JPH0686067A - Gradation conversion system in picture processor - Google Patents

Abstract

PURPOSE:To attain the reduction of the capacity of RAM and ROM by composing a gradation conversion system of an under color removing means executing black plate generation and under color removal, a space filter executing smoothing processing and edge emphasis, an arithmetic circuit calculating the coefficient of a color material signal and a correction means executing density adjustment and color balance adjustment. CONSTITUTION:In an under color removing circuit 1, ink plate generation and under color removal are executed by the color material signal YMC and at the time of ink plate generation, a maximum/minimum values detection circuit detects the maximum/minimum values of the signal YMC and a subtracter determines their difference and subtracts a value converted by a chroma function corresponding to the difference from the minimum value. In under color removal, the circuit 1 subtracts the generated value to subtract the value from the signal YMC. Besides the space filter 2 executes smoothing-processing to a halftone in accordance with an original type and the result of area discrimination to remove moire and executes edge emphasis to a character to recover from out-of-focus. The arithmetic circuit 3 executes calculation to the color material signal and a color tone correction control circuit 4 improves reproducibility such as density adjustment, contrast adjustment, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation conversion system in an image processing apparatus for reproducing an image by generating a black plate from a color material signal and adjusting the black plate.

[0002]

2. Description of the Related Art In a color copying machine, a full-color original is reproduced by reading a color original with a color separation signal, converting the color original into a color material signal, and superimposing images of the respective color materials. In this case, reproducibility such as density, contrast, and color tone is different depending on the characteristics of the document reading unit and the image output unit, so that it is actually necessary to add various corrections and adjustments to the image data. The outline will be described by taking the configuration proposed by the applicant (for example, Japanese Patent Laid-Open No. 2-223275) as an example. FIG. 7 is a diagram showing a configuration example of a conventional color digital copying machine.

In FIG. 7, the IIT 100 uses the CCD line sensor to provide three primary colors of light B (blue), G (green),
IOT11 is used for color separation into R (red), reading a color original, and converting it into digital image data.
Reference numeral 5 is for exposing and developing with a laser beam to reproduce a color image. And IIT100 and IOT
The END conversion circuit 101 to the IOT interface 110, which are located between the END conversion circuit 115 and the END conversion circuit 115, edit the image data (I
PS; image processing system),
The image data of B, G, and R are converted into Y (yellow) and M of color materials.
(Magenta), C (cyan), K is generated, undercolor is removed, and a color material signal corresponding to the developed color is output to the IOT 115 for each development cycle.

Further, in the IIT100, one pixel for each of B, G and R is used by using a CCD sensor.
Read at a size of 6 dots / mm and save the data in 24
Bits (3 colors x 8 bits; 256 gradations) are output. The CCD sensor is equipped with B, G, and R filters on the upper surface, and has a density of 16 dots / mm and is 300 mm.
Since 16 lines / mm are scanned at a process speed of 190.5 mm / sec, the read data is output at a speed of 15 MPixels per second for each color. And in IIT100, B, G, R
By converting the analog data of the pixels of
The reflectance information is converted into density information and then converted into digital data.

In IPS, IIT100 to B, G, R
The color separation signal of the development process color is turned on / off by applying various data processing in order to improve the color reproducibility, gradation reproducibility, definition reproducibility, etc. Outputting to IOT. END conversion (Equivalen
The t Neutral Density (equivalent neutral density conversion) module 101 adjusts (converts) a gray-balanced color signal, and the color masking module 10
Reference numeral 2 is for converting the B, G, and R signals into a signal corresponding to the Y, M, and C color material amounts by performing a matrix operation. The document size detection module 103 performs document size detection during prescanning and platen color erasing (frame erasing) processing during document reading scanning, and the color conversion module 104 is input from the area image control module. According to the area signal, the specified color is converted in a specific area. And U
The CR (Under Color Removal) & black generation module 105 generates an appropriate amount of K so as not to cause color turbidity, and reduces Y, M, and C by an equal amount according to the amount, and a monocolor mode. 4 gates the K signal and the signals after Y, M, and C undercolor removal according to each signal in the full-color mode. Spatial filter 106
Is a non-linear digital filter that has the function of emphasizing edges to restore blur and the function of removing moire.
A TRC (Tone Reproduction Control) module 107 performs density adjustment, contrast adjustment, negative / positive reversal, color balance adjustment and the like for improving reproducibility. Reduction processing module 10
Reference numeral 8 is for performing the enlargement / reduction processing in the main scanning direction, and the enlargement / reduction processing in the sub-scanning direction is performed by adjusting the scan speed of the document. The screen generator 109 converts the color material signal of the process color expressed in multiple gradations into a signal which is binarized on / off in accordance with the gradation and outputs the binarized signal. Is output to the IOT 115 through the IOT interface module 110. The area image control module 111 has an area generation circuit and a switch matrix, and the edit control module has an area command memory 112, a color palette video switch circuit 113, a font buffer 114, etc. Is to do.

In the area image control module 311, seven rectangular areas and their priorities can be set in the area generation circuit, and area control information is set in the switch matrix corresponding to each area. The control information includes color conversion, color mode such as mono-color or full-color, modulation selection information such as photographs and characters, TRC selection information, screen generator selection information, etc., and the color masking module 1
02, color conversion module 104, UCR module 105, spatial filter 106, TRC module 10
It is used to control 7. The switch matrix is
It can be set by software.

The edit control module enables a coloring process such that a document such as a pie chart is read instead of a rectangle, and a designated area whose shape is not limited is filled with a designated color. It is written in four plane memories, and the edit command for each point of the document is set by 4 bits by the four plane memories.

[0008]

As described above, in the color digital copying machine, color separation signals B, G and R are used for color originals.
Read it with color masking and color material Y such as color toner and ink, ink donor film,
The M, C, and K recording signals (for example, toner signals) are converted and supplied to the image output unit. In this case, normally, in order to facilitate the processing, the B, G, and R signals and the Y, M, and C signals are expressed by END, and the color separation signal when gray is read is B = G = R. (Equivalent neutral concentration), and conversely Y
= M = C signal is subjected to color tone correction control by the TRC and sent to the recording section to reproduce gray. As described above, in the data processing of the color image, in order to faithfully reproduce the color of the document, the END conversion is performed before the color masking, and the UCR,
Each processing by a spatial filter, TRC, etc. is performed.

The color separation signal obtained by the image reading section is the spectrum of the illumination light source, the characteristics of the dichroic mirror,
Further, it is often affected by color characteristics of photoelectric conversion elements, color filters, lenses, and the like. Therefore, the signals obtained by color-separating and reading the color original are extracted as B, G, and R signals, but the color-separated signals B, G, and R when the gray (achromatic) original is read are obtained by the reading device. The values do not become equal due to variations in various characteristics and conditions. EN
The D conversion is to convert the color separation signals B, G, and R in such a case into gray densities of equal value.

Even in the image recording section, since the coloring material used for recording the color image has unnecessary absorption due to its spectral characteristics, there are various color-related factors such as when the desired image cannot be obtained due to the difference in saturation and hue. It has an element whose characteristics should be corrected. Furthermore, there are many factors that affect the gradation reproducibility, such as the characteristics of paper and color ink. For this reason, it is extremely difficult to faithfully reproduce the color of the document by simply performing color conversion processing.

That is, the color separation signals B, G and R are converted into recording signals Y, M and C of color materials such as toner and ink to be printed, and the signals Y, M and C, and further from these, black plates. A signal K (black or black) is generated, and the removal processing is performed for Y, M, and C of an amount corresponding to that, and a color image is reproduced by supplying it to the recording unit. Even if a gray signal in which the material signals Y, M, and C are set to the same value is output, the gray is not faithfully reproduced due to the influence of the characteristics of the color material of the recording portion and the environment. The TRC reproduces a gray of a corresponding density when the color material signals Y, M, and C have the same value.

Further, the TRC in the conventional color copying machine
Uses a conversion method based on a table (LUT). For example, depending on the document type (picture / character mixture, characters, photos, maps, etc.) and image quality, such as linear for pictures and high γ for characters. Switching characteristics (in addition to the above proposal,
See, for example, JP-A-62-226768). Therefore, there is a problem in that various types of tables have to be held according to the type of document and the capacity of the table (RAM) becomes large. Furthermore, K which passed the UCR circuit
The signal is generated and output from a certain start point set for the minimum value of YMC. In that case, depending on the change of the UCR parameter,
The signal amount of K changes, which causes a problem that the parameter of the spatial filter located in the latter stage cannot be handled with a fixed value.

An object of the present invention is to make it possible to easily adjust the characteristics of a TRC with a table having a small number of standard curves. Another object of the present invention is to reduce the table held by the TRC and reduce the memory capacity. Yet another object of the present invention is to allow the use of filter parameters that are unaffected by UCR parameter changes.

[0014]

To this end, the present invention is directed to an image processing apparatus for generating a black plate from a color material signal and performing adjustment to reproduce an image. An undercolor removing means for performing processing, a spatial filter for performing smoothing processing and edge enhancement, a coefficient a for the color material signal x,
An arithmetic circuit for performing ax + b operation using b and a color tone correction control means for performing density adjustment, contrast adjustment, negative / positive inversion, color balance adjustment, etc. are provided, and the coefficients a and b are set according to the original type and the result of area identification. The arithmetic circuit has a plurality of coefficients a and b, and is configured to be switched.

[0015]

In the gradation conversion method in the image processing apparatus of the present invention, the undercolor removing means for performing black plate generation and undercolor removal processing from the color material signal, the spatial filter for performing the smoothing process and the edge enhancement, and the color material signal x. Since a calculation circuit for calculating ax + b using the coefficients a and b and a color tone correction control means for performing density adjustment, contrast adjustment, negative / positive inversion, color balance adjustment, etc. are provided, the setting of the coefficients a and b of the calculation circuit is performed. Thus, even if there is a change in the parameter of the undercolor removing means such that the amount of black plate changes, the parameter of the spatial filter that is not affected by this can be used. Further, since the arithmetic circuit calculates ax + b, the table of the color tone correction control means can be standardized by changing the coefficients a and b.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of a gradation conversion system in an image processing apparatus of the present invention.

In FIG. 1, the UCR circuit 1 performs black plate generation and undercolor removal processing from the color material signal YMC. In the generation of the black plate (K), the maximum value / minimum value detection circuit detects the maximum value and the minimum value of the color material signal YMC, the subtracter obtains the difference between the maximum value and the minimum value, and further, according to the difference. The value converted by the chroma function is subtracted from the minimum value by the subtractor. Further, in the undercolor removal, the value K ′ obtained by converting the generated K by the UCR function is subtracted from the value of the color material signal YMC by the subtractor. Spatial filter 2
According to the document type and the result of area identification, smoothing processing is performed on halftones to remove moire, and edge enhancement is performed on characters to restore blurring. The calculation circuit 3 calculates ax + b with respect to the color material signal x, and the TRC circuit 4 uses a conversion table (LUT) to adjust density, contrast and negative / positive inversion for improving reproducibility. , Color balance adjustment and the like.

In the above structure, the arithmetic circuit 3 has a TR
The C circuit 4 is operated to perform linear high γ conversion, or only the K signal, which is particularly important for image reproduction, is used for the spatial filter 2 so that the filter parameter that is not affected by the UCR parameter change can be used. Therefore, the TRC circuit 4 need only have a standard curve as a table, and the linear high γ conversion coefficient may also have the coefficient of multiplication a and the coefficient of addition b. Therefore, the parameters of the initial value are reduced, and not only the RAM capacity as a table but also the ROM capacity having the parameters can be reduced.

FIG. 2 is a diagram showing a configuration example of an arithmetic circuit used in the gradation conversion system in the image processing apparatus of the present invention.

In FIG. 2A, the register 5 holds the multiplication coefficient a and the register 6 holds the addition coefficient b. Then, in the multiplication circuit 7, the image signal x and the register 5 are added.
The multiplication coefficient a of the register 6 is multiplied by the multiplication coefficient a, the addition coefficient b of the register 6 is added to the multiplication result ax of the multiplication circuit 7, and ax + b is output to the TRC circuit 4. On the other hand, FIG. 2B uses a register 5'holding a plurality of multiplication coefficients and a register 6'holding a plurality of addition coefficients,
Each coefficient is configured to be switched by a coefficient switching signal based on a document type and a region identification signal.

Next, an example of generating a TRC conversion table will be described. FIG. 3 is a diagram for explaining how to obtain a polygonal line approximation curve (virtual TRC) (color balance), and FIG. 4 is a TRC.
It is a figure for demonstrating the creation process of a conversion table.

The TRC circuit 4 uses an LU as a conversion table.
The density, contrast and color balance are adjusted using T. For example, the parameter ROM has a standard TRC curve and coordinate data for line approximation, a TRC curve is generated using these, and written in the RAM of the LUT. Be done. The polygonal line approximation curve (virtual TRC) is obtained by approximating the y coordinate corresponding to the x coordinate of 0, x1, x2, 255 as shown in FIG. 3A when the image data has 256 gradations. . The coordinate values of x1 and x2 are stored in, for example, a parameter ROM, and 0, x1, x
The y coordinate values for 2, 255 take coordinate values of 16 steps in total, 8 steps up and down around a straight line of y = x. Further, the parameter ROM stores values of -8 to 7 (step value) and one step width (step width).

In the method of converting the TRC curve, as shown in FIG. 3B, the values corresponding to 0 to 255 are converted by the virtual TRC approximated by the polygonal line approximation curve. Then the parameter R
Converted by the standard TRC held in OM, and the obtained value is TRC It is set to the address corresponding to 0 to 255 of the LUT.

As described above, according to the data of the four-point polygonal line approximation consisting of 0, x1, x2, 255, the bright area,
The conversion characteristics can be set separately for the dark areas and their intermediate areas, and the desired TR can be efficiently achieved with a small number of data points.
A C conversion table can be generated. In addition, since the TRC conversion table is generated by the butting method based on the line approximation data and the standard TRC curve, the table can be generated by a simple process. The number of data points may be four or more. It goes without saying that a more accurate approximate curve can be obtained by setting the number of points to be set to about 10, for example.

As shown in FIG. 4, the data of the polygonal line approximation includes density adjustment, contrast adjustment, color balance adjustment, reversal, monocolor, and the like. For example, the case of obtaining the data to be written in the address X of the LUT will be described. First, in the virtual TRC for density adjustment shown in FIG. 9A obtained from the data of the polygonal line approximation for density adjustment, the OUT value corresponding to the X value of IN The value Y ₁ ′ is obtained, and then, based on this Y ₁ ′, the virtual TRC for contrast adjustment shown in FIG.
The UT value Y ₂ 'is determined. Below, the same figure (c), (d),
'Seek, this Y _5' Y ₅ performs the same processing in the virtual TRC of (e) to IN standards TRC showing a in FIG. 5 (f), reading the Y of OUT. Then, this Y becomes a value corresponding to the X value of the LUT, and the value of X is written from the CPU to the LUT. The above-mentioned polygonal line approximation data has a plurality of data corresponding to toner signals Y, M, C, and K, and also corresponds to the types of images of photographs, characters, prints, and mixed images. , TRC curves consisting of one normal and seven for each area adjustment are generated and written in the LUT. Therefore, in full-color copying, if the TRC curve of the toner signal is written in the LUT at the time of carriage return, it is sufficient to write eight TRC curves. However, if such writing is not performed for each carriage return, copying is performed. 32 TRCs at start
Curve writing is required.

Next, an embodiment of the image processing apparatus to which the present invention is applied will be described. FIG. 5 is a diagram showing a configuration example of a signal processing system of the image processing device, and FIG. 6 is a diagram showing a configuration example of a mounting mechanism of the image processing device.

In FIG. 5, the image input unit 100 includes, for example, three CCs B, G, and R arranged at right angles in the sub-scanning direction.
A reduction type sensor including a D line sensor is provided, and an image is read by scanning in the main scanning direction in synchronization with the timing signal from the timing generation circuit 12 while moving in the sub-scanning direction at a speed according to the expansion / contraction ratio. It is IIT, and is converted from analog image data into gradation-represented 8-bit digital image data, for example. The shading correction circuit 11 performs shading correction on the image data for variations between pixels due to various factors, and the gap correction circuit 13 performs gap correction between the line sensors. The gap correction is FIFO14
Is to delay the image data read by the amount corresponding to the gap of the CCD line sensor so that the B, G, and R image data at the same position can be obtained at the same time. An ENL (Equivalent Neutral Lightness) conversion circuit 15 performs gray balance processing of image data using a parameter according to a document type, and a negative / positive inversion signal from an edit processing unit 400 described later. This makes it possible to invert the way gray is taken for each pixel and invert the negative / positive, for example, to invert the negative / positive only in a certain designated area.

B, G, processed by the ENL conversion circuit 15
The R image data is converted into signals L ^* , a ^* , b ^* in the uniform color space by the matrix circuit 16a. Signal uniform color space L ^*, a ^*, b ^* respectively represent the lightness L ^* coordinate axes orthogonal is, a ^*, b ^* chromaticity plane (hue,
Represents the saturation. Such a uniform color space signal L ^* ,
The memory system 20 is converted into a ^* and b ^*.
It is possible to easily interface with the outside such as a computer through 0, and to facilitate color conversion, edit processing, and detection of image information. The selector 17 is the matrix conversion circuit 1
The output of 6a or the image data from the memory system 200, which is an interface with the outside, is selectively taken out, or both image data are taken in at the same time to perform texture composition and watermark composition processing. Therefore, the selector 17 has a function of setting a combination ratio, calculating processing, and combining processing for a combined image.

The background removal circuit 18 detects the background density by creating a histogram of the document density by pre-scanning, for example, and skips pixels below the background density to improve the copy quality for a fogged document such as a newspaper. It is for. The document detection circuit 19 detects and stores the document size by detecting the boundary between the back surface of the black platen and the document and determining the circumscribed rectangle. In the background removal circuit 18 and the document detection circuit 19, the lightness information of the signals L ^* , a ^* , and b ^{* in} the uniform color space is signal L ^*.
Is used.

The edit processing section 400 sets area commands for performing edit processing and switching of parameters and the like for each area and generates area control signals based on the area commands, thereby performing color editing and color editing on image data. Conversion, marker color detection, and other processing are performed. Then, the processed image data is input to the matrix conversion circuit 16a and the pictogram separation circuit (TIS circuit) 20.

In the matrix conversion circuit 16a, L ^* , a ^* , b ^* to Y, and Y
After being converted into M and C toner colors, the picture character separation circuit 20 divides a plurality of pixels into blocks to identify areas of color character / black character / picture (character / halftone). In the under color removal circuit 21, Y converted by the matrix conversion circuit 16b,
Generation of a black plate (K) from M and C image data according to a mono-color / full-color signal and removal of equal amounts of Y, M, and C to output process color image data A judgment is made to generate a hue signal (Hue). When the pictographic character separation circuit 20 performs the identification processing, the area identification signal is delayed by, for example, 12 lines because it is divided into blocks. Therefore, a timing is taken to synchronize the hue signal and the image data with the delay. FIFO2
2a and 22b.

The enlargement / reduction circuit 23b is for performing enlargement / reduction processing on the image data in accordance with the designated enlargement / reduction ratio. In the sub-scanning direction, the image input unit 100 changes the scanning speed in accordance with the enlargement / reduction ratio. Since the image is expanded, the image data is thinned out or interpolated in the main scanning direction. The expansion / contraction circuit 23a is for expanding / contracting the area command so that the execution area of the area control information does not shift in correspondence with the expansion / contraction processing on the image data. The area control information subjected to the reduction / expansion processing is the area decoder 24.
Is decoded by and processed by each processing block. The area decoder 24 uses an area command, an area identification signal,
The switching signal of the parameter 25 of the filter, the coefficient of the multiplier 26, and the parameter of the TRC circuit 27 is generated and distributed from the hue signal.

The filter 25 removes halftone moire and character edge enhancement according to the spatial frequency of the image data reduced or enlarged by the reduction / enlargement circuit 23b. The TRC circuit 27 is for adjusting the density according to the characteristics of the IOT using a conversion table,
29 indicates TRC depending on the signal of the developing process and the area identification.
It is a decoder that switches the parameters of the conversion table of the circuit 27. The multiplier 26 performs ax + b calculation on the image data x using the coefficients a and b, and the coefficient is switched between through in the case of halftone and high γ in the case of character. Then, the color adjustment for color characters, black characters, and patterns is performed by appropriately selecting the coefficient and conversion table for each color component used in combination with the TRC circuit 27.
The density is adjusted. Further, the parameters of the filter 25 can be standardized, and the edge emphasis of the character can be adjusted by the coefficients a and b. The image data adjusted by these is stored in the memory system or dot-developed by the screen generation unit 28 of the ROS 300 and output as a halftone image.

The edit processing section 400 performs color conversion, color editing, area control signal generation, etc., and receives image data L ^* , a ^* , b ^* from the selector 17. Then, the LUT 415a converts the chromaticity information from a and b in the orthogonal coordinate system to C and H in the polar coordinate system so that the marker color and other colors can be easily detected, color edited, and converted. The color conversion & palette 413 has, for example, 32 types of colors used in color conversion and color editing, and the delay circuit 411
According to the area command input through a, the image data L, C, and H are subjected to marker color detection, color editing, color conversion, and other processing. Then, only the image data of the area where the processing such as color conversion is performed is performed by the color conversion & palette 41.
After being processed by the LUT 415b and converted from C, H to a, b by the LUT 415b, the image data of the other areas is directly output from the selector 416 and the matrix conversion circuit 16
sent to b.

The marker color (3 colors) detected from the image data by the color conversion & palette 413 and the 4-bit signal of the closed area are sent to the density conversion / area generation circuit 405. Density conversion
In the area generation circuit 405, the FIFOs 410a and 410 are
In the 4 × 4 window using b and 410c, if the number of black pixels is equal to or larger than a predetermined number among 16 pixels, a binarization process of setting “1” is performed and density conversion from 400 spi to 100 spi is performed. The marker signal (closed loop or marker dot) thus generated is written in the plane memory 403 from the density conversion / region generation circuit 405 through the DRAM controller 402.

As for the marker / dot signal, the FIF is set so that small dust or the like will not be erroneously detected as a marker.
The coordinate value generation circuit 407 detects marker dots and generates coordinate values and stores them in the RAM 406 by delaying them by 3 lines by O408 to form a 3 × 3 window. For the marker dot, the plain memory 40
3 is stored, but this processing is performed to prevent erroneous detection.

The plane memory 403 is a memory for storing an area command for performing color conversion, color editing, and other area editing. For example, the area is designated from the edit pad and the area command is written in the area. be able to. That is, the area command of the area designated by the edit pad is transferred to the graphic controller 401 via the CPU bus and written from the graphic controller 401 to the plane memory 403 via the DRAM controller 402. The plane memory 403 is composed of four sides and has 16 numbers from 0 to 15.
Area commands of various types can be set.

The 4-bit area command stored in the plane memory 403 is read in synchronism with the output of the image data, and the color conversion & palette editing process and the process shown in FIG.
Image data processing system, ENL conversion circuit 15, matrix conversion circuit 16, selector 17, undercolor removal circuit 21,
Further, it is used for switching parameters such as the filter 25, the multiplier 26, the TRC circuit 27, and the screen generator 28 via the area decoder 24. When this area command is read from the plane memory 403 and used for color conversion & palette 413 editing processing, parameter switching in the image data processing system, etc., density conversion from 100 spi to 400 spi is necessary. The processing is performed by the density conversion area generation circuit 405. In the density conversion area generation circuit 405, 3 × 3 blocks are formed using the FIFOs 409a and 409b, and data interpolation is performed from the pattern to prevent the boundary of the closed loop curve or the editing area from becoming jagged so that the boundary is 100 spi to 400 spi. The density conversion to The delay circuits 411a, 411b, 1M FIFO412, etc. are for adjusting the timing between the area command and the image data.

The multiplier 26 in the above system is an arithmetic circuit for performing gradation conversion in the image processing apparatus of the present invention.

In the color copying machine shown in FIG. 6, the base machine 30 includes a platen glass 31 on which an original is placed, an image input terminal (IIT) 32, an electrical system control housing 33, and an image output terminal (IOT) 34. , A paper tray 35, and a user interface (U / I) 36, and optionally an edit pad 61,
Auto Document Feeder (ADF) 62, Sorter 6
3 and a film image reading device including a film projector (F / P) 64 and a mirror unit (M / U) 65.

The image input terminal 32 includes an imaging unit 37, a wire 38 for driving the imaging unit 37,
The imaging unit 37 includes a drive pulley 39 and the like.
Primary color of light B (blue), G (green), R
The image information of a color original which is color-separated into (red) and read using a CCD line sensor is converted into multi-tone digital image data BGR and output to an image processing system. The image processing system is housed in the electric system control housing unit 33, and inputs various BGR image data to perform various conversions, corrections, and editings to improve color, gradation, definition, and other image quality and reproducibility. And the like, and converts the toner primary colors Y (yellow), M (magenta), C (cyan), and K (black) into the process color gradation toner signal. The converted toner signal is output to the image output terminal 34. The image output terminal 34 includes a scanner 40,
The photosensitive material belt 41 is provided, and the laser output unit 40a converts the image data into an optical signal, and the polygon mirrors 40b, F
The latent image corresponding to the original image is formed on the photosensitive material belt 41 via the / θ lens 40c and the reflection mirror 40d, the image is transferred to the paper conveyed from the paper tray 35, and the color copy is discharged.

In the image output terminal 34, the photosensitive material belt 41 is driven by the drive pulley 41a, and the cleaner 41b, the charger 41c, the YMCK developing devices 41d, and the transfer device 41e are arranged around the photosensitive material belt 41.
A transfer device 42 is provided opposite to e. And
In the case of a four-color full-color copy by gripping the paper sent from the paper tray 35 through the paper transport path 35a, the transfer device 42 is rotated four times to transfer each latent image of YMCK onto the paper, and then the paper is transferred. Is transferred from the transfer device 42 through the vacuum transfer device 43 and fixed by the fixing device 45 and discharged. SSI
The (single sheet inserter) 35b is the paper transport path 3
Paper can be selectively supplied to 5a by manual feeding.

The user interface 36 is used by the user to select a desired function and instruct execution conditions thereof. The user interface 36 is provided with a color display 51 and a hard control panel 52. Further, an infrared touch board 53 is combined with the soft button on the screen. You can directly instruct.

The electric system control housing portion 33 is composed of a plurality of control boards which are divided into processing units such as the image input terminal 32, the image output terminal 34, the user interface 36, the image processing system, and the film projector 64. Further, an MCB board (machine control board) for controlling the operation of the mechanism such as the image output terminal 34, the automatic document feeder 62, the sorter 63, etc., and a SYS board for controlling all of these are housed.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the above-described embodiment, the arithmetic circuit calculates ax + b. However, by setting a to 1 and b to 0, the data through mode can be set or a to 0 can be set to the data reset mode. Of course, you can also do it.

[0046]

As described above, according to the present invention,
Undercolor removing means for performing black plate generation and undercolor removal processing from the color material signal, a spatial filter for performing smoothing processing and edge enhancement, and an arithmetic circuit for performing ax + b operation on the color material signal x using coefficients a and b. , And density adjustment and contrast adjustment,
Since the color tone correction control means for performing negative / positive reversal, color balance adjustment, and the like is provided, the arithmetic circuit performs the linear high γ conversion operation on the TRC circuit, or only the K signal, which is particularly important for image reproduction, on the spatial filter. Filter parameters can be used that are not affected by UCR parameter changes. Therefore, the TRC circuit need only have a standard curve as a table, and the linear high γ conversion coefficient may also have the coefficient of multiplication a and the coefficient of addition b. Therefore, the parameters of the initial value are reduced, and not only the RAM capacity as a table but also the ROM capacity having the parameters can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a gradation conversion method in an image processing apparatus of the present invention.

FIG. 2 is a diagram showing a configuration example of an arithmetic circuit used in a gradation conversion method in the image processing apparatus of the present invention.

FIG. 3 is a diagram for explaining how to obtain a polygonal line approximation curve (virtual TRC) (color balance).

FIG. 4 is a diagram illustrating a process of creating a TRC conversion table.

FIG. 5 is a diagram illustrating a configuration example of a signal processing system of the image processing apparatus.

FIG. 6 is a diagram showing a configuration example of a mounting mechanism of the image processing apparatus.

FIG. 7 is a diagram showing a configuration example of a conventional color digital copying machine.

[Explanation of symbols]

1 ... UCR circuit, 2 ... Spatial filter, 3 ... Arithmetic circuit,
4 ... TRC circuit

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[Procedure amendment]

[Submission date] June 16, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a gradation conversion method in an image processing apparatus of the present invention.

FIG. 2 is a diagram showing a configuration example of an arithmetic circuit used in a gradation conversion method in the image processing apparatus of the present invention.

FIG. 3 is a diagram for explaining how to obtain a polygonal line approximation curve (virtual TRC) (color balance).

FIG. 4 is a diagram illustrating a process of creating a TRC conversion table.

FIG. 5A is a diagram showing a configuration example of a signal processing system of the image processing apparatus.

FIG. 5B is a diagram showing a configuration example of a signal processing system of the image processing apparatus.

FIG. 6 is a diagram showing a configuration example of a mounting mechanism of the image processing apparatus.

FIG. 7 is a diagram showing a configuration example of a conventional color digital copying machine.

[Explanation of Codes] 1 ... UCR circuit, 2 ... Spatial filter, 3 ... Arithmetic circuit,
4 ... TRC circuit

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 6]

[Figure 5a]

[Fig. 5B]

[Figure 7]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Fukutomi 3-16-5 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Fuji Xerox Information Systems Co., Ltd.

Claims (2)

[Claims] 1. An under color removal means for performing black plate generation and under color removal from a color material signal in an image processing apparatus for producing an black plate from a color material signal, performing adjustment to reproduce an image, and smoothing processing. And spatial filter for edge enhancement, colorant signal x
, An arithmetic circuit for calculating ax + b using coefficients a and b, density adjustment, contrast adjustment, negative / positive inversion,
Equipped with color tone correction control means for adjusting color balance,
A gradation conversion method in an image processing apparatus, characterized in that the coefficients a and b are set according to a document type and a result of area identification. 2. The arithmetic circuit has a plurality of coefficients a and b,
The gradation conversion method in the image processing apparatus according to claim 1, wherein the gradation conversion method is configured to be switched.