JP2004012699A - Image processor, its method and image processing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is difficult to obtain a similar printing result at different printers, especially in a printing system constituted by connecting several printers through a network, because printing characteristics are changed by changes with time or the like in the printer. <P>SOLUTION: In the printer selected as a processing object by a server, a patch image of specified gradation is outputted on a recording medium (S41), a reading size for the patch image is set in accordance with the printer by the server (S42), the patch image with the reading size is read by a scanner (S43), and a calibration table is prepared based on a patch data by the server (S44). Then, the calibration table is down-loaded to an object printer (S45). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus and method, and an image processing system, and more particularly, to an image processing apparatus and method capable of performing stable color reproduction, and an image processing system.
[0002]
[Prior art]
Generally, when color printing is performed by a color printer connected to a personal computer (PC), the printing result changes because the printing characteristics of the color printer change over time. Such a change in printing characteristics in a printer is generally called aging. The secular change is caused by the printing environment such as temperature and humidity, remaining amount of toner, use degree of the printer drum, and the like.
[0003]
Also, for example, even between the printers A and B, which are the same model, the printing characteristics do not always coincide with each other due to the above-mentioned external factors, and variations usually occur.
[0004]
[Problems to be solved by the invention]
As described above, since the print characteristics of a color printer change over time, if print data created based on the printer characteristics at a certain time is printed after a further time has passed, a desired print No results were obtained.
[0005]
Similarly, between printers of the same model, when print data created based on the characteristics of the printer A is printed by the printer B, a desired print result is often not obtained.
[0006]
Therefore, in a print system in which a plurality of printers are connected via a network, it is difficult to obtain similar print results between different printers.
[0007]
The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an image processing apparatus and a method that can always obtain stable color reproducibility.
[0008]
It is another object of the present invention to provide an image processing system that realizes substantially the same color reproduction between a plurality of models.
[0009]
[Means for Solving the Problems]
As one means for achieving the above object, the image processing apparatus of the present invention has the following configuration.
[0010]
That is, a patch output unit that outputs a patch image having a predetermined gradation on a recording medium, a reading size setting unit that sets a reading size for the patch image, and reading the patch image based on the reading size, It is characterized by comprising reading means for obtaining patch data and correction data generating means for generating color correction data based on the patch data.
[0011]
Similarly, the image processing system of the present invention has the following configuration.
[0012]
That is, an image processing system in which a server device, a scanner, and a plurality of image forming devices are connected via a network, wherein the server device transmits an image forming device to be subjected to color correction from the plurality of image forming devices. Selecting means for selecting, and setting a reading size for a patch image of a predetermined gradation output from the selected image forming apparatus on a recording medium according to the image forming apparatus, and instructing the scanner on the reading size information; Reading size setting means, patch data obtaining means for obtaining patch data obtained by reading the patch image based on the reading size information in the scanner, and the selected image forming apparatus based on the patch data. Correction data creating means for creating color correction data for And having a correction data transfer means for transferring the-option image forming apparatus.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0014]
<First embodiment>
[System Configuration] FIG. 1 is a diagram showing a configuration of an image processing system according to the present embodiment. In FIG. 1, reference numeral 1 denotes a server PC connected to a network 5, on which software for realizing the present system is installed.
[0015]
Reference numeral 2 denotes a printer connected to the network 5, which is a target of correction (calibration) in the present system. The printer 2 is configured to perform printing according to instructions from a plurality of PCs connected to the network 5. The printer 2 further includes a calibration data storage unit 21 therein, and downloads and stores calibration data, which will be described later, from the PC 1.
[0016]
Here, the server PC1 is connected with the scanner 3 for measuring the patch data output from the printer 2, but it is of course possible to use the scanner 3 for other purposes such as document input.
[0017]
Reference numeral 4 denotes a client PC connected to the network 5, which performs creation, editing, and printing instructions of desired print data. Generally, calibration for the printer 2 is performed by the system administrator from the server PC 1, and normal print data printing is performed by the client PC 4.
[0018]
In the printer 2 of the present embodiment, stable color reproduction is always possible by performing calibration based on calibration data created as described later. Hereinafter, a method of creating calibration data according to the present embodiment will be described with reference to the flowchart of FIG.
[0019]
Output of Patch Data First, in step S41, the PC 1 instructs the printer 2 to output patch data, and the printer 2 outputs the patch data. Here, it is assumed that a plurality of printers are connected to the network 5. In this case, it is necessary to specify in advance a printer to be calibrated. Hereinafter, a method for specifying a printer according to the present embodiment will be described.
[0020]
FIG. 3 is a diagram illustrating an example of a user interface (UI) for specifying an output target printer. In the UI shown in the drawing, the user selects a printer name to be calibrated from the pull-down menu 122 in the dialog 121. At this time, the server PC 1 sets a scan size (details will be described later) corresponding to the characteristics of the selected printer. This setting is performed by referring to a table associating the printer name with the scan size as shown in FIG. Note that this association table is created in advance and stored in the server PC1.
[0021]
Note that a protocol and a command for specifying a printer follow a rule of network management, but a specific example is not particularly limited in the present embodiment.
[0022]
FIG. 5 is a diagram illustrating an example of the patch data output in step S41. As shown in the drawing, a total of 1024 blocks, each of which is divided vertically and horizontally into 32 within one page, are prepared as the patch data of the present embodiment. In the horizontal direction of the patch data, 256 blocks are arranged respectively for cyan (C), magenta (M), yellow (Y), and black (K), which are the basic colors of the printing toner. The numerical values described in each block indicate the subscript of the array, and the relationship between the subscript of the array and the actual data value is configured as shown in the table of FIG. That is, one block in the present embodiment is composed of single-color, single-tone data. For example, the actual output data value for array 0 in FIG. 5 is 0 according to FIG. , 255 for array 63. In this embodiment, a system of 8-bit representation for each color of CMYK is assumed, and an example in which a numerical value of 0 to 255 is used as an output data value is shown. What is necessary is just to change the output data value in the correspondence table shown. In FIG. 5, the same arrangement is described for every four blocks adjacent in the horizontal direction, but the four blocks indicate blocks of M, C, Y, and K colors sequentially from the left.
[0023]
In the patch data shown in FIG. 5, four blocks each of 32 gradations of arrays 0 to 31 belonging to the highlight side are arranged, and the arrays 33, 35, 37,. . . Eight blocks each having 16 gradations of 61 and 63 are arranged. In the present embodiment, the difference in the number of gradations between the highlight side and the shadow side is that more detailed gradation information is required on the highlight side of the present system than on the shadow side. That's why. Further, the reason why the number of blocks arranged on the shadow side is larger than that on the highlight side is that there is a tendency that the variation in input values in the scanner is larger on the shadow side than on the highlight side.
[0024]
The patch data shown in FIG. 5 is output from the printer 2 in accordance with an instruction from the PC 1 as described above. According to the instruction, the patch data may be generated based on the information, or the patch data may be generated by transmitting the patch data configuration information from the PC 1 to the printer 2. The patch data configuration information depends on the command system of the printer 2, but is not particularly limited here.
[0025]
-Scan Size Setting Next, in step S42, the scan size for scanning the above-described patch data is set.
[0026]
First, the scan size in the present embodiment will be described with reference to FIG.
[0027]
One block constituting the patch data shown in FIG. 5 has a size of, for example, 7 mm × 7 mm. This size corresponds to, for example, the block area 31 shown in FIG. It is desirable that the density in the block area 31 is uniform, but in the case of an electrophotographic printer engine, the density at the periphery of one block tends to be higher than the density at the center. This is called the edge effect and is mostly due to the development process, but will not be described in detail here. Further, the degree of these edge effects differs depending on the type of the printer engine because the developing process is a main factor.
[0028]
In the present embodiment, in consideration of the edge effect, all the pixels in the block area 31 are not read at the time of scanning, but are read while avoiding the peripheral portion of the block area 31. Then, an average of the read predetermined number of pixel values is obtained, and this is used as a block signal. Therefore, it is desirable to read as many pixels as possible in order to absorb the density fluctuation in the patch surface, the cause of the variation in the scanner sensor, and the like. Therefore, the present embodiment is characterized in that the scan size is set as large as possible according to the characteristics of the edge effect of the printer engine.
[0029]
In FIG. 7, areas 32, 33, and 34 located within a block area 31 of 7 mm × 7 mm have scan sizes of 2 mm × 2 mm, 3 mm × 3 mm, and 4 mm × 4 mm, respectively. Equivalent to.
[0030]
The scan in the present embodiment is executed by the scanner 3 via a scanner driver configured on the PC 1, and the scanner driver specifies a scan resolution, a scan size, and the like. Specifically, a table indicating the correspondence between the printer name and the scan size as shown in FIG. 4 is stored in advance in the memory in the server PC 1, and the scanner driver determines the scan size (scan level) corresponding to the printer 2. Determined based on the table and set in the scanner 3. That is, if the printer 2 corresponds to the scan level 1, the area 32 in FIG. 7 is set as the scan size, and if the printer 2 corresponds to the scan level 2, the area 33 is set.
[0031]
[Scan Processing] Next, in step S43, the patch data output from the printer 2 is measured by the scanner 3 based on the scan level as described above, and the RGB signal values for each block are sent to the PC1. The PC1 calculates an average of four locations (for 32 gradations) on the highlight side and an average of eight locations (for 16 gradations) on the shadow side based on the input values and the block arrangement of the patch data. As a result, RGB signal values of 48 gradations for each color of CMYK are obtained. Here, by referring to a previously prepared brightness / density conversion table (not shown) showing the correspondence between the RGB brightness signal of the scanner 3 and the CMYK density signal of the printer 2, the 48-level brightness signal is converted to the 48-level brightness signal. (CMYK value) can be obtained.
[0032]
Next, in step S44, a calibration table is created in the PC1. Hereinafter, the process of creating the calibration table in the present embodiment will be described with reference to FIG.
[0033]
FIG. 8A is a diagram showing density characteristic values of 48 gradations obtained by the preceding scanning process. FIG. 3 shows an input / output relationship curve, which is obtained by interpolation calculation based on values for 48 gradations. Although only one color is described here, the same process is actually performed for each of CMYK colors.
[0034]
Here, a linear curve as shown in FIG. 8C is defined in advance as an ideal value of the density characteristic. Therefore, in order to bring the current density characteristic shown in FIG. 8A close to the ideal characteristic shown in FIG. 8C, based on the characteristic shown in FIG. 8B corresponding to the inverse function of FIG. Calculate the calibration table. That is, by performing correction based on the characteristic shown in FIG. 8B with respect to the characteristic shown in FIG. 8A, the ideal characteristic shown in FIG. 8C is obtained as a result.
[0035]
Next, in step S45, the calibration table created by the PC 1 is downloaded to the printer 2 and stored in the calibration data storage unit 21. Note that commands related to download depend on the command system of the printer 2, but detailed description is omitted here.
[0036]
FIG. 9 is a flowchart illustrating a download data receiving process in the printer 2. First, it is determined in step S70 whether data has been received. If it has not been received, step S70 is repeated. If it has been received, the received data is analyzed in step S71. The analysis result is determined in step S72. If the received data is a calibration download command, the flow advances to step S73 to store the calibration data in the calibration data storage unit 21 as described above. On the other hand, if it is determined that the received command is not the calibration download command, a process corresponding to the received data is performed in step S74.
[0037]
Calibration Process The calibration process in the printer 2 will be described below.
[0038]
Normally, print data is sent from the application on the PC 1 to the printer 2 via the printer driver on the PC 1. In the printer 2, the analysis of the print data, the configuration of the page layout, the image processing, the print processing, and the like are performed in the above-described step S74 of FIG.
[0039]
Here, FIG. 10 shows a flowchart of the calibration process in the printer 2. First, in step S110, color fine adjustment processing such as luminance correction and contrast correction is performed on the input signals RGB. Next, in step S111, a color matching process for matching the color of the monitor with the color of the printer print is performed. Next, in step S112, a luminance / density conversion process of converting the luminance RGB as the input signal into the density CMYK as the print signal of the printer is performed. Then, in step S113, a calibration process is performed. That is, the CMYK 8-bit multivalued signals are used as input / output signals, and the output characteristics are corrected to be linear using the calibration table data stored in the calibration data storage unit. Next, in step S114, the CMYK 8-bit signal after the calibration is converted into a signal conforming to the output system, for example, binarized into a CMYK 1-bit signal.
[0040]
Thereby, the gradation characteristic of the output signal of each color in the present embodiment can be made linear.
[0041]
[User Interface] An example of a user interface (UI) related to calibration in the PC 1 will be described below with reference to FIGS. Note that the calibration data creation system according to the present embodiment is realized as a type of application on the PC 1.
[0042]
FIG. 11 is a diagram illustrating a UI screen transition example according to the present embodiment. When the application is started in step S800, it is first determined in step S801 whether necessary printer drivers and scanner drivers are installed in the PC1 system. If the necessary driver has not been installed, a driver check error is displayed in step S814, and the process ends in step S813.
[0043]
If the necessary driver has been installed in step S801, the main screen is displayed in step S802. FIG. 12 shows an example of the main screen. Basically, the other screens are shifted to other related screens by pressing the “next”, “return”, “cancel”, and “help” buttons as in FIG. In the main screen of FIG. 12, three types of selection menus, "new measurement", "open existing measurement data file", and "delete download data" are prepared.
[0044]
If “new measurement” is selected and “next” is pressed, the process proceeds to step S804. In step S804, the patch data is output to the printer 2, and then in step S807, the patch data is measured in the scanner 3 as described above. Then, in step S808, calibration is applied, that is, calibration data is created and downloaded to the printer 2 (S43 and S44 in FIG. 2).
[0045]
In the UI of step S808, a button for shifting to steps S809 and S810 is prepared, and the screen shifts to each screen when the user presses the button. Step S809 is a screen for saving the measurement data, and instructs to save the scan data measured in step S807. The scan data storage file is used in a process using existing measurement data described later. Step S810 is a display screen for detailed information, and displays detailed information such as measured density characteristics. After exiting steps S809 and S810, the process returns to step S808.
[0046]
Then, in step S811, a processing end screen is displayed. If "end of application" is designated on the screen, the process ends in step S813, and if "return to main screen" is designated, the process returns to step S802.
[0047]
When "Open measurement data" is selected on the main screen in step S802 and "Next" is pressed, a measurement data instruction screen in step S805 is displayed. Here, when the "reference" button is pressed, the screen shifts to the measurement data reading screen in step S812, and it is possible to search for detailed measurement data. The measurement data read here is the data file saved in step S809 described above. Then, in step S808, calibration is applied. Since the subsequent processing is as described above, the description will be omitted.
[0048]
On the main screen in step S802, selecting "delete download data" and pressing "next" deletes the calibration data stored in the calibration data storage unit 21 of the printer 2 in step S806. Note that this deletion processing is performed based on an instruction by a command from the PC 1 to the printer 2, but this command is not particularly mentioned here. Then, in step S811, the process proceeds to the processing end screen S811.
[0049]
[Summary] As described above, according to the present embodiment, calibration data can be created and downloaded to the printer 2 according to an instruction from the server PC 1. Color printing can be performed.
[0050]
Further, by setting a scan size when scanning a patch in accordance with the characteristics of the printer to be calibrated, more accurate calibration data corresponding to the printer can be created.
[0051]
Therefore, highly accurate calibration can be realized using an existing device without using an expensive densitometer or the like.
[0052]
In the present embodiment, an example is shown in which a color laser beam printer (LBP) is used as a printer device constituting the system. However, the present invention can be similarly applied to a printer device using another printing method such as an ink jet printer. . Further, the connection form and the protocol in the network are not particularly described in detail, but any embodiment can be similarly implemented.
[0053]
[Other embodiments]
The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but may be a device including one device (for example, a copying machine, a facsimile machine, etc.). May be applied.
[0054]
Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus to store the storage medium. Needless to say, this can also be achieved by reading out and executing the program code stored in the.
[0055]
In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
[0056]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.
[0057]
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. It goes without saying that a case where a part of the actual processing is performed and the function of the above-described embodiment is realized by the processing is also included.
[0058]
Further, after the program code read from the storage medium is written into a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that a CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0059]
【The invention's effect】
As described above, according to the present invention, stable color reproducibility can always be obtained in the image forming apparatus. Further, substantially the same color reproduction can be realized between a plurality of models.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an image processing system according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating calibration data creation processing according to the present embodiment.
FIG. 3 is a diagram illustrating an example of a UI screen for specifying an output target printer.
FIG. 4 is a diagram showing a correspondence table between a printer name and a scan size.
FIG. 5 is a diagram illustrating an example of patch data according to the embodiment.
FIG. 6 is a diagram illustrating a relationship between subscripts and actual data values in a patch data array.
FIG. 7 is a diagram for explaining a scan size in the embodiment.
FIG. 8 is a diagram illustrating a calibration table according to the embodiment.
FIG. 9 is a flowchart showing a calibration data receiving process in the printer of the embodiment.
FIG. 10 is a flowchart illustrating a calibration process in the printer of the embodiment.
FIG. 11 is a diagram illustrating an example of a UI screen transition according to the embodiment.
FIG. 12 is a diagram illustrating an example of a main screen according to the present embodiment.
[Explanation of symbols]
1 server PC
2 Printer 3 Scanner 4 Client PC
5 Network 21 Calibration data storage

Claims (13)

Patch output means for outputting a patch image having a predetermined gradation on a recording medium,
Reading size setting means for setting a reading size for the patch image;
Reading means for obtaining patch data by reading the patch image based on the read size;
Correction data creating means for creating color correction data based on the patch data,
An image processing apparatus comprising: 2. The image processing apparatus according to claim 1, wherein the reading size setting unit sets a reading size for a predetermined block of the patch image. 3. The image processing apparatus according to claim 2, wherein the predetermined block of the patch image is a block composed of a single color and a single tone. The image processing apparatus according to claim 3, wherein the reading size setting unit sets a reading size such that the reading is performed excluding an outer peripheral portion of the block. 2. The image processing apparatus according to claim 1, further comprising a correction unit configured to perform color correction of the image data using the color correction data. The image processing apparatus according to claim 5, further comprising an image forming unit that forms an image based on the image data after the color correction by the correction unit. An image processing system in which a server device, a scanner, and a plurality of image forming apparatuses are connected via a network,
The server device,
Selecting means for selecting an image forming apparatus to be subjected to color correction from the plurality of image forming apparatuses;
Reading size setting means for setting a reading size for a patch image of a predetermined gradation outputted from the selected image forming apparatus on a recording medium in accordance with the image forming apparatus, and instructing the scanner of the reading size information; ,
Patch data acquisition means for acquiring patch data obtained by reading the patch image based on the read size information in the scanner,
Correction data creating means for creating color correction data for the selected image forming apparatus based on the patch data,
Correction data transfer means for transferring the color correction data to the selected image forming apparatus;
An image processing system comprising: The image processing system according to claim 7, wherein the reading size setting unit sets a reading size for a block including a single color and a single tone in the patch image. 9. The image processing system according to claim 8, wherein the reading size setting unit sets a reading size so as to read the block except for an outer peripheral portion of the block. The image processing system according to claim 9, wherein the reading size setting unit sets an outer peripheral portion size to be excluded from a predetermined block in the patch image according to the image forming apparatus. A patch output step of outputting a patch image having a predetermined gradation on a recording medium,
A reading size setting step of setting a reading size for the patch image;
A reading step of obtaining patch data by reading the patch image based on the reading size;
A correction data creating step of creating color correction data based on the patch data,
An image processing method comprising: A program which operates on a computer to cause the computer to operate as the server device according to any one of claims 7 to 10. A recording medium on which the program according to claim 12 is recorded.

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