, 4 is an interface control unit, 5 is a PDL interpreting unit, 6 is a drawing unit, and 7 is 2
A value processing unit, 8 is a drawing memory, 11 is a color conversion unit, 12 is a data conversion unit, and 13 is a data correction unit.

[0004] The drawing data supplied from the host computer 1 is input to an image processing unit (controller) 2,
After performing predetermined image processing, the image is output to the print unit 3 to obtain a color image. The host computer 1 outputs drawing data in an RGB color space described in a printer description language (PDL) typified by PostScript (PostScript).

The interface control unit 4 of the image processing unit 2
Receives the RGB drawing data sent from the host computer 1 and transfers it to the PDL interpreter 5. PD
The L interpreting unit 5 interprets the RGB data, converts it into CMYK data, and outputs it to the drawing unit 6. The PDL interpreter 5
Typically, it consists of a PostScript interpreter. The drawing unit 6 receives the CMY input from the PDL interpretation unit 5
The rendering process is performed in accordance with the instruction content included in the K data to create, for example, 8-bit CMYK data.
It performs logical operation processing such as processing and OR processing, and outputs the result to the binarization processing unit 7. The binarization processing unit 7 binarizes the CMYK data represented by 8 bits according to a predetermined pattern, and outputs the CMYK data to the drawing memory 8 as binary CMYK data. When, for example, one page of binary data (CMYK data) is accumulated in the drawing memory 8, the binary data is sequentially output to the printing unit 3.

[0006] The PDL interpreter 5 has a color converter 11. The color conversion unit 11 converts the supplied RGB data into CMY
A data conversion unit 12 for converting data into data, and a data conversion unit 1
And a data correction unit 13 for performing a density correction process so that the CMY data has a density change suitable for the printing unit 3.

In the black generation process in the data correction unit 13, for example, an equal amount is removed from each component of the CMY data, and black (K) is generated based on the removed CMY data. In the under color removal process, for example, an equal amount is removed from each component of the CMY data to generate black. Since an equal component is removed from each of the CMY data by the under color removal processing, there is an effect of suppressing wasteful consumption of toner. The under color removal processing and the black generation processing are performed using a BG function and a UCR function, respectively.

[0008] As a color image forming apparatus having an under color removal processing means, for example, an apparatus described in Japanese Patent Publication No. 7-36609 is known.

The color image forming apparatus shown in FIG. 10 has the following problems. In recent years, Windows
ows) printer, GDI (Graphic
2. Description of the Related Art A printer having a simplified function by performing drawing based on a cal display interface has been known. A printer that performs drawing based on GDI needs to have a function called a raster operation (ROP process). The ROP process has a feature that various image processes can be performed because the calculation method of the process in the drawing unit 6 can be selected.

This ROP processing is performed for RGB data or CM data.
Can be performed on Y data, and CMY
When processing is performed on CMYK data generated based on data, a desired processing result may not be obtained. However, as described above, conventionally, the CMY
It is input after being converted into K data. Therefore, when the ROP processing function is to be realized in the drawing unit 6, the CMY data (or RGB data) is stored in the drawing unit 6.
Must be input in the form of the drawing data.

When the printing unit 3 is configured to output an image based on CMYK data, it is necessary to generate black (K) from the CMY data.
However, there is a problem that a desired hue cannot be obtained by simply replacing the point where the CMY components overlap with each other with black (K) based on the CMY data after the ROP processing.

In order to solve such a problem, it has been considered that the undercolor removal processing and the black generation processing are performed after the ROP processing in the drawing unit 6. FIG. 11 is a block diagram showing another example of the conventional color image forming apparatus. In the figure, the same parts as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. 9 is a data correction unit. This configuration is described, for example, in Japanese Patent Application No. 9-343868. In FIG. 11, the color conversion unit 11 of the PDL interpretation unit 5
Has a function of converting input RGB data into CMY data, but does not have a function of performing undercolor removal processing and black generation processing.

In the configuration shown in FIG. 11, the drawing unit 6
ROP processing is performed on the CMY color data, and after binarization by the binarization processing unit 7, under color removal processing and black generation processing are performed by the data correction unit 9, and binary CMYK color data is obtained. In this configuration, since the ROP processing is performed on the CMY color data, a desired processing result can be obtained. Further, by performing the under color removal processing and the black generation processing after the binarization processing, a desired color is reproduced.

FIG. 12 is a block diagram showing an example of a data correction unit in another example of a conventional color image forming apparatus. In the figure, 21 is a density determination unit, 22 is a black generation correction value calculation unit, 23 is a black pattern generation unit, 24 is an under color removal correction value calculation unit, and 25 is an under color removal pattern generation unit. The under color removal processing and the black generation processing are basically processing of the density for each color. Data correction unit 13 in FIG.
When the under color removal processing and the black generation processing are performed, since multi-valued CMY color data is handled, the processing can be performed by treating the density as a numerical value. However, when undercolor removal processing and black generation processing are performed on binary CMY color data as shown in FIG. 11, density processing cannot be performed as it is.

For this reason, first, in the density judgment section 21,
For example, the density of each component of the CMY data is detected for each predetermined region of interest. The black generation correction value calculator 22 calculates multi-valued black data K ′ from the input density of each color component. The black pattern generating section 23 generates a predetermined pattern based on the multi-valued black data K ′ and outputs the same as K color print data for black.

On the other hand, the undercolor removal correction value calculation unit 24 removes the common part from the density for each color component to obtain multi-valued color data C ', M', Y '. Under color removal pattern generator 2
5 generates a predetermined pattern based on the multi-valued color data C ′, M ′, Y ′ and outputs it as CMY color print data for each color.

In the above-described example, the undercolor removal pattern generation unit 2
When generating CMY color print data for each color in step 5,
When the black pattern generating unit 23 generates the K color print data for black, the same pattern is used uniformly for each color. However, depending on the characteristics of the printing unit 3, the size, shape, position,
In some cases, it is better to change the arrangement for each density for each color. For example, if a large amount of toner overlaps on the same point, the image will be blurred.Therefore, when it is better to disperse the toner of each color, or when the screen angle is made different for each color to prevent moiré, etc. Different binarization patterns may be used.

In such a case, if the same pattern is used uniformly, even if a different pattern is used in the binarization processing,
In the CMYK color print data after the under color removal processing and the black generation processing, all the colors are generated according to the same pattern, and the performance of the printing unit 3 may not be brought out. Therefore, it has been desired to further improve the image quality.

In the configuration shown in FIG. 11, for example, a density adjustment process according to the characteristics of the printing unit 3 is performed by the color conversion unit 11.
It is done in. However, the undercolor removal processing and the black generation processing can be performed better before the density adjustment processing according to the characteristics of the printing unit 3. Therefore, in the configuration shown in FIG. 11, it is desired that the density adjustment processing according to the characteristics of the print unit 3 is further performed after the undercolor removal processing and the black generation processing, so that the image quality is further improved.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances.
It is an object of the present invention to provide an image processing apparatus capable of outputting color print data to a printing unit and further improving the image quality.

[0021]

SUMMARY OF THE INVENTION The present invention provides a multivalued CMY
An image processing apparatus or image processing method for generating binary CMYK color print data from color data.
The black density or the density of each color of CMY is detected in the target area of the CMY color data binarized by the binarizing means, and based on the detected density, the black pattern generating means generates K color print data, Under color removal pattern generation means provided for each color of CMY generates an under color removal pattern to generate CMY color print data. Each under-color removal pattern generating means can generate an under-color removal pattern in consideration of a screen used for a corresponding color when the binarization means performs the binarization processing.
Alternatively, the undercolor removal pattern generation means generates an undercolor removal pattern for at least one of CMY based on a binarization pattern used in the binarization processing. With such a configuration, for example, changing the size, shape, position, pixel arrangement for each density, and the like of the pattern used in binarization for each color can improve the image quality of the image recorded by the printing unit. Can be improved, and a high-quality image can be obtained.

According to another aspect of the present invention, there is provided an image processing apparatus or image processing method for generating binary CMYK color print data corresponding to the characteristics of a printing means from multi-valued CMY color data. Binary C that has been subjected to black generation processing and under color removal processing
The density correction processing means performs density correction processing on the MYK color print data according to the characteristics of the printing means. With this, the density correction process according to the characteristics of the printing unit can be performed after the black generation process and the undercolor removal process, so that the black generation process and the undercolor removal process are not affected by the characteristics of the printing unit. Appropriate black generation processing and undercolor removal processing can be performed. Therefore, a high quality image can be formed by the printing unit.

The density correction processing means can generate and output a density correction pattern for each predetermined region of interest based on the characteristic amount in the region of interest. The density correction pattern at this time may be set in consideration of the screen used for each color when the binarization means performs the binarization processing. Thus, for example, by changing the size, shape, position, pixel arrangement, and the like of the pattern used for binarization for each color, the image quality of the recorded image can be improved. The density correction processing corresponding to such a printing means can be performed.

Further, the black density or the density of each color of CMY is detected in the target area of the CMY color data binarized by the binarizing means as described above, and the K color print data and the CMY color data are detected based on the detected densities. When generating the CMY color print data, the K color print data and the CMY color print data may be generated after performing the processing including the density correction processing.

[0025]

FIG. 1 is a block diagram showing a configuration of a color image forming apparatus to which an embodiment of an image processing apparatus according to the present invention is applied. 10 and 11 are denoted by the same reference numerals and description thereof is omitted. Reference numeral 10 denotes a density correction processing unit. In FIG. 1, the color conversion unit 1 of the PDL interpretation unit 5
Reference numeral 1 has a function of converting input RGB data into CMY data, but does not have a function of undercolor removal processing, black generation processing, and density adjustment processing. Therefore, PD
The data input from the L interpretation unit 5 to the drawing unit 6 is a CM that has not been subjected to undercolor removal, black generation processing, and density adjustment processing.
This is Y data.

Since the input data is CMY data, the drawing unit 6 correctly returns RO data to the CMY data.
P processing can be performed. The drawing unit 6 performs arithmetic processing on the CMY data according to the instruction content, and the processed CMY data is input to the binarization processing unit 7. The binarization processing unit 7
The input data is converted into 1-bit binary data using a predetermined binary pattern for each color of CMY, and the binary data is input to the data correction unit 9. Since the data after the binarization processing performed by the binarization processing unit 7 is also CMY data, if the data correction unit 9 does not perform the color conversion from the CMY space to the CMYK space, the binary ROP processing can be performed on CMY data. Binary CMY
When performing ROP processing on data, the processing can be performed at high speed because the amount of data is small. Further, since the ROP processing is performed in the CMY space, accurate color reproduction can be expected.

The data correction section 9 performs under color removal processing and black generation processing on the CMY data binarized by the binarization processing section 7 to generate CMYK color print data.
The data is input to the density correction processing unit 10. The generation of CMYK color print data is performed according to a pattern set for each color. As the pattern, a pattern based on a predetermined binarization pattern used in the binarization processing unit 7 is used.

The density correction processing section 10 performs density correction processing for each color according to the characteristics of the printing section 3 and inputs binary CMYK color print data corresponding to the characteristics of the printing section 3 to the drawing memory 8. . At this time, based on the predetermined binarization pattern for each color used in the binarization processing unit 7, color print data corresponding to the characteristics of the printing unit 3 for each color is generated.

FIG. 2 is an explanatory diagram of an example of a binarization pattern used in a binarization processing section in an embodiment of the image processing apparatus of the present invention. As described above, depending on the characteristics of the printing unit 3, it may be better to change the size, shape, position, arrangement for each density, etc. of the binarized pattern for each color. For example, when an image is blurred when a large amount of toner is overlapped on the same point, it is better to disperse the toner of each color, and it is better to shift the position of the binarized pattern or change the arrangement for each density. . If the printing unit 3 has a characteristic that it is better to arrange toners of the same color adjacent to each other as much as possible, the binary unit is arranged so that toner adhering positions are arranged as close as possible to each density. It is good to form a conversion pattern. Further, in order to prevent moire by changing the screen angle for each color, it is preferable to use a binarized pattern having a different size (shape) for each color and a different arrangement for each density. As described above, by using the binarized pattern according to the characteristics of the printing unit 3, it is possible to improve the image quality when an image is formed by the printing unit 3.

FIG. 2 shows an example in which the position of the pattern is shifted for each color. This unit is configured by repeating a unit surrounded by a thick line as a unit. The number in each unit represents the arrangement for each concentration.
That is, when the density changes from 0 to 8, the density of the pixel corresponding to each cell is compared with the indicated numerical value. Then, binarization is performed based on whether or not the pixel density is greater than the numerical value described. By such processing, for example, in a uniform image having a density of 4, pixels marked 1, 2, 3, and 4 are recorded, and other pixels are not recorded. As a result, an image having a half density is obtained as a whole.

FIG. 2A shows an example of a binary pattern for the Y color. In the following description, the printing unit 3
From the characteristics of FIG.
As shown in FIG. 2B, a pattern obtained by shifting the binary pattern of the Y color shown in FIG. In addition, the binarized pattern for the C color also depends on the characteristics of the printing unit 3 as shown in FIG.
It is assumed that a pattern obtained by shifting the Y-color binarized pattern shown in (A) by two pixels to the right is used.

FIG. 2 shows an example in which patterns whose positions are shifted are used as the binarized patterns corresponding to the respective colors. However, as described above, the binarized pattern of each color is determined according to the characteristics of the printing unit 3, and is not limited to this example. In accordance with the characteristics of the print unit 3, the size, shape, position, arrangement of each binarization pattern (for example, the arrangement of numerals in FIG. 2), etc., may be appropriately determined.

The pattern for K color shown in FIG. 2D is not used in the binarization processing section 7. It is used in the black pattern generator 23 as described below. The pattern for the K color shown in FIG.
The color binarization pattern is shifted downward by two pixels.
In the printing unit 3 in this example, it is assumed that the image quality can be improved by recording the black pattern with the pattern shifted.

FIG. 3 is a block diagram showing an example of the configuration of the data correction unit 9 in one embodiment of the image processing apparatus of the present invention. In the figure, the same parts as those in FIG. 12 are denoted by the same reference numerals, and description thereof will be omitted. Reference numerals 25C, 25M, and 25Y denote C, M, and Y undercolor removal pattern generation units, respectively.
As in FIG. 12, the density determination unit 21 uses the binarization processing unit 7
The density of each component of the quantified CMY data is detected.
For example, a predetermined region of interest may be set, and the number of pixels to be recorded included therein may be counted for each color. The count value of each color is input to the black generation correction value calculation unit 22 and the under color removal correction value calculation units 24C, 24M, and 24Y.

The black generation correction value calculator 22 calculates an output value K 'of black (K) from the input count value of each color.
For example, the minimum value of the count value of each color is extracted as the feature amount of the CMY data, and the output value K ′ of the black (K) color is extracted from the extracted value.
Can be determined. The black pattern generation unit 23
Based on the black (K) output value Kout calculated by the black generation correction value calculator 22, black K color print data is generated. At this time, it may be generated using a pattern according to the characteristics of the printing unit 3. For example, a pattern shown in FIG. 2D can be used. In this way, binary CM
Black K color print data is generated from the Y data.

The under color removal correction value calculation unit 24 calculates an under color removal correction value based on the count value of each color detected by the density determination unit 21, and calculates the count value of each color as the under color removal correction value. The output values Cout, Mout, and Cout are output to the under-color removal pattern generators 25C, 25M, and 25Y of the respective colors.
Yout output. When calculating the under color removal correction value,
For example, the minimum value of the count value of each color is extracted as the feature amount of the CMY data, and the under color removal correction value UCR is obtained from the extracted value. Then, the under color removal correction value UC is calculated from the count value of each color.
By subtracting R, the output value Cout, M of each color is obtained.
out, Yout can be determined.

The under color removal pattern generation section 25C outputs the C color output value Cou output from the under color removal correction value calculation section 24.
The C color print data Coutptn is generated based on t. At this time, it may be generated using a pattern according to the characteristics of the printing unit 3. Similarly, the under color removal pattern generation units 25M and 25Y follow the characteristics of the printing unit 3 based on the output values Mout and Yout of the M and Y colors output from the under color removal correction value calculation unit 24. Using patterns
M color print data Moutptn and Y color print data Youptn are generated. For example, the pattern shown in FIG. 2C is used when generating C color print data, the pattern shown in FIG. 2B when generating M color print data, and the pattern shown in FIG. 2B when generating Y color print data. 2A can be used.

FIG. 4 is a flowchart showing an example of the operation of one example of the configuration of the data correction unit 9 in an embodiment of the image processing apparatus of the present invention. In S1, the density determination unit 21 counts the number of pixels to be recorded for each of the colors C, M, and Y from the binary CMY data passed from the binarization processing unit 7 with reference to a region of interest of M × N pixels. I do. Here, the count values are Cin, Min, and Yin.

Steps S2 and S3 are black color generation processing.
In S2, the black generation correction value calculator 22 calculates the count values Cin, Min, Yin of the respective colors counted by the density determiner 21.
Thus, the output value Kout of black (K) is calculated. For example,
Kout = BG (Cin, Min, Yin) using a function BG for black color generation. The function BG can be, for example, a function that multiplies the minimum value of Cin, Min, and Yin by a predetermined coefficient. Of course, other functions may be used. Then, in S3, the black pattern generation unit 2
3 is 2 from the output value Kout of black (K) obtained in S2.
Generate value K color print data.

On the other hand, S4 to S7 are undercolor removal processing.
In S4, the under color removal correction value calculation unit 24 calculates the count values Cin, Min, Yin of the respective colors counted by the density determination unit 21.
Then, the under color removal correction value UCRout is calculated. For example, the function UCRout = UCR (Cin, Min, Yin) can be obtained by using a function UCR for undercolor removal. As the function UCR, for example, a function of multiplying a minimum value of Cin, Min, and Yin by a predetermined coefficient can be used. Of course, other functions may be used.

Further, the under color removal correction value calculating section 24 performs the processing in S5.
, The under color removal correction value UCRout calculated in S4
, The output values Cout, Mout, Yout of each color
To determine. For example, the undercolor removal correction value UCR is calculated from the count values Cin, Min, and Yin of each color counted by the density determination unit 21.
By subtracting out, the output value Cou of each color is obtained.
t, Mout, Yout can be determined. That is, output values Cout, Mout, and Yout of each color can be determined by Cout = Cin-UCRout Mout = Min-UCRout Yout = Yin-UCRout. Of course, the output value Cout, M of each color
The method of determining out and Yout is not limited to this example.

In S6, the under color removal pattern generating section 2
5C generates a binary UCR pattern Cucrptn from the output value Cout of the C color. Similarly, the under color removal pattern generation unit 25M outputs a binary UCR from the output value Mout of the M color.
Generate a pattern Mucrptn. The under color removal pattern generation unit 25Y outputs a binary U from the output value Yout of the Y color.
A CR pattern Yucrptn is generated.

In this example, further, in S7, C color print data Coutptn, M color print data Moutptn, and Y color print data from the CMY data output from the binarization processing Youtp
Create tn. This process is performed for the case where the CMY data is generated by a process other than the binarization pattern normally used in the binarization processing unit 7.
For example, in the case of printing a character image, if binarization is performed using a binarization pattern as shown in FIG. 2, the image quality deteriorates. Therefore, it is desirable to perform another binarization process while retaining edges. In such a case, the UCR pattern Cucrpt
If n, Mucrptn, and Yucrptn are output as they are, the image quality deteriorates for the same reason. This S
In the process of 7, it is possible to perform a process for preventing such image quality deterioration. Here, as an example, CMY
The logical product of the data and the UCR pattern is used as color print data. That is, Cputtn = C & Cucrptn Moutptn = M & Mucrpt Youptn = Y & Yucrptn C-color print data Coutptn, M-color print data Moutptn, Y-color print data Yout
ptn can be created. Of course, the present invention is not limited to this example, and color print data of each color may be created according to other processes. The processing in S7 may be omitted if not necessary. That is, if the binary pattern is fixed, the UCR pattern Cucrptn, Mu
crptn and Yucrptn are used as they are as C color print data Coutptn and M color print data Moutpt
The n, Y color print data Youptn may be used.

As described above, the K color print data is obtained from S3, and the CMY print data is obtained from S7 (or S6).
Color print data is obtained. The CMYK color print data obtained in this way is input to the density correction processing unit 10.

The above-described black generation processing and undercolor removal processing are performed as follows.
This will be described using a specific example. FIG. 5 is an explanatory diagram of a specific example of the operation of one configuration example of the data correction unit 9 in one embodiment of the image processing apparatus of the present invention. Here, an 8 × 8 region is assumed as the region of interest, and only this 8 × 8 region is shown. In addition, the binarization processing unit 7 performs the binarization processing using the binarization patterns shown in FIGS.

FIG. 5A shows an example of binary CMY data after binarizing the multi-valued CMY data output from the drawing unit 6 by the binarization processing unit 7. C data is
This is a pattern for recording the squares denoted by 1 to 5 in FIG. Similarly, the M data is a pattern for recording squares marked 1 and 2 in FIG. 2B. Furthermore, the Y data
This is a pattern for recording squares marked 1 to 3 in FIG. It is assumed that such CMY data is input to the data correction unit 9.

In S1, the density determining section 21 determines that the 8 × 8
, The number of pixels to be recorded for each of the colors C, M, and Y is counted, and count values Cin, Min, and Yin are obtained. When the number of pixels is counted from the CMY data shown in FIG. 5A, Cin = 40, Min = 16, and Yin = 24.

In the black generation processing, the count values Cin, Min, Yi of the respective colors counted as described above in S2 are obtained.
The output value Kout of black (K) is calculated from n using the function BG. For example, if the function BG is BG (c, m, y) = min (c, m, y) × 0.5, then Kout = BG (Cin, Min, Yin) = 8.

In S3, the black pattern generator 23 calculates the binary K value from the black (K) output value Kout obtained in S2.
Generate color print data. Black (K) output value Kou
Since t = 8, it suffices to generate a pattern for performing recording on eight pixels out of 8 × 8. At this time, FIG.
Using the pattern shown in (D), for example, a pattern for recording a pixel marked 1 is represented by K color print data K.
outptn is generated and output. The generated K color print data Koutptn is shown at the right end of FIG.

On the other hand, in the under color removal processing, first, in S 4, the under color removal correction value calculation unit 24 calculates the under color using the function UCR based on the count values Cin, Min, and Yin of the colors counted by the density determination unit 21. The removal correction value UCRout is calculated. For example, if the function UCR is UCR (c, m, y) = min (c, m, y) × 0.5, UCRout = UCR (Cin, Min, Yin) = 8.

Further, the under color removal correction value calculation section 24 performs the processing in S5.
, The under color removal correction value UCRout calculated in S4
= 8 is subtracted from the count value Cin, Min, Yin of each color to determine the output value Cout, Mout, Yout of each color. That is, Cout = Cin−UCRout = 40−8 = 32 Mout = Min−UCRout = 16−8 = 8 Yout = Yin−UCRout = 24−8 = 16

In S6, the under color removal pattern generating section 2
5C, 25M, and 25Y are output values Cout, Mo of each color.
From Ut, Yout, UCR pattern Cucrp of each color
tn, Mucrptn, and Yucrptn are generated. For example, the under color removal pattern generation unit 25C outputs the C color output value C
Based on out = 32, a pattern having 32 pixels to be printed out of 64 8 × 8 pixels is generated as a UCR pattern Cucrptn using the binarized pattern shown in FIG. 2C. For example, a pattern to be recorded for squares 1 to 4 in FIG. 2C may be generated. As a result, a pattern as shown at the left end of FIG. 5B is generated.

Similarly, the undercolor removal pattern generation unit 25M
Is based on the output value Mout = 8 of the M color, using a binarization pattern shown in FIG.
UCR pattern M
ucrptn. For example, a pattern to be recorded for the square indicated by 1 in FIG. 2B may be generated. As a result, a pattern as shown in the center of FIG. 5B is generated.

Further, the under color removal pattern generating section 25Y
Is based on the Y-color output value Yout = 16, as shown in FIG.
Is generated as a UCR pattern Yucrptn using 16 binarized pixels out of 64 8 × 8 pixels. For example, a pattern to be recorded for the squares marked 1 and 2 in FIG. 2A may be generated. As a result, a pattern as shown at the right end of FIG. 5B is generated.

In this example, further in S7, FIG.
The binary CMY data shown in FIG. 5A and the UCR patterns Cucrptn, Mucrptn, UCR patterns shown in FIG.
The logical product with Yucrptn is calculated, and C color print data Coutptn and M color print data Moutpt are calculated.
Create n, Y color print data Youptn. In this example, the UCR pattern Cucrptn, Mucrp
tn and Yucrptn are used as they are for the C color print data Coutptn and the M color print data Moutpt.
n, Y color print data Youptn. This is because the under-color removal processing is performed in the direction of decreasing the density using the same binary pattern. Therefore, UCR
Patterns Cucrptn, Mucrptn, Yucrup
tn always matches or becomes part of the CMY data,
UCR pattern Cucrptn, Mucrptn, Yu
crptn is the C color print data Coutpt
n, M color print data Moutptn and Y color print data Youptn.

It should be noted that each of the above-described undercolor removal pattern generation units 2
In 5C, 25M, and 25Y, a UCR pattern Cucrptn, Muc
When rptn and Yucrptn are generated, if an AND operation with CMY data is performed, a part of the UCR pattern is lost, and the undercolor removal process cannot be performed accurately. Since the UCR pattern is created using the same binary pattern as when the CMY data is created as in the present invention,
Even if the logical product of the CR pattern and the CMY data is calculated, an accurate result of the undercolor removal processing can be obtained. Also, U
By calculating the logical product of the CR pattern and the CMY data, coexistence with other binarization methods can be allowed.

In this manner, the C color print data Coutptn, the M color print data Moutptn, and the Y color print data Yououtpt as shown in FIG.
The n, K color print data Koutptn is obtained. In the above-described specific example, an example has been described in which the target area is 8 × 8 and color print data is generated based on the pattern shown in FIG. 2, but the present invention is not limited to this. .

FIG. 6 is a block diagram showing an example of the configuration of the density correction processing section 10 in an embodiment of the image processing apparatus of the present invention. In the figure, reference numeral 31 denotes a density determination unit, 32 denotes a density correction unit, and 33 denotes a correction pattern generation unit. Density determination unit 3
1 detects the density of each component of the CMYK color print data that has been subjected to black generation processing and undercolor removal processing by the data correction unit 9. For example, a predetermined region of interest may be set, and the number of pixels to be recorded included therein may be counted for each color. The count values Cin, Min, Yin, and Kin of each color are input to the density correction unit 32.

The density correction section 32 performs density correction processing according to the characteristics of the printing section 3 on the input count values Cin, Min, Yin, and Kin of each color, and outputs the corrected output values Cout, Mout of each color. , Yout, and Kout are output. The density correction process can be performed using, for example, a table provided for each color. Alternatively, a predetermined calculation may be performed.

The correction pattern generating section 33 includes the density correcting section 3
Output values Cout, Mout, Y for each color processed in 2
color print data Coutptn, Moutptn, Youptn, K after correction of each color from out, Kout
outptn is generated and output. At this time, it may be generated using a pattern according to the characteristics of the printing unit 3.
For example, the pattern shown in FIG. 2 can be used. In this way, it is possible to generate binary CMYK color print data that has been subjected to density correction processing according to the density characteristics of the printing unit 3.

FIG. 7 is a flow chart showing an example of the operation of a configuration example of the density correction processing section 10 in an embodiment of the image processing apparatus of the present invention. In S11, the density determination unit 31 outputs the binary CM passed from the data correction unit 9.
The number of pixels to be recorded for each of the colors C, M, Y, and K is counted by referring to the target area of M × N pixels from the YK color print data. Here, the count values are represented by Cin, Min, Yin,
Kin.

In S12, the density correction section 32 calculates the count values Cin, Min, Y of the respective colors counted by the density determination section 31.
in and Kin are subjected to density correction processing according to the characteristics of the printing unit 3, and the corrected output values Cout, M for each color
out, Yout, and Kout are output. For example, functions TRCc, TRCm, T for density correction processing for each color
Using RCy and TRCk, Cout = TRCc (Cin) Mout = TRCm (Min) Yout = TRCy (Yin) Kout = TRCk (Kin) Generally, the density characteristic of the print unit 3 is often non-linear, so the count values Cin, M
in, Yin, Kin and output values Cout, Mout, Y
By using a table in which out and Kout are associated, density correction processing can be easily performed. Of course, the calculation may be performed using a non-linear function, or may be performed using a table and linear interpolation.

In S13, the correction pattern generator 33
Are output values Cout, Mout, Yout, Ko of each color.
ut, the comparison patterns Ccom, Mco
m, Ycom, and Kcom are generated. At this time, each pattern shown in FIG. 2 can be used.

In this example, in step S14, the C color print data Coutptn after density correction is obtained from the CMYK color print data output from the data corrector 9 and the comparison patterns Ccom, Mcom, Ycom, and Kcom.
M color print data Moutptn and Y color print data Youptn are created. This process is CMY
This is performed for the case where the data is generated by processing other than the binarization pattern normally used in the binarization processing unit 7. For example, when printing a character image,
Since binarization using a binarization pattern as shown in FIG. 2 degrades image quality, it is desirable to perform another binarization process while retaining edges. In such a case, if the comparison patterns Ccom, Mcom, Ycom, and Kcom are output as they are, the image quality deteriorates for the same reason.
Here, processing for preventing such deterioration of image quality can be performed.

Here, as an example, the count value Pin of the color print data of each color is compared with the corrected output value Pout, and when Pin <Pout, the logical product of the color print data of that color and the comparison pattern is compared. Color print data. That is, Coutptn = C & Ccom Moutptn = M & Mcom Youptn = Y & Ycom Koutptn = K & Kcom, and the corrected C color print data Coutptn,
M color print data Moutptn and Y color print data Youptn can be created. Also, Pi
When n ≧ Pout, the logical sum of the color print data of the color and the comparison pattern is used as the corrected color print data. That is, Coutptn = Cor Ccom Moutptn = Mor Mcom Youptn = Yor Ycom Koutptn = Kor Kcom, and the corrected C color print data Coutptn,
M color print data Moutptn and Y color print data Youptn can be created. Note that the logical product operation and the logical sum operation may be performed by judging the condition for each color.

Of course, the present invention is not limited to this example, and color print data of each color after correction may be created according to other processes. The processing in S14 may be omitted if not necessary. That is, the comparison pattern Ccom, M
C, Ycom, and Kcom as they are, and the C color print data Coutptn and the M color print data Mo
uptn, Y color print data Youptn may be used.

As described above, CMYK color print data that has been subjected to density correction processing according to the characteristics of the printing unit 3 is obtained. CM after correction processing obtained in this way
After storing the YK color print data in the drawing memory 8,
The data is transferred to the printing unit 3 and recorded on the recording medium.

The above-described density correction processing will be described using a specific example. FIG. 8 is an explanatory diagram of a specific example of the operation of one configuration example of the density correction processing unit 10 in one embodiment of the image processing apparatus of the present invention. Here, an 8 × 8 region is assumed as the region of interest, and only this 8 × 8 region is shown. Also,
The binarization processing unit 7 performs a binarization process using the binarization patterns shown in FIGS. 2A to 2C. When the data correction unit 9 generates K color print data, It is assumed that the image is generated using the pattern shown in FIG.

FIG. 8A shows an example of binary CMY data obtained by binarizing multi-valued CMY data output from the drawing unit 6 by the binarization processing unit 7. C data is
This is a pattern for recording the squares denoted by 1 to 5 in FIG. Similarly, the M data is a pattern for recording squares marked 1 and 2 in FIG. 2B. Furthermore, the Y data
This is a pattern for recording squares marked 1 to 3 in FIG. Further, the K data is a pattern for recording the cell marked 1 in FIG. 2 (D). It is assumed that such CMYK color print data is input to the density correction processing unit 10.

In S11, the density determination section 31 determines that the 8 ×
8, the number of pixels recorded for each color of C, M, Y, and K is counted, and the count values Cin, Min, Yi
n, Kin are obtained. When the number of pixels is counted from the CMYK color print data shown in FIG. 8A, Cin = 40, Min = 16, Yin = 24, Kin =
8

In S12, the output values Cout, Mout, Yout, Kout of each color are calculated using the functions TRCc, TRCm, TRCy, TRCk from the count values Cin, Min, Yin, Kin of each color counted as described above. I do. For example, Cout = TRCc (Cin) = TRCc (40) = 3
9 Mout = TRCm (Min) = TRCm (16) = 1
8 Yout = TRCy (Yin) = TRCy (24) = 2
It is assumed that 5 Kout = TRCk (Kin) = TRCk (8) = 10 has been obtained.

In S13, the correction pattern generating section 33
Are output values Cout, Mout, Yout, Ko of each color.
ut, the comparison patterns Ccom, Mco
m, Ycom, and Kcom are generated. For example, based on the C color output value Cout = 39, using a binarized pattern shown in FIG. 2C, a pattern having 39 pixels to be printed out of 64 8 × 8 pixels is compared with a comparison pattern. Generated as Ccom. For example, in FIG. 2C, a pattern for recording the squares 1 to 4 and the squares 7 among the squares 5 may be generated. As a result, a pattern shown as Ccom at the left end of FIG. 8B is generated.

Similarly, based on the output value Mout = 18 of the M color, using the binarization pattern shown in FIG.
A pattern having 18 pixels to be printed out of 64 of 8 is generated as a comparison pattern Mcom. For example, FIG.
In (B), a pattern for recording two of the squares marked 1 and 3 and the square marked 3 may be generated. As a result, a pattern shown as Mcom at the center left of FIG. 8B is generated.

Further, based on the output value Yout = 25 of the Y color, the binary pattern shown in FIG.
A pattern having 25 pixels to be recorded out of 64 of 8 is generated as a comparison pattern Ycom. For example, FIG.
In (A), a pattern to be recorded for one of the squares marked 1 and 2 and the square marked 3 may be generated. As a result, a pattern shown as Ycom at the center right of FIG. 8B is generated.

Further, based on the output value Kout = 10 of the K color, the pattern shown in FIG.
A pattern having ten pixels to be printed out of four is generated as a comparison pattern Kcom. For example, FIG.
In the above, a pattern for recording two of the squares marked 1 and the squares marked 2 may be generated. As a result, a pattern shown as Kcom on the right end of FIG. 8B is generated.

In this example, further, in S14, based on the count values Cin, Min, Yin, and Kin of each color and the output values Cout, Mout, Yout, and Kout of each color, the CMYK color print data shown in FIG. ,
The comparison patterns Ccom, Mcom, and Ccom shown in FIG.
The logical product or logical sum with Ycom and Kcom is calculated. By performing the logical product or logical sum operation, the corrected C color print data Coutptn, M color print data Moutptn, and Y color print data Youuppt
Create n, K color print data Koutptn.

For example, for the C color, Cin = 40, C
Since out = 39 and Cin ≧ Cout, C
The logical product of the color print data and the comparison pattern Ccom is calculated. As a result, Coutp is displayed at the left end of FIG.
The corrected C color print data indicated as tn is obtained.

For the M color, Min = 16, Mout
= 18 and Min <Mout, the logical sum of the M color print data and the comparison pattern Mcom is calculated. As a result, Moutptn is displayed at the center left of FIG.
, The corrected M color print data is obtained.

For the Y color, Yin = 24, Yout
= 25 and Yin <Yout, so the logical sum of the Y color print data and the comparison pattern Ycom is calculated. As a result, Youptn at the center right of FIG.
Y color print data after correction is obtained.

For the K color, Kin = 8, Kout =
10, since Kin <Kout, the logical sum of the K color print data and the comparison pattern Kcom is calculated. As a result, corrected K color print data indicated as Koutptn at the right end of FIG. 8C is obtained.

The result obtained by performing the logical product or logical sum operation in S14 is obtained by the binarization processing unit 7 using the binarization patterns shown in FIGS. When generating K color print data, FIG.
As long as the pattern (D) is used, the comparison patterns Ccom, Mcom, Ycom, Kc
om as it is becomes the corrected CMYK color print data.

As described above, the binary CMYK color print data is subjected to the density correction processing according to the characteristics of the printing unit 3, so that the binary corrected CMYK color print data can be obtained. In the above specific example,
Although an example of generating the corrected color print data based on an 8 × 8 region of interest and the pattern shown in FIG. 2 has been described, it is needless to say that the present invention is not limited to this.

In the above example, the data correction unit 9 and the density correction processing unit 10 perform the same processing, that is, the number of pixels in the target area is counted for each color, the count value is converted, and a pattern is generated. Processing is in progress. Thus, the processes of the data correction unit 9 and the density correction processing unit 10 can be shared at the level of the count value. FIG. 9 illustrates a data correction unit 9 according to an embodiment of the image processing apparatus of the present invention.
FIG. 4 is a block diagram illustrating another configuration example of the density correction processing unit 10. The reference numerals in the figures are the same as those in FIGS.
Output value Kou output from black generation correction value calculation unit 22
t and the output values Cout, Mout, and Yout output from the under color removal correction value calculation unit 24 are
2 is input. The density correction unit 32 performs density correction processing for each color, and outputs the density-corrected output value Cou.
From t ′, Mout ′, Yout ′, Kout ′, a black pattern generation unit 23 and an under color removal pattern generation unit 25
C, 25M, and 25Y can be configured to generate CMYK color print data after performing black generation processing, undercolor removal processing, and density correction processing. In addition,
Black pattern generator 23 and undercolor removal pattern generator 2
5C, 25M and 25Y may be the correction pattern generator 33 shown in FIG.

[0084]

As is apparent from the above description, according to the present invention, color print data is created for each color in consideration of, for example, a pattern at the time of binarization processing. , The optimum black generation processing and undercolor removal processing can be performed, and the image quality of the image recorded by the printing unit can be improved.

Further, the density correction processing according to the characteristics of the printing means can be performed on the binary color print data after the black generation processing and the under color removal processing. Therefore, the black generation processing and the undercolor removal processing can be performed in a state in which the density characteristics do not depend on the printing unit, so that more appropriate black generation processing and undercolor removal processing can be performed. Thus, there is an effect that the image quality of the image recorded by the printing unit can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a color image forming apparatus to which an embodiment of an image processing apparatus according to the present invention is applied.

FIG. 2 is an explanatory diagram illustrating an example of a binarization pattern used in a binarization processing unit according to an embodiment of the image processing apparatus of the present invention.

FIG. 3 is a block diagram illustrating a configuration example of a data correction unit 9 according to the embodiment of the image processing apparatus of the present invention.

FIG. 4 is a flowchart illustrating an example of an operation of a configuration example of the data correction unit 9 according to the embodiment of the image processing apparatus of the present invention.

FIG. 5 is an explanatory diagram of a specific example of an operation of a configuration example of the data correction unit 9 in the embodiment of the image processing apparatus of the present invention.

FIG. 6 is a block diagram illustrating a configuration example of a density correction processing unit according to an embodiment of the image processing apparatus of the present invention.

FIG. 7 is a flowchart illustrating an example of an operation of a configuration example of the density correction processing unit 10 according to the embodiment of the image processing apparatus of the present invention.

FIG. 8 is an explanatory diagram of a specific example of the operation of one configuration example of the density correction processing unit 10 in the embodiment of the image processing apparatus of the present invention.

FIG. 9 is a block diagram illustrating another configuration example of the data correction unit 9 and the density correction processing unit 10 according to the embodiment of the image processing apparatus of the present invention.

FIG. 10 is a block diagram illustrating an example of a conventional color image forming apparatus.

FIG. 11 is a block diagram illustrating another example of a conventional color image forming apparatus.

FIG. 12 is a block diagram illustrating an example of a data correction unit in another example of a conventional color image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Host computer, 2 ... Image processing part, 3 ... Printing part, 4 ... Interface control part, 5 ... PDL interpretation part,
6 drawing unit, 7 binarization processing unit, 8 drawing memory, 9 ...
Data correction unit, 10: density correction processing unit, 11: color conversion unit, 12: data conversion unit, 13: data correction unit, 21 ...
Density determination unit, 22: black generation correction value calculation unit, 23: black pattern generation unit, 24: under color removal correction value calculation unit, 25,
25C, 25M, 25Y: Under color removal pattern generating section, 3
Reference numeral 1 denotes a density determination unit, 32 denotes a density correction unit, and 33 denotes a correction pattern generation unit.

Claims (11)

[Claims] 1. A binary CMY color data from binary CMY color data
In an image processing apparatus that generates MYK color print data, a binarizing unit that converts multi-valued CMY color data into binary CMY color data, and a binary CMY color data output from the binarizing unit. Density determining means for detecting the black density of the region of interest; black pattern generating means for generating K color print data based on the density detected by the density determining means; An image processing apparatus comprising: a plurality of undercolor removal pattern generating means for generating an undercolor removal pattern for each of CMY colors to generate CMY color print data. 2. A binary C based on multi-valued CMY color data.
In an image processing apparatus that generates MYK color print data, a binarizing unit that converts multi-valued CMY color data into binary CMY color data, and a binary CMY color data output from the binarizing unit. CM in the area of interest
Density determination means for detecting the density of each color of Y; black pattern generation means for generating K color print data based on the density detected by the density determination means; and CMY color detection data detected by the density determination means. An image processing apparatus comprising: a plurality of undercolor removal pattern generating means for generating an undercolor removal pattern for each of CMY colors based on density and generating CMY color print data. 3. Each of the undercolor removal pattern generating means generates an undercolor removal pattern in consideration of a screen used for a corresponding color when the binarization means performs a binarization process. The image processing apparatus according to claim 1, wherein: 4. An image processing apparatus for generating binary CMYK color print data according to the characteristics of a printing means from multi-valued CMY color data, wherein the multi-valued CMY color data is converted to binary CMY color data. A binarizing unit, a black generation and under color removal processing unit that generates binary CMYK color print data from the binary CMY color data output from the binarization unit, and An image processing apparatus comprising: a density correction processing unit that performs a density correction process on output binary CMYK color print data in accordance with characteristics of the printing unit. 5. The apparatus according to claim 4, wherein the density correction processing means generates and outputs a density correction pattern for each predetermined region of interest based on a feature amount in the region of interest. Image processing device. 6. The density correction processing means sets the density correction pattern in consideration of a screen used for each color when performing the binarization processing in the binarization means. The image processing apparatus according to claim 5, wherein 7. The image processing apparatus according to claim 1, wherein said binarizing means and said black generation and under color removal processing means are used. An image processing apparatus according to claim 6. 8. An image processing apparatus for generating binary CMYK color print data according to characteristics of a printing means from multi-valued CMY color data, converts the multi-valued CMY color data into binary CMY color data. Binarizing means, density determining means for detecting the black density of a region of interest of the binary CMY color data output from the binarizing means, and printing means for the density detected by the density determining means Black pattern generating means for generating K color print data based on the density after the density correction processing after performing the density correction processing according to the characteristics of the CMY, and the density detected by the density determination means for each color of CMY. On the other hand, after performing density correction processing according to the characteristics of the printing means, an undercolor removal pattern is generated based on the density after the density correction processing, and color printing data is generated. An image processing apparatus comprising: a plurality of under-color removal pattern generating means for generating data. 9. Binary C based on multi-valued CMY color data
In an image processing apparatus that generates MYK color print data, a binarizing unit that converts multi-valued CMY color data into binary CMY color data, and a binary CMY color data output from the binarizing unit. CM in the area of interest
Density determining means for detecting the density of each color of Y; and performing density correction processing on the density detected by the density determining means in accordance with the characteristics of the printing means, based on the density after the density correction processing. Black pattern generating means for generating K color print data; and performing density correction processing on the densities of the respective colors of CMY detected by the density determination means in accordance with the characteristics of the printing means. An image processing apparatus comprising: a plurality of undercolor removal pattern generating means for generating an undercolor removal pattern for each of CMY colors based on density and generating CMY color print data. 10. An image processing apparatus for generating binary CMYK color print data from multi-valued CMY color data, wherein the binarizing means converts the multi-valued CMY color data into binary CMY color data. Density determining means for detecting the black density of the target area of the binary CMY color data output from the binarizing means, and black pattern generation for generating K color print data based on the density detected by the density determining means Means for generating CMY color print data by generating an undercolor removal pattern for each of the CMY colors based on the density detected by the density determination means. The pattern generation means determines an undercolor removal pattern for at least one of CMY based on a binarization pattern used in the binarization processing by the binarization means. An image processing apparatus characterized in that the image processing apparatus generates the image. 11. An image processing method for generating binary CMYK color print data from multilevel CMY color data, wherein the multilevel CMY color data is converted into binary CMY color data, and the binary CMY color data is converted to binary CMY color data. Detecting the black density of the target area of the data, generating K color print data based on the detected density, and generating the under color removal pattern for each of the CMY colors based on the detected density to generate C color print data.
MY color print data is generated, and the undercolor removal pattern for at least one of CMY is used in the binarization process when the undercolor removal pattern for each color is generated. An image processing method, wherein the method is generated based on a pattern.