JP4673768B2 - Color image processing apparatus, color image processing method, and storage medium - Google Patents

Description

  The present invention relates to generation of a color test pattern.

  Conventionally, various techniques for efficiently executing various types of image data processing executed when an image is printed out in an image processing apparatus have been devised.

  For example, when converting RGB image data into CMYK image data, a character or line drawing in the image data is separately extracted and replaced with a predetermined CMYK value (C = M = Y = 0, K = 255). There is an image processing apparatus. Conventionally, in order to execute such processing, a frame memory for storing data for identifying characters and line drawings has been required. Therefore, a technique has been devised that eliminates the need for a memory for character identification by using some bits of image data for character recognition (see Patent Document 1).

  In addition, for example, a process of converting RGB image data into five or more colors (for example, converting into image data including a total of six components of Lc, Lm in addition to four components of C, M, Y, and K) is executed. There are possible image processing devices. Conventionally, in order to execute such processing, dedicated hardware corresponding to color conversion of five or more colors has been required. Therefore, first, RGB image data is converted into image data composed of two components of LcLm by using a processing unit used for normal color conversion processing to four colors (conversion processing to CMYK image data). A technique for converting RGB image data into 6-component CMYKLcLm image data by converting RGB image data into CMYK image data has been devised (see Patent Document 2).

  By the way, many image forming apparatuses have a configuration for outputting a color test pattern. The color test pattern is, for example, an image in which a predetermined color is displayed in a predetermined order in a rectangular area of 10 mm × 10 mm size. Printer characteristics (color reproduction range, gradation reproduction characteristics, etc.) can be obtained by measuring the image arranged in the color test pattern with a spectrophotometer or reading with a scanner, and based on the obtained information Calibration correction and the like.

  Conventionally, in order to generate a color test pattern, it has been necessary to provide function units M1, M2, and M3 as shown in FIGS. 7A and 7B, respectively, and cause each of these function units to execute predetermined processing. . However, in the drawing, functional units T1 to T6 exemplify functional units for performing normal image output processing other than color test patterns.

  For example, generation of a color test pattern has been realized by providing dedicated hardware M1 for generating a color test pattern as shown in FIG. In this case, when a color test pattern output instruction is issued by the user, color test pattern data including four components of CMYK is generated by the dedicated hardware M1, and binarized by the binarization processing unit T4. Later, it was printed out at the image recording unit T5. Here, it is also necessary to provide a switching unit M2 for switching between the output of color test pattern data and the output of normal image data as an exception. In this case, the processing of the pattern generation unit (dedicated hardware M1) has to be executed at a data processing speed corresponding to the data processing speed of the image processing unit. Although it is possible to deal with the image processing unit by processing at low speed, in this case, a plurality of hardware operation clocks are required.

  Further, for example, as shown in FIG. 7B, a color test pattern is generated by a memory (four-component image data memory M3) that stores image data of CMYK four-component color patterns and is processed by software. Sometimes it was realized. In this case, when the user gives an instruction to output a color test pattern, the CPU generates image data of the CMYK 4-component color test pattern, and once the generated image data is stored in the 4-component image data memory M3. The image data stored in the memory M3 is read out, binarized in the binarization processing unit T4, and printed out in the image recording unit T5.

  Hereinafter, in this specification, in addition to an image acquired by reading an original image, an image acquired from a data processing device or a communication line, or an image input by these and temporarily stored in a storage unit is used. Images used for image formation, in other words, images other than those for testing are collectively referred to as “real images”.

JP 11-355594 A JP 2004-254033 A

  However, it is not desirable in terms of cost to provide dedicated hardware for generating a color test pattern and a dedicated memory for storing image data of a four-component color test pattern. There was a need for technology that could generate color test patterns.

  The present invention has been made in view of such circumstances, and a color test pattern can be obtained with a simple configuration without special hardware and a memory for storing four-component image data. An object of the present invention is to provide a color image processing apparatus, a color image processing method, and a storage medium.

The color image processing apparatus according to the present invention stores storage means for storing three-component color test pattern image data expressed only by lattice point coordinate values in a three-dimensional coordinate space, and image data expressed in color by three component values. Conversion processing means for converting into CMYK image data by interpolation using a three-dimensional lookup table; and image forming means for forming the CMYK image data on a recording medium. A first image data is output from the image data of an actual image color-represented by one component value, and the data value is composed of four CMYK components with respect to the data value composed of coordinate values in the color space representing the image data of the actual image. The three-component color test pattern image data is converted into CMYK image data by interpolation using the three-dimensional lookup table of Interpolation calculation using the second three-dimensional lookup table dedicated to the three-component color test pattern image data for outputting data values consisting of four components of CMYK to the data values consisting of the grid point coordinate values in the original coordinate space To convert to CMYK image data.
The color image processing method according to the present invention includes a color test pattern image data generation step for generating color test pattern image data, and an interpolation operation using a three-dimensional lookup table for the color test pattern image data. Performing a conversion processing step of converting the image data of the color test pattern into CMYK image data, and an image forming step of forming an image of the CMYK image data on a recording medium, the image data of the color test pattern Is expressed only by the lattice point coordinate values in the three-dimensional coordinate space, and the three-dimensional lookup table is composed of four components of CMYK with respect to the data value composed of the lattice point coordinate values in the three-dimensional coordinate space. Outputs the data value and is a rule dedicated to the image data of the color test pattern. And wherein the click-up table der Rukoto.
In addition, the computer-readable storage medium according to the present invention converts color test pattern image data expressed only by lattice point coordinate values in a three-dimensional coordinate space, and converts the color test pattern image data into CMYK image data. A conversion that converts the image data of the color test pattern into CMYK image data by performing an interpolation operation using the three-dimensional lookup table on the image data of the color test pattern and the possible 3D look-up table A program for executing a processing step, and the three-dimensional lookup table outputs a data value composed of four components of CMYK with respect to a data value composed of the grid point coordinate values in the three-dimensional coordinate space. Look-up table dedicated to image data of the color test pattern And characterized in that.

According to the first to seventh aspects of the present invention, the image data of the color test pattern expressed by the grid point coordinate values in the three-dimensional coordinate space is converted into CMYK image data by interpolation using a three-dimensional lookup table. A color test pattern is generated by converting and forming an image. In other words, the color test pattern is generated by executing the same process as the actual image forming process of converting the three-component image data such as RGB image data into CMYK image data to form an image. There is no need to provide dedicated hardware for generating test patterns. Further, a memory for accumulating the four component image data is also unnecessary. That is, a color test pattern can be obtained with a simple configuration.

  In particular, according to the second and third aspects of the present invention, since a plurality of types of three-dimensional lookup tables used for converting color test pattern image data into CMYK image data are provided, an image of one color test pattern is provided. Multiple types of color test patterns can be generated from the data.

In particular, according to the first, fourth, and seventh aspects of the present invention, the image data of the color test pattern is expressed only by the lattice point coordinate values in the three-dimensional coordinate space, and therefore corresponds to adjacent lattice points. The color test pattern image data can be converted into CMYK image data using a three-dimensional lookup table in which the CMYK values take discontinuous values. That is, a three-dimensional lookup table for converting the image data of the color test pattern can be freely generated.

[1. First Embodiment]
<1-1. Digital MFP>
FIG. 1 is a block diagram showing a configuration of a digital multi-function peripheral 1 in which a function of a color image processing apparatus corresponding to the first embodiment of the present invention is incorporated.

  Please refer to FIG. The digital multifunction machine 1 is a multifunction machine having a color facsimile function and a color copying machine function, and is configured as a multifunction machine (MFP apparatus) having a plurality of functions such as a FAX function, a copy function, a scan function, and a print function. Yes.

  The digital multifunction peripheral 1 includes a control unit 11, a RAM 12, a ROM 13, an operation unit 14, a display unit 15, an image processing unit 16, an image reading unit 17, an image recording unit 18, and an image memory 19. The large-capacity storage unit 20, the image transmission / reception unit 21, and the communication-related functional units 22 to 25 are electrically connected via a bus line 26.

  The control unit 11 is composed of a CPU. The control unit 11 controls each of the above hardware units based on a program stored in the ROM 13 and realizes the function of the digital multi-function peripheral 1.

  The RAM 12 is a storage device that can be read and written, and temporarily stores various data that are temporarily stored such as image data, FAX numbers, and mail addresses, and data that is generated during arithmetic processing by the control unit 11. Remember me. The RAM 12 is configured by SRAM, flash memory, or the like.

  The ROM 13 is a read-only storage device that stores programs and data necessary for controlling the digital multifunction device 1 in advance.

  The operation unit 14 includes various keys such as character keys, numeric keys, and function keys, and accepts user operations such as input of commands and text data. The user operation received by the operation unit 14 is input to the control unit 11 as a signal. The control unit 11 controls the operation of each unit based on a user operation.

  The display unit 15 is a display device that displays the operation state of the digital multi-function peripheral 1 and image data. The display unit 15 is configured by a display device such as a liquid crystal display. Various keys provided on the operation unit 14 may be realized by a touch panel provided on the display screen of the display unit 15.

    The image processing unit 16 performs various processes such as A / D conversion, color system conversion, color adjustment, and image composition on the image data received by the image transmission / reception unit 21 and the image data acquired from the image reading unit 17. Is a processing unit.

  The image processing unit 16 includes an LUT conversion processing unit 161. The LUT conversion processing unit 161 performs four-component C (cyan), M (magenta), Y (yellow), and K (black) by performing interpolation calculation using a three-dimensional lookup table. This is a processing unit for performing processing (hereinafter referred to as “LUT conversion processing”) for converting the image data (hereinafter referred to as “CMYK image data”).

  The image processing unit 16 includes an LUT selection unit 162. The LUT selection unit 162 is a processing unit for selecting a three-dimensional lookup table used in the LUT conversion process. More specifically, the LUT selection unit 162 stores in the LUT storage unit 163 according to the type of image data to be converted (more specifically, the type of the three-dimensional color space in which the image data is expressed). One lookup table is selected from the plurality of types of three-dimensional lookup tables (more specifically, “general lookup table” described later). In addition, the LUT selection unit 162 selects a plurality of types of three-dimensional lookup tables stored in the LUT storage unit 163 according to an instruction operation from the user (more specifically, a “color test pattern lookup table to be described later). )) To select one three-dimensional lookup table.

  Further, the image processing unit 16 includes an LUT storage unit 163. The LUT storage unit 163 stores a plurality of types of three-dimensional lookup tables a1, a2, b1, and b2. The LUT storage unit 163 stores two types of three-dimensional lookup tables.

  The first is a look-up table for performing LUT conversion of image data expressed by a three-dimensional color space into CMYK image data. That is, CMYK 4 for data values (input values) composed of coordinate values (three components) in various color spaces (RGB color space, Lab color space, etc.) expressing “three-component image data” described later. It is a look-up table that outputs data values composed of components. In FIG. 1, the RGB LUT (a1) and the Lab LUT (a2) correspond to this. Hereinafter, the first lookup table is referred to as a “general lookup table”. That is, the general look-up table is a look-up table used in the image forming process of the actual image.

  The second is a look-up table for performing LUT conversion of “three-component color test pattern image data” to be described later into CMYK image data. That is, a data value (input value) composed of coordinate values (three components) in a coordinate space expressing three-component color test pattern image data (however, this coordinate space may not have a physical meaning such as a color space). Is a look-up table for outputting data values composed of four components of CMYK. In FIG. 1, the color test pattern LUT1 (b1) and the color test pattern LUT2 (b2) correspond to this. Hereinafter, this second lookup table is referred to as a “color test pattern lookup table”.

  Furthermore, the image processing unit 16 includes a binarization processing unit. The binarization processing unit performs a binarization process on the CMYK image data (more specifically, a process for binarizing each color component of CMYK using a dither method, an error diffusion method, or the like). Part.

  The image reading unit 17 is a full-color scanner that reads an image on a document with a reading element such as a CCD line sensor. By reading a document image by a full-color scanner for each pixel, image data of the image on the document is acquired for each of the RGB color components. Like the image data acquired here, it is composed of three components of R (red), G (green), and B (blue) (more specifically, RGB signals for each pixel output from the reading element). This image data is referred to as “RGB image data”. The image reading unit 17 may be a scanner of a type in which a reading element scans the surface of a document placed on a glass table and reads an image, and is placed on a document placement table (not shown). It is also possible to use a scanner of a type that conveys an original by an ADF (Auto Document Feeder), scans the surface of the conveyed original by a stationary reading element, and reads an image.

  The image recording unit 18 is a printer that records image data and the like stored in the image memory 19 on recording paper. As the image recording unit 18, for example, an electrophotographic printer can be employed.

  The image memory 19 temporarily stores image data received from the external devices 4, 5, 6 through the LAN I / F 24 or the NCU 25, image data acquired by the image reading unit 17, image data processed by the image processing unit 16, and the like. Is a storage device. The image memory 19 includes a memory such as a DRAM that can be read and written.

  The image memory 19 can store image data (hereinafter referred to as “three-component image data”) defined by coordinate values (three components) in various three-dimensional coordinate spaces. The three-component image data includes image data (for example, RGB image data, Lab image data, Ycc image data) expressed by various three-dimensional color spaces. In addition, data defined by three coordinate values in a coordinate space having no physical meaning such as a color space (that is, “three-component color test pattern image data” described later) is also included.

  The image memory 19 has a three-component color test pattern image data storage unit 191. The three-component color test pattern image data storage unit 191 is a storage unit for storing three-component color test pattern image data. However, “three-component color test pattern image data” is image data of a color test pattern expressed by coordinate values in a three-dimensional coordinate space (that is, three components). However, the three-dimensional coordinate space expressing the three-component color test pattern image data may not have a physical meaning like a color space.

  The large capacity storage unit 20 is configured by a hard disk or the like. The large capacity storage unit 20 can store the image data processed by the image reading unit 17.

  The image transmission / reception unit 21 receives image data by e-mail communication from the external terminal 4 connected via the LAN 100 and the external terminal 5 connected via the Internet 200. In addition, image data is received by fax communication from an external terminal 6 connected via a PSTN (public switched telephone network) 300.

  Further, the digital multi-function peripheral 1 includes a codec (CODEC) 22 that encodes / decodes image data and the like corresponding to a plurality of protocols, and a modem 23 that modulates and demodulates transmission / reception data as communication-related functional units. In addition, a LAN I / F 24 corresponding to an interface with a LAN (local area network) 100 and an NCU 25 for controlling opening / closing of a telephone line are electrically connected via a bus line 26.

  Next, the communication environment of the digital multifunction device 1 will be described. The digital multifunction device 1 is connected to the LAN 100. A mail server 7 and an external terminal 4 are connected to the LAN 100. The LAN 100 is connected to the Internet 200 via a router 8 or the like. With such a configuration, the digital multi-function peripheral 1 can perform e-mail communication with the external terminal 4 connected via the LAN 100 and the external terminal 5 connected via the Internet 200. Further, the digital multifunction peripheral 1 is connected to a PSTN 300 that is a data communication network for analog lines. Thus, the digital multi-function peripheral 1 can communicate with the external terminal 6 connected via the PSTN 300. The external terminals 4, 5, and 6 are a personal computer connected with a modem, a device similar to the digital multi-function peripheral 1, a fixed telephone, a mobile phone, a FAX dedicated machine, and the like.

<2. Normal image output processing>
First, a processing operation in the case where the actual image data (RGB image data) read by the image reading unit 17 is printed out on a recording medium such as paper will be described with reference to FIGS. 2 and 4A. FIG. 2 is a flowchart showing a processing operation when the image data read by the image reading unit 17 is printed out. FIG. 4A shows image data to be processed in each functional unit shown in FIG. It is the figure which showed typically a mode that received a process in order. However, unless otherwise specified, the following operations are automatically performed under the control of the control unit 11.

  When image data (RGB image data) is acquired by the image reading unit 17, predetermined correction processing (shading correction, γ correction, etc.) is performed on the acquired RGB image data, and then stored in the image memory 19. (Step 1).

  After the predetermined correction processing is performed, the RGB image data is further converted into a color space such as Lab or Ycc having one achromatic axis in a three-dimensional space by matrix operation or the like and stored in the image memory 19. May be. In the following, image data represented by the respective color spaces of Lab and Ycc (that is, image data composed of three components of L, a, and b (or Y, c, and c)) will be referred to as “Lab images. Data ”and“ Ycc image data ”.

  Furthermore, enlargement / reduction processing, color adjustment processing, or the like may be performed on Lab image data obtained by the conversion processing. For example, when an enlargement instruction is given from the user, a predetermined enlargement process is performed on the Lab image data, and then the image data is stored in the image memory 19.

  Subsequently, the three-component image data is read from the image memory 19 (step S2), and the LUT conversion process is performed on the read three-component image data.

  This LUT conversion process will be described more specifically. First, the LUT selection unit 162 selects the three-dimensional lookup table according to the type of the three-component image data to be converted (more specifically, the type of the three-dimensional color space in which the image data is expressed) ( Step S3). In this case, however, one lookup table is selected from the general lookup tables a1 and a2. For example, when the three-component image data to be converted is RGB image data, the LUT selection unit 162 selects the RGB LUT (a1). For example, when the three-component image data to be converted is Lab image data, the LUT selection unit 162 selects the Lab LUT (a2).

  Subsequently, the three-dimensional lookup table selected by the LUT selection unit 162 in step S3 is read from the LUT storage unit 163, and the LUT conversion processing unit 161 applies the three-component image data read in step S1. Interpolation calculation processing using the read three-dimensional lookup table is executed (step S4). As a result, the three-component image data is converted into CMYK image data (that is, four-component image data).

  When CMYK image data is generated after the processing in step S4 is completed, the binarization processing unit 164 next executes binarization processing on the generated CMYK image data (step S5). ). The CMYK image data that has undergone the binarization processing is then sent to the image recording unit 18 and printed out on a recording medium such as paper (step S6).

<3. Color test pattern generation process>
Next, the color test pattern generation processing operation will be described with reference to FIGS. 3 and 4B. FIG. 3 is a flowchart showing the color test pattern generation processing operation, and FIG. 4B schematically shows how the image data to be processed is sequentially processed in each functional unit shown in FIG. It is a figure. However, unless otherwise specified, the following operations are automatically performed under the control of the control unit 11.

When the user is judged to have performed a predetermined operation for instructing the operation unit 14 the output of the color test pattern generation process of the color test pattern is started (step S 11).

First, three-component color test pattern image data stored in the three-component color test pattern image data storage unit 191 is read (step S 12).

  Subsequently, an LUT conversion process is performed on the read three-component color test pattern image data.

  This LUT conversion process will be described more specifically. First, the LUT selection unit 162 selects a three-dimensional lookup table in accordance with a user instruction operation received in an LUT selection reception unit (not shown) included in the LUT selection unit 162. In this case, however, one lookup table is selected from the color test pattern lookup tables b1 and b2 (step S13).

  Specifically, this selection process is performed as follows.

  First, a LUT selection accepting unit (not shown) displays a list of types of color test patterns that can be generated on the display unit 15 and a predetermined message (for example, for causing the user to select a color test pattern to be generated) (for example, “Select a color test pattern to output” message is displayed. When the user selects a color test pattern type, the LUT selection unit 162 selects a three-dimensional lookup table capable of generating the selected type of color test pattern. However, the types of color test patterns include, for example, a red gradation color test pattern, a blue gradation color test pattern, and the like.

Subsequently, the three-dimensional lookup table selected by the LUT selection unit 162 in step S13 is read from the LUT storage unit 163, and the three-component color test pattern image data read in step S12 by the LUT conversion processing unit 161. On the other hand, an interpolation calculation process using the read three-dimensional lookup table is executed (step S 14 ). As a result, the three-component color test pattern image data is converted into CMYK image data (hereinafter, particularly referred to as “four-component color test pattern image data”).

  When the processing of step S14 is completed and CMYK image data (that is, four-component color test pattern image data) is generated, the binarization processing unit 164 then applies 2 to the four-component color test pattern image data. A valuation process is executed (step S15). The four-component color test pattern image data subjected to the binarization processing is then sent to the image recording unit 18 and printed out on a recording medium such as paper (step S16). That is, a color test pattern is generated.

<4.3 component color test pattern image data>
<4-1. Possible data values>
The three-component color test pattern image data has the following characteristics in relation to the color test pattern look-up tables b1 and b2.

  That is, data values that can be taken in the three-component color test pattern image data are limited to three-component input values (so-called “lattice points”) corresponding to the output values of the three-dimensional lookup table. In other words, the data values that can be taken in the three-component color test pattern image data are limited to data values such that the weighting coefficient of the interpolation calculation in the LUT conversion is “0”.

  For example, when the configuration of the interpolation calculation using a three-dimensional lookup table is such that the upper 3 bits in 8 bits refer to the table and the weighting coefficient in the interpolation calculation is determined in the lower 5 bits, a three-component color test pattern Data values that can be taken in the image data (that is, values that can be taken as component values of each coordinate in the coordinate space defining the three-component color test pattern image data) are “0x00, 0x20, 0x40, 0x60, 0x80, 0xA0, 0xC0, Limited to “0xE0, 0xFF”. That is, all the data constituting the three-component color test pattern image data corresponds to the lattice points on the coordinate space.

  As a result, the value itself defined as the output value in the three-dimensional lookup table is directly output to the four-component color test pattern image data. That is, the value obtained by referring to the three-dimensional lookup table is output as it is.

  By configuring the three-component color test pattern image data with such data values, the following effects can be obtained.

  That is, in the case of normal image LUT conversion processing, each data in the three-component image data is not necessarily located at a lattice point in a three-dimensional space representing the image data. When a three-component data value (for example, RGB value) that is not located at a grid point is input, the output data value (CMYK value) is a CMYK value corresponding to a grid point adjacent to the input three-component data value. And is calculated by interpolation calculation. Therefore, CMYK values corresponding to adjacent grid points need to be defined so as to be related to each other. That is, CMYK values corresponding to adjacent lattice points are not allowed to take non-continuous values.

  On the other hand, in the case of the LUT conversion processing of the color test pattern in this embodiment, each data in the three-component color test pattern image data is always located at a lattice point in the three-dimensional space representing the image data. Since three-component data values that are not located at grid points are not input, the CMYK values corresponding to the grid points need not be defined so as to be related to each other. That is, the CMYK values corresponding to adjacent lattice points are allowed to take non-continuous values.

  This makes it possible to freely generate a color test pattern lookup table corresponding to one three-component color test pattern image data. In addition, it is possible to generate a plurality of types of color test patterns by performing LUT conversion on one three-component color test pattern image data using different color test pattern lookup tables.

<4-2. Correspondence with Lookup Table for Color Test Pattern>
Referring to FIG. 5, a plurality of types of color test patterns (four-component color test pattern image data in FIG. 5) are obtained from one three-component color test pattern image data (three-component color test pattern image data D3 in FIG. 5). The case where D4 (b1) and D4 (b2)) can be generated will be specifically described. However, in FIG. 5, the data value of the three-component color test pattern image data D3 is defined by the three components (x, y, z).

  For example, in the color test pattern LUT (b1), for an input value of (x, y, z) = (0x20, 0x00, 0x00), (C, M, Y, K) = (20%, 20%, 20%, 20%), and (C, M, Y, K) = (40%, 20) for an input value of (x, y, z) = (0x20, 0x20, 0x00) %, 20%, 20%). When the 3-component color test pattern image data D3 shown in FIG. 5 is LUT-converted using this LUT (b1), 4-component color test pattern image data D4 (b1) is generated. In this case, in the generated color test pattern, a color of (C, M, Y, K) = (20%, 20%, 20%, 20%) appears in the a block.

  On the other hand, in another test pattern LUT (b2), (C, M, Y, K) = (60%, 20) with respect to the input value of (x, y, z) = (0x20, 0x00, 0x00) %, 20%, 20%), and (C, M, Y, K) = (80%) for an input value of (x, y, z) = (0x20, 0x20, 0x00) , 20%, 20%, 20%). When the 3-component color test pattern image data D3 shown in FIG. 5 is LUT-converted using this LUT (b4), 4-component color test pattern image data D4 (b2) is generated. In this case, in the generated color test pattern, a color of (C, M, Y, K) = (60%, 20%, 20%, 20%) appears in the a block.

  In this way, by defining a plurality of color test pattern lookup tables, a plurality of types of color test patterns can be generated from a single three-component color test pattern image data.

<5. effect>
In this embodiment, the following effects can be obtained.

  The first effect is that dedicated hardware for generating a color test pattern is not required as in the prior art. In this embodiment, as shown in FIG. 4, a color test pattern is generated by executing a process that is substantially the same as a print output process of a real image. As apparent from a comparison between FIG. 4 and FIG. 7A, the color test pattern can be generated without providing the dedicated hardware M1 for generating the color test pattern.

  The second effect is that a memory for storing four-component image data is not required. A normal image processing apparatus has a storage unit that stores at least three-component image data. In this embodiment, the color test pattern can be stored not as four components but as three-component color test pattern image data. Therefore, it is possible to generate a color test pattern without providing a storage unit for storing four-component image data. As is apparent from a comparison between FIG. 4 and FIG. 7B, it is possible to generate a color test pattern without providing a memory M3 for storing four-component image data.

  A third effect is that a plurality of types of color test patterns can be generated while reducing the required storage capacity. In this embodiment, it is possible to generate a plurality of types of color test patterns from one three-component color test pattern image data by switching the three-dimensional lookup table used for LUT conversion. For example, when generating an A4 size color test pattern, the storage capacity for further storing one lookup table is smaller than the storage capacity for storing one more A4 size image data. That is, it is possible to efficiently generate a plurality of types of color test patterns with a small amount of data.

  Note that by generating a plurality of types of color test patterns, the user can perform highly accurate printer calibration. For example, a color test pattern lookup table for generating a red gradation color test pattern and a color test pattern lookup table for generating a blue gradation color test pattern may be stored in the LUT storage unit 163. It is possible to generate color test patterns with gradations of red, blue, and blue. By generating a plurality of types of color test patterns in this way, many color patterns can be obtained, and highly accurate printer calibration is possible.

<6. Modification>
<6-1. Modification 1>
In the above embodiment, the data values that can be taken in the three-component color test pattern image data are limited to data values such that the weighting factor of the interpolation calculation in the LUT conversion is “0”. Any data value that is not limited to a simple data value may be taken. That is, in this case, in the LUT conversion processing of the three-component color test pattern image data, as in the case of the normal image LUT conversion processing, when a three-component data value not positioned at a grid point is input, the output data value (CMYK) (Value) is calculated by interpolation using CMYK values corresponding to grid points adjacent to the inputted three-component data value. In this case, in the color test pattern look-up table, CMYK values corresponding to adjacent grid points need to be defined so as to be associated with each other.

  In other words, when the CMYK values corresponding to adjacent grid points are defined in the color test pattern lookup table so as to be related to each other, the data values that can be taken in the three-component color test pattern image data are: Any data value that is not limited to a data value such that the weighting coefficient of the interpolation calculation in the LUT conversion is “0” can be taken.

  In the case of such a configuration, data values that can be taken in the three-component color test pattern image data may be limited within a predetermined numerical range. By doing this, it is possible to reduce the number of output values to be defined in the corresponding color test pattern lookup table, and to reduce the storage capacity of the color test pattern lookup table.

<6-2. Modification 2>
In the above embodiment, the three-component color test pattern image data storage unit is configured to store one three-component color test pattern image data. It may be stored. As a result, it is possible to generate three-component color test pattern image data of various designs.

  By defining a plurality of three-component color test pattern image data, a plurality of types of color test patterns can be generated from each of the three-component color test pattern image data. For example, if the three-component color test pattern image data E3 shown in FIG. 6 is stored in addition to the three-component color test pattern image data D3 shown in FIG. 5, each of the color test pattern look-up tables b1 and b2 is stored. It is possible to generate four types of four-component color test pattern image data D4 (b1), D4 (b2), E4 (b1), and E4 (b2).

  In this case, not only the color type of the color test pattern to be generated (that is, the type of the color test pattern lookup table) but also the color test pattern to be generated for the user who has instructed the generation of the color test pattern. Are selected (that is, the type of three-component color test pattern image data).

<6-3. Modification 3>
A program (hereinafter referred to as a “color test pattern generation program”) that causes the digital multi-function peripheral 1 in the first embodiment and each modification to execute the above-described color test pattern generation processing (hereinafter referred to as “color test pattern generation program”) is a computer-readable storage. It can also be stored in a medium (for example, a magneto-optical disk, an optical disk (including a CD or DVD), a magnetic disk, a memory card, an IC card, etc.). That is, the color test pattern generation program is stored in these storage media, and the color test pattern generation program is read from the computer by, for example, mounting these storage media on the magneto-optical disk device of the computer, etc. The function of the color image processing apparatus or the color image processing method may be executed.

Further, the three-component color test pattern image data and the color test pattern look-up table capable of converting the three-component color test pattern image data into CMYK image data in the first embodiment and each modification described above (that is, The three-component color test pattern image data and the color test pattern look-up table related to each other can be stored in a computer-readable storage medium. In this case, it is preferable to store the above program in the same storage medium.

Also in this case, by mounting the storage medium storing these data on the magneto-optical disk device of the computer, etc., LUT conversion of the three-component color test pattern image data and the three-component color test pattern image data from the computer is performed. The color test pattern lookup table to be used may be read out and stored in the three-component color test pattern image data storage unit 191 and the LUT storage unit 163, respectively.

1 is a block diagram illustrating a configuration of a digital multifunction peripheral according to an embodiment. FIG. It is a flowchart which shows the processing operation in the case of printing out the image data read in the image reading part. It is a flowchart which shows the production | generation processing operation | movement of a color test pattern. It is the figure which showed typically a mode that the image data used as a process target received in order in each function part shown in FIG. It is explanatory drawing which showed typically a mode that several types of color test patterns were produced | generated from one three-component color test pattern image data. It is explanatory drawing regarding the case where it has two or more 3 component color test pattern image data. It is the figure which showed typically the production | generation process of the color test pattern performed conventionally.

Explanation of symbols

1 Digital MFP 16 Image processing unit 17 Image reading unit 18 Image recording unit 19 Image memory 161 LUT conversion processing unit 162 LUT selection unit 163 LUT storage unit 164 Binary processing unit 191 Three-component color test pattern image data memory

Claims (7)

Storage means for storing three-component color test pattern image data expressed only by grid point coordinate values in a three-dimensional coordinate space;
Conversion processing means for converting image data color-expressed with three component values into CMYK image data by interpolation using a three-dimensional lookup table;
Image forming means for forming an image of the CMYK image data on a recording medium;
With
The conversion processing means is
A data value composed of four components of CMYK is output from image data of an actual image color-represented by three component values with respect to a data value composed of coordinate values in a color space representing the image data of the actual image. 1 is converted into CMYK image data by interpolation using a three-dimensional lookup table,
For the three-component color test pattern image data, the third-component color test pattern image data dedicated to the three-component color test pattern image data for outputting a data value composed of four components of CMYK with respect to a data value composed of the lattice point coordinate values in the three-dimensional coordinate space. A color image processing apparatus, wherein the image data is converted into CMYK image data by interpolation using a two-dimensional lookup table. The color image processing apparatus according to claim 1,
A color image processing apparatus comprising a plurality of types of the second three-dimensional lookup table. The color image processing apparatus according to claim 2,
A three-dimensional lookup table that allows the user to select which of the plurality of types of the second three-dimensional lookup tables to use when performing the CMYK conversion on the three-component color test pattern image data. Selection acceptance means,
A color image processing apparatus, further comprising: A color test pattern image data generation process for generating color test pattern image data;
A conversion processing step of converting the image data of the color test pattern into CMYK image data by performing an interpolation operation using a three-dimensional lookup table on the image data of the color test pattern;
An image forming step of forming an image of the CMYK image data on a recording medium;
With
The image data of the color test pattern is expressed only by lattice point coordinate values in a three-dimensional coordinate space ,
The three-dimensional lookup table is
And outputs the data value consisting of 4 components of the CMYK to data values consisting of the grid point coordinate values of the three-dimensional coordinate space, and wherein the look-up table der Rukoto dedicated to image data of the color test pattern Color image processing method. The color image processing method according to claim 4,
The conversion process step
A three-dimensional lookup table selection step of selecting one of a plurality of three-dimensional lookup tables;
With
A color image processing method comprising: performing an interpolation operation on the image data of the color test pattern using the three-dimensional lookup table selected in the three-dimensional lookup table selection step.   A computer-readable storage medium storing a program for causing a computer to execute the color image processing method according to claim 4. Image data of a color test pattern expressed only by grid point coordinate values in a three-dimensional coordinate space;
A three-dimensional lookup table capable of converting the image data of the color test pattern into CMYK image data;
A program for executing a conversion processing step for converting the image data of the color test pattern into CMYK image data by performing an interpolation operation using the three-dimensional lookup table on the image data of the color test pattern;
Stores,
The three-dimensional lookup table is
A computer dedicated to image data of the color test pattern, which outputs data values composed of four components of CMYK to data values composed of the grid point coordinate values in the three-dimensional coordinate space. Is a readable storage medium.

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