JP2000196904A - Color image forming device and method for generating lookup table - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform color tone adjustment without increasing the number of lookup tables related to masking conversion. SOLUTION: When an adjusted value is inputted from an operation panel 25, a CPU generates data for masking calculation by multiplying the inputted adjusted value for chrominance component by the reference data for masking operation corresponding to the chrominance component stored in a ROM 3 and the generated data are superscribed on a lookup table composed of the data for masking operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus and a method for generating a lookup table.

[0002]

2. Description of the Related Art Conventionally, in a device for reading a color image, performing image processing and printing out, generally, R (red)
), G (green) and B (blue) light sources are turned on to read the original, perform color separation of the original, and perform luminance-density conversion, masking conversion, output γ conversion, and binarization processing, and output devices. Output image data to

In order to speed up image processing, table conversion using a look-up table is generally used for each of the luminance-density conversion, masking conversion, and output γ conversion.

[0004]

In order to enable color tone adjustment, it is necessary to prepare a plurality of lookup tables. For example, a simple input 4 component-output 4 component input 8
The data capacity of the matrix for matrix operation with 8 bits and table precision is 4 KB (= 16 × 256 × 8 bits), and the total capacity of the table is increased by the number of color tone adjustment stages.

According to the method of generating a table by calculation, although the table capacity does not increase, there is a problem that it is difficult to generate a complicated table and to make fine adjustments.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to increase the capacity of a look-up table related to masking conversion in a storage device without increasing the capacity of the look-up table by a simple coefficient operation. It is an object of the present invention to provide a color image forming apparatus and a look-up table generating method capable of generating a color image and adjusting a color tone.

[0007]

According to a first aspect of the present invention, there is provided a lookup table storing means for storing a lookup table comprising masking calculation data for a color component to be used for forming a color image, and the lookup table store. And a masking operation unit for performing color conversion on the color density based on the look-up table stored in the unit. Storing means for storing one reference table, input means for inputting a color tone adjustment value,
Generating means for generating masking calculation data by multiplying the adjustment value for the input color component by the masking calculation reference data corresponding to the color component when the adjustment value is input by the input means; Overwriting means for overwriting the look-up table with the masking calculation data generated by the generating means.

According to the first aspect, the precision of the masking calculation reference data can be greater than the precision of the masking calculation data.

In the present invention, the generation means adjusts the precision of the masking calculation reference data corresponding to the color not input by the input means to the precision of the masking calculation data of the lookup table. The data for the masking calculation can be generated by the adjustment.

According to a fourth aspect of the present invention, there is provided a look-up table storing means for storing a look-up table comprising masking calculation data for a color component to be used for forming a color image, and the look-up table storing means. In a lookup table generating method for a color image forming apparatus, comprising: a masking operation unit for performing color conversion on a color density based on a lookup table, when a tone adjustment value is input, an adjustment value for the input color component is input. Reading out from a storage means storing a single reference table consisting of masking calculation reference data for color components provided for color image formation, an adjustment value for the input color component,
A generating step of generating masking operation data by multiplying the masking operation reference data corresponding to the color component by the masking operation reference data read from the storage means; and generating the generated masking operation data. Overwriting to the look-up table.

In the present invention, the precision of the masking calculation reference data can be made larger than the precision of the masking calculation data.

According to a fourth aspect of the present invention, in the generation step, when the adjustment value is input, the accuracy of the masking operation reference data corresponding to the color that has not been input is adjusted to the accuracy of the masking operation data of the lookup table. The data for the masking operation can be generated by adjusting them together.

[0013]

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

FIG. 1 shows an embodiment of the present invention. This is an example of a color image forming apparatus, and this color image forming apparatus includes a CPU (central processing unit) 1
OM (read only memory) 3 and SRAM (static ran
dom access memory) 4, modem 5, image processing gate array 16, and multifunctional gate array 26
Are connected to each other.

The ROM 3 stores a control program and a look-up table for luminance-density conversion (hereinafter referred to as a "look-up table").
A lookup table is abbreviated as LUT), an output γ conversion LUT, and masking calculation reference data. The masking calculation reference data is a masking process when C is a cyan component value, M is a magenta component value, Y is a yellow component value, and K is a black component value.

[0016]

(Equation 1)

A signed 12-bit constant used in the calculation of A11 A12 A13 A14 A21 A22 A23 A24 A31 A32 A33 A34 A41 A42 A43 A44. However, the constants A14, A24, A34, A44
A14 '= A14-A11-A12-A13 A24' = A24-A21-A22-A23 A34 '= A34-A31-A32-A33 A44' = A44-A41-A42-A43, Actually, A11 A12 A13 A14 'A21 A22 A23 A24' A31 A32 A33 A34 'A41 A42 A43 A44' are adopted as constants.

The CPU 1 controls each section of the image forming apparatus according to a control program in the ROM 3. SR
AM4 is for storing transmission source information, user registration information and the like.

The modem 5 modulates and demodulates image signals and audio signals.

Reference numeral 10 denotes a cross point for selectively connecting a network control unit (hereinafter, referred to as NCU) 6, a telephone set 8, and a cordless telephone base unit 9. The NCU 6 controls connection between the modem 5, the wired telephone 8, or the cross point 10 and the public telephone line 7. 11 is a cordless handset. Reference numeral 32 denotes a speaker for transmitting information such as the state of the image forming apparatus to the user by voice.

The image processing gate array 16 performs shading correction processing, binarization processing when an image is read in a single color, gamma conversion processing when an image is read in a color, and RGB.
Conversion processing for converting image data into YMCK and reading sensor 1
Resolution conversion processing for converting the image data read by the recording head 2 into a resolution that can be recorded by the recording head in the main scanning direction, and a red, green, and blue LED (light emitting diode) light source 1
Lighting control of 3, 14, and 15 is performed.

The reading sensor 12 reads one line of data at 8 pels in an image in the main scanning direction. red,
The green and blue LED light sources 13, 14, 15 are respectively
The reading sensor 12 is a light source for reading an image. Here, the use of the LED as the light source allows the size of the device to be reduced, and the LED light source has a more stable light quantity, faster response characteristics, and faster switching of the light source than fluorescent lamps and the like. This is because a sheet-through type high-speed image forming apparatus can be provided. This is because the current consumption of the LED light source is smaller than that of a fluorescent lamp or the like, so that it is possible to provide an image forming apparatus suitable for homes with low power consumption.

The multi-function gate array 26 includes a print head 17, a DRAM (dynamic RAM) 18, a print cartridge sensor 20, a document detection sensor 21, a paper detection sensor 22, a motor driver 24 of a reading motor 23, It is connected to the operation panel 25. Further, the multi-function gate array 26 includes the print head 1.
7, the image data arranged in the main scanning direction is transferred to the print head 17 for converting the image data arranged in the sub-scanning direction into image data arranged in the sub-scanning direction, and key input data inputted from the keyboard of the operation panel 25 And a process of converting output signals of various sensors into code signals that can be determined by the CPU 1 and a timing process of the reading motor 23.

The print head 17 is for recording an image. The print head 17 is interchangeable between a recording head capable of recording in color and a recording head capable of recording in monochrome. Here, an ink jet type recording head is employed as a print head, and a plurality of nozzles are arranged in the sub-scanning direction to form a head recording surface. At the time of the recording operation, an image is formed in a region corresponding to a recording width by a plurality of nozzles by reciprocating a carriage mounted with a head in a main scanning direction (intersecting the arrangement direction of the nozzles). Then, the image is formed on the sheet by conveying the sheet by the recording width in the sub-scanning direction and repeating the recording operation. The print head 17 may be of a thermal transfer type. The print head 17 is an ink cartridge having a built-in tank for storing ink.

The DRAM 18 is for temporarily storing image data to be supplied to the print head 17. The print cartridge sensor 20 is for detecting the presence and type of the print cartridge. The document detection sensor 21 detects a document width and the presence or absence of a document. The paper detection sensor 22 is for detecting the paper size and the presence or absence of the paper.

The reading motor 23 is for conveying a document. The motor driver 24 drives the reading motor 23. The operation panel 25 has a keyboard and an LCD for displaying the status of the image forming apparatus and the like.
As will be described later, the keyboard is provided with a color copy key for reading a document in color and instructing recording in color, and a monochrome copy key for reading in monochrome and instructing recording in monochrome.

Reference numeral 27 denotes an LF motor for conveying a sheet in the sub-scanning direction. A motor driver 28 drives the LF motor 27. A CR motor 29 drives a carriage on which the print head 17 is mounted. A motor driver 30 drives the CR motor 29.

The space for accommodating unused print cartridges not mounted on the carriage may be provided in the apparatus, or may be accommodated in another container outside the apparatus.

FIG. 2 shows the configuration of the image processing gate array 16 of FIG. 2, reference numerals 2, 12 to 15 denote the same parts as in FIG. 301 is A / D (analog-to-digital)
The conversion circuit converts an output signal of the reading sensor 12 into a 10-bit digital signal. Reference numeral 308 denotes a peak detection circuit.
It detects the peak value of the converted image signal.
Reference numeral 309 denotes an AGC (automatic gain control) circuit which, based on the output of the peak detection circuit 308, determines an optimal 8-bit luminance area of the luminance represented by the 10-bit digital signal from the A / D conversion circuit 301. To choose. 310 is a shading / black correction circuit,
The shading correction and the black correction are performed based on the correction data stored in the correction data storage unit 311, and the correction data obtained by the shading / black correction circuit 310 is stored in the correction data storage unit 311. 312 is R
This is a GB / YMCK conversion circuit that converts the image signal corrected by the shading / black correction circuit 310 into Y (yellow),
It is converted into M (magenta), C (cyan), and K (black).

Reference numeral 304 denotes a light amount overflow detection circuit for detecting whether or not the output of the A / D conversion circuit 301 overflows due to an excessive light amount.
Reference numeral 302 denotes a lighting time control register connected to the bus 2 for setting the lighting time of the LED light source from the CPU 1. 303 is a lighting time counter, LE
This is for controlling the lighting time of the D light source. 305
Is a lighting time automatic adjustment circuit for automatically adjusting the lighting time of the LED light source so as not to overflow.
Reference numeral 316 denotes an overflow register connected to the bus 2 for enabling the CPU 1 to detect a light amount overflow.

A light source switching circuit 317 switches the lighting time of the light source in a time-division manner. 306 is bus 2
A current setting for controlling the amount of light of the LED light source, and a light source switching circuit 3.
This is for setting a lighting mode for controlling the lighting device 17 and for setting a light source to be turned on in each mode. A lighting current control circuit 307 controls the lighting current supplied to the LED light source. 318 is a clock (XSH) for switching the lighting of the light source of the light source switching circuit 317. 2.5ms for color reading
The clock (XSH) is input to the light source switching circuit 317 every ec, and each time the clock (XSH) is input, the red, green, and blue LED light sources 1
3, 14, and 15 are switched in this order and lighted. 2.51msec for monochrome reading
A clock (XSH) is input every time, and in this case, only the green light source is turned on for a necessary time. Switching between color reading and monochrome reading is set by the lighting mode setting register 306. A reading trigger 319 input from the CPU 1 is a light source switching circuit 317 for each line.
And the read trigger 319 activates the image processing gate array 16.

Reference numeral 314 denotes a reduction rate / mask area setting register for setting a mask area and a reduction rate of an image from the CPU 1.

Reference numeral 313 denotes a resolution conversion circuit, which outputs RGB /
8 pe in the main scanning direction from the YMCK conversion circuit 312
The image of l is converted into a resolution of 360 dpi of the printer, the size of the read image is reduced, and unnecessary images are masked.

A signal line 320 is composed of three signal lines. The signal line 320 indicates which one of red, green and blue light sources is to be turned on. The signal line 320 is connected to the lighting current control circuit 307 and the lighting time setting register 302, and performs loading of the lighting time of each of the red, green, and blue light sources into the lighting time counter 303 and selection of the light source that supplies the lighting current. ing. 321 signal lines, which are three signal lines for enabling various processes to be performed based on the color of the light source being lit, AGC 309, shading / black correction circuit 310, and RGB / YMCK conversion circuit 3
12, a resolution conversion circuit 313, and an output register 315
And connected to. The signal line 321 is connected to the signal line 32.
A timing delayed by a predetermined time from the timing of the signal line 320 is output so that various processes of the light source color lit based on 0 can be performed.

FIG. 3 is a flowchart showing an example of the control program stored in the ROM 8 of FIG. It is determined whether the operator has operated the operation panel 25 and has instructed monochrome copying (S20).
1). If it is determined that the monochrome copy has not been instructed, the operator operates the operation panel 25 to determine whether or not the color copy has been instructed (S202). If it is determined that the color copy has not been instructed, the process returns to S201.

On the other hand, when it is determined that the color copy is instructed, it is determined whether or not a document is set based on the output of the sensor 21 (S203). If it is determined that the original is not set, a message prompting you to set the original is displayed.
The information is displayed on the LCD display on the operation panel 25, and is notified by voice through the speaker 32 (S
213), and then return to S201. This message allows the user to know that the cause of the non-execution of the copy is that there is no original, so that the user can take immediate action. In addition, since the message is output not only by the display but also by voice, even a person who cannot easily see the display on the LCD display can easily understand the coping method.

On the other hand, if it is determined that a document is set (S203), it is determined whether there is a sheet based on the output of the sheet detection sensor 22 (S204). If it is determined that the paper is not set, a message prompting the user to set the paper is displayed on the LCD display on the operation panel 25, and the speaker 32 notifies the user by voice. (S214), and then return to S201. By this message, the user knows that the cause of the non-execution of copying is that there is no paper, and can take immediate action. In addition, since the message is output not only by the display but also by voice, even a person who is difficult to see the display on the LCD display can easily understand the coping method.

On the other hand, if it is determined that the paper is set (S204), it is determined whether or not the print head 17 is mounted on the carriage based on the output of the print cartridge sensor 20 (S205). And if it is determined that it is not mounted on the carriage,
A message prompting the user to set the print head 17 "Please set the cartridge" is displayed on the LCD display on the operation panel 25, and is notified by voice through the speaker 32 (S215), and thereafter, the process returns to S201. By this message, the user knows that the cause of the non-execution of the copy is the absence of the print head 17, and can take an immediate action. In addition, since the message is output not only by the display but also by voice, even a person who is difficult to see the display on the LCD display can easily understand the coping method.

On the other hand, if it is determined that the print head 17 is mounted on the carriage (S205), it is determined whether a color cartridge is mounted (S205).
206). If it is determined that the color cartridge is not mounted, a message prompting to set the color print head 17 "Please set the color cartridge" is displayed on the LCD display on the operation panel 25 and the speaker 32 is displayed.
, And then returns to S201. By this message, the user knows that the cause of the non-execution of copying is that the color cartridge is not mounted, and can take immediate action. In addition, since the message is output not only by the display but also by voice, even a person who cannot easily see the display on the LCD display can easily understand the coping method. Further, since the color copy operation is started after the type of the cartridge is determined, there is no problem that the color copy operation (document reading / recording) is executed even though the color cartridge is not mounted.

On the other hand, if it is determined that the color cartridge is mounted (S206), the size of the paper is detected by the output of a paper size detection sensor (not shown) (S207). Then, the width of the document is detected (S208). After detecting the width of the document, a prescan operation is performed (S209). The pre-scan operation will be described later. After the prescan, the reading width that can be recorded on the paper is stored in the mask area / reduction ratio setting register 314 in the image processing gate array 16 in FIG. 2 based on the paper size and the document size, and the color lookup table is stored. Write (S210). Here, the image processing gate array 16 performs mask processing other than the reading width in the main scanning direction and resolution conversion, and performs DRAM conversion.
The CPU 1 performs resolution conversion in the sub-scanning direction based on the data in. As a result, the image data read by the reading sensor 12 and which cannot be recorded on the sheet is subjected to masking processing.

In the present image forming apparatus, when the size of the original is larger than the size of the paper, an image area corresponding to the size of the paper can be read. Here, the reason why the image is read despite the difference between the paper size and the original size is that the image forming apparatus is mainly designed for home use, and homes are always equipped with various sizes of paper. This is because it is not common.
If copying is not performed simply because the size of the sheet and the document are different, the user often has a disadvantage of purchasing a new sheet. The reason why the reduction process is not performed according to the size of the sheet is that in the case of a color image, the image is significantly deteriorated due to the scaling process. In particular, if an expensive color scaling process is performed, it becomes impossible to provide an inexpensive home-use device like the present image forming apparatus.

The read width that can be recorded on the paper is determined by the mask area / reduction ratio setting register 3 in the image processing gate array 16.
14 (FIG. 2), a color image reading process is performed (S211), and a color image recording process is performed (S2).
12) Then, the copy processing ends.

On the other hand, if it is determined that monochrome copying has been instructed (S201), it is determined whether or not a document has been set based on the output of the document detection sensor 21 (S217). If it is determined that the original is not set, a message urging the user to set the original is displayed on the LCD display on the operation panel 25, and the speaker 32 issues a voice message. (S22
6) Then, the process returns to S201. By this message, the user knows that the cause of the non-execution of copying is that there is no original, and can take immediate action. In addition, since the message is output not only by the display but also by voice, even a person who cannot easily see the display on the LCD display can easily understand the coping method.

On the other hand, if it is determined that a document is set (S217), it is determined whether there is a sheet based on the output of the sheet detection sensor 22 (S218). If it is determined that the paper is not set, a message prompting the user to set the paper is displayed on the LCD display on the operation panel 25, and the speaker 32 notifies the user by voice. (S227), and then return to S201. By this message, the user knows that the cause of the non-execution of copying is that there is no paper, and can take immediate action. In addition, since the message is output not only by the display but also by voice, it is easy for a person who cannot easily see the display on the LCD display to understand the coping method.

On the other hand, if it is determined that a sheet is set (S218), it is determined by the print cartridge sensor 20 whether the print head 17 is mounted on the carriage (S219). If it is determined that the print head is not mounted on the carriage, the print head 17 "set a cartridge" is displayed.
Operation panel 2
5 is displayed on the LCD display, and is notified by voice through the speaker 32 (S228).
Return to 01. By this message, the user knows that the cause of the non-execution of the copy is the absence of the print head 17, and can take an immediate action. In addition, since messages are output not only by display but also by voice, LC
The coping method is easy to understand even for a person who cannot easily see the display on the D display.

On the other hand, when the print head 17 is mounted on the carriage (S219), the size of the sheet is detected by the output of a sheet size detection sensor (not shown) (S220), and the width of the document is determined by the output of the document detection sensor 21. Is detected (S221). Then, a prescan is performed (S222). The pre-scan will be described later.

After performing the pre-scan, the reduction ratio is set based on the paper size and the original size so as to have a size suitable for the paper, by setting the mask area / reduction ratio setting register 314 (of the image processing gate array 16). 2), and a monochrome lookup table is written (S223). Here, the image processing gate array 16 performs mask processing other than the reading width in the main scanning direction and resolution conversion in accordance with the reduction ratio.

A monochrome image reading process is performed (S22).
4) A monochrome image recording process is performed (S225), and then the copy process ends.

FIG. 4 shows the image processing gate processing array 1 of FIG.
6 is a flowchart illustrating an example of a pre-scan operation according to Example 6. When the prescan is instructed while the hand scan unit is stored in the main body, the prescan is started. The pre-scan operation is the same in both color reading and monochrome reading.

The color mode is set in the lighting mode setting register 306 (S501). By the setting of the lighting mode setting register 306, the time division switching of the three color light sources is set in the lighting light source switching circuit 317. And
Lighting of the red, green, and blue LED light sources 13, 14, 15 is set in the lighting mode setting register 306 (S502). Next, the automatic adjustment mode is set in the lighting time control register 302 (S503). In this image forming apparatus, a color image is 7.5 msec per line.
Is read, the monochrome image is 2.5ms per line
Read in ec.

Thereafter, when a trigger is given by the CPU 1, the red LED light source 13 is first turned on for a maximum lighting time, for example, 2.5 msec. The maximum lighting time is counted by the lighting time counter 305, and the output of the lighting current control circuit 307 is turned ON for the time set by the counter, and the current is supplied to the red LED light source 13 and the red LE
The D light source 13 is turned on.

Then, a white plate (not shown) is illuminated by the red LED light source 13 and the reflected light from the white plate is received by the reading sensor 12.
The signal is photoelectrically converted and output to the A / D conversion circuit 301 as an analog electric signal. In the A / D conversion circuit 301, the input analog electric signal is converted into a 10-bit digital signal. Next, the light amount overflow detection circuit 304 detects whether or not the digital signal has overflowed. When the light amount overflow detection circuit 304 detects a light amount overflow,
A trigger is given to the lighting time automatic adjustment circuit 305.

When an overflow of the light amount is detected, a value obtained by subtracting a predetermined time from the maximum lighting time (here, 2.5 ms)
(a value obtained by subtracting 2.5 / 16 msec from ec) is set in the lighting time counter 303. Then, based on the newly set value, the red LED light source 13 is turned on again, and the light amount overflow detection circuit 304 detects the light amount overflow. When the light amount overflows, the automatic lighting time adjustment circuit 305 subtracts the predetermined time again from the value of the lighting time set in the lighting time counter 303 and newly sets the obtained value. Thereafter, this process is repeated, and the first value at which the overflow of the light amount has disappeared is set in the lighting time register 302 as the lighting time of the red LED light source 13. Then, based on the lighting time of the red LED light source 13,
The set document is read.

This process is similarly performed for the green LED light source 14 and the blue LED light source 15 while switching over time division every 2.5 msec.

When the adjustment of the lighting time of the LED light source of each color is completed, the CPU 1 turns off all the LED light sources of each color (S1).
504) In the state where all the light sources are turned off, a black correction instruction is issued to the shading / black correction circuit 310. Then, black correction for correcting variations in output of each pixel of the reading / reading sensor 12 is performed (S505). When the black correction data is obtained, the black correction data is stored in the correction data storage unit 311, and the CPU 1 sets the type of the light source to be turned on (red, green, and blue LED light sources) in the lighting mode setting register 506 ( S506). Based on the lighting time of each light source obtained in S503, the image processing gate array 16 is instructed to perform shading correction in a time division manner for each color (S507). The shading / black correction circuit 310 reads a white plate (not shown) to perform shading correction, and stores correction data for each color in the correction data storage unit 311.

It is determined whether or not the shading correction of all colors has been completed (S508). If it is determined that the shading correction has not been completed, the process waits for completion. The process ends.

If monochrome reading is instructed, S
The green LED light source 14 is turned on according to the lighting time of the green LED light source 14 obtained in 503. Since the shading / black correction data is shared with the data for color, it is not newly acquired.

In the case of sheet reading, adjustment of the lighting time of the LED light source and acquisition of white reference and dark output data are performed for each reading operation. The same operation is performed at the time of initial setting at power-on. Is also performed. This is to enable the hand scan operation immediately after the power is supplied. If the hand scanner is detached from the main unit when the power is turned on, a message prompting the user to attach the main unit to the main unit is displayed on the LCD panel of the operation panel 25. At the same time, and the sound is notified by the speaker 32.

FIG. 5 is a flowchart showing an example of a lighting time control procedure at the time of hand scanning. If there is a reading instruction in the hand scan mode, the presence or absence of valid shading data is checked (S401). If there is no data, an error message is displayed on the LCD display of the operation panel 25 and the speaker 32 is used. Notification is made by voice (S410), and the processing ends with an error.

On the other hand, if there is valid shading data (S401), various settings are made according to the monochrome mode or the color mode (S402), and it is determined whether the mode is the color mode or the monochrome mode (S401). S403). If the color mode is determined, R,
The lighting control parameters for each of the G and B colors are set (S40).
4) If it is determined that the mode is the monochrome mode, the lighting control parameter of G is set (S405). As the lighting time designated at this time, the value determined when the pre-scanning operation is performed with the hand scanner unit stored in the main body described above is used.

Next, the lighting control register 30 controls the lighting according to the written value without automatically adjusting the lighting time.
2 is set to the main adjustment mode (S406), the LED light source is turned on (S407), and then the prescan operation ends.

FIG. 6 shows the RGB / YMCK conversion circuit 3 shown in FIG.
12 shows the configuration. In FIG. 6, reference numeral 601 denotes a register for storing one pixel of luminance data input in the order of R (red), G (green), and B (blue) lines.

Reference numeral 602 denotes an R component luminance-density conversion LUT RAM having an output from the register 601 as an address. Reference numeral 603 denotes a G component luminance-density conversion LUT RAM having an output from the register 601 as an address.
Reference numeral 604 denotes B whose address is the output from the register 601.
This is a LUT RAM for luminance-density conversion of components.

Reference numeral 605 denotes a selector, which is a luminance-density conversion LUTRAM 602, 60 according to the input pixel color.
3, 604. 6
Reference numeral 07 denotes a delay buffer for synchronizing R, G, and B data input in line order. 60
A buffer control circuit 6 controls writing and reading of image data to and from the delay buffer 607.

608 is UCR (under color removal)
A circuit for generating a black component value K from a set threshold value (UCRT / H), an input cyan component value C, a magenta component value M, and a yellow component value Y. is there. That is, when the value K of the black component is min (C, M, Y)> UCRT / H, K = min (C, M, Y) −
In the case of UCR T / H, min (C, M, Y) <UCRT / H, K = 0.

The register 609 is for temporarily storing cyan component pixels. The register 609 is for temporarily storing the magenta component pixel. Register 60
Numeral 9 is for temporarily storing yellow component pixels. The register 609 is for temporarily storing a black component pixel.

613 to 628 are registers 609 to 612
LUT RA for masking operation using the output of
M.

Reference numeral 629 denotes an adder for adding the outputs of the masking calculation LUT RAMs 613 to 616. 630 is an adder, which is an LUT for masking operation
The outputs of the RAMs 617 to 620 are added.
Reference numeral 631 denotes an adder, which is an LUT RA for masking operation.
The outputs of M621 to M624 are added. 632
Is an adder, and a masking calculation LUT RAM 62
5 to 628 are added.

Reference numeral 633 denotes a cyan component output γ conversion LUT RAM having the output from the adder 629 as an address. Reference numeral 634 denotes an output gamma conversion LUT RAM for a magenta component whose address is the output from the adder 629. 6
Numeral 35 denotes an LUT RAM for output component γ conversion of a yellow component having an output from the adder 629 as an address. Reference numeral 636 denotes an LUTRAM for black component output γ conversion using the output from the adder 629 as an address.

Next, the RGB / YMCK conversion circuit 3 shown in FIG.
Operation 12 will be described. When the color copy operation is started, various settings are made from the CPU 1 to the image processing gate array 16 and the above-described pre-scan operation is performed (S2 in FIG. 2).
09). When the prescan operation is completed, the luminance-density conversion LUT stored in the ROM 3 is replaced with the luminance-density conversion LUT RAM 60 in the image processing gate array 16.
2 to 604, and a masking calculation table generated by multiplying the color tone set value by the masking calculation reference data is written to the masking calculation LUT RAMs 613 to 628 in the image processing gate array 16 (S2 in FIG. 2).
10).

The color tone adjustment values include cyan, magenta,
It can be set to ± 50% for each color of yellow and black, that is, in the range of 50% to 150%. The operator adjusts the color tone by using the operation panel 25.
Can be set by operating.

For example, when the adjustment value of the cyan component is set to 110%, the cyan component data of the masking calculation reference data in the ROM 3, that is, the signed 12-bit constants A11, A21, A31, and A41.
Are multiplied by 110/100, respectively. Then, in order to suppress the error of the operation result, the obtained 12-bit multiplication result is rounded to the upper 9 bits, and 9-bit constants α11, α21, α31, α41 are generated.

For example, when the adjustment value of the magenta component is not set, the magenta component data, that is, the signed 12-bit constants A12, A22, A32, and A42
Is read from the ROM 3 and rounded to the upper 9 bits to suppress an error in the operation result, and the 9-bit constant α
12, α22, α32 and α42 are generated.

Therefore, the masking calculation LUT RAMs 613, 617, and 62 in the image processing gate array 16 are provided.
1,625, the cyan component value C (C = 0 to 255) stored in the register 609 and the constants α11, α12, α13 stored in the masking calculation LUT RAMs 613, 617, 621, and 625, respectively. The product with α14 is stored, and the input cyan component value C
Are used as addresses, and the respective products are output.

LUT RAM 614 for masking operation
618, 622, and 626 store the value M (M = 0 to 255) of the magenta component stored in the register 610 and the LUT RAMs 614, 618, and 62 for the masking operation.
Constants α21 and α2 stored in
The product of 2, α23, and α24 is stored, and the respective products are output using the input cyan component value C as an address.

LUT RAM 615 for masking operation
619, 623, and 627, the yellow component value Y (Y = 0 to 255) stored in the register 611 and the masking calculation LUT RAMs 615, 619, and 62
Constants α31 and α3 stored in
The product of 2, α33, and α34 is stored, and the respective products are output using the input cyan component value C as an address.

LUT RAM 616 for masking operation
620, 624, and 628 store the value K (K = 0 to 255) of the black component stored in the register 612 and the LUT RAMs 616, 620, and 62 for the masking operation.
Constants α41 and α4 stored in
The product of 2, 43, and 44 is stored, and each product is output using the input cyan component value C as an address. That is, the masking calculation LUT
The calculation result of α11 × C is stored in the RAM 613,
The masking calculation LUT RAM 617 has α21 ×
The calculation result of C is stored and the masking calculation LUT R
The AM 621 stores the calculation result of α31 × C, and the masking calculation LUT RAM 625 stores α41 × C
Of the masking calculation LUT RA
The calculation result of α12 × M is stored in M614, and the calculation result of α22 × M is stored in the LUT RAM 618 for masking calculation, and the LUT RAM for masking calculation is stored.
622 stores an operation result of α32 × M, and a masking operation LUT RAM 626 stores an operation result of α42 × M, and a masking operation LUT RAM6.
15 stores the calculation result of α13 × Y, and the LUT RAM 619 for masking calculation stores the calculation result of α23 × Y, and the LUT RAM 62 for masking calculation.
3 stores the calculation result of α33 × Y, and the LUT RAM 627 for masking calculation stores the calculation result of α43 × Y, and the LUT RAM 616 for masking calculation.
Stores the calculation result of α14 × K, the masking calculation LUT RAM 620 stores the calculation result of α24 × K, and the masking calculation LUT RAM 624 stores the calculation result of α34 × K. The calculation LUT RAM 628 stores the calculation result of α44 × K.

Next, the color conversion processing will be described. R, G, B
Data input to the RGB / CMYK conversion circuit 312 in line order is input as an address of a luminance-density conversion table RAM 602 to 604 provided for each of R, G, and B components. Is performed, and the density signals C, M, Y
Is converted to The data from the selector 605 once
The data is accumulated in the delay buffer 607. Delay buffer 607
Has a capacity for one line of cyan and magenta components. The data stored in the delay buffer 607 is read out of the delay buffer 607 in synchronization with the input of the Y component, a black component is generated by the UCR circuit 608, and cyan, magenta, yellow, and black components are respectively These are stored in registers 609 to 612.

The outputs of the registers 609 to 612 are input as addresses of masking calculation LUT RAMs 613 to 628.

LUT RAM 613 for masking operation
The output of the adder 616 is added by an adder 629. If the addition result is negative, it is clamped to 0. If the addition result is 255 or more, it is clamped to 255.
Output to the RAM 633.

LUT RAM 617 for masking operation
The output of the adder 620 is added by the adder 630. If the addition result is negative, it is clamped to 0, and if it is 255 or more, it is clamped to 255.
Output to RAM 634.

LUT RAMs 621 to 621 for masking operation
The output from the adder 624 is added by an adder 631, and if the addition result is minus, it is clamped to 0;
Output to the RAM 635.

LUT RAM 625 for masking operation
The output of the adder 628 is added by the adder 632. If the addition result is negative, it is clamped to 0; if it is 255 or more, it is clamped to 255.
Output to RAM 636.

Therefore, the RGB / YMCK conversion circuit 312
Then

[0085]

(Equation 2)

Is performed.

The above Amn (1 ≦ m ≦ 4, 1 ≦ n ≦ 4),
.alpha.mn (1.ltoreq.m.ltoreq.4, 1.ltoreq.n.ltoreq.4) actually corresponds to a reference table and a table generated based on the reference table, and a conversion table based on 256.times.16 reference table data. Data is generated.

In the above, an example in which the concept of the present invention is simplified and the reference data is treated as 16 constants has been described. In practice, however, the reference data has a signed precision of 12 bits. 256 in the table corresponding to A11,
In all, the table data consists of 256 × 16 table data.

Therefore, the calculation LUT RA for the α term
In the above example, the generation of data actually written to M is performed by multiplying 256 reference data corresponding to A11 by 110/100, and rounding up to the upper 9 bits to obtain 256 data. Is being done.

Therefore, finer adjustment is possible than when the reference data is a constant.

[0091]

As described above, according to the present invention, as described above, the color tone can be adjusted without increasing the number of lookup tables related to masking conversion. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image processing gate array 16 of FIG.

FIG. 3 is a flowchart showing an example of a control program stored in a ROM 3 of FIG.

FIG. 4 is a flowchart illustrating an example of a prescan operation performed by the image processing gate processing array 16 of FIG. 1;

FIG. 5 is a flowchart illustrating an example of a lighting time control procedure during hand scanning.

FIG. 6 is a block diagram showing a configuration of an RGB / YMCK conversion circuit 312 in FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 CPU 2 bus 3 ROM 4 SRAM 12 read sensor 13 red LED light source 14 green LED light source 15 blue LED light source 16 image processing gate array 18 DRAM 25 operation panel 26 multifunctional gate array

Continued on the front page F-term (reference) 2H030 AA02 AD07 AD12 BB02 5B057 CA01 CA08 CA12 CB01 CB08 CB12 CC01 CE17 CE18 CH01 CH11 5C077 LL17 MP08 NP01 PP33 PP37 PP38 PQ12 PQ23 5C079 HB03 HB12 LA21 LB04 MA05 NA10

Claims (6)

[Claims] 1. A look-up table storing means for storing a look-up table comprising masking calculation data for a color component to be used for forming a color image, and a look-up table stored in the look-up table storing means. A color image forming apparatus having a masking operation unit for performing color conversion on color density, a storage unit storing a single reference table including masking operation reference data for color components provided for color image formation; Input means for inputting an adjustment value of a color tone; and when the adjustment value is input by the input means, multiplying the adjustment value for the input color component by the masking calculation reference data corresponding to the color component Generating means for generating masking calculation data, and generating by the generating means Color image forming apparatus characterized by comprising a overwriting means for overwriting the look-up table the masking operation for data. 2. The color image forming apparatus according to claim 1, wherein the precision of the masking calculation reference data is greater than the precision of the masking calculation data. 3. The masking calculation data of the look-up table according to claim 1, wherein, for a color that has not been input by the input means, the generation unit determines the precision of the masking calculation reference data corresponding to the color. A color image forming apparatus that generates data for a masking operation by adjusting according to the accuracy of the image. 4. A look-up table storing means for storing a look-up table comprising masking calculation data for a color component to be used for forming a color image, and a look-up table stored in the look-up table storing means. In a lookup table generating method for a color image forming apparatus having a masking operation unit for performing color conversion on a color density, when an adjustment value of a color tone is input, the adjustment value for the input color component is converted to a color image formation value. A reading step for reading out from a storage means storing a single reference table comprising masking calculation reference data for the color component provided to the color component; an adjustment value for the input color component; and a masking calculation reference corresponding to the color component. Data, read from the store means A look-up table comprising: a generating step of multiplying by masking calculation reference data to generate masking calculation data; and an overwriting step of overwriting the lookup table with the generated masking calculation data. Generation method. 5. The lookup table generating method according to claim 4, wherein the precision of the masking calculation reference data is greater than the precision of the masking calculation data. 6. The masking operation according to claim 4, wherein, when the adjustment value is input, the accuracy of the masking operation reference data corresponding to the color that has not been input is adjusted for the masking operation of the lookup table. A lookup table generation method, wherein data is adjusted in accordance with data accuracy to generate masking calculation data.