JP2000287089A - Image binarizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent each color dot from being cancelled by black dots by binarizing color components other than a black color component in the order of higher density, when the binarized result of the black (K) color of a pixel is in an OFF state. SOLUTION: A K binarized result ON/OFF discrimination means 103 of an error propagation device 102 references K color component ON/OFF data of a stored pixel under notice, an error weighting computing element 104 references error data of pixels around the pixel under notice stored in an error data storage means 107 to give the weight of the error data to image data of a cyan (C) component of the target pixel, when the K color component indicates ON data. A binarizing means 105 compares the weighted data with a threshold and outputs an OFF signal, without conducting binarizing processing. If the K color component indicates OFF data, a cyan (C)-magenta (M)-yellow (Y)-density data comparison means 109 compares the density data in C, M, Y colors and binarizing processing by error propagation is applied to the color components in the order of higher density, so that does in each color component do not mutually overlap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image binarization method applied to a printer, a scanner, a copying machine, a facsimile, etc., for reproducing multi-valued color image information as a binary image.

[0002]

2. Description of the Related Art An error diffusion method is known as one of the methods for converting a multi-valued image into a binary image.

FIG. 5 is a block diagram showing a conventional image binarizing apparatus using the error diffusion method.

As shown in FIG. 5, an image binarizing apparatus uses an image memory 1 in which multi-value data of a target pixel is read, and print characteristics of an output device such as a printer by referring to stored correction data. Γ correction R for correcting multi-valued data according to
It comprises an OM2 and an error diffusion device 8 that performs a binarization process on an image by an error diffusion method and outputs a binary signal.

The error diffusion device 8 includes an adder 3 for adding the error data stored in the error memory 4 to the multi-value data from the gamma correction ROM 2, a multi-value data to which the error data has been added, and a binarization threshold. And a subtractor 7 for calculating a binarization error in a binarization process from the binary signal and the multi-value data obtained by adding the error data to the comparator 5. And a weighting error calculator 6 for weighting the binarization error and outputting the weighted error to the error memory 4.

According to such an image binarizing apparatus, multivalued data D for performing a binarizing process is read from the image memory 1, and the γ correction ROM 2 refers to the correction data to determine the printing characteristics of the output device. Γ correction is performed to the corresponding multi-value data D ′. The gamma-corrected multi-value data D ′ is supplied to the error diffusion device 8.
Adder 3 adds error data E and outputs multi-valued data F.

Next, in the comparator 5, the multi-value data F of the target pixel to which the error data E has been added is compared with a binarization threshold Th, and when F> = Th, the binary signal B = “1”. Is output, and when F <Th, the binary signal B = "0" is output. Then, from this output result, a binarization error E ′ at the time of the binarization processing is calculated by the subtractor 7 as E ′ = FB ′.

Here, B ′ = B × 255 when the input data has 256 gradations (0 to 255).
Therefore, for example, the input multi-value data D is 23
If the threshold value Th of the binarization is 0, the output data after the binarization is B = 1, and the binarization error E is E = D−B × 255 = 230−1 × 255 = − 25.

The binarization error E is stored in the error memory 4 by a predetermined error matrix Mxy in the weighting error calculator 6 so as to be distributed to pixel data to be processed thereafter. Is added to the multi-value data of the next pixel, and error data is propagated.

In other words, here, since the input multi-value data D is 230, the output data after binarization is 1 as a result of comparison with the binarization threshold value Th = 128, and 255 at 256 gradations. Therefore, 23 of the input multi-value data D
There are 25 errors for 0. Therefore, the error 25 with respect to the multi-valued data D = 230 is defined as a binarization error E, and the binarization error E is distributed to the error memory 4 of the unprocessed pixel by using the error matrix in the weighting error calculator 6, This is reflected in the binarization processing for the subsequent pixels.

FIG. 6 is an explanatory diagram showing an example of the error matrix Mxy.

In FIG. 6, the pixel indicated by * is the current pixel of interest, and binarization processing is performed on this pixel.

The error that occurs when the target pixel is binarized is
With the weighting coefficients (7, 1, 5, 3) shown in FIG. When performing the binarization process for the pixel of interest indicated by *, the error distribution value stored in the error memory 4 is read, and the next input read from the image memory 1 using this error distribution value. Make corrections to the values.

As described above, according to the error diffusion method, a binarization error generated in a binarization process of a certain pixel is distributed to pixel data to be binarized thereafter, and the binarized image data is And the original multi-valued image data.

[0015]

In a binary image of a multi-valued image by gradation processing using such an error diffusion method, cyan (C), magenta (M), and yellow (Y) A black (K) dot overlaps the ON dot, and color unevenness occurs. In other words, CMY dots that should be originally reproduced as colors are canceled by K dots, and a phenomenon occurs in which the color of the original image cannot be faithfully reproduced, resulting in deterioration of image quality.

Accordingly, the present invention provides an image after binarization processing, in which cyan, magenta,
An object of the present invention is to provide an image binarization method capable of suppressing occurrence of a phenomenon in which yellow dots are canceled.

[0017]

In order to solve this problem, an image binarization method according to the present invention provides a method for simulating multi-tone image data having a plurality of color components including at least black (K). This is an image binarization method for generating a binary image by halftone processing. First, a K color component of a target pixel is subjected to a binarization process, and the K binarization result of the pixel is turned on.
If the binarization result of the other color component is OFF, and if the binarization result of K in the pixel is OFF, the other color components are output in descending order of density and Is performed so that the dots of the color components do not overlap each other.

As a result, it is possible to prevent a phenomenon that dots of other color components overlap with K and are canceled out, thereby causing color unevenness. In addition, it is possible to generate a binarized image with good dot dispersibility and color reproducibility and more faithful to the original image.

Further, the image binarization method of the present invention provides a pseudo-intermediate method for multi-tone image data having color components of cyan (C), magenta (M), yellow (Y) and black (K). This is an image binarization method for generating a binary image by tone processing, in which binarization processing of a K color component of a target pixel is first performed, and then binarization processing of a CMY color component of the target pixel is performed. Are performed in the order of MCY and such that the dots of these color components do not overlap with each other.

As a result, binarization processing is performed in the order of KMCY having a higher degree of recognition from the viewpoint of human visual characteristics, so that a higher quality binarized image can be obtained at the pixel of interest.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a binary image is formed by pseudo halftone processing on multi-tone image data having a plurality of color components including at least black (K). In the image binarization method to be generated, first, the binarization process of the K color component of the target pixel is performed, and when the binarization result of K in the pixel is ON, the other color components are The binarization result is output as OFF, and K
If the binarization result is OFF, this is an image binarization method that performs a binarization process on the other color components in descending order of density and so that the dots of these color components do not overlap each other. , Dots of other color components overlap with K and are canceled out,
This has the effect that the phenomenon that color unevenness occurs can be prevented. In addition, there is an effect that the dot dispersibility and color reproducibility are good, and a more faithful binary image can be generated from the original image.

According to a second aspect of the present invention, there is provided a pseudo-intermediate image for multi-tone image data having color components of cyan (C), magenta (M), yellow (Y) and black (K). This is an image binarization method for generating a binary image by tone processing, in which binarization processing of a K color component of a target pixel is first performed, and then binarization processing of a CMY color component of the target pixel is performed. Is performed in the order of MCY and in such a manner that the dots of these color components do not overlap each other, and the binarization process is performed in the order of KMCY with a high degree of recognition from human visual characteristics. This has the effect that a higher quality binarized image can be obtained at the pixel of interest.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a block diagram showing an image binarization apparatus for executing an image binarization method according to an embodiment of the present invention.
FIG. 2 is a block diagram showing another image binarization device for executing the image binarization method according to one embodiment of the present invention, and FIG. 3 shows a processing procedure by the image binarization device of FIGS. FIG. 4 is a flow chart, and FIG. 4 is a block diagram showing still another image binarizing device for executing the image binarizing method according to one embodiment of the present invention. FIG. 1 shows a case where CMY is output as OFF for a pixel whose K binarization result is ON, and FIG. 2 shows a case where CMY is output as ON or OFF for a pixel whose K binarization result is OFF. To
FIG. 4 shows a case where the binarization process is performed in the order of KMCY on the target pixel.

The image binarizing apparatus shown in FIG. 1 is composed of an image memory 101 in which original image CMYK data to be binarized is stored.
And an error diffusion device 102 that binarizes the multivalued data in the image memory 101 by an error diffusion method, outputs a predetermined binary signal, and generates a binary image by a pseudo halftone process.

The error diffusion device 102 stores the ON / OFF information of the binarization result of the K component at the pixel of interest.
A K-binarization result ON / OFF judging unit 103 which judges whether the binarization processing result of the multi-value data of the K component from the image memory 101 is ON or OFF with reference to the data of the binarization result storage unit 108; An error weighting calculator 104 for referring to the binarization error generated in the surrounding binarized pixels from the error data storage unit 107 and performing weighting processing of the error on the image data of the target pixel; Binarization processing means 105 for performing binarization processing on the output weighted data with reference to the binarization threshold, and image data generated when binarization is performed by the binarization processing means 105 Is calculated, and the calculated error is stored in the error data storage unit 107 described above.
And an error calculating means 106 for storing the data.

In such an image binarization apparatus, first, the CMYK image data stored in the image memory 101 is
The multi-value density data of the K component in the target pixel is transferred to the error diffusion device 102.

In the error diffusion device 102, binarization is performed by an error diffusion process.

Here, in the target pixel read from the image memory 101, first, the K color component is subjected to a binarization process.

That is, in the error diffusion processing of the K component, the processing in the K binarization result ON / OFF determination means 103 is omitted, and the error weighting arithmetic unit 104 uses the peripheral pixels stored in the error data storage means 107 to perform the processing. , The K component data of the target pixel is weighted with the error data. The weighted data is binarized by the binarization processing unit 105 based on the threshold value, a predetermined binary signal is output, and the K binarization result storage unit is used as ON / OFF data. 108. Note that the binarization error generated at the time of binarization is calculated by the error calculation unit 106.
And the calculated error data is stored in the error data storage means 107.

When the binarization of the K color component is completed, the binarization process of the C color component is performed.

That is, the image data of the C color component at the target pixel is transferred from the image memory 101 to the error diffusion device 102 in the same manner as the K color component.

In the error diffusion device 102, first, K
The binarization result ON / OFF determination unit 103 refers to the K color component ON / OFF data at the target pixel stored in the K binarization result storage unit 108, and turns the K color component ON.
Therefore, the error weighting calculator 104 refers to the error data of the surrounding pixels stored in the error data storage unit 107, and weights the C component image data of the target pixel with the error data.

The weighted data is converted to binary data
After being compared with the threshold value at 5, an OFF signal is output without performing the binarization process. The error of the result of the OFF output is calculated by the error calculating means 106, and the calculated error data is stored in the error data storing means 107.

Similarly to the processing of C, in the binarization processing of the M and Y color components, the image data of the M and Y color components at the target pixel is transferred from the image memory 101 to the error diffusion device 102.
Is forwarded to Then, in the error diffusion device 102, the K binarization result ON / OFF determination unit 103 refers to the K color component ON / OFF data at the target pixel stored in the K binarization result storage unit 108, Is turned on, the error weighting calculator 104 refers to the error data of the surrounding pixels stored in the error data storage unit 107, and weights the M and Y component data of the target pixel with the error data. . The weighted data is compared with the threshold value in the binarization processing means 105, and an OFF signal is output without performing the binarization processing. The error data resulting from the OFF output is calculated by the error calculation means 106, and the calculated error data is stored in the error data storage means 10.
7 is stored.

For color components other than K, CMY
However, the present invention is not limited to this.

According to this, if K of the target pixel is ON, the binarization result of the other color components is OFF, so that the dots of other color components overlap with K and are canceled out, causing color unevenness. Can be prevented.

Next, the binarization result of K at the pixel of interest is O
The case of the FF will be described with reference to FIG.

The image binarizing device shown in FIG. 2 also has an image memory 1 in which original image CMYK data to be binarized is stored.
01, and an error diffusion device 102 that binarizes the multi-valued data in the image memory 101 by an error diffusion method, outputs a predetermined binary signal, and generates a binary image by pseudo halftone processing. .

Here, the error diffusion device 102 refers to the CMYK binarization result storage means 110 in which the data of all the CMYK binarization results in the target pixel are stored, and reads the multi-valued K component from the image memory 101. K binarization result ON / OF which determines whether the binarization processing result of data is ON or OFF
F determination means 103 and CMY density data comparing means 10 for comparing CMY density data to determine the order of increasing density
9 and an error weighting computing unit 1 that refers to the binarization error generated in the surrounding binarized pixels from the error data storage unit 107 and weights the image data of the target pixel.
04, a binarization processing unit 105 for performing binarization processing on the weighted data output from the error weighting calculator 104 with reference to a binarization threshold, and a binarization processing unit 10
5, an error calculator 106 for calculating an error of the image data generated when the binarization is performed and storing the calculated error in the error data storage 107, and a CMYK binarization result storage 1
A threshold value for binarizing CMY is determined from the ten data and sent to a binarization processing unit 105.

In such an image binarizing apparatus, first, the CMYK image data stored in the image memory 101 is
The multi-value density data of the K component in the target pixel is transferred to the error diffusion device 102.

In the error diffusion device 102, binarization is performed by error diffusion processing.

Here, in the pixel of interest read from the image memory 101, first, the binarization process is performed on the K color component.

That is, during the error diffusion processing of the K component, the processing by the K binarization result ON / OFF determination means 103 and the CMY density data comparison means 109 is omitted, and the error weighting calculator 104 stores the error data in the error data storage means 107. The error data is weighted to the K component data of the target pixel with reference to the stored error data of the surrounding pixels. The weighted data is binarized by the binarization processing unit 105 based on the threshold value, a predetermined binary signal is output, and the CMYK binarization result storage unit is used as ON / OFF data. Stored in 110. Note that a binarization error generated at the time of binarization is calculated by the error calculation unit 106, and the calculated error data is stored in the error data storage unit 107.

After the binarization of the K color component is completed, the CMY color component binarization processing is performed.

That is, the image data of the CMY color component at the target pixel is stored in the image memory 10 like the K color component.
1 to the error diffusion device 102.

In the error diffusion device 102, first, K
The binarization result ON / OFF determination unit 103 refers to the K color component ON / OFF data at the target pixel stored in the K binarization result storage unit 108, and determines whether the K color component is OF.
Since it is F, the CMY density data comparison unit 109 compares the CMY density data, and performs binarization processing by error diffusion in order from the color component having the largest density data.

Here, assuming that the first color component, the second color component, and the third color component are arranged in descending order of the density in the CMY density data, first, the error weighting calculator 104 applies error data to the first color component data. The error data at the surrounding pixels stored in the storage unit 107 is referred to, and the color component data for processing the target pixel is weighted with the error data. The weighted data is referred to the threshold value determined by the binarization threshold value determination unit 111, and the binarization processing unit 105 performs the binarization process. The binarization threshold value determining unit 111 refers to ON / OFF information of each of CMY in the CMYK binarization result storage unit 110,
A threshold value is set so that dots do not overlap as much as possible in the target pixel.

The error data is calculated by the error calculating means 106 based on the result of the binarized and output binary information, and the calculated error data is stored in the error data storing means 107. Further, the binarization result of the first color component indicates that the dot is ON.
CMYK binarization result storage means 11 as / OFF information
0 is stored.

Similarly to the processing of the first color component, in the binarization processing of the second color component and the third color component, the binarization processing is performed by the error diffusion device 102 in the order of the second color component and the third color component. The image data of the color components of the second color component and the third color component in the pixel of interest is referred to the error data of the surrounding pixels stored in the error data storage unit 107, and the error weighting calculator 104 outputs the image data of the pixel of interest. Are weighted with error data.

The weighted data is referred to the threshold value determined by the binarization threshold value determining means 111, and the binarization processing means 105 performs the binarization processing. The binarization threshold value determining unit 111 refers to the ON / OFF information of the first color component in the CMYK binarization result storage unit 110 and sets a threshold value so that dots do not overlap as much as possible in the target pixel. If the binarization result of the first color component is ON, a threshold value is set so that the second color component is likely to be OFF.

Error data is calculated by the error calculating means 106 based on the result of the binarized binary information and output.
The calculated error data is stored in the error data storage unit 107. The binarization results of the second color component and the third color component are stored in the CMYK binarization result storage unit 110 as dot ON / OFF information.

Here, the color components other than K are not limited to CMY.

As described above, if K of the target pixel is OFF, the binarization processing is performed in the order of the density of the other color components so that the dots of these color components do not overlap each other. It is possible to generate a binarized image with good dot dispersibility and color reproducibility and more faithful to the original image.

The overall processing by the two types of image binarizing devices described above will be described with reference to the flowchart of FIG.

In FIG. 3, first, the density data of the K component is obtained from the CMYK data of the original image, and the error data of the K pixel which has already been binarized is weighted with reference to the error matrix. (S200).

Next, the binarization process of K is compared with a default threshold value, and a binary result of ON / OFF for the K data is obtained (S210).

If the data of K is ON (S2
20), all the data of CMY are turned OFF, a binary result is output (S230), a binary error is calculated from each of the binary results of CMYK (S330), and the calculated error data is converted to error data. The data is stored in the storage buffer (S340).

If the binarization result of K is OFF in S220, each density data of CMY is obtained from the image memory, the densities of CMY are compared, and C1, C2, C2,. It is defined as C3 (S240).

Next, the error data of the binarized pixel of the C1 color component having the highest density is weighted with respect to the density data of the pixel data of interest, and compared with a default threshold value. The processing is performed (S250). The binarization result of the C1 color component is stored as ON / OFF information (S26).
0).

Next, the C2 color component is binarized following the C1 color component. The threshold value used for the binarization is set according to the binarization result of the C1 color component. (S2
70). The threshold value set here is set such that if the binarization result of C1 is ON, C2 tends to be OFF.
If the binarization result of C1 is OFF, C2 is set to be ON. Based on the threshold set here,
The binarization processing of the C2 density data obtained by weighting the binarized pixel data of C2 is performed (S280). The binarization result of the C2 color component is stored as ON / OFF information (S2
90).

Finally, binarization processing of the C3 color component having the lowest density is performed, and the threshold value used for binarization is set to C1.
Set according to the binarization result of the color component and the C2 color component (S
300). The threshold value set here is set so that C3 tends to be OFF if the binarization result of C1 is ON, and C3 tends to be ON if the binarization result of C1 is OFF. Set. Further, the binarization result of C2 is O
If N, C3 is set to be more likely to be turned OFF, and if the binarization result of C2 is OFF, it is set to be more likely to be turned ON. Based on the threshold value set here, C3 is obtained by weighting the binarized pixel data of C3.
The three density data is binarized (S310).

In the above processing, each of the binarized CMs
Based on the YK ON / OFF result, a binarization error of each color component at the target pixel is calculated (S320), and the calculated error data is stored in an error memory of each color component, and is used when the next pixel is binarized. It is referred to as weighted error data (S330).

By performing such a series of processes for all the pixels of the image data, binarized image data is generated (S340).

Next, a case where the binarization process is performed on the target pixel in the order of KMCY will be described with reference to FIG.

The image binarizing device shown in FIG. 4 also has an image memory 1 in which original image CMYK data to be binarized is stored.
01, and an error diffusion device 102 that binarizes the multi-valued data in the image memory 101 by an error diffusion method, outputs a predetermined binary signal, and generates a binary image by pseudo halftone processing. .

Here, the error diffusion device 102 acquires KMCY density data from the image memory 101.
A density data acquisition unit 112, an error weighting calculator 104 that refers to a binarization error generated in surrounding binarized pixels from the error data storage unit 107, and performs an error weighting process on the image data of the target pixel. , Error weighting calculator 1
Binarization processing means 105 for performing a binarization process on the weighted data output from reference numeral 04 with reference to a binarization threshold
Error calculating means 106 for calculating an error of image data generated when binarizing is performed by the binarizing processing means 105 and storing the calculated error in the error data storing means 107; CMY at the pixel of interest output from
CMYK binarization result storage means 110 in which data of all K binarization results are stored, and a threshold value for CMY binarization determined from data in CMYK binarization result storage means 110 Is sent to the binarization processing means 105.

In such an image binarization device, the image data of the CMYK color components at the target pixel is transferred from the image memory 101 to the error diffusion device 102.

The error diffusion device 102 performs binarization by error diffusion processing.

Here, first, KMCY density data is obtained by the KMCY density data obtaining means 112,
Binarization processing by error diffusion is performed in the order of MCY. Then, referring to the error data of the surrounding pixels stored in the error data storage unit 107, the error data weighting unit 104 weights the K color component data of the target pixel with the error data. The weighted data is referred to the threshold value determined by the binarization threshold value determination unit 111, and the binarization processing unit 105 performs the binarization process. During the processing of K, the processing by the binarization threshold value determining means 111 is omitted, and error data is calculated by the error calculating means 106 based on the result of the binarized and output binary information.
The calculated error data is stored in the error data storage unit 107. Further, the binarization result of K is the ON / OF of the dot.
It is stored in the CMYK binarization result storage unit 110 as F information.

Similarly to the processing of K, in the binarization processing of MCY, binarization processing is performed by the error diffusion device 102 in the order of MCY, and the image data of the MCY color component at the target pixel is stored in the error data storage means. The MCY component data of the pixel of interest is weighted by the error weighting calculator 104 with reference to the error data of each of the MCYs of the surrounding pixels stored in 107. The weighted data is subjected to binarization processing in the binarization processing unit 105 with reference to the threshold value determined by the binarization threshold value determination unit 111.

Here, the binarization threshold value determining means 111
Refers to the ON / OFF information of K which has already been binarized in the CMYK binarization result storage unit 110, and sets a threshold value so that dots do not overlap as much as possible in the target pixel. At this time, if M is binarized, a threshold value for preventing dots from overlapping is set based on K ON / OFF information, and if C is binarized, K and M are binarized.
Is set based on the ON / OFF information, and if the threshold value is set so that the dots do not overlap, if Y is binarized, the dots do not easily overlap based on the ON / OFF information of K, M, and C. Set the threshold. Error data for each of the MCYs is calculated by the error calculating means 106 based on the binarized and output binary information result, and the calculated error data is stored in the error data storage means 107 as error data for each of the MCYs. You. The MCY binarization result is stored as CMYK binarization result storage means 1 as dot ON / OFF information.
10 respectively.

According to this, the binarization process is performed in the order of KMCY having a higher degree of recognition from the viewpoint of human visual characteristics.
It is possible to obtain a higher quality binary image at the target pixel.

Further, since the processing load is small and it is not necessary to hold the binarization results of other colors, it is possible to reduce the memory used.

[0075]

As described above, according to the present invention, if K of the target pixel is ON, the binarization results of other color components are turned OFF.
Therefore, an effective effect is obtained in that it is possible to prevent a phenomenon in which dots of other color components overlap with K and are canceled out and color unevenness occurs.

As a result, it is possible to obtain an effective effect that a high-quality binary image in which the occurrence of color unevenness is suppressed can be generated.

According to the present invention, K of the pixel of interest is O
In the case of FF, since the binarization process is performed in the order of higher density for the other color components and so that the dots of these color components do not overlap each other, the dispersibility and color reproducibility of the dots are good, An advantageous effect is obtained that a more faithful binary image can be generated from the original image.

After performing the binarization processing of the K color component of the target pixel, the binarization processing is performed in the order of the MCY color components so that the dots of these color components do not overlap with each other. Therefore, the binarization processing is performed in the order of KMCY having a higher degree of recognition from the viewpoint of human visual characteristics, and an effective effect that a higher quality binarized image can be obtained at the target pixel can be obtained.

Since the processing load is small and there is no need to hold the binarization results of other colors, an effective effect that it is possible to reduce the memory to be used is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an image binarization device that executes an image binarization method according to an embodiment of the present invention;

FIG. 2 is a block diagram showing another image binarization device for executing the image binarization method according to one embodiment of the present invention;

FIG. 3 is a flowchart showing a processing procedure performed by the image binarizing apparatus shown in FIGS. 1 and 2;

FIG. 4 is a block diagram showing still another image binarizing device for executing the image binarizing method according to one embodiment of the present invention;

FIG. 5 is a block diagram showing a conventional image binarization device using an error diffusion method.

FIG. 6 is an explanatory diagram showing an example of an error matrix.

[Explanation of symbols]

 Reference Signs List 101 Image memory 102 Error diffusion device 103 K binarization result ON / OFF determination unit 104 Error weighting calculator 105 Binarization processing unit 106 Error calculation unit 107 Error data storage unit 108 K binarization result storage unit 109 CMY density data Comparison means 110 CMYK binarization result storage means 111 Binarization threshold value determination means 112 KMCY density data acquisition means

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 5B057 CA01 CA08 CA12 CA16 CB01 CB07 CB12 CB16 CC01 CE13 CE16 5C077 LL19 MP08 NN07 NN11 NP01 PP33 PQ18 RR02

Claims (2)

[Claims] An image binarization method for generating a binary image by performing a pseudo halftone process on multi-tone image data having a plurality of color components including at least black (K). The binarization process of the K color component of the pixel is performed. If the binarization result of K in the pixel is ON, the binarization result of another color component is output as OFF, and the K in the pixel is output. If the binarization result is OFF, binarization processing is performed in the order of higher density for other color components and so that dots of these color components do not overlap each other. Value method. 2. An image for generating a binary image by performing pseudo halftone processing on multi-tone image data having color components of cyan (C), magenta (M), yellow (Y) and black (K). This is a binarization method, in which binarization processing of the K color component of the target pixel is first performed, and then binarization processing of the CMY color component of the target pixel is performed by M
An image binarization method characterized in that the dots are performed in the order of CY and such that the dots of these color components do not overlap each other.