JPH09200544A - Color printing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically prepare a table for performing transformation from an editing color space to a printing color space. SOLUTION: An editing device 12 is provided with a CMYK editing color space and a printer 14 is provided with a C'M'Y'K' printing color space. Plural color samples are successively displayed at a display device 22 and the color samples are color-measured in an XYZ absolute color space by a colorimeter 26. The colorimetry result is transmitted to the printer 14 as a colorimetry table. A table arithmetic part 48 collates the contents of the colorimetry table (CMYK=>XYZ) and a printing color table (XYZ=>C'M'Y'K') and prepares a color space transformation table (CMYK=>C'M'Y'K').

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printing system, and more particularly to a system provided with a color space conversion table for converting each color in an editing color space into a color in a printing color space.

[0002]

2. Description of the Related Art With the progress of computer technology and printing technology, it has become possible to easily edit and print a print image by using a workstation, a personal computer, a color printer connected to the workstation or the like. Such desktop publishing (DTP)
In response to the demand for more economical and higher quality printing, recently, color printers and various DTP software, which are relatively inexpensive and have good performance, have been provided. On the other hand, a color printer is connected to a network, and one color printer is shared by a plurality of computers via such a network. In the DTP via the above network, in order to efficiently transmit print data, various page description languages (page d
An escription language (PDL) has been developed, and print data is transmitted from a computer to a printer in such a PDL format.

Conventionally, a general color printing system used for the above-mentioned DTP is composed of an editing device for editing a document and a printing device connected to the editing device for printing a document. If they do not match, a color for converting the color from the editing color space of the editing device (for example, CMYK) to the printing color space unique to the printing device (for example, C'M'Y'K '). Space conversion processing is required.

As one of such color space conversion means, one using a direct lookup table [DLUT] is known, and print data from the editing device is color-converted in such a color space conversion table. Will be printed later.

[0005]

However, even if such a color space conversion table is used, the color tone of the display of the editing device may change over time or the display characteristics may vary. There is a problem in that the color displayed on the display of the editing device and the printed color are different. To deal with such problems, it is difficult and cumbersome for the user to adjust the hue of the display, while modifying the color space conversion table is also very difficult for users who have little knowledge about color conversion. There was a problem.

[0006] Some DTP software is designed to perform color designation on the premise of the CMYK color space unique to the ink used in a printing company. However, print data with such color designation is used. When printing with a toner-type printer owned by a general user, it is necessary to convert the color space corresponding thereto. For example, in an editing device, a single color is (C, M, Y, K) = (100, 0,
Even if you specify (0, 0), if you actually print (C,
M, Y, K) = (90,5,5,0) unless the composite color is used, it is often impossible to match the colors. In such a case, it is necessary to modify the color space conversion table in order to accurately reproduce the color, but in the conventional system, the user cannot simply modify the color space conversion table.

Some application software for reading an image has a function of designating CMYK corresponding to a desired ink when converting a photographic image scanned in RGB into CMYK. In this case, even if the CMYK is the same, the colors reproduced by different devices are different. Therefore, in order to faithfully reproduce the colors, it is necessary to correct the contents of the color space conversion table.

Further, when the editing software is changed and the input color space is changed, it is necessary to update the contents of the color space conversion table. However, the conventional system sufficiently copes with the problem. There wasn't.

Incidentally, Japanese Patent Application Laid-Open No. 7-87521 discloses that
In order to reduce the difference between the preview screen and the print result, a device is disclosed which detects the light emission amount of the preview screen and compensates the color reproduction range, the linearity of luminance, and the color reproducibility based on the detection result. There is. However, such a device corrects the preview screen, and cannot automatically create the color space conversion table.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to match a color displayed on a monitor of an editing apparatus with a color actually printed,
Another object of the present invention is to make it possible to very easily create a color space conversion table that allows even a user who has little knowledge to accurately match colors.

[0011]

In order to achieve the above object, the present invention provides an editing device for editing a print image, and a color in the editing color space of the editing device to a color in the printing color space. In a color printing system including a color space conversion table for converting, and a printing device for performing color printing of the print image after the color conversion, in the display unit on which the edited print image is displayed, the edited color is displayed. Color sample output means for displaying each color in the space as an image as a color sample, a colorimeter for measuring the color sample displayed on the display as a color in the absolute color space, and a color measurement result of the colorimeter. Conversion table creating means for creating the color space conversion table based on the above.

According to the above arrangement, the color space conversion table is automatically created by utilizing the color measurement for the color sample displayed on the display. That is, by the color sample output means, an edit color space (eg CM
A color sample showing a plurality of typical colors in the YK color space is displayed, and a colorimeter is used at that time to measure the color of each color sample as a color in an absolute color space (for example, XYZ color space). To be colored. Then, the color space conversion table creating means creates a color space conversion table based on the color measurement result. Therefore, according to the present invention, the color space conversion table can be automatically created only by the color measurement, and thus the color on the display and the color to be printed can be accurately matched.

In the present invention, preferably, the conversion table creating means creates a colorimetric table in which each color sample in the editing color space is associated with a colorimetric value in the absolute color space. And a print color table storage unit that stores a print color table in which each color on the absolute color space is associated with a color on the print color space, and the contents of the color measurement table and the print color table are compared. ,
Table calculation means for creating the color space conversion table.

That is, a colorimetric table is created by colorimetry, and the contents of the table and the print color table stored in advance are matched to create a color space conversion table. For example, the edit color space is composed of CMYK, the print color space is composed of C′M′Y′K ′, and the absolute color space is XY.
In the case of Z, the colorimetric table is configured by associating the XYZ colorimetric values with the CMYK representative values, and the print color table is C'M'Y'K with the XYZ representative values.
It is configured as an association of the values of '. The table calculation means basically specifies the CMYK value and the C′M′Y′K ′ value for the same XYZ, and associates them to convert CMYK to C′M′Y′K ′. A color space conversion table is created automatically.

Since the contents of the print color table are based on the third objective standard of absolute color space, the contents are not influenced by the circumstances on the editing device side. That is, the print color table is unique to the printing apparatus.

In a preferred aspect of the present invention, the table calculation means creates the color space conversion table within a range in which the printing device can reproduce colors. Thereby, for example, it is possible to prevent the problem that the toner is excessively overlapped and the black solid is generated, and the capacity of the table can be suppressed to the necessary minimum.

Further, in a preferred aspect of the present invention, there is further provided a color sample adding means for adding the color sample. As color samples, various kinds are usually prepared for the number necessary for creating the color space conversion table, but if there are colors that you want to express accurately, use the color sample adding means. The user can specify the color and reflect the color measurement result in the color space conversion table.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of the printing system according to the present invention. This printing system includes an editing device 12 equipped with document editing software,
It is composed of a printing device 14 connected to the editing device 12 by a data bus 13. Data bus 1
If a plurality of editing devices are connected to the printer 3, the printer 14 can be shared among these devices.

The editing device 12 is substantially composed of a computer and has a main body 20, a display 22 and a keyboard 24. In this embodiment, the colorimeter 26 is further provided in the main body 2.
Connected to 0. The colorimeter 26 is a device for optically measuring a patch (color sample) 28, which will be described later, displayed on the screen of the display 22, and has a plurality of light emitting elements and light receiving elements built therein. On the other hand, the printing device 14 is roughly classified into
It is composed of a printer server 16 and a printer 18. The printer server 16 is essentially a computer,
It has a main body 30, a display 32, and a keyboard 34. The print data processed by the printer server 16 is the printer 1
8 and the print image is printed. This printer 1
Although various types of printers can be applied as the printer 8, a toner type printer is used in this embodiment.

FIG. 2 shows a specific configuration of the system shown in FIG. 1 as a functional block diagram. In the editing device 12, the DTP editing unit 36 is composed of software for editing a document including characters, photographs, figures, etc., and the print data described in the PDL is sent to the printing device 14 as its output. The patch image forming unit 38 functions as a color sample output unit that images a plurality of patch data read from the patch data storage unit 40 and outputs the image data to the display unit 22. In this embodiment, the color sample (patch) shows a representative color in the CMYK color space as the editing color space, and, for example, about 100 color samples are prepared. FIG. 3 shows an example of a group of patch data, and each patch data is a combination of the respective values of CMYK.

The addition unit 44 of FIG. 2 is for adding a color desired by the user as a color sample, and new CMYK values are added as patch data to the patch data storage unit 40. The added patch data is illustrated at the bottom of FIG. For example, when there is a color to be reproduced more accurately such as a corporation color, the user uses the keyboard 24 to add the additional portion 4
4, the contents of the patch data can be given.

The colorimetric table creating unit 42 forms a colorimetric table in which each color sample is associated with its colorimetric value. Each color sample is represented by each value of CMYK, and the colorimetric value is X.
It is shown by each value of YZ. That is, the colorimeter 26 is XYZ.
Color measurement is performed in the color space, and the colorimeter 26 measures the color sample displayed on the display device 22 with each value of XYZ and outputs the measurement result to the color measurement table creating unit 42. FIG. 5 shows an example of the colorimetric table, and the group of patch data shown in FIG. 4 (left side of FIG. 5) and each colorimetric value (right side of FIG. 5) acquired by colorimetry are associated with each other. Has been. X
Basically all colors can be expressed in YZ color space,
Since the expression range thereof is wider than that of the CMYK color space or the RGB color space, and the output of the colorimeter 26 is given in XYZ, the XYZ color is used as the color space (absolute color space) for color measurement in this embodiment. Utilizes space. Of course, it is possible to use another color space as the absolute color space.

On the other hand, in FIG. 2, the printing device 14 converts a CMYK editing color space into a device-specific C'M'Y'K 'printing color space (described later) as in the conventional device. (See FIG. 7)). That is, the print data transmitted from the editing device 12 is sent to the color space conversion table, and the color data is sent to the CM.
The YK format is converted into the C'M'Y'K 'format unique to the device. The print data after the conversion is the printer 1
8 and printing is performed.

In FIG. 2, the print color table storage unit 50 is shown.
In the table, a print color table in which the values of the print color space (C′M′Y′K ′) are associated with the respective colors in the absolute color space (XYZ) is stored. FIG. 6 exemplifies the contents of the print color table, and the representative values of XYZ (on the left side of FIG. 6).
Is associated with the value of C′M′Y′K ′ (on the right side of FIG. 6). That is, this table shows what kind of color each color represented by XYZ is described in the color space of the printing apparatus 14, and the contents of this table are unique to the printing apparatus 14 and It is not affected by the circumstances on the side. In other words, even if the edit color space is changed, it is not necessary to change the print color table. The contents of this table are obtained in advance by experiments or the like, and are written in the print color table storage unit 50 including a ROM or the like before the product is shipped.

The contents of the printing color table may be rewritten when the characteristics of the printing apparatus change with time or the toner is changed. Alternatively, when there are a plurality of print modes, a print color table can be provided for each mode and switched.

The table calculation unit 48 matches the contents of the color measurement table sent from the editing device 12 via the data bus 13 with the print color table stored in the print color table storage unit 50, and the color space conversion unit. Create 46. That is, by referring to the color measurement table of FIG. 5 and the print color table of FIG. 6, the CMYK value and the C′M′Y′K ′ value associated with the same XYZ value in both tables are specified, The two are associated with each other and tabulated. By the way, when the same XYZ value does not exist in the print color table for a certain XYZ value in the color measurement table, one closest XYZ value in the print color table is specified and associated with CMYK. C′M′Y′K ′ may be obtained, or a certain X, Y, Z value in the color measurement table may be approximated to a plurality of X values in the print color table.
CMYK is specified by specifying YZ and using interpolation processing.
C′M′Y′K ′ corresponding to As described above, various methods can be applied as a method of associating CMYK and C′M′Y′K ′ between the two tables using the XYZ values as a common key. The color space conversion table thus obtained is written in the color space conversion unit 46 according to a command from the table calculation unit 48.

In FIG. 2, the conversion table creating means is shown by 100, and the means is constructed across the editing device 12 and the printing device 14. In this embodiment, the table calculation unit 48 and the print color table storage unit 50 are provided in the printing device 14, but they may be provided in the editing device 12. On the contrary, the colorimetric table creating unit 42 may be provided in the printing device 14, and in this case, necessary data such as the colorimetric result of the colorimeter 26 needs to be transmitted to the printing device 14. .

Incidentally, the CPU incorporated in the main body 20 of the editing apparatus 12 shown in FIG. 1 is the DTP editing unit 36 shown in FIG.
And the patch image forming unit 38, the adding unit 44, and the colorimetric table creating unit 42, and the storage unit in the main body 20 realizes the patch data storage unit 40, DTP editing software, and the above-described functions. The software for is stored. This is the same as in the printing device 14 of FIG. 1, and the CP built in the main body 30 of the printer server 16 is used.
U functions as the color space conversion unit 46 and the table calculation unit 48 of FIG. 1, and the storage unit in the main body 30 stores the print color table storage unit 50 and the like, as well as software for executing the color space conversion. To be done.

Next, an operation example in the case of creating a color space conversion table in this system will be described.

First, when the user selects the color space conversion table creating mode in the editing device 12, the adding unit 44
By the action of, the display as shown in FIG. 8A appears on the screen of the display 22. In this case, if the user does not want to add the color sample, the input is passed, and if the user wants to add the color sample, the user uses the keyboard 24 to specify the color to be added with each numerical value of CMYK. 0 in this embodiment
Each value can be entered between ~ 100%, for example (C,
Input colors such as M, Y, K) = (20, 25, 30, 27). Upon receiving this input, the adding unit 44 adds the patch data of the added color sample to the patch data storage unit 40 (see FIG. 4).

Thereafter, the patch image forming section 38 operates to display a display as shown in FIG. 8B, so that the user brings the colorimeter 26 into close contact with the frame on the display 22 where the patch appears. After that, the patch image forming unit 38 sequentially displays images of the colors represented by each patch data stored in the patch data storage unit 40. At this time, each color is XYZ by the colorimeter 26.
Are measured as the respective values, and the colorimetric values are output to the colorimetric table creation unit 42. On the other hand, the patch data from the patch data storage unit 40 is also supplied to the colorimetric table creation unit 42. The colorimetric table storage unit 42 creates a colorimetric table by associating the patch data with the colorimetric values thereof (see FIG. 5). This process is sequentially executed for each patch data, and the colorimetric table creating unit 42 finally completes the colorimetric table. Note that the time required for color measurement is, for example, about several seconds, and the burden on the user is extremely small.

When the colorimetric table 42 is created as described above, the colorimetric table is transmitted to the printing device 14 via the data bus 13. Of course, data may be transmitted every time a colorimetric result is obtained. Further, if the CMYK values in the colorimetric table are known on the printing device 14 side, the transmission of the CMYK values becomes unnecessary.

The table calculation unit compares the sent colorimetric table with the print color table stored in the print color table storage unit 50, and the combination of each CMYK in the edit color space is stored in the print color space. Which C'M'Y'K
It is determined whether or not it corresponds to the combination of '. In this case, as described above, XY existing in the two tables
By using the Z value as a key and the two XYZ values being the same or similar between the two tables, CMYK and C '
Correlate M'Y'K '. As a result, the color space conversion table shown in FIG. 7 is created and written in the color space conversion unit 46. As a result, the printing device 14 notifies the editing device 12 of the completion of table writing, and the editing device 12 that has received the notification displays a display as shown in FIG. It becomes a state.

After that, if the print data of the print image is transmitted from the editing device 12 to the printing device 14, an appropriate color space conversion is executed, and the color expression of the display 22 and the printing color can be made the same. , The printed image can be reproduced accurately. There is almost no burden on the user in creating the color space conversion table, and the color space conversion table can be created almost automatically.

Of course, such correction / replacement of the color space conversion table is preferably performed when the software in the editing device is changed or the characteristics of the display are changed, or periodically. Is desirable.

In the above embodiment, the editing device 12 and the printing device 14 were connected by the data bus 13. However, the editing device 12 is installed on the user side, and the printing device 14 is installed in a printing company (print shop or the like). It can also be installed to configure the system. That is, the user brings in a floppy disk or the like in which print data and a colorimetric table are written to a printing company, causes the printing company to create a color space conversion table similar to the above, and then prints it. Of course, in such a case, the print data and the colorimetric table can be transmitted online using a telephone line or the like.

In the above embodiment, the color space conversion unit 4
Although only one color space conversion table was stored in 6, it is now possible to store multiple color space conversion tables.
The color space conversion table may be quickly switched and used when the document editing software or the like is changed. This is also the case when a single printing device is shared by a plurality of editing devices, and the editing device can be identified and the color space conversion table corresponding to the editing device can be selected and used.

Next, a method for reducing the scale of the color space conversion table will be described.

When each value of CMYK can take 256 gradations, the color represented by the combination of each value of CMYK is 256 × 256 × 256 × 256 = about 67 million colors (see FIG. 9). In such a case, the amount of data in the color conversion table becomes huge, which is not realistic. Therefore, it is possible to set a plurality of representative points in the color space and to associate the converted C′M′Y′K ′ value only with the representative points. Then, when the CMYK between the representative points is input, for example, two CMYKs in the vicinity thereof are specified, and the two C′M′Y′K ′ values associated with them are interpolated, The target value of C'M'Y'K 'can be obtained.

CMYK from an ink company is often used as CMYK in the editing device.
When C′M′Y′K ′ is calculated for MYK by the above method, the difference between ink and toner results in (C, M, Y,
Even if K) = (100,0,0,0), the corresponding one is (C ′, M ′, Y ′, K ′) = (90,5,5)
5, 0) in some cases. That is, even if the color at the time of editing is a single color, the color at the time of printing does not always become a single color. Against this background, there may be some colors that cannot be actually used for printing in CMYK.

For example, if each CMYK is required only up to a certain upper limit value, it is desirable to deliberately exclude more unreproducible colors from the color space conversion table and downsize the table. For example, if each value of each CMYK is required only up to 90%, the conventional table is set to 1 and the table size is 0.9 × 0.9 × 0.9 × 0.9 = 0.5661 times. Can be configured. In this way, the table can be downsized by deleting the area in which only the same color can be expressed no matter how many toners are piled up, that is, the unreproducible area, and if the table capacity is the same, The density of dots can be improved. FIG. 10 shows a case where the input color space is limited in consideration of such a situation.
The K axis is omitted in the figure.

Note that, in addition to the difference in the hue of a single color as described above, the difference between the printer that directly applies the ink and the printer that indirectly applies the toner is (C, M, Y, K).
= (50,60,40,80), (C, M,
Even if (Y, K) = (40, 50, 50, 90), the equivalents are (C ′, M ′, Y ′,
Since K ′) = (40, 40, 40, 80) in some cases, it is desirable to create the table in consideration of this situation. Further, when a color that cannot be reproduced by printing is designated in the editing device 12, the editing device 12 itself may judge it and give the user attention.

[0044]

As described above, according to the present invention,
A color space conversion table that can match the colors reproduced on the monitor of the editing device with the colors actually printed, and allows even users who do not have knowledge about color space conversion to obtain such color matching. Very easy to create. According to the present invention, DTP can be performed with higher accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a color printing system according to the present invention.

FIG. 2 is a diagram showing a specific configuration of an editing device and a printing device.

FIG. 3 is a diagram showing patch data corresponding to each color sample.

FIG. 4 is a diagram for explaining addition of a color sample.

FIG. 5 is a diagram showing the contents of a color measurement table.

FIG. 6 is a diagram showing the contents of a print color table.

FIG. 7 is a diagram showing the contents of a color space conversion table.

FIG. 8 is a diagram showing a screen displayed on a display unit.

FIG. 9 is a diagram showing a color space.

FIG. 10 is a diagram showing a color space excluding a portion in which color cannot be reproduced.

[Explanation of symbols]

12 editing devices, 14 printing devices, 18 printers, 2
2 display, 26 colorimeter, 36 DTP editor, 38
Patch image forming unit, 40 patch data storage unit, 42
Colorimetric table creation unit, 44 addition unit, 46 color space conversion unit, 48 table calculation unit, 50 printing color table storage unit, 100 conversion table creation means.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 1/60 H04N 1/40 D

Claims (4)

[Claims] 1. An editing apparatus for editing a print image, and a color space conversion table for converting each color on the editing color space of the editing apparatus into each color on the printing color space, and printing after the color conversion. A color printing system including a printing device for printing an image in color; and a color sample output means for displaying an image of each color in the edited color space as a color sample on a display device on which the edited print image is displayed. A colorimeter for measuring the color sample displayed on the display as a color in an absolute color space, and a conversion table creating means for creating the color space conversion table based on the colorimetric result of the colorimeter. And a color printing system including. 2. The system according to claim 1, wherein the conversion table creating means creates a colorimetric table in which each color sample in the editing color space is associated with a colorimetric value in the absolute color space. A color table creating unit; a printing color table storage unit that stores a printing color table in which each color in the absolute color space is associated with a color in the printing color space; and a colorimetric table and a printing color table. A color printing system comprising: a table calculation unit that matches the contents and creates the color space conversion table. 3. The color printing system according to claim 2, wherein the table calculation means creates the color space conversion table within a range in which the printing device can reproduce colors. 4. The color printing system according to claim 1, further comprising color sample adding means for adding the color sample.