JP2001218041A - Picture processor, picture processing method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically discriminate the presence or absence of the occurrence of moire when picture data to be generated, whose magnification is already varied, is outputted and to freely change a picture processing on picture data where moire occurs. SOLUTION: An inputted RGB signal is analyzed by a luminance/hue separation mechanism 50 and an FET/moire discrimination mechanism 51. It is discriminated whether a specified picture phenomenon is to occur in picture data whose magnification is already varied. An output correction mode is designated to a prescribed picture processing by a binary picture processing conversion part 109 based on the discrimination result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus having an image processing means for executing predetermined image processing on an image signal of an original to be read to generate printable image data, an image processing method, and storage. It is about media.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic system or a printing system typified by a digital copying machine, a dot density (dpi (do)) is determined by laser writing or display.
(t / inch) to record or display an image.

For example, in the above-mentioned image forming apparatus, the original of the image to be recorded is a printed matter, more specifically, 100, 133, 1
Printed matter having a plurality of line densities (lines / inch) such as 50, 175, 200, and 250 lines (lpi), in which the writing density of the image forming apparatus is 400 dpi and the magnification ratio of the original to the output image is 50%. When considered, moiré occurs in the output image of the 200-line portion of the document.

[0004] This phenomenon is caused by reducing the 200 lines of a document to 50% and reducing the writing density of the image forming apparatus to 400 dpi.
The spatial frequencies are substantially the same as those described above, and moire occurs due to interference. This relationship can be summarized into an equation: ρ = κ / M (1) In the above equation (1), ρ is the image writing density (dpi or lpi), and κ is the original recording density (lp)
i) and M correspond to the magnification.

Since the occurrence of moiré is the worst point at the point satisfying the above equation (1), providing a filter for cutting a specific frequency band as a spatial frequency filter has the effect of reducing moiré.

Conventionally, with respect to such moire, the occurrence of moire has been reduced by performing a filtering process on image data using a spatial filter at the time of image processing after reading a document or at the time of image processing before writing.

The moiré occurrence detection method and the accompanying spatial filter processing are configured as in the image forming apparatus described in Japanese Patent Application Laid-Open No. 08-242364.

In order to reduce the occurrence of moire, the image forming apparatus described in Japanese Patent Application Laid-Open No. 08-23444 frequency-converts an image before a screen and an image after a process, and converts the image after a screen process. When a peak in the low frequency band appears in the image, it is determined that moire is present, and the occurrence of moire is reduced by switching the screen size.

[0009]

However, since the spatial frequency of the spatial filter is set irrespective of the magnification and the linear density of the original image, the appropriate spatial frequency is not used for the moiré which may be generated due to the relationship between the magnification and the density. It is necessary to calculate each time so that

That is, different frequencies to be cut,
I had to prepare multiple spatial filters.

Also, an image having a plurality of line densities in the same original, for example, an original in which a photograph is pasted on a printed original of 133 lines or 175 lines, cannot be processed by the filter, and the moire cannot be reduced. There was a point.

Further, the above image processing method of detecting the occurrence of moiré and changing the screen size calculates the frequency of the image before and after the screen processing and generates a peak in the low frequency band that is not before the processing. Moire occurrence detection is performed depending on whether or not there is.

That is, this process must be continued until a screen size where no moiré occurs is determined.
There have been problems such as a long processing time until the first copy is output and a decrease in throughput.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to analyze an image signal after scaling processing before outputting the image data and output the image data. It is determined whether or not a specific image phenomenon can occur during printing, and based on the determination result, an output correction mode is designated for predetermined image processing by the image processing means, so that the image correction processing can be performed in parallel with the normal original image reading processing. Image signal, and automatically determines whether or not moiré has occurred when outputting the generated image data after scaling, and can freely change image processing on image data in which moiré occurs. Even if a complicated operation instruction is not issued from the user, the occurrence of moiré can be suppressed quickly without delaying the output processing of the image data, and it is essential By changing the image processing in accordance with the above, it is possible to maintain high image quality for an image in which moire does not occur, and by automatically calibrating the writing density, the image density can be set in the image forming apparatus main body. Even if the required writing density becomes mismatched due to the aging of the image forming apparatus, the writing density is corrected and rewritten to correct the writing density. An object of the present invention is to provide an image processing apparatus, an image processing method, and a storage medium that can minimize the deterioration.

[0015]

According to a first aspect of the present invention, there is provided an image processing apparatus having an image processing means for executing predetermined image processing on an image signal of a document to be read to generate printable image data. A processing unit that determines whether a specific image phenomenon can occur in the output image data by analyzing the image signal after the scaling process before outputting the image data; 2) and the image processing means (corresponding to the binary image processing conversion unit 109 shown in FIG. 2) based on the result of the discrimination by the discriminating means. It has a designating means (for example, equivalent to the FFT / moiré discriminating mechanism 51 shown in FIG. 2) for designating an output correction mode for predetermined image processing.

According to a second aspect of the present invention, the discrimination means analyzes the image signal, and after the image processing by the image processing means, can a specific image phenomenon occur in the output image data? It is to determine whether or not.

According to a third aspect of the present invention, the discriminating means extracts a recording density of the original image data by executing a fast Fourier transform process on a luminance signal extracted at the time of analyzing the RGB signal. This is to determine whether a specific image phenomenon can occur from the recording density.

According to a fourth aspect of the present invention, the designating means includes an output for causing the image data to be subjected to a binarization process when the determining means determines that a specific image phenomenon may occur. When a correction mode is specified and the determination means determines that a specific image phenomenon does not occur, the output correction mode is not specified.

According to a fifth aspect of the present invention, there is provided an extracting means for extracting a continuous image area by analyzing a luminance signal extracted at the time of analyzing an RGB signal (for example, corresponds to a continuous image area identifying mechanism 52 shown in FIG. 16). And the specifying means determines whether or not a specific image phenomenon can occur for each continuous image area extracted by the extracting means.

In a sixth aspect according to the present invention, the discriminating means includes a step of determining a specific density in the output image data based on a calculation result of a recording density of the extracted original image data and a preset writing density. This is to determine whether an image phenomenon can occur.

According to a seventh aspect of the present invention, the discriminating means (corresponding to, for example, the writing density comparing mechanism 53 shown in FIG. 18) determines the recording density of the extracted original image data and the preset writing density. In comparison, the recording density of the extracted original image data is automatically corrected to a preset writing density.

An eighth invention according to the present invention is directed to an image processing method in an image processing apparatus having image processing means for executing predetermined image processing on an image signal of a document to be read to generate printable image data. A determination step of analyzing the image signal after the scaling process to determine whether a specific image phenomenon may occur in the output image data before outputting the image data (see FIG. 15). Step (1)-
(5)) and a designation step (step (8) shown in FIG. 15) of designating an output correction mode for predetermined image processing by the image processing means on the basis of a result of the discrimination in the discrimination step. is there.

According to a ninth aspect of the present invention, in the determination step, after the image signal is analyzed by the image processing means, a specific image phenomenon can occur in the output image data. It is to determine whether or not.

In a tenth aspect according to the present invention, in the discrimination step, a fast Fourier transform process (for example, step (4) shown in FIG. 15) is performed on a luminance signal extracted at the time of analysis of an RGB signal, and The recording density of the data is extracted, and it is determined whether or not a specific image phenomenon can occur based on the extracted recording density.

According to an eleventh aspect of the present invention, in the specifying step, when the determining step determines that a specific image phenomenon can occur, an output for causing the image data to perform a binarization process When a correction mode is specified and the determination step determines that a specific image phenomenon does not occur, the output correction mode is not specified.

According to a twelfth aspect of the present invention, there is provided an extracting step (step (1) shown in FIG. 17) for analyzing a luminance signal extracted at the time of analyzing an RGB signal to extract a continuous image area.
4)), wherein the specifying step determines whether or not a specific image phenomenon can occur for each continuous image area extracted in the extracting step.

According to a thirteenth aspect of the present invention, in the determining step, the specific image data to be output is output based on a calculation result of a recording density of the extracted original image data and a preset writing density. This is to determine whether an image phenomenon can occur.

According to a fourteenth aspect of the present invention, in the determining step, the recording density of the extracted original image data is compared with a preset writing density (step (36) shown in FIG. 19). The recording density of the extracted document image data is automatically corrected to a preset writing density (step (37) shown in FIG. 19).

According to a fifteenth aspect of the present invention, there is provided an image processing apparatus having image processing means for performing predetermined image processing on an image signal of a document to be read to generate printable image data. A determination step (Steps (1) to (1) shown in FIG. 15) of analyzing the image signal after the scaling process to determine whether or not a specific image phenomenon may occur in the output image data before outputting the data. 5)) and a designation step (step (8) shown in FIG. 15) of designating an output correction mode for a predetermined image processing by the image processing means based on a result of the discrimination in the discrimination step. The program is recorded on a recording medium in a computer-readable manner.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a schematic sectional view of a full-color copying machine to which an image processing apparatus according to a first embodiment of the present invention can be applied.

In FIG. 1, reference numeral 201 denotes an image scanner unit which reads a document and performs digital signal processing. A printer unit 200 prints an image corresponding to a document image read by the image scanner unit 201 on recording paper.

In the image scanner unit 201, 20
Reference numeral 2 denotes a document pressing plate, and the document 20 on the platen glass 203
4 is irradiated by a halogen lamp 205. Light reflected from the document is guided to mirrors 206 and 207, and forms an image on a light receiving surface of a linear CCD image sensor 210 (hereinafter simply referred to as CCD 210) by a lens 208.
The lens 208 has an infrared cut filter 231-1.
To 231-1 (hereinafter, may be simply referred to as an infrared cut filter 231).

The CCD 210 separates the light from the original into red (R), green (G), and blue (B) colors, reads them, and sends them to the image processing unit 209.

The CCD 210 has, for example, three lines of light receiving pixels of about 5000 pixels each for RGB.
It is possible to read in dpi (dot / inch).
Similarly, the 297 mm width direction of the A3 size document is set to 60
In order to read at 0 dpi, about 750 each of RGB
A one-dimensional image sensor with 0 pixels is required.

The halogen lamp 205 and the mirror 20
6 is the speed V, and the mirror 207 is V / 2 at the sub-scanning direction (C
The sensor 210 of the CD 210 and the direction perpendicular thereto are mechanically moved, so that the CCD 210 can read the entire surface of the document.

Reference numeral 211 denotes a reference white plate having a uniform density.
A reference density for correcting sensitivity unevenness of each pixel 210 is provided.

The image processing unit 209 converts the signal read by the CCD 210 into a digital signal, and forms each color component of magenta (M), cyan (C), yellow (Y), and black (K). Send to section 200. Also, for one original scanning scan (corresponding to one sub-scanning time) in the image scanner unit 201, one component of M, C, Y, and K is sent to the printer unit 200, and four scans are sequentially performed. That is, one print is completed by sequentially sending data of four colors to the printer unit 200.

The M, C, Y, and K image signals sent from the image scanner unit 201 are transmitted to the printer unit 200.
In, first, it is sent to the laser driver 212. The laser driver 212 causes a laser diode to emit light according to the image signal of each pixel. Laser light is polygon mirror 21
4, scanning is performed on the photosensitive drum 217 via the f-θ lens 215 and the mirror 216.

The developing unit includes a developing unit 219 for magenta, a developing unit 220 for cyan, a developing unit 221 for yellow, and a developing unit 222 for black. These four developing devices sequentially approach the photosensitive drum 217, and develop the electrostatic latent image formed on the photosensitive drum 217 by the laser beam irradiation with toner of a corresponding color.

A transfer drum 223 wraps recording paper fed from the paper cassette 224 or 225, and transfers a toner image developed on the photosensitive drum 217 onto the recording paper.

After the four colors of M, C, Y, and K are sequentially transferred as described above, the recording sheet passes through the fixing unit 226 and is discharged outside the apparatus. The above is the outline of the image forming operation of the digital copying machine in the present embodiment.

Hereinafter, the image signal processing of this embodiment, which is performed in the above-described image processing unit 209, will be described.

FIG. 2 is a block diagram illustrating the configuration of the image processing apparatus according to the first embodiment of the present invention, and corresponds to the detailed configuration of the image processing unit 209 illustrated in FIG.

In FIG. 2, reference numeral 210 denotes the above-mentioned CCD, which reads an original image at 400 dpi, and outputs the read signal output of the RCB to the image processing unit 209.

In the image processing unit 209, reference numeral 102 denotes A /
The D converter converts each input RGB signal output into a digital signal. Reference numeral 103 denotes a shading correction unit that corrects unevenness in the amount of illumination, unevenness in the amount of light generated on the lens optical system on the light receiving surface of the CCD 210, and unevenness in the sensitivity of each pixel of the CCD 210.

Reference numeral 104 denotes an input masking unit which reads RG
The color of the B signal is correctly corrected by an RGB matrix operation. A scaling unit 105 converts image data to be output into image data having an output magnification. Reference numeral 106 denotes a LOG converter, which converts each designated RGB signal into each CMY density signal.

Reference numeral 107 denotes a UCR / output masking unit.
A UCR (under color removal) operation for removing the K (black) signal from the MY signal to convert it into four colors of CMYK, and a matrix operation for correcting the color reproducibility of the printer is performed on the CMYK signal. The UCR / output masking section 107 sequentially outputs one of the four CMYK signals corresponding to each print color in the printer section 200 for each reading scan.

In FIG. 2, the output signal is described as "C / M / Y / K" to indicate this output operation.

Reference numeral 108 denotes a resolution conversion unit that converts a 400 dpi read signal read by the CCD 210 into 600 dpi. Note that the resolution conversion unit 108 is
, On / off control of the resolution conversion can be performed. Reference numeral 109 denotes a binary image processing conversion unit which converts a multilevel signal into a binary image processing signal by an arithmetic method such as an average density preservation method, and turns on / off binary conversion under the control of the CPU 110.
Off control is possible. The binary image processing conversion unit 10
The configuration of No. 9 will be described later. The C, M, Y, and K binary signals output from the resolution conversion unit 108 are sequentially transmitted to the printer unit 200.

The other output side of the scaling unit 105 is connected to a luminance / hue separation unit 50 for separating into a luminance signal and a hue signal built in the CPU 110.

An FFT / moire discriminating mechanism 51 performs a Fourier transform to determine whether or not moiré occurs.

The CPU 110 controls the components in the binary image processing conversion unit 209 based on the control program stored in the ROM 113. For example, UCR
-It also performs parameter setting control for the output masking unit 107 and the resolution conversion unit 108. The CPU 110 operates and
It is connected to the display unit 112 and the external 1 / Fll. A RAM 114 mainly serves as a work area of the CPU 110.

Hereinafter, the image processing unit 20 having the above-described configuration will be described.
9 and the configuration of a conversion unit that converts a multi-level signal into a binary error diffusion process will be described.

First, as a method of converting a multilevel signal into a binary signal, a method of performing conversion processing using an average density preservation method (MD method) will be described as an example. The binarization method is not applied only to the MD method.

FIG. 3 is a block diagram illustrating the configuration of the binary image processing conversion unit 109 shown in FIG. 2, and is, for example, an example corresponding to the MD method as a binary image processing method.

In the figure, D is an image signal, which is an 8-bit digital image signal of 256 gradations, to which a result of A / D conversion of an analog signal of a CCD or the like and image data such as CG are inputted.

Reference numeral 8-1 denotes an MTF correction means, which is an MTF for improving the contrast of the image signal D, which will be described later.
The corrected image signal Dl is provided to the error correction unit 8-3.

The error correcting means 8-3 outputs the image signal Dl,
A binary error data E described later is input, an image signal D2 obtained by performing an error correction described later on the image signal Dl is calculated, and output to the binarizing means 8-2.

The binarizing means 8-2 receives the image signal D2 and a binarized slice value S, which will be described later, and compares them to obtain a binary output N and a binarized plot difference data E. Perform output.

The binarization result delay means 8-4 has a binary output N
Is input, a predetermined number of lines are delayed, and a plurality of lines 2
The data is sent to the slice setting means 8-5 as the valuation result Nmn.

[0062] The slice setting means 8-5
The binarization means 8- inputs the binarization result Nmn, performs a product-sum operation on the preset coefficient and the delayed binary result, and performs binarization.
The binarized slice value S used in 2 is output. The details of the image processing means will be described below with reference to FIGS.

The MTF correction means 8-1 outputs the image signal D
To improve the contrast, which will be described later.
The means for outputting the image signal Dl subjected to the F correction is shown in FIG.
It has a configuration as shown in FIG.

FIGS. 4 and 5 are block diagrams for explaining the detailed configuration of the MTF correction means 8-1 shown in FIG.
The same components as those described above are denoted by the same reference numerals.

In the figure, an input image signal 1: D
Are from a line buffer 9-1 to a line buffer 9-for one line of a plurality of bits (8 bits in this embodiment).
6, and the data is delayed line by line.

The data which is not delayed is successively delayed by one pixel by the delay units 9-7 to 9-12 each composed of a delay circuit for one pixel.
The data of D17 is input to the MTF calculation means 9-49.

The image data delayed by one line by the line buffer 9-1 is supplied to the delay units 9-13 to 9-13.
9-18, the data D21-D
The data is input to the MTF calculation means 9-49 as 27 data.

Delay units 9-19 to 9-2 each consisting of a delay circuit for one pixel by other line buffers 9-2 to 9-6.
4, delay units 9-25 to 9-30, delay units 9-31 to 9-
36, delay units 9-37 to 9-42, delay units 9-43 to 9
−48, the data D31 to D37, which are also delayed one pixel at a time,
Data D41 to D47, data D51 to D57, data D61 to D67, and data D71 to D77 are input to the MTF calculation means 9-49.

That is, the two-dimensional image data is subjected to delay processing for a plurality of lines and a plurality of pixels, and is input to the MTF calculating means 9-49 in a data array as shown in FIG.

FIG. 7 is a block diagram showing an example of the MTF calculating means 9-49 shown in FIGS. 4 and 5.
The same components as those described above are denoted by the same reference numerals.

In the figure, reference numerals 11-1 to 11-49 denote multiplication circuits for multiplying image data input in the data arrangement state shown in FIG. 6 by coefficients in the arrangement state shown in FIG.

Reference numeral 11-50 denotes an addition circuit, which is a multiplication circuit 11-.
The data multiplied by 1 to 11-49 are added to generate an image signal D1.

That is, the multiplication circuit 11-1 receives the image data D17 and the coefficient K17 and outputs the result of multiplication of the two. In the multiplication circuit 11-2, the image data D16 and
The coefficient K16 is input, and the result of multiplication of the two is output. A similar operation is performed by all the circuits of the multiplication circuits 11-3 to 11-49, and the multiplication result is added to the addition circuit 1
Add all by 1-50. The image signal D
Output as l.

By changing the coefficients of the data array shown in FIG. 8, the effect of edge enhancement, the effect of smoothing, and the like can be set.

Hereinafter, the detailed configuration of the binarizing means 8-2 shown in FIG. 3 will be described with reference to FIG. The binarizing means 8-2 inputs the image signal D2 and a binarized slice value S described later, and outputs a binarized output N and binarized error data E by comparing the two. .

FIG. 9 is a block diagram for explaining a detailed configuration of the binarizing means 8-2 shown in FIG.

In FIG. 9, the input image signal D2
And the binarized slice value S are divided into two systems, one of which is input to the comparison circuit 13-1 and the other is input to the subtraction circuit 13-2.

The comparison circuit 13-1 compares the image signal D2 with the value of the binarized slice value S. When D2> S, N = 1. When D2 ≦ S, N = 1. The binary output N is output as 0.

The subtraction circuit 13-2 subtracts the value of the image signal D2 from the binarized slice value S and outputs the result as binarized error data E (E = S-D2).

The error correcting means 8-3 outputs the image signal Dl
The binarized error data E is input, an image signal D2 obtained by performing an error correction on the image signal Dl is calculated, and output to the binarizing means 8-2, as shown in FIG. It consists of a configuration.

FIG. 10 is a block diagram of the error correction means 8-- shown in FIG.
FIG. 4 is a block diagram illustrating a detailed configuration of the third embodiment, and the same components as those in FIG. 3 are denoted by the same reference numerals.

In FIG. 10A, when the input binarized difference data E is halved by the division circuit 14-1, the result is branched into two systems.
-2, and the other is input to the line buffer 14-3.

The subtraction circuit 14-2 calculates the difference EB between the binarized error data E and E / 2, and inputs the result to the addition circuit 14-4.

In the adder circuit 14-4, E is delayed by one line by the line buffer 14-3 for one line of a plurality of bits (for example, 8 bits in the present embodiment).
/ 2 (EA) and the sum of EE / 2 (EB) are calculated and output to the adding circuit 14-5.

The adder circuit 14-5 calculates the sum of E / 2 (EA) and EE / 2 (EB) delayed by one line and the sum of the image signal Dl and outputs the sum as the image signal D2. I do.

That is, in the error correction means 8-3, FIG.
(B), the value of the binarization error EA when binarizing A on one line with respect to the target pixel and the value of binarization error EB when binarizing B one pixel before. Is added to the data of the target pixel.

The binarization result delay means 8-4 has a binary output N
Is input, a predetermined number of lines are delayed, and a plurality of lines 2
The data is sent to the slice setting means 8-5 as the value Nmn, and has a configuration as shown in FIG.

FIG. 11 is a block diagram for explaining a detailed configuration of the binarization result delay means 8-4 shown in FIG.
The same components as those described above are denoted by the same reference numerals.

In FIG. 11, the input binary output N
Is sent from the line buffer 15-1 for one bit to one line to the line buffer 15-2, and data is delayed line by line.

The data which is not delayed is successively delayed by one pixel by the delay units 15-3 to 15-6 each composed of a delay circuit for one pixel. The outputs of the delay unit 15-5 and the outputs N14, N14 of the delay unit 15-6
15 is output.

On the other hand, 1 is set by the line buffer 15-1.
The binarized data delayed by the line is supplied to the delay unit 15-
7 to the output N21
N25, the binarized data delayed by another line by the line buffer 15-2 is delayed by the delay units 15-11 to 15-14.
These are output as outputs N31 to N35.

That is, the data obtained by binarizing the two-dimensional image is subjected to delay processing for a plurality of lines and a plurality of pixels, and as a plurality of lines binarization result Nmn, the slice setting means 8-- 5 will be input.

FIG. 13 is a block diagram for explaining the detailed configuration of the slice setting means 8-5 shown in FIG. 3, and the same components as those in FIG. 3 are denoted by the same reference numerals.

In the figure, the slice setting means 8-5 comprises:
A multi-line binarization result Nmn is input, and a multiply-accumulate operation is performed by using a preset coefficient and a delayed binary result.
The binarizing slice value S used by the binarizing means 8-2 is output.

That is, the multiplication circuit 17-1 receives the binary data N15 and the coefficient M15 shown in FIG. 14, and outputs the result of multiplication of the two. The multiplication circuit 17-2 receives the binary data N14 and the coefficient M14 shown in FIG. 14, and outputs the result of multiplication of the two. A similar operation is performed by the multiplication circuit 17-
Performed by all the circuits of the multiplication circuits 17-12 from 3;
All of the multiplication results are added by the adder circuit 17-13. The result is output as a binarized slice value S.

By sequentially performing the above processing for each pixel, multi-valued image data is converted into binary data and output.

In the present embodiment, the line (dot) density (document recording frequency) of the document image is calculated, and the calculation result is compared with the magnification,
And whether or not moire is generated from the writing density, and if moire is generated, the image forming method is changed to PWM.
The image processing method is converted to a binary image processing method by the MD method. When no moiré occurs, the image processing method is not changed.
An image is formed by a PWM image processing method.

Since the binary image processing method does not have a fixed frequency, moire does not occur. By using this principle, it is possible to provide an image processing apparatus or an image forming apparatus that executes image processing that does not automatically generate moiré.

First, in the image processing unit 209, a luminance / hue separation mechanism 50 for separating into a luminance signal and a hue signal built in the CPU 110 is connected to the output side of the scaling unit 105. An FFT / moiré discrimination mechanism 51 is connected to the output side of the luminance component of the luminance / hue separation mechanism 50.

The FFT / moiré discriminating mechanism 51 determines whether or not moire is generated by a Fourier transform unit that performs a fast Fourier transform (FFT) process on the luminance signal from the luminance / hue separating mechanism 50. Value image processing converter 109
ON / OFF of whether to convert to binary image processing method
It is composed of a moire discriminating and transmitting unit for transmitting a signal.

The Fourier transform unit performs an FFT process on the target document image data to extract the recording density κ of the document image data. The extracted recording density κ is a common multiple (ρ)
In the case of = κ / M (M is a magnification), moire occurs, so that the image forming method is changed to the binary image processing method.

In the present embodiment, the above-described common-magnitude relational expression is converted into (−5 ≦ ρ− (κ / M) ≦ 5), and the occurrence of moiré is predicted based on whether or not the relational expression is satisfied. Change the method as needed.

For example, if the magnification is 1 × and the original recording density is 19
5 lines (line / inch), PWM writing density is 20
In the case of the zero line, (ρ− (κ / M) = 5), which is applicable to the above relational expression.

That is, the image processing method is changed to binary error diffusion and output. On the other hand, if the above relational expression is not satisfied, the image is output by PWM without changing the image processing method.

Hereinafter, the flow of image formation in the above configuration will be described with reference to the flowchart shown in FIG.

FIG. 15 is a flowchart showing an example of a first data processing procedure in the image processing apparatus according to the present invention. Note that (1) to (10) indicate each step.

First, in step (1), copying is started by designating the output magnification M, the number of output sheets, the output size, and the like.
In step (2), the image data read from the document is input as RGB signals from the image scanner 201 to the image processing unit 209, and after being appropriately subjected to necessary signal processing, is sent to the scaling unit 105. It is input and undergoes scaling processing according to the specified magnification.

Then, the image data after the scaling process has the luminance
Only the luminance data input to the hue separation mechanism 50 is input to the FFT / moiré discrimination mechanism 51, and in step (3), RG
A luminance component is extracted from the B signal, and in step (4), F
FT processing is performed.

Since the image data after the scaling process is converted by the image forming method by the binary image processing conversion unit 109 as necessary, in the next step (5), the FFT / moiré discrimination mechanism 51 Since the FFT is performed on the image data, it is determined whether or not moire occurs according to the relationship [−5 ≦ ρ− (κ / M) ≦ 5] between the recording density, the magnification, and the writing density of the original image data. ON when it is determined that moiré will occur (when the relational expression holds)
When it is determined that no signal is generated (when the relational expression does not hold), an OFF signal is given to the binary image processing conversion unit 109.

If the binary image processing conversion unit 109 is ON based on the applied signal, it is determined in step (8)
Then, the image is converted by the binary image processing method based on the MD method, and in step (9), the image is output by the binary image processing method. In step (10), it is determined whether or not the specified number of images has been formed. If the judgment is YES, the process ends, and N
If O, return to step (9).

On the other hand, if it is determined in step (5) that the switch is OFF, then in step (6), the image is formed by the image forming method using PWM as it is, and in step (7), It is determined whether or not the specified number of image formation sheets has been completed, and if YES, the processing ends, and
If NO, the process returns to step (6).

Thus, when moiré is likely to occur, image formation is performed by a binary image processing method having no periodicity, so that moiré does not occur.

[Second Embodiment] FIG. 16 shows a second embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of an image processing apparatus according to an exemplary embodiment, and the same components as those in FIG. 2 are denoted by the same reference numerals.

The second embodiment is characterized in that an image forming method is converted into a binary image processing method only for a continuous image in which moire occurs using the image forming apparatus used in the first embodiment. I have.

In FIG. 16, reference numeral 52 denotes a continuous image area discriminating mechanism, which is provided between the output destination of the luminance component of the luminance / hue separating mechanism 50 and the FFT / moiré discriminating mechanism 51. An image area is identified based on whether or not the above-mentioned luminance signal is continuous, and FFT is performed by the FFT / moire discriminating mechanism 51 for each image area.
The frequency components of the document image data are extracted, and it is determined whether or not moire occurs.

In this embodiment, the luminance signal is two-dimensionally eight.
An area in which not less than 100 continuous pixels exist with 5 or more <L ^* ≧ 85> is identified, divided, and FFT and moire occurrence determination processing are performed.

At this time, an ON signal is given to the binary image processing conversion unit 109 in the image area where moiré occurs, and the image forming unit is converted to the binary image processing method.

On the other hand, in an image area where moire does not occur, an image is formed by PWM without conversion to the binary image processing method.

That is, the continuous image area and the moiré occurrence state are discriminated using the luminance signal separated from the image data, and only the continuous image data area where the moiré occurs is converted to the binary image processing method. Since the image is formed by PWM, it is possible not only to prevent moiré but also to minimize image quality deterioration in the binary image processing method.

FIG. 17 is a flowchart showing an example of the second data processing procedure in the image processing apparatus according to the present invention. Note that (11) to (21) indicate each step.

First, in step (11), the output magnification M,
Copying is started by designating the number of output sheets, the output size, and the like. In step (12), the image data read from the original is sent from the image scanner 201 to the image processing unit 20.
9 is input as an RGB signal, appropriately subjected to necessary signal processing, and then input to the scaling unit 105 to be subjected to scaling processing according to the designated magnification.

Then, the image data after the scaling process has the luminance
Only the luminance data input to the hue separation mechanism 50 is input to the FFT / moiré discrimination mechanism 51, and at step (13), R
A luminance component is extracted from the GB signal, and step (14)
Then, the continuous image area identification mechanism 52 identifies an image area based on whether or not a luminance signal of a certain level or more is continuous.
^* ≧ 85> is used to identify an area where 100 or more continuous pixels do not exist, and divide the image k into a plurality (k = 1 to n).

Next, in step (16), the FFT
The moiré discriminating mechanism 51 calculates the recording density κ of each continuous image by performing FFT on each image data. Next, in step (17), for each continuous image, it is determined whether or not moire is generated based on the relationship between magnification and writing density (−5 ≦ ρ− (κ / M) ≦ 5). An ON signal is determined when it is determined to be generated (when the relational expression holds), and an ON signal is determined when it is determined not to occur (when the relational expression does not hold).
The FF signal is provided to the binary image processing conversion unit 109.

If the binary image processing / conversion unit 109 is ON based on the given signal, the process proceeds to step (19).
Then, the image is converted by the binary image processing method based on the MD method. In step (20), the image is output by the binary image processing method. In step (21), it is determined whether or not the specified number of images has been formed. Determine, if YES, end the process,
If NO, return to step (20).

On the other hand, if it is determined in step (17) that the switch is OFF, then in step (18), the image is formed by the image forming method with the PWM unchanged, and in step (21), It is determined whether or not the specified number of image forming sheets has been completed. If YES, the process is terminated. If NO, the process returns to step (20).

Thus, it is possible to correspond to various document line densities and halftone dot densities in order to identify continuous image areas and determine whether or not moire occurs. For example,
When copying an original on which a photo is pasted on a printed matter output in 200 lines, the moiré occurrence state is determined by dividing the image into continuous images. Therefore, the printed portion matches the moiré occurrence relational expression, and the photograph does not match. In other words, the binary image processing method is applied only to the print portion, and an image is formed by PWM in the other portions including the photograph. In other words, this copied image can achieve both moiré-free printed document copying and high-quality photo copying.

[Third Embodiment] In the first and second embodiments, the value of the image output writing density stored in advance is used. However, the actual value of the writing density depends on the durability, environment and the like. , Especially high resolution output (400 lines or more)
The variation is large. Therefore, in the present embodiment, the current writing density of the airframe is measured, and the calculation formula (ρ = κ / M
(M: magnification).

FIG. 18 is a block diagram illustrating the configuration of an image processing apparatus according to a third embodiment of the present invention.
The same components as those described above are denoted by the same reference numerals.

In FIG. 18, reference numeral 53 denotes a writing density comparison mechanism, which is a writing density ρi calculated as described later.
Is compared with the pre-recorded writing density (ρ). If there is a certain difference or more, the calculated writing density ρi is stored as ρ.

First, a halftone image whose writing density is easy to calculate is output on paper. The output halftone image is read by the image scanner unit 201, and the FFT processing is performed on the luminance component in the same manner as in the first and second moiré occurrence discrimination, and the current writing density (ρi) of the machine is calculated.

Then, the calculated writing density ρi is compared with the previously recorded writing density (ρ) by the writing density comparing mechanism 53, and if there is a difference of not less than a certain value, the calculated writing density ρi is set as ρ. Remember.

In the present embodiment, when the difference between the previously stored writing density ρ and the actually calculated writing density ρi is 10 lines or more, the calculated writing density ρi is replaced with ρ, and Set to.

This series of operations is defined as "writing density calibration". Then, from the next instruction, it is determined whether or not moiré occurs using the value of ρ thus calculated, and when moiré occurs, the image processing method is changed to the binary image processing method.

FIGS. 19 and 20 are flowcharts showing an example of the third data processing procedure in the image processing apparatus according to the present invention. Incidentally, (31) to (48) indicate each step.

First, in a step (31), a writing density calibration is executed, and in a step (32), a halftone image whose writing density is easily calculated is output on paper. In step (33), the output halftone image is read by the image scanner unit 201 and input as RGB signals.

Next, in step (34), a luminance component is extracted from the RGB signals. In step (35), the output halftone image is read by the image scanner unit 201, and when the first and second moire occurrences are determined. Similarly to F
After the FT processing, the current writing density (ρ
i) is calculated.

Then, in step (36), the calculated write density ρi is calculated by the write density comparing mechanism 53.
Compared with the previously recorded write density (ρ), if there is a certain difference or more, in step (37),
The calculated writing density ρ is stored as ρi.

On the other hand, if it is determined in step (36) that there is no difference equal to or greater than a predetermined value, in step (38), copying is started by specifying the output magnification M, the number of output sheets, the output size, and the like. ), The image data read from the original is input as RGB signals from the image scanner 201 to the image processing unit 209, and after being appropriately subjected to necessary signal processing, input to the scaling unit 105. The image is subjected to scaling processing according to the specified magnification.

Then, in step (40), after the scaling process
Are input to the luminance / hue separation mechanism 50,
A luminance component is extracted from the GB signal, and step (41)
Then, the continuous image area identification mechanism 52 outputs a luminance signal of a certain level or more.
The image area is identified by whether or not
In step (42), the luminance signal is two-dimensionally 85 or more <L
^* ≥85> to identify areas where more than 100
Separately, the image k is divided into a plurality (k = 1 to n).

Next, in step (43), the FFT / moiré discriminating mechanism 51 performs the FFT on each image data to calculate the recording density κ of each continuous image. Next, in step (44), the relationship between the recording density of the original image data, the magnification, and the writing density (−5 ≦ ρ− (κ /
M) ≦ 5) to determine whether moiré occurs,
An ON signal is supplied to the binary image processing conversion unit 109 when it is determined that moiré is generated (when the relational expression is satisfied), and when it is determined not to be generated (when the relational expression is not satisfied).

If the binary image processing conversion unit 109 is ON based on the given signal, the process goes to step (46).
Then, the image is converted by the binary image processing method by the MD method, and in step (47), the image is output by the binary image processing method.
In step (48), it is determined whether or not the specified number of image forming sheets has been completed. If YES, the process ends. If NO, the process returns to step (47).

On the other hand, if it is determined in step (44) that the switch is OFF, then in step (45), the image is formed by the image forming method with the PWM unchanged, and in step (47), An image is output based on each piece of continuous image information, and it is determined in step (48) whether or not the specified number of image formations has been completed. If YES, the process is terminated; if NO, step (47) Return to

Accordingly, since the image processing is changed so as not to generate moiré in accordance with the state of the image forming apparatus main body, the occurrence of moiré due to the writing density mismatch is suppressed, and it is not necessary to change to the binary image processing method. The image quality of good image data does not decrease. That is,
More appropriate image processing change is possible, and image data that does not generate moiré is formed with high image quality by PWM image forming processing, and image data that generates moiré is subjected to image processing by a binary image processing method so that moiré is not generated. , And high image quality can be achieved.

According to the above-described embodiment, the occurrence of moire can be suppressed automatically and speedily. Further, since the image processing is changed as necessary for each successive image, high image quality can be maintained for an image in which moire does not occur. Furthermore, even when the writing density to be set in the image forming apparatus main body is mismatched due to the temporal change of the image forming apparatus main body, the writing density can be corrected and rewritten to an appropriate writing density by the writing density calibration. Therefore, it is possible to minimize the occurrence of moiré due to the mismatch of the writing density and the deterioration of the image quality due to the binary image processing method.

Hereinafter, the configuration of a data processing program readable by an image processing system to which the image processing apparatus according to the present invention can be applied will be described with reference to a memory map shown in FIG.

FIG. 21 is a view for explaining a memory map of a storage medium for storing various data processing programs which can be read by an image processing system to which the image processing apparatus according to the present invention can be applied.

Although not shown, information for managing a group of programs stored in the storage medium, for example, version information, a creator, etc. are also stored, and information dependent on the OS or the like on the program reading side, for example, a program is stored in the storage medium. An icon or the like for identification display may also be stored.

Further, data subordinate to various programs is also managed in the directory. In addition, a program for installing various programs on a computer or a program for decompressing a program to be installed when the program to be installed is compressed may be stored.

FIGS. 15, 17, and 1 in the present embodiment.
9. The functions shown in FIG. 20 may be performed by a host computer by a program installed from the outside. In this case, the present invention is applied even when a group of information including a program is supplied to the output device from a storage medium such as a CD-ROM, a flash memory, or an FD, or from an external storage medium via a network. Things.

As described above, the storage medium storing the program code of the software for realizing the functions of the above-described embodiments is supplied to the system or the apparatus, and the computer (or CPU or MP) of the system or the apparatus is supplied.
It goes without saying that the object of the present invention is also achieved when U) reads and executes the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

Examples of a storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk,
D-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, EEPROM, etc. can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) And the like perform part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

[0155]

As described above, the first embodiment according to the present invention is described.
According to the fifteenth aspect, before the image processing unit starts image processing on the input image signal, the image signal after the scaling process is analyzed, and the image data output after the image processing by the image processing unit is performed. It is determined whether or not a specific image phenomenon can occur during printing. Based on the determination result, an output correction mode is designated for predetermined image processing by the image processing means. The image signal is analyzed, and the presence or absence of moiré is automatically determined at the time of generating the scaled image data to be generated, and image processing for image data in which moiré occurs can be freely changed. Even if the complicated operation instruction is not issued, it is possible to quickly suppress the occurrence of moire without delaying the output processing of the image data.

Further, since the image processing is changed as necessary for each continuous image area, high image quality can be maintained for an image in which moire does not occur.

Further, even if the writing density to be set in the image forming apparatus main body is mismatched due to the aging of the image forming apparatus main body, the writing density can be corrected and rewritten to an appropriate writing density by the writing density calibration. Therefore, it is possible to minimize the occurrence of moiré due to the mismatch of the writing density and the deterioration of the image quality due to the binary image processing method.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a full-color copying machine to which an image processing apparatus according to a first embodiment of the present invention can be applied.

FIG. 2 is a block diagram illustrating a configuration of an image processing apparatus according to the first exemplary embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a binary image processing conversion unit illustrated in FIG. 2;

FIG. 4 is a block diagram illustrating a detailed configuration of an MTF correction unit illustrated in FIG. 3;

FIG. 5 is a block diagram illustrating a detailed configuration of an MTF correction unit illustrated in FIG. 3;

FIG. 6 is a diagram showing a data array example of image data input to the MTF correction means shown in FIGS. 4 and 5;

FIG. 7 is a block diagram illustrating an example of an MTF correction unit illustrated in FIGS. 4 and 5;

8 is a diagram illustrating an example of a data array of coefficients set in the multiplication circuit illustrated in FIG. 7;

FIG. 9 is a block diagram illustrating a detailed configuration of a binarizing unit illustrated in FIG. 3;

FIG. 10 is a block diagram illustrating a detailed configuration of an error correction unit illustrated in FIG. 3;

FIG. 11 is a block diagram illustrating a detailed configuration of a binarization result delay unit illustrated in FIG. 3;

12 is a diagram illustrating an example of a multi-line binarization result generated by a binarization result delay unit illustrated in FIG. 11;

FIG. 13 is a block diagram illustrating a detailed configuration of a slice setting unit illustrated in FIG. 3;

FIG. 14 is a diagram illustrating an example of a data array of coefficients set in a multiplication circuit of the slice setting unit illustrated in FIG. 13;

FIG. 15 is a flowchart illustrating an example of a first data processing procedure in the image processing apparatus according to the present invention.

FIG. 16 is a block diagram illustrating a configuration of an image processing apparatus according to a second embodiment of the present invention.

FIG. 17 is a flowchart illustrating an example of a second data processing procedure in the image processing apparatus according to the present invention.

FIG. 18 is a block diagram illustrating a configuration of an image processing apparatus according to a third embodiment of the present invention.

FIG. 19 is a flowchart illustrating an example of a third data processing procedure in the image processing apparatus according to the present invention.

FIG. 20 is a flowchart illustrating an example of a third data processing procedure in the image processing apparatus according to the present invention.

FIG. 21 is a diagram illustrating a memory map of a storage medium that stores various data processing programs that can be read by an image processing system to which the image processing device according to the present invention can be applied.

[Explanation of symbols]

 Reference Signs List 50 luminance / hue separation mechanism 51 FFT / moiré discrimination mechanism 102 A / D converter 103 shading section 104 input masking section 105 scaling section 106 LOG conversion section 107 UCR output masking section 108 resolution conversion section 109 binary image processing conversion section 110 CPU 113 ROM 114 RAM

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) H04N 1/393 G06F 15/68 410 F term (reference) 2C262 AA24 AA26 AB01 AC02 BA16 BB08 BB18 BB44 DA15 DA16 EA04 EA06 FA20 5B057 CA01 CA08 CB01 CB07 CD05 CE13 CG05 CH09 CH18 DA01 DA08 DB02 DB06 DC14 5C076 AA21 AA22 CB04 5C077 LL03 MP08 NN11 NN17 NN19 PP20 PP32 PP36 PP49 PP65 PQ08 PQ20 RR02 RR03 RR16

Claims (15)

[Claims] An image processing apparatus comprising: an image processing unit configured to execute predetermined image processing on an image signal of a document to be read to generate printable image data; Determining means for analyzing the image signal after the scaling process to determine whether or not a specific image phenomenon can occur in the output image data; and determining by the image processing means based on the determination result by the determining means. Specifying means for specifying an output correction mode for the image processing. 2. The image processing apparatus according to claim 1, wherein the determining unit analyzes the image signal and determines whether a specific image phenomenon can occur in output image data after the image processing by the image processing unit. The image processing device according to claim 1. 3. The discrimination means extracts a recording density of original image data by executing a fast Fourier transform process on a luminance signal extracted at the time of analyzing an RGB signal, and determines a specific image phenomenon from the extracted recording density. 3. The image processing apparatus according to claim 2, wherein it is determined whether or not it can occur. 4. The method according to claim 1, wherein the specifying unit specifies an output correction mode for causing the image data to perform a binarization process when the determining unit determines that a specific image phenomenon may occur. 2. The image processing apparatus according to claim 1, wherein when the means determines that the specific image phenomenon does not occur, the output correction mode is not specified. 5. An extracting means for analyzing a luminance signal extracted at the time of analyzing an RGB signal to extract a continuous image area, wherein said specifying means specifies a specific image for each continuous image area extracted by said extracting means. 2. The image processing apparatus according to claim 1, wherein it is determined whether an image phenomenon can occur. 6. A method according to claim 1, wherein said determining means determines whether a specific image phenomenon can occur in the output image data based on a calculation result of a recording density of the extracted document image data and a preset writing density. The image processing apparatus according to any one of claims 1 to 3, wherein the image processing apparatus determines. 7. The discrimination means compares the recording density of the extracted original image data with a preset writing density, and automatically changes the recording density of the extracted original image data to a preset writing density. The image processing apparatus according to claim 1, wherein the correction is performed. 8. An image processing method in an image processing apparatus having image processing means for performing predetermined image processing on an image signal of a document to be read to generate printable image data, the image processing method comprising: Before output, a determining step of analyzing the image signal after the scaling process to determine whether a specific image phenomenon can occur in the output image data, and determining the image based on the determination result of the determining step A designation step of designating an output correction mode for predetermined image processing by the processing means. 9. The method according to claim 1, wherein the determining step determines whether or not a specific image phenomenon can occur in the output image data after the image processing by analyzing the image signal. 9. The image processing method according to claim 8, wherein: 10. The discrimination step includes executing a fast Fourier transform process on a luminance signal extracted at the time of analyzing an RGB signal to extract a recording density of original image data, and determining a specific image phenomenon from the extracted recording density. The image processing method according to claim 9, wherein it is determined whether or not it can occur. 11. The specifying step specifies an output correction mode for causing the image data to perform a binarization process when the determining step determines that a specific image phenomenon can occur. 9. The image processing method according to claim 8, wherein the output correction mode is not specified when the process determines that the specific image phenomenon does not occur. 12. An extracting step of analyzing a luminance signal extracted at the time of analyzing an RGB signal to extract a continuous image area, wherein the specifying step includes a step of specifying a specific image area for each continuous image area extracted by the extracting step. 9. The image processing method according to claim 8, wherein it is determined whether an image phenomenon can occur. 13. The method according to claim 1, wherein the determining step determines whether a specific image phenomenon can occur in the output image data based on a calculation result of a recording density of the extracted document image data and a preset writing density. 11. The image processing method according to claim 8, wherein: 14. The discriminating step compares the recording density of the extracted original image data with a preset writing density, and automatically changes the recording density of the extracted original image data to the preset writing density. The image processing method according to claim 8, wherein the correction is performed. 15. An image processing apparatus comprising: an image processing unit configured to perform predetermined image processing on an image signal of a document to be read to generate printable image data; A step of analyzing the image signal after the scaling process to determine whether or not a specific image phenomenon can occur in the image data to be processed, and a predetermined image by the image processing means based on the determination result in the determination step. A computer-readable storage medium storing a program for executing a process of designating an output correction mode for a process.