JP2000101856A - Data generator for special color printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data generator that easily generates data for special color printing such as two-color printing or single color printing from normal four-color separation data. SOLUTION: This data generator is provided with a 1st storage section 22 that stores four-color printing data, an edit means 28 that reads the four-color printing data from the 1st storage section 22, edits the data and generates four-color printing edit data, a 2nd storage section 26 that uses a color management system to store a profile that is used to convert the four-color printing data into special color printing data, and a conversion means 30 that uses the profile read from the 2nd storage section 26 to convert the four-color printing edit data into the special color printing edit data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to creation of spot color printing data, and more particularly to a technique of creating spot color printing image data from ordinary four-color printing image data.

[0002]

2. Description of the Related Art Conventionally, in printing a newspaper insert advertisement, in addition to the usual four-color process printing, two-color printing or single-color printing with special ink (hereinafter, these are also referred to as "special color printing") are frequently used. Have been. The two-color printing is mainly performed using red and green (or red and blue) inks, but an image is made by using any two plates (mainly cyan and magenta) of a four-color separated image. For example, in the case of red and green printing colors, the image portion uses a cyan plate as a green plate and a magenta plate as a red plate. In the case of single color printing, 4
The image is subjected to monochrome separation separately from the color-separated color data, and a monochrome image is used.

In recent years, in the production of advertisements, it has been common practice to register and accumulate product images and the like in a database, call them up as needed, and use them many times. However, in the layout of the advertisement, various printing colors are used depending on the balance between the plan contents of the advertisement and the cost. For example, there are cases where the front side of the advertisement is printed in four colors and the back side is printed in two colors, and where the front side is printed in two colors and the back side is printed in single color, and the configuration of printing colors frequently changes. For this reason, as image data of a product, four-color-separated data, two-color-separated data, and single-color (monochrome) data are used as needed.

[0004]

In the case of two-color plate making, which is mainly used for advertisement, the tone of the two plates may not be sufficiently reproduced depending on the color tone of a subject in an image to be printed. Therefore, in order to correct this, the image is separated into two colors. At that time, the setting is changed according to the color of the ink used in the two-color printing instead of the four-color separation in the normal process printing. Will be done. In this case, a function such as so-called auto-setup of the scanner cannot be used, so that a skilled person needs to perform a setting operation of color separation after trial and error, which imposes a heavy burden on an operator and also requires time for the operation.

[0005] In addition, when two of the four color separations are used as described above, tone reproduction failure may occur due to loss of tone of an unused plate.
The color-separated data must also be stored in the database. In other words, for an image of a product in which poor tone reproduction occurs, three types of color data obtained by separating the same image into four colors, two-color separated color data, and single-color data must be stored in the database. Cases arise. However, if a plurality of image data of the same product are stored, the management of the data becomes complicated, and there is a problem that an accident due to mistaking of the data during plate making tends to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made in view of the above points. Special color printing in which data for special color printing such as two-color printing and single-color printing can be easily created from ordinary four-color separated data. An object of the present invention is to provide an apparatus for creating data for use.

[0007]

According to a first aspect of the present invention, there is provided a spot color printing data creating apparatus, wherein a first storage unit for storing four-color printing data, and the four-color printing data are stored in the first storage unit. And a profile for converting the four-color printing data into the special-color printing data by using an editing unit that reads and edits the four-color printing data from the storage unit and creates the four-color printing editing data by using a color management system. A second storage unit that stores the data; and a conversion unit that converts the four-color print edit data into the special color print edit data using the profile read from the second storage unit.

According to the special-color printing data creating device configured as described above, the editing means reads the four-color printing data from the first storage unit and edits the data to create the four-color printing editing data. I do. Next, the conversion unit reads the profile from the second storage unit and converts the four-color printing edit data into two-color printing edit data.

Therefore, it is possible to easily create two-color, single-color, etc. special-color printing data from the four-color printing data stored in the first storage unit.

According to a second aspect of the present invention, in the spot color printing data generating apparatus according to the first aspect, the profile is used to convert the four-color printing data into color data in a standard color space. A first profile; and a second profile for converting the color data in the standard color space into the special color printing data. Thus, since the data is converted through the color data in the standard color space, it is possible to convert various forms of four-color printing data.

According to a third aspect of the present invention, in the spot color printing data creating apparatus according to the second aspect, the conversion means converts the four-color printing edit data to the standard color data using the first profile. Means for converting color data in the standard color space into the edit data for special color printing using the second profile. Thus, since the data is converted through the color data in the standard color space, it is possible to convert various forms of four-color printing data.

According to a fourth aspect of the present invention, in the special color printing data creating apparatus according to the first aspect, the conversion unit is included in a range that can be reproduced in two-color printing of the four-color printing editing data. Mapping means for mapping data not to be reproduced within a reproducible range in two-color printing. Therefore, color data that cannot be converted to two-color printing as it is can be converted to two-color printing data.

According to a fifth aspect of the present invention, in the spot color printing data creating apparatus according to the fourth aspect, the standard color space is an L * a * b * space, and the mapping means includes the four colors. Data that is not included in the reproducible range in two-color printing of the print editing data is located at the shortest distance on the L * a * b * space among data in the reproducible range in the two-color printing. Map to data. Therefore, the four-color printing edit data can be converted to the closest two-color printing data.

According to a sixth aspect of the present invention, in the data processing apparatus for spot color printing according to the fourth aspect, the mapping means is included in a range reproducible in two-color printing of the four-color printing edit data. Data that is not reproducible in the two-color printing by first changing only the hue without changing the lightness and saturation, and then changing the saturation or lightness to the two colors. Maps to data within a reproducible range in printing. Therefore, the original image of the four-color printing data can be converted into the two-color printing data without largely changing the image.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the present invention, a color management system used in the present invention will be described.

A color management system (hereinafter referred to as "C
MS ". ) Means that when there are a plurality of printing devices (collectively, "devices") such as scanners, printing machines, and digital printers,
This function realizes color matching of output. In recent years, a color management system has been realized at the level of an OS (Operating System) of a personal computer, and a DTP (Desk T
op Publishing) system, color conversion can be easily performed without depending on the application.

Usually, the same image data (for example, CMYK) is used by different devices (for example, printing and electrostatic copying).
), The color of the output product actually obtained will be different. This is because the CMYK color description does not directly describe the color represented by the human sense, but only describes the output signal of the device.
MYK and RGB can be called "device-dependent colors". In contrast, CIE (International Commission on Illumination) is absolutely “color expressed as a human sense” regardless of the device.
Can be described in a standard color space (XYZ or L * a * b *) defined by The function of the CMS is to describe in advance which colors, such as CMYK and RGB, of each device correspond to in the standard color space, by using a description data called a profile in advance (a conversion parameter used when performing color conversion. This means that the same color can be output from different devices by performing color conversion on the image while referring to the profile.

The profile is a conversion parameter for converting a color of a specific device (for example, an offset printer, a color printer, etc.) into the above-mentioned standard color space (L * a * b * space). The profile format is being standardized internationally by an organization called ICC (International Color Consotium) (ICC Profile Sp
ecification).

Here, the standard color space (L * a * b)
* Space) is briefly explained. The L * a * b * space is a chromaticity diagram called CIELAB recommended by CIE.
* Indicates lightness, a * indicates the degree of red or green, and b * indicates the degree of yellow or blue. FIG. 3 schematically shows the relationship between the L * a * b * space and the colors positioned in the space. The horizontal axis running from right to left in the figure is the a * axis. The value of a * approaches green as it goes to the minus side, and approaches red as it goes to the plus side. On the b * axis, the color approaches blue as it goes to the minus side, and approaches yellow as it goes to the plus side. The L * axis running up and down is white at the top (total reflection, L = 100)
And the bottom part is black (total absorption, L = 0). Then, the center of these three axes is an intermediate color (gray). That is,
Movement in the L * -axis direction indicates a change in brightness, movement in the radial direction on the a * b * plane indicates a change in saturation, and movement in the circumferential direction on the a * b * plane indicates a change in hue. Note that the distance in the L * a * b * space corresponds to the closeness of the color, and the closer the distance, the closer the color.

FIG. 1 schematically shows the contents of a profile defined by the ICC. The basic configuration of a portion describing the color characteristics of a device is, as shown in FIG. 1, an n-dimensional → three-dimensional or three-dimensional → n having an l-dimensional look-up table (hereinafter also referred to as “LUT”) before and after. This is a LUT format of dimension (n is the number of colors). That is, an n-dimensional → three-dimensional profile is
The n-dimensional color notation of a specific device is associated with a standard three-dimensional color space (L * a * b *). The three-dimensional → n-dimensional profile is a standard three-dimensional color space (L * a * b *)
Is associated with the n-dimensional color notation of the specific device. Note that the front and rear one-dimensional LUTs are usually linear (input and output values are the same), but they may be set to special characteristics and used for correcting aging fluctuation of the device. FIG. 1 illustrates the format of the LUT of a device of three colors (that is, n = 3) for the sake of simplicity.

The printing device type profile used in the present invention includes an n-dimensional → three-dimensional LUT for converting a device color notation into a notation in a standard color space, and a paired standard color space with a device in a standard color space. 3D converted to color notation → n
This is a format that includes a dimension LUT.

Next, FIG. 2 shows a method of using a profile of a print-type device in the above-described format for color conversion in the CMS. When the color of one printing type device (for example, offset printing press, CMYK 4 colors) is reproduced by another printing type device (for example, digital printer, CMYK 4 colors), the profile of the offset printing press is set as the conversion target profile. Device profile for reproducing colors (hereinafter referred to as "reproduction profile")
As the digital printer profile. Then, the CMS calculates the color data of the given image
Using the four-dimensional → three-dimensional LUT of the profile of the target offset printing press, it is calculated where the color notation in the offset printing is located in the L * a * b * space. Next, the CMS calculates the device color notation of the digital printer that reproduces this color by using the 3D → 4D LUT of the profile of the digital printer. The color conversion operation of the CMS is mathematically equivalent to obtaining a mapping between the color reproduction of the target device and the color reproduction of the output destination device.

Next, a method of creating the profile will be described. Now, considering a case of creating a profile of a digital printer, a target device (digital printer in this example) outputs a multiplication chart image of each color (normally, four colors of CMYK) and performs color measurement of each color. Obtain the corresponding L * a * b * values. As a result, each CM
The correspondence between the multiplication color of YK and the combination of L * a * b * values is obtained. Next, based on this correspondence, a look-up table of L * a * b * values (hereinafter, also referred to as “LUT”) for the multiplied colors of CMYK is created, and the LUT is back-calculated to obtain L *. CMYK for a * b * value
To create a multiplication color LUT. By combining both LUTs into one file, a profile for a digital printer can be obtained.

Next, creation of spot color printing data according to the present invention will be described. FIG. 4 schematically shows a conversion process from four-color separation data to two-color separation data.

In FIG. 4, the target profile is a profile for converting ordinary four-color separation data into L * a * b * values, and is a profile from four dimensions to three dimensions. The two-color printing profile is a profile for converting L * a * b * values into two-color printing data.
It is a profile to a dimension. FIG. 5 shows the configuration of the two-color printing profile. The method of creating this profile is basically the same as the above-described four-color printing profile. That is, the target device outputs a multicolor chart of the ink colors used in two-color printing, and measures the color of the output chart to obtain the L * a * b * values of each color. And
An LUT from the two colors to the L * a * b * value and an LUT from the L * a * b * value to the two colors are created as two-color printing profiles. In FIG. 5, C1 and C2 indicate two colors of ink used in two-color printing.

The two-color printing profile thus created is registered in the database. When it is necessary to perform two-color printing on a normal four-color-separated image, the four-color separation data stored in the database and the above-described two-color printing profile are called, and two-color printing is performed according to the flow shown in FIG. Performs conversion to data. This eliminates the need to store both the four-color separation data and the two-color separation data for the same image in the database.

The two-color printing profile is basically created as described above. However, since the reproducible color range is different between the four-color image data and the two-color image data, the adjustment is made in the two-color printing profile. Need to do. This will be described with reference to FIG. In FIG. 6, the left is 4
FIG. 3 is a diagram schematically showing a color range reproducible by color printing on L * a * b * space, and the right side is a schematic diagram showing a color range reproducible by two-color printing on L * a * b * space. FIG. The characteristic A in FIG. 6 is the color reproduction range of four-color printing, and the characteristic B is the color reproduction range of two-color printing. As can be seen from the figure, there is a limit on the color reproduction range that can be expressed in two-color printing. In four-color printing, the range in which color can be reproduced is a closed surface (three-dimensional), whereas in two-color printing, the surface is a curved surface including two colors of ink to be used, their multiplication color, and white of paper. Therefore, in the two-color printing, only a specific color range in the L * a * b * space can be reproduced.

Therefore, when converting four-color printing data to two-color printing data, two colors that cannot be reproduced by two-color printing are converted to two-color printing data.
The LUT of the two-color printing profile must be configured so as to map according to some rules to colors that can be reproduced by color printing. The rules for mapping are described below.

FIG. 7 shows one of the rules for converting four-color printing data into two-color printing data. FIG. 7 shows L * a * b
* Shows a method of converting two colors (points C and D) in space into two-color printing data (a * b * for simplicity of the figure)
Represents a view of the plane). Specifically, for a color that cannot be reproduced by two-color printing, the color is shifted to the color with the smallest color difference (closest color). That is, it moves to the shortest point on the reproduction characteristic B of two-color printing in the L * a * b * space. In the example of FIG. 7, the color of the point C is within the range that can be reproduced by two-color printing (characteristic B).
Since it is located in (top), the colors can be used as they are. On the other hand, since the color of the point D is not on the characteristic B, the color of the point D moves to the color closest to the color of the point D on the characteristic B (point D ′). According to this rule, in the two-color printing data converted by the two-color printing profile, although the saturation may be low, the hue does not largely change and an image with clear gradation is obtained.

FIG. 8 shows still another example. The example of FIG. 8 is a method of changing the hue while maintaining the saturation. More specifically, regarding a triangle constituted by two points (g, r) of the highest saturation color by two ink colors to be used and the center of the a * b * plane (corresponding to achromatic color), two points middle point of g, r and a * b *
Assuming a dividing line connected to the center of the plane, the hue is rotated within an area defined by the dividing line to map to a point on a characteristic that can be reproduced by two-color printing. Next, in each hue reproducible by two-color printing, the point where L * = 50 and a * = b * = 0 so that the hue does not change at the point where the brightness and the saturation are out of the reproducible range. , And is mapped to a point on the characteristic B that can be reproduced by two-color printing. At this time, for the point where the lightness and the saturation are within the reproducible range, L * =
50, move in the direction of the point of a * = b * = 0. The value of L * a * b * determined by this is defined as a mapping value in two-color printing. Although the reproduced color of the ink is actually a curve or a curved surface, it is approximated to a straight line or a plane as shown in FIG. It is better to replace the value that does not ride on the actual curve or curved surface with the closest value on the curve or curved surface.

As described above, for colors that cannot be reproduced by two-color printing, predetermined rules for mapping them to colors reproducible by two-color printing are determined, and their relationship is determined by the LUT of the two-color printing profile. In advance. Since the profile has a multidimensional LUT structure, the mapping position can be set to some extent freely according to such rules. Further, once the LUT is determined and the two-color printing profile is created, if there is a color to be partially changed, the contents of the LUT for the color are partially changed to thereby change the two-color printing profile. Content can be improved.

FIG. 9 shows the structure of a monochrome printing profile. The single-color printing profile can be created in the same way as the two-color printing profile. The simplest method is to change only the L * value from 0 to 100% from the L * a * b * value converted by the four-color printing profile of the target device.
To create a profile that outputs the value as one color (color C1 in FIG. 9).

FIG. 10 shows the structure of a double-tone two-color printing profile. Double tone refers to a method in which an image is overprinted with two inks having different densities or hues in order to smoothly reproduce a gradation. In this case, as described above, of the L * a * b * values, only the L * value, which is the lightness component, is normalized, and the portion corresponding to white is output as 0 and the portion corresponding to black is output as 1 and inverted. This is set as a first color (color C1). Further, a three-dimensional to two-dimensional profile is created so that the value of 1/2 is set as the second color (color C2). As a result, a two-color printed matter to which the double tone method has been applied can be obtained.

As described above, by creating a profile for two-color printing or single-color printing, color data for two-color printing or single-color printing can be easily obtained from color separation data for four-color printing. be able to. Therefore, there is no need to store a plurality of color separation data for the same image in the database.

Next, the configuration of a two-color print data creation system according to an embodiment of the present invention will be described. In FIG. 11, the two-color print creation system includes a scanner 20 and an image database 22. The scanner 20 separates a required image into colors and outputs color separation data for CMYK four-color printing. The four-color printing data is stored in the image database 22, and is used for editing and layout work by the DTP system.

The profile database 26 stores a profile used for color conversion for two-color printing of a print original created using the four-color printing data stored in the image database 22. Specifically, as shown in FIG. 4, a profile used for converting four-color printing data into L * a * b * values as a target profile, and a target profile for two-color printing using L * a * b * values. A two-color printing profile used for conversion to data is stored. When the present system is used for the above-described single-color printing and double-tone printing, profiles for single-color printing and double-tone printing as shown in FIGS. 9 and 10 are stored in the profile database 26.

The color conversion section 30 is a section for converting the data for four-color printing into the data for two-color printing using the above-mentioned profile, and the film output section 32 creates a film of the data for two-color printing. ,Output.

Next, processing by the present system will be described.

First, when the plan of the advertisement is decided, the contents are reported to the work contents management section 24. Specifically, information such as the colors used on the front and back surfaces of the advertisement and the items to be posted are given. The work content management unit 24 reads necessary image data from the image database 22 based on this information, and together with the color information of the surface on which those images are posted, the DTP system 2
8 The DTP system 28 corrects an image, lays out an image, creates original data, and converts the original
Send to 0. The color conversion unit 30 calls a profile used for color conversion from the profile database 26 based on the information provided from the work content management unit 24, and performs color conversion of the document data. Thereby, the color conversion from the four-color printing data to the two-color printing data is performed, and the two-color printing data is supplied to the film output unit 32. The film output unit 32 outputs the two-color printing data as a film.
This enables two-color printing of advertisements and the like.

When performing other special color printing such as monochrome printing, the corresponding profile may be read from the profile database 26 and used for conversion by the conversion unit 30.

As described above, according to the present invention, image color conversion from four-color printing data to special-color printing data can be performed using an inexpensive DTP plate making system. Therefore, only the four-color printing data needs to be stored and managed, and image management becomes easy. Also, even if the color of the ink used in spot color printing is changed,
It is only necessary to create and store a profile corresponding to a new ink combination, and there is no need to perform color separation processing on a new special color printing ink. Therefore, by storing only general-purpose four-color separation data in the image database and preparing a profile for special color printing in the profile database, it is possible to easily perform various kinds of special color printing.

[0042]

According to the first aspect of the present invention, two-color printing data can be easily created from four-color printing data stored in the first storage unit.

According to the second aspect of the present invention, since the data is converted through the color data in the standard color space, it is possible to convert various forms of four-color printing data.

According to the third and fourth aspects of the present invention, color data that cannot be converted into two-color printing as it is can be converted into two-color printing data.

According to the fifth aspect of the invention, it is possible to convert four-color printing edit data into two-color printing data of the closest color.

According to the present invention, the original image of the four-color printing data can be converted into the two-color printing data without largely changing the image.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a profile used in a color management system.

FIG. 2 is a diagram showing a flow of a color conversion process in the color management system.

FIG. 3 is a diagram showing a standard color space (L * a * b * space).

FIG. 4 is a diagram schematically illustrating a process of creating two-color printing data according to the present invention.

FIG. 5 is a diagram illustrating a configuration of a two-color printing profile.

FIG. 6 is a diagram schematically illustrating a color reproduction range by four-color printing and two-color printing.

FIG. 7 is a diagram illustrating an example of a mapping method from four-color printing colors to two-color printing colors.

FIG. 8 is a diagram illustrating another example of a mapping method from four-color printing colors to two-color printing colors.

FIG. 9 is a diagram illustrating a configuration of a monochrome printing profile.

FIG. 10 is a diagram showing a configuration of a double tone two-color printing profile.

FIG. 11 is a block diagram showing a configuration of a two-color printing data creation system according to the present invention.

[Explanation of symbols]

 Reference Signs List 20 scanner 22 image database 24 work content management unit 26 profile database 28 DTP system 30 color conversion unit 32 film output unit

Continued on front page F-term (reference) 2C087 AA15 BD24 BD34 BD37 CB03 2C262 AB11 AC17 BA11 BC19 CA09 5B021 CC02 DD15 LG07 LG08 LL05 5C077 LL17 MP08 MP09 NP01 PP33 PP36 PP37 PQ23 TT08 5C079 HA11 HA12 HA13 HB11 HA02 HA13 HB03 HAB11

Claims (6)

[Claims] A first storage unit that stores four-color printing data; and an editing unit that reads out the four-color printing data from the first storage unit and edits the data to create four-color printing editing data. Means, a second storage unit for storing a profile for converting the four-color printing data into special-color printing data using a color management system, and the profile read from the second storage unit. A conversion unit for converting the four-color printing edit data into the special color printing edit data using the special color printing data. 2. The profile includes a first profile for converting the four-color printing data into color data in a standard color space, and converting the color data in the standard color space into the special color printing data. The second to convert to
The spot color printing data creating apparatus according to claim 1, further comprising: 3. The conversion unit converts the four-color printing edit data into color data in the standard color space using the first profile, and uses the second profile. Means for converting the color data in the standard color space into the edit data for special color printing,
The spot color printing data creating apparatus according to claim 2, further comprising: 4. The mapping means for mapping data which is not included in a reproducible range in two-color printing out of the four-color printing editing data to data in a reproducible range in two-color printing. The spot color printing data creating apparatus according to claim 1, further comprising: 5. The standard color space is an L * a * b * space, and the mapping means converts data not included in a reproducible range in two-color printing from the four-color printing edit data. The spot color printing data creating apparatus according to claim 4, wherein the data is mapped to data located at the shortest distance in the L * a * b * space among data within a reproducible range in the two-color printing. 6. The mapping means changes data which is not included in a reproducible range in two-color printing out of the four-color printing edit data by first changing only hue without changing brightness and saturation. The spot color according to claim 4, wherein the spot color is mapped to data within a range of hues that can be reproduced in the two-color printing, and then the data is mapped to data within a range that can be reproduced in the two-color printing by changing brightness or saturation. Printing data creation device.