JP2001078036A - Device and method for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable suitable gray compensation to any image by converting the color of a pixel showing the achromatic color in an inputted color image to one prescribed color component only and controlling whether or not conversion is to be performed corresponding to whether an object showing a multi-level image in the relevant color image is composed of pixels having prescribed luminance or not. SOLUTION: A command discriminating part 1102 of a printer (LBP) 1000 for receiving print data from a host computer 2000 discriminates respective print control commands and the corresponding to each command, the print data are analyzed in a command analytic part 1103. This analyzed command is converted into the intermediate code of a form easier to process by a command executing part 1104. When it is discriminated in the command discriminating part 1102 the print control command is a command with expansion to the intermediate code of character or graphic, in a gray compensation control part 1106, the gray compensation is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and method for processing a color image.

[0002]

2. Description of the Related Art In a typical printing apparatus, printing is performed after converting a color designated in RGB format into data in YMCK format. In general, a pixel in which each color component is R = G = B is monochrome, but when the pixel constitutes a character or a graphic, a black (K) monochrome Print only by As a result, a sharp output without blurring the outline of the character or figure can be obtained.

[0005] Conversely, when a monochrome image constitutes image data such as a photograph, it is common to print with YMC colors. As a result, a beautiful output with a good balance with other colors can be obtained.

In the above-described conventional printing apparatus, a function of printing a pixel having a monochrome RGB value with only K color is called "gray compensation". Enable / Disable (On /
Off).

Whether to turn on the gray compensation is determined depending on the contents of the print data.
On, graphic area = on, image area = off, etc.

[0006]

However, in recent advanced applications, image data can be used as graphic parts and some characters in many applications. For example, only a part of characters in a character string or only a part of a background pattern of a document can be an image.

Here, when gray compensation is applied to image data created by such an application, if the above criterion is applied, gray compensation is simply turned on for characters and figures, and gray compensation is applied for images. Is turned off, if printing is performed as it is, for example, only the portion of the character string where the image is used will have a different color from the other portions, and for example, there will be a problem that the portion looks like blurred.

Here, an example in which this problem occurs is shown in FIG.
This will be specifically described with reference to FIG.

FIG. 7A shows that one rectangle is 71, 72,
An example constituted by four oblique line patterns indicated by 73 and 74 is shown. A pattern 71 is obtained by drawing the oblique line pattern as a multi-valued image.
Is drawn as a rectangle with a diagonal pattern.

Here, each pattern 71 shown in FIG.
When the gray compensation based on the above-described conventional criterion is performed when all the colors of R to G = R, that is, R = G = B, that is, monochrome, the result is as shown in FIG. Only the image drawing portion is blurred because it is output in a mixed color of YMCK.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image processing apparatus and a method thereof that enable appropriate gray compensation for any image. I do.

[0012]

As one means for achieving the above object, the image processing apparatus of the present invention has the following arrangement.

That is, input means for inputting a color image,
A conversion unit that converts a color of a pixel representing an achromatic color in the color image into only a predetermined one color component, and whether an object representing a multi-valued image in the color image is configured of pixels having a predetermined luminance. And control means for controlling whether or not to perform conversion by the conversion means in accordance with

For example, the conversion means converts the color of a pixel representing an achromatic color into only a black component.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to the drawings.

First Embodiment Apparatus Configuration First, a configuration of a laser beam printer (hereinafter, referred to as “LBP”) suitable for applying this embodiment will be described with reference to FIG.
This will be described with reference to FIG. The printer to which the present embodiment is applied is not limited to the LBP, and it goes without saying that a printer using another printing method may be used.

FIG. 1 is a cross-sectional view showing the internal structure of a laser beam printer to which this embodiment is applied. This LBP is used to register a character pattern from a data source (not shown) and register a fixed format (form data). Can be performed. In FIG. 1, reference numeral 1000 denotes an LBP main body, which inputs and stores character information (character code), form information, macro instructions, and the like supplied from an externally connected host computer, and responds according to the information. A character pattern, a form pattern, and the like are created, and an image is formed on recording paper, which is a recording medium. Reference numeral 1012 denotes an operation panel on which switches for operation, an LED display, and the like are arranged. Reference numeral 1001 denotes a printer control unit that controls the entire LBP 1000 and analyzes character information supplied from a host computer.

The control unit 1001 mainly converts character information into a video signal having a corresponding character pattern and outputs the video signal to a laser driver 1002. Laser driver 100
Reference numeral 2 denotes a circuit for driving the semiconductor laser 1003, and the semiconductor laser 1003 is driven in accordance with an input video signal.
The laser light 1004 emitted from 3 is switched on and off. The laser 1004 is swung right and left by a rotary polygon mirror 1005 to scan on an electrostatic drum 1006. As a result, an electrostatic latent image of a character pattern is formed on the electrostatic drum 1006. This latent image is developed by a developing unit 1007 around the electrostatic drum 1006 and then transferred to a recording sheet. A cut sheet is used as the recording paper. The cut sheet recording paper is stored in a paper cassette 1008 mounted on the LBP 1000, is taken into the apparatus by a paper feed roller 1009 and transport rollers 1010 and 1011, and is transferred to an electrostatic drum 1006. Supplied.

[Functional Configuration] FIG. 2 is a block diagram showing a functional configuration of the above LBP1000.

In FIG. 2, reference numeral 2000 denotes an LBP 1000
Is a host computer connected to the LBP 1000 and outputs print information including print data and a control code to the LBP 1000.

The LBP 1000 is roughly divided into a formatter control unit 1100, an interface 1200, an output control unit 1300, and a printer engine unit 1400.

The formatter control unit 1100 includes a reception buffer 1101, a command discrimination unit 1102, a command analysis unit 1103, a command execution unit 1104, and a page memory 1.
105, and a gray compensation control unit 1106.

The reception buffer 1101 is storage means for temporarily storing print information received from the host computer 2000. The command determination unit 1102 determines each print control command, and the print data is analyzed by the command analysis unit 1103 according to each command. The command analysis unit 1103 analyzes each print control command. The command analyzed by the command analysis unit 1103 is an intermediate result obtained by analyzing the print data, and is converted by the command execution unit 1104 into an intermediate code in a format that can be more easily processed.

When the command discriminating unit 1102 determines that the print control command is a command accompanied by expansion into an intermediate code such as a character or a figure, the gray compensation control unit 1106 controls gray compensation. The gray compensation control unit 1106 determines whether to print with YMCK or only with K when the designated color is monochrome.

The command execution unit 1104 executes each command according to the above-mentioned intermediate code, and commands relating to drawing and printing are sequentially developed in the page memory 1105.

Generally, the formatter control unit 11
Reference numeral 00 denotes a computer system using a CPU, a ROM, a RAM, and the like.

The output control unit 1300 includes the page memory 11
05 is converted into a video signal, and an image is transferred to the printer engine unit 1400. The printer engine unit 1400 is a printing mechanism for forming the received video signal into a permanent visible image on recording paper.

System Configuration FIG. 3 is a block diagram showing a configuration of a printer control system for controlling the LBP 1000 in the present embodiment. If the function of the present embodiment is executed,
Needless to say, the present invention can be applied to a single device, a system including a plurality of devices, and a system in which processing is performed via a network such as a LAN.

In FIG. 3, a host computer 200
0 is a C for executing document processing in which graphics, images, characters, tables (including spreadsheets and the like) are mixed based on a document processing program or the like stored in the program ROM of the ROM 3.
The CPU 1 is provided with a PU 1 and controls each device connected to the system device 4 as a whole. Also, this ROM
The ROM 3 stores a control program of the CPU 1 and the like, and the font ROM of the ROM 3 stores font data and the like used in the document processing.
The M3 data ROM stores various data used when performing the above-described document processing and the like. Reference numeral 2 denotes a RAM, which functions as a main memory, a work area, and the like of the CPU 1.

5 is a keyboard controller (KBC)
Controls the key input from the keyboard 9 or a pointing device (not shown). 6 is a CRT controller (C
RTC) controls the display on a CRT display (CRT) 10. Reference numeral 7 denotes a memory controller (MC) for controlling access to an external memory 11 such as a hard disk (HD) for storing a boot program, various applications, font data, user files, editing files, and the like, and a floppy disk (FD). Reference numeral 8 denotes a printer controller (PRTC) which controls the printer 1000 via a predetermined bidirectional interface (interface) 21.
And executes communication control processing with the printer 1000.

The CPU 1 executes a process of developing (rasterizing) the outline font in the display information RAM set on the RAM 2, for example, and outputs the W on the CRT 10.
YSIWYG is possible. Further, the CPU 1
Various registered windows are opened based on a command specified by a mouse cursor or the like (not shown) on the RT 10,
Perform various data processing.

On the other hand, in the LBP 1000, reference numeral 12 denotes a printer CPU, and various devices connected to the system bus 15 based on a control program or the like stored in the program ROM of the ROM 13 or a control program or the like stored in the external memory 14. , And outputs an image signal as output information to a printing unit (printer engine) 17 connected via a printing unit interface 16. The program RO of the ROM 13
M has a CP as shown in a flowchart described later.
The control program of U12 may be stored. ROM1
The font ROM 3 stores font data and the like used when generating the output information. If the data ROM of the ROM 13 does not have an external memory 14 such as a hard disk, the font ROM is used on the host computer 2000. Information and the like.

The CPU 12 is capable of performing communication processing with the host computer via the input unit 18.
000 can be notified to the host computer 2000. Reference numeral 19 denotes a RAM that functions as a main memory, a work area, and the like of the CPU 12, and is configured so that the memory capacity can be expanded by an optional RAM connected to an additional port (not shown).
The RAM 19 is used for an output information development area, an environment data storage area, an NVRAM, and the like. The access to the external memory 14 such as a hard disk (HD) and an IC card is controlled by a memory controller (MC) 20. The external memory 14 is optionally connected,
It stores font data, emulation programs, form data, and the like.

Reference numeral 18 denotes the operation panel 1012 described above.
, A switch for the operation in, an LED display, and the like.

It should be noted that the above-mentioned external memory is not limited to one,
At least one or more may be provided so that a plurality of external memories storing an option font card and a program for interpreting a printer language of a different language system in addition to the built-in fonts can be connected. Further, an NVRAM (not shown) may be provided to store the printer mode setting information from the operation panel 1012.

Next, a print control procedure in the LBP 1000 having the above-described configuration will be described with reference to flowcharts shown in FIGS. 4, 5 and 6.

FIG. 4 is a flowchart showing the main processing from the start to the end of the operation of the LBP 1000.

First, in step S 401, print data sent from the host computer 2000 is received and stored in the reception buffer 1101. Next, in step S402, the print data stored in the reception buffer is read, and in step S403, a drawing process is performed. afterwards,
Whether or not a print end command has been received in step S404
Alternatively, it is determined whether or not the print data has been completed. If the printing has been completed, the printing operation ends, but if not, the processing from step S401 is repeated.

FIG. 5 is a flowchart showing details of the drawing process in step S403 of FIG. This drawing process is a process for performing actual printing.

First, in step S501, the command analysis unit 1103 checks whether or not the data to be processed is a paper ejection command.
If not, the flow advances to step S502 to determine whether or not the analyzed data is a command that involves development processing to a page memory, such as character printing or graphic drawing.

If the expansion processing is not performed in step S502, the flow advances to step S505 to immediately execute the command. If the expansion processing is performed, the flow advances to step S509 to perform gray compensation and then execute step S509.
In step 503, an intermediate code in a format that facilitates command execution is generated. In step S504, upon receiving the intermediate code, the command execution unit 1104 performs the development processing on the page memory 1105. After the completion of the development processing, the process returns to step S402 in FIG. 4 to repeat the data analysis processing.

On the other hand, if it is determined in step S501 that the data is a paper ejection command, the process proceeds to step S501.
Proceeding to 506, the output control unit 1300 converts the contents of the page memory 1105 into a video signal for the printer engine unit 1400 and transfers and outputs the image. In step S507, the printer engine unit 1400 permanently converts the received video signal to recording paper. Form a visible image and print. Then, in step S508, the printed result is discharged, thereby completing the print control process for one page.

[Gray Compensation Processing] FIG. 6 is a flowchart showing details of the gray compensation processing in step S509 of FIG. In other words, this process is a process for determining whether to print an object using YMCK or only K.

First, in step S601, it is determined whether or not the object is a multi-valued image. Here, the multi-valued image refers to an image having a gradation and each pixel being composed of a plurality of bits. If it is a multi-valued image, the process proceeds to step S602, and the luminance of each pixel constituting the image is sequentially detected. Next, step S60
At 3, all the pixels that make up the image have maximum brightness (RGB = (255, 255, 255))
Then, it is determined whether or not the image is constituted only by the minimum luminance (RGB = (0, 0, 0)).

If all the pixels are constituted only by the maximum and minimum luminances, the flow advances to step S608 to turn on the gray compensation.
A conversion table from B to K is set.

On the other hand, if the object is not a multi-valued image in step S601, the flow advances to step S604 to acquire the color of the object. Here, an object is a unit graphic (character / graphic / graphic) composed of intermediate codes.
Image), and details are described below,
The drawing position, the coordinate point of the outer shape, the width, the designated color, and the like are described, and the color of the object can be detected from the information.

Next, in step S605, it is determined whether or not the color of the object is monochrome with R = G = B. If it is monochrome, the process proceeds to step S606, and NVR
The gray compensation setting value (GRC) is obtained from the AM. Here, GRC is used for each of characters, graphics, and images.
On / off of gray compensation is set. In addition, GRC
Are stored in the NVRAM, and the settings can be changed by the user by operating the operation panel 1012.

Here, in step S607, if the GRC corresponding to the object is on, step S60
8, the gray compensation is set to ON, but the GRC is set.
Is off, the process proceeds to step S610, where gray compensation =
After the setting of OFF, in step S611, R
A conversion table from GB to YMCK is set.

On the other hand, in step S605, R = G =
If it is not B, that is, if it is not monochrome, the process directly proceeds to step S611, and the conversion table from RGB to YMCK is set.

If the multi-valued image contains pixels other than the maximum luminance and the minimum luminance in step S603, the flow advances to step S606 to acquire the GRC of the image from the NVRAM.

As described above, in the gray compensation processing of this embodiment, either a conversion table from RGB to K (step S609) or a conversion table from RGB to YMCK (step S611) is set.

Object Details Here, the configuration of the above-described object will be described with reference to FIG.
This will be described with reference to FIG.

In FIG. 10, reference numeral 101 denotes an object management table, which manages objects on the same page. In the object management table 101, types such as character strings, polygons, rectangles, and images are described, and the tables shown in (a) to (h) are respectively linked. Each of the tables (a) to (h) has a drawing position,
Object 10 in which attributes such as size and outline are described
Nos. 2 to 109 are linked, and color information specified in RGB format is described as one of the information. Here, the objects 102 to 109 are in an intermediate code format after the command analysis.

For example, the color information specified in the object 102 is RGB = (200, 200, 200)
And the color information specified in the object 107 is RGB = (100, 100, 100).

Therefore, the objects 102 and 107 are
Since the color is monochrome, it is subject to gray compensation. The object 109 is an image object, and from the described information, it can be understood that the object 109 is a multi-value image of 24 bits per pixel in RGB format. The image object has a data pointer to binary data, and the actual data is read into another memory.

Specific Example of Gray Compensation Next, a specific example of gray compensation in the present embodiment will be described with reference to FIG.

FIGS. 8A and 8B show multi-valued image data, and FIG. 8C is an enlarged view of an area 81 which is a part of the image data shown in FIG. 8A. .

According to FIG. 8C, the area 81 is composed of a maximum luminance pixel 82 whose color is RGB = (255, 255, 255) and a minimum luminance pixel 82 whose color is RGB = (0, 0, 0). It can be seen that it is composed of 83. That is, the image data shown in FIG. 8A is image data in which all pixels are composed of these two colors, and composed only of the maximum luminance and the minimum luminance. Therefore,
Gray compensation for the image data shown in FIG. 8A is turned on, and printing is performed with K single color.

On the other hand, the image data shown in FIG. 8B is a photographic image, and each pixel is composed of various colors. Therefore, the image data shown in FIG. 8B is set according to the conventional gray compensation setting standard.
Printing is performed using YMCK mixed color or K single color.

As described above, according to the present embodiment,
For image data consisting of only the maximum luminance (white) and minimum luminance (black), high-quality output can be performed by forcibly switching gray compensation on regardless of the gray compensation setting. Becomes

<Second Embodiment> Hereinafter, a second embodiment according to the present invention will be described.
An embodiment will be described.

In the above-described first embodiment, an example will be described in which, when the pixels forming the multi-valued image are only the maximum luminance and the minimum luminance, the automatic gray compensation for forcibly turning on the gray compensation is performed. did. The second embodiment is further characterized in that a setting item as to whether or not to enable the automatic gray compensation is provided as a panel menu of the operation panel 1012 so that switching by a user's panel operation is possible.

The configuration of the apparatus and its main processing in the second embodiment are the same as those described with reference to FIGS. 1 to 5 in the first embodiment.
Description is omitted.

FIG. 9 is a flowchart showing the gray compensation processing in step S509 of FIG. 5 in detail according to the second embodiment. This process is also a process of determining whether to print an object using YMCK or only K.

First, in step S901, it is determined whether or not the object is a multi-valued image. If the object is a multi-valued image, the flow advances to step S912 to acquire a set value of automatic gray compensation (hereinafter, AUTO-GRC) from the NVRAM. I do. Here, the AUTO-GRC is held in the NVRAM and one of ON and OFF is set, and this setting can be changed by the user by operating the operation panel 1012.

Next, in step S913, AUTO
Determine whether GRC is on or off; If it is off, the process proceeds to step S906, and if it is on, the process proceeds to step S902 to sequentially detect the luminance of each pixel constituting the image. Next, in step S903, it is detected whether or not all the pixels constituting the image are constituted only by the maximum luminance and the minimum luminance. If it is composed of only the maximum luminance and the minimum luminance, the process proceeds to step S908, where gray compensation is set to ON, and a conversion table from RGB to K is set in step S909.

On the other hand, if the object is not a multi-valued image in step S901, the flow advances to step S904 to acquire the color of the object. Next, step S90
In step S5, it is determined whether the color of the object is monochrome with R = G = B.
6 and the gray compensation setting value (GR
C) is obtained. In the GRC, on / off of gray compensation is set for each of characters, graphics, and images, as in the first embodiment. GRC is NVRA
M, and the setting can be changed by the user by operating the operation panel 1012.

If it is determined in step S907 that the GRC corresponding to the object is on, the process proceeds to step S90.
8, the gray compensation is set to ON, but the GRC is set.
Is off, the process proceeds to step S910, where gray compensation =
After the setting of OFF, in step S911, R
A conversion table from GB to YMCK is set.

On the other hand, in step S905, R = G =
If it is not B, that is, if it is not monochrome, the process directly proceeds to step S911, and a conversion table from RGB to YMCK is set.

If the multi-valued image contains a pixel other than the maximum luminance and the minimum luminance in step S903, the flow advances to step S906 to acquire the GRC of the image from the NVRAM.

As described above, according to the second embodiment, the automatic gray compensation shown in the first embodiment is performed only when the AUTO-GRC is set to ON (steps S912 and S913). be able to. Further, since the setting of AUTO-GRC can be changed by the user, gray compensation with a high degree of freedom according to the needs of the user can be performed.

In each of the embodiments described above, the example in which the gray compensation set value (GRC) and the automatic gray compensation set value (AUTO-GRC) are held in the NVRAM has been described. It may be possible.

Also, an example in which gray compensation is forcibly turned on for an image composed of only the maximum luminance and the minimum luminance has been described. It is also effective to set them together. In this case, it is more effective to provide a user interface that allows the user to select which of the character and the graphic to be matched with the gray compensation value.

Further, a case has been described where the color of an object is specified in the RGB format. However, as long as the color can be specified, the object is not limited to the RGB format but may be L * a * b * or Luv.
Needless to say, color designation may be performed in another color format, such as.

In each embodiment, the printing apparatus (L
The example in which print control is performed inside the BP1000) has been described.
000 may be controlled. In this case, it is necessary to provide a color designation item in the YMCK format as a print control command.

[0076]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, an object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and a computer (a computer) of the system or the apparatus. It is needless to say that the present invention can also be achieved by a CPU or an MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. Also,
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the operating system (OS) running on the computer based on the instructions of the program code.
It goes without saying that a case where the functions of the above-described embodiments are implemented by performing some or all of the actual processing, and the processing performs the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. Needless to say, the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts shown in FIGS. 4, 5, 6, and 9 described above. .

[0080]

As described above, according to the present invention, appropriate gray compensation can be performed for any image.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an LBP according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a functional configuration of the LBP according to the embodiment;

FIG. 3 is a block diagram illustrating a configuration of a printer control system according to the embodiment.

FIG. 4 is a flowchart illustrating a print control procedure according to the embodiment;

FIG. 5 is a flowchart illustrating a drawing processing procedure according to the embodiment;

FIG. 6 is a flowchart showing a gray compensation processing procedure in the embodiment;

FIG. 7 is a diagram showing a specific example of conventional gray compensation;

FIG. 8 is a diagram showing an example of gray compensation according to the embodiment;

FIG. 9 is a flowchart illustrating a gray compensation processing procedure according to the second embodiment;

FIG. 10 is a diagram illustrating a configuration example of an object.

[Explanation of symbols]

 1 CPU 2 RAM 3 ROM 4 System bus 5 KBC 6 CRTC 7 MC 8 PRTC 9 KB 10 CRT 11 External memory 12 CPU 13 ROM 14 External memory 15 System bus 16 Printing interface 17 Printing section 18 Input section 19 RAM 20 MC 1012 Operation Unit 1000 printing apparatus 1002 laser driver 1003 semiconductor laser 1004 laser beam 1005 rotating polygon mirror 1006 electrostatic drum 1007 developing unit 1008 paper cassette 1009 paper feed roller 1010 transport roller 1011 transport roller 1012 operation panel 1100 formatter controller 1101 receive buffer 1102 command discrimination Unit 1103 command analysis unit 1104 command execution unit 1105 page memory 1106 gray compensation control unit 12 0 interface 1300 output control unit 1400 printer engine unit 2000 host computer

Claims (10)

[Claims] An input unit for inputting a color image; a conversion unit for converting a color of an achromatic pixel in the color image into only a predetermined one color component; and an object indicating a multi-valued image in the color image. And a control unit for controlling whether or not to perform the conversion by the conversion unit according to whether or not the pixel is constituted by pixels having a predetermined luminance. 2. The image processing apparatus according to claim 1, wherein the conversion unit converts a color of a pixel representing an achromatic color into only a black component. 3. The control unit controls the conversion unit to perform conversion when the object representing the multi-valued image is composed of only pixels having the predetermined luminance. 2. The image processing device according to 1. 4. The image processing apparatus according to claim 3, wherein the predetermined brightness is a predetermined maximum brightness range and a predetermined minimum brightness range. 5. The image processing apparatus according to claim 1, further comprising image forming means for forming a visible image based on the color image. 6. The image processing apparatus according to claim 5, further comprising a color component conversion unit that converts a color component of a pixel that is not converted by the conversion unit into a color component corresponding to the image forming unit. Image processing device. 7. The image processing apparatus according to claim 1, further comprising setting means for setting whether to control the conversion means by the control means. 8. An image processing apparatus according to claim 7, wherein said setting means is set based on a user instruction. 9. An inputting step of inputting a color image, a determining step of determining whether or not an object representing a multi-valued image in the color image is composed of pixels of a predetermined luminance, based on the determination result Converting a color of a pixel representing an achromatic color in the object into only a predetermined one color component. 10. A recording medium on which a program code for controlling color image processing is recorded, wherein the program code includes at least a code for an input step of inputting a color image, and a multi-valued image in the color image. And a code for a determination step of determining whether or not the object is composed of pixels having a predetermined luminance. Based on the determination result, the color of the pixel indicating an achromatic color in the object is converted into only a predetermined one-color component. And a conversion process code.