JP2005271355A - Method of determining consumption amount of ink realizing high density printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of determining a consumption amount of ink capable of printing a high density color in a simple structure. <P>SOLUTION: When ink amount data for outputting a specific color in a maximum density is determined, measured color values of a specific color patch recorded so as to be in the maximum density by the ink of the single specific color and a plurality of synthesized patches recorded by combining the ink of the specific color and the other inks are acquired. The densities of the patches are compared with each other from the measured color values and one of the synthesized patches of which the density is higher than that of the specific color patch is selected. Data indicative of the consumption amounts of the other ink and the ink of the specific color in the selected synthesized patch is made to be the ink amount data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for determining the amount of ink used for a specific color when determining the amount of ink used in a printing apparatus.

In recent printing apparatuses such as ink jet printers, various factors such as the type of printing medium, the type of ink, and the amount of ink used are adjusted in order to obtain higher quality printing. For example, an upper limit is set on the amount of ink used per unit area in order to prevent ink from being mixed without being absorbed by the print medium, or to prevent wrinkles from occurring on the print medium. At this time, in order to surely perform high-quality printing, a process for preventing a phenomenon called bronzing from occurring on a specific print medium is performed (for example, see Patent Document 1).
JP 2001-138555 A

  In the above-described prior art, it is difficult to print a specific color (particularly black) with a high density. For example, an ordinary printing apparatus often uses CMYK (C: cyan, M: magenta, Y: yellow, K: black) ink, and black is expressed by a combination of CMY inks or K ink. In general, since the density of the K ink alone is higher than the combination of the CMY inks, only the K ink is often used to output the highest density black. However, in some cases, a darker black than the density of black recorded using only the K ink is desired. In particular, as the accuracy of inkjet printers increases, it is considered that low-cost inkjet printers can replace high-precision printing devices called proofers. It is desirable to output the black density with an inkjet printer.

However, even if the K ink is replaced with a combination of CMY inks as in the prior art, it is difficult to record darker black than the K ink alone, and the above-mentioned demands cannot be met. Further, the density can be adjusted by adjusting the composition of the ink, but this kind of adjustment requires much research such as trial and error, and it is not easy to improve the density. If a color with the darkest possible density can be output, the color near the boundary of the color gamut in the printing apparatus can be used with certainty, and the expressive power in the printing apparatus is improved. This is a common problem for all colors.
The present invention has been made in view of the above problems, and provides a method of determining the amount of ink used that can print a high density color with a simple configuration.

  In order to achieve the above object, in the present invention, a patch printed by combining a specific color ink and another ink is measured, and a patch that is darker than the density when the maximum density is output with only the specific color ink is obtained. select. If such a patch can be selected, the ink amount when printing the patch is used as the ink amount data for outputting the specific color with the highest density. As a result, it is possible to acquire ink amount data for outputting a specific color at a higher density than that obtained with a specific color ink. Further, by using the ink amount indicated by the ink amount data when printing a specific color having a high density, it is possible to easily print a specific color having a high density.

  In the specific color patch, the ink amount of the specific color is adjusted so as to obtain the maximum density that can be obtained with a single ink of the specific color. In ordinary print media, the density increases with increasing ink, so if you record ink up to the upper limit of ink that can be recorded per unit area of the print medium, it is often the maximum that can be obtained with a single color of a specific color. Concentration. However, depending on the type and characteristics of the specific color ink or the characteristics of the print medium, the density may not increase as the ink amount of the specific color increases, and the density may reach a peak at a specific color ink amount. Of course, in this case, a patch recorded with an ink amount having the maximum density is set as a specific color patch.

  Specific examples of the specific color may be black, cyan, magenta, or yellow, and various colors can be used as long as a high density output can be obtained by combining with other inks. It is. Of course, it may be red, violet, or green, and various colors can be adopted as the specific color. Further, by adding other ink to the specific color ink, the hue and the like can be changed as compared with the output of only the specific color ink. That is, the color can vary. However, in the present invention, it is assumed that the specific color ink is dominant, and even if the hue or the like slightly changes by adding other ink to the specific color ink, the color after the change also changes. Suppose that it is a specific color.

  Other inks combined with the specific color ink in the composite patch may be inks other than the specific color ink. That is, any ink other than the specific color ink may be used regardless of whether it is chromatic color ink or achromatic color ink. Of course, light ink that is lighter than the specific color ink may be used. In the synthetic patch, it is preferable to consider the upper limit of ink that can be recorded per unit area of the print medium. That is, even if ink amount data that gives the maximum density in a state where the upper limit is exceeded, printing cannot be performed using this ink amount. Therefore, the amount of other ink used for recording on the composite patch is within a predetermined limit.

  If the upper limit of ink that can be recorded per unit area is increased by increasing the ink color, for example, two inks when the upper limit for one ink is defined as 100% There is a case where the upper limit by 110 becomes 110% or the like. In this case, it is preferable that another ink can be added without reducing the specific color ink from the state where the density of the specific color ink is the highest. That is, the ink of a specific color is maintained at an ink amount that gives the highest density for a single color, and the amount of ink used for a plurality of composite patches is changed by changing the amount of other ink used.

  Even if the upper limit of the ink amount when two or more inks are used is larger than the upper limit of a specific color ink, the amount is at most about 20% or less. Therefore, if only the usage amount of the other ink is changed, the number of patches that can be assumed as a composite patch is not excessively large, and color measurement can be easily performed. Of course, if a high density output can be obtained by combining with the above-mentioned other inks, even if the amount of the ink of the specific color is not maintained and the amount is slightly reduced, the amount of the ink of the specific color It is possible to change both the amount of other ink used.

  The colorimetric value acquisition unit only needs to be able to acquire the colorimetric value of each patch. For example, the colorimetric value acquisition unit acquires the patch actually recorded on the print medium by measuring the color with a colorimeter. Of course, if an accurate colorimetric value can be obtained by simulation, simulation or the like can be used. Here, the colorimetric value may be a value for comparing the densities of the printed materials, and for example, an OD value (Optical Density) can be adopted. That is, the OD value is defined as “−log (reflected light intensity of sample / incident light intensity)”, and according to the OD value, the density of the printed matter can be evaluated.

  The patch selection means only needs to be able to select a composite patch having a higher density than the specific color patch by comparing the colorimetric values of the specific color patch with the colorimetric values of a plurality of composite patches. That is, since the densities can be compared according to the colorimetric values, a composite patch having a higher density than the specific color patch is specified based on the comparison. If the identified patch can be grasped later, it can be said that the patch has been selected. As a configuration for selecting a patch, various configurations can be employed, and a configuration such as adding a flag to data indicating the colorimetric value of the patch can be employed.

  Since there are a plurality of composite patches, a plurality of composite patches having a higher density than the specific color patch may be selected by the patch selection means. In the present invention, the purpose is to output a specific color at a high density. Therefore, when a plurality of synthesized patches are selected, it is preferable to select the synthesized patch having the highest density among them. . Of course, when a plurality of composite patches are selected, it is also possible to select a patch in consideration of this other viewpoint. For example, it is possible to adopt a configuration such as selecting a composite patch that is a combination of inks that hardly gives a graininess.

  The ink amount data determining means acquires ink amount data indicating the amount of ink used for each color for printing the composite patch selected as described above. The amount of ink used for printing the composite patch is known in advance when the composite patch is created, and the amount used can be easily obtained. For example, data used when printing a composite patch may be stored, and this data may be acquired and used as ink amount data for outputting a specific color having the highest density.

  In the above invention, the specific color is output at the highest density in the printing device by comparing the specific color patch of the specific color ink with the combined patch of the combination of the specific color ink and other ink. To grasp the ink combination. Therefore, by using the inks used for the comparison in the above combination, it is possible to output a specific color with the highest density in the printing apparatus. Therefore, the specific color ink and the other ink are preferably inks that are simultaneously mounted on a predetermined printing apparatus.

  In other words, if the ink set changes, the combination and amount of ink used to achieve the highest density may change. The ink amount data for outputting a specific color is grasped. As a result, a specific color can be output at the highest density when the ink set is used in the predetermined printing apparatus. Further, according to the configuration using the ink set mounted on the printing apparatus, the specific color patch and the composite patch can be printed by the printing apparatus. In this case, the ink amount data can be easily obtained from the data used for printing the patch.

  In the synthetic patch, it is only necessary to obtain a specific color having a higher density than a patch of a specific color ink by combining a specific color ink and another ink. Therefore, the number of the other inks added to the specific color ink is not particularly limited. In terms of not excessively increasing the number of comparison objects, one or two colors are preferable. According to the applicant of the present application, it has been confirmed that when cyan ink is added to a certain black ink and when cyan ink and light black ink (light black ink) are added, the density becomes higher than that of a single black ink color. Yes.

  As described above, the method of increasing the density of the specific color by combining the specific color ink and another ink is not necessarily limited to a substantial apparatus, and is effective as a method invention. Further, the idea of the invention includes various aspects, such as the case where the above-described ink amount determination device may exist alone or may be used in a state of being incorporated in a certain device. Further, it can be changed as appropriate, such as software or hardware.

  When the software of the ink amount determination device is realized as an embodiment of the idea of the invention, it naturally exists and is used on a recording medium on which such software is recorded. Of course, the recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium that will be developed in the future.

  Further, in general printing apparatuses, printing is often performed by acquiring image data indicating a printing target, and performing color conversion to data indicating the amount of ink used in the printing apparatus. In such a configuration, color conversion is performed by a color conversion profile, and as an aspect to which the present invention is applied, the invention can be specified as a color conversion profile creation apparatus, creation method, and creation program.

  That is, the color conversion profile is created by printing a plurality of color measurement patches and associating an arbitrary ink usage amount with image data indicating an output color at the ink usage amount based on the color measurement result. . Therefore, when determining the patch data for specifying the ink usage amount in the colorimetric patch, the ink usage amount in the patch for outputting the specific color having the highest density is specified by the ink amount data. As a result, a color conversion profile is obtained in which the amount of ink used for obtaining a specific color with the highest density is an amount that conforms to the ink amount data.

  By referring to the color conversion profile, it is possible to acquire image data designating a specific color and convert it into an ink usage amount for outputting a specific color with the highest density. Further, if configured to refer to this color conversion profile, it is possible to provide a print control device, a print control method, and a print control program that output a specific color with a very dark density.

  Note that the patch data acquisition unit only needs to acquire a plurality of patch data and use the ink amount data as a part of the patch data. The patch data other than the ink amount data can be generated by various methods. For example, various rules such as a rule called a color separation rule can be used. That is, the number of inks used in a general printing apparatus is four or more colors, and inks of six to eight colors may be used. In this way, a color measuring patch is printed by combining a number of colors. .

  Here, the actual number of patches that can be actually measured is limited (for example, 1000). If the amount of ink used is determined without any idea, the limited number of patches can sufficiently provide the color gamut of the printing apparatus. It is difficult to measure colors for patches that enable high-precision conversion. Therefore, it is preferable to temporarily determine the patch data according to a predetermined rule such as a color separation rule. After the patch data is provisionally determined, the patch data can be easily determined by distributing a part of the specific color ink after the provisional determination to the specific color ink and the other ink.

  That is, when the patch data is provisionally determined according to the rules described above, a part of the specific color ink in the provisionally determined patch data is distributed to the other ink. As a result, the patch data temporarily determined to output the specific color only with the specific color ink is converted into the ink use amount according to the ink amount data, and the patch data can be determined.

  Of course, at this time, not only the patch data tentatively determined to output the specific color with only the specific color ink but also the surrounding color patch data by distributing a part of the specific color ink to the other inks, It is possible to gradually change the amount of ink used between each piece of patch data. Therefore, it is possible to perform color conversion while suppressing the occurrence of tone jump in a color conversion profile created based on a patch printed according to the patch data. In the predetermined rule, it is possible to consider various indexes such as an index for improving the conversion accuracy of the color conversion profile.

  The color conversion profile creating means only needs to be able to associate an arbitrary ink usage amount and image data based on the colorimetric values of a plurality of colorimetric patches, and various configurations can be employed. For example, colorimetric values of colors indicated by image data such as RGB data are obtained by colorimetry or a predetermined conversion formula, and interpolated from the correspondence between image data and colorimetric values and the correspondence between patch data and colorimetric values. What is necessary is just to prescribe | regulate the correspondence of arbitrary ink usage-amount and image data by a calculation etc.

In the color conversion profile, it is only necessary to be able to define a correspondence relationship between an arbitrary ink usage amount and image data. Table data that associates a plurality of ink usage amounts with image data and functions that define the correspondence relationship are shown. Data etc. can be adopted. The image data in the color conversion profile may be device-dependent colors such as RGB data or device-independent colors such as L ^* a ^* b ^* .

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of the apparatus according to the present invention:
(1-1) Schematic configuration of computer:
(1-2) Printer driver configuration:
(1-3) Configuration of LUT creation program:
(2) LUT creation processing:
(2-1) Ink amount data determination process:
(3) Example:
(4) Other embodiments:

(1) Configuration of the apparatus according to the present invention:
(1-1) Schematic configuration of computer:
FIG. 1 is a block diagram showing a schematic configuration of a computer serving as a print control device, an ink amount determination device, and a color conversion profile creation device according to the present invention. The computer 10 includes a CPU (not shown) serving as the center of arithmetic processing, a ROM, a RAM, and the like as a storage medium, and can execute a predetermined program using peripheral devices such as the HDD 15. An operation input device such as a keyboard 31 and a mouse 32 is connected to the computer 10 via a serial communication I / O 19a, and a display 18 is also connected via a video board (not shown). Further, it is connected to the printer 40 via a USB I / O 19b. In addition, the colorimeter 50 is connected via the USB I / O 19b.

  The printer 40 according to the present embodiment includes a mechanism in which an ink cartridge filled with a plurality of colors of ink is detachable for each color, and each ink of CMYKlclm (cyan, magenta, yellow, black, light cyan, light magenta) is included in this mechanism. A cartridge filled with is mounted. In the printer 40, these inks can be combined to form a large number of colors, thereby forming an image on a print medium. The printer 40 in this embodiment is a so-called inkjet printer, and ejects each ink by applying an ejection force to the ink inside a head filled with each ink. At this time, a voltage may be applied to the piezo element to cause the ejection force to act on the ink, or bubbles may be formed in the head to cause the ejection force to act on the ink.

  In this embodiment, the discharge amount of each ink droplet of CMYKlclm is constant, but the present invention can of course be applied to various configurations such as a configuration in which the discharge amount of the ink droplet is changed in three stages. Further, the present invention can be applied to various printers such as a laser system in addition to the ink jet system. Further, as shown in FIG. 1, a configuration using six colors of CMYKlclm is not essential, and a configuration using four colors of CMYK or seven colors of CMYKlclmDY (DY is dark yellow) may be used. Of course, other colors such as R (red) and V (violet) may be used instead of the lclm ink, and a dark and light ink may be used for the K ink.

In the colorimeter 50, the printed material is irradiated with a known light source, the reflected light is detected to detect the spectral reflectance of the printed material, and the color values, for example, L ^* a ^* b ^* values and XYZ values are output. Is possible. Further, the colorimeter 50 according to the present embodiment can detect the OD value. In this embodiment, an OD value is measured to determine ink amount data, and L ^* a ^* b ^* is measured to create an LUT.

  Furthermore, in the present embodiment, the print control apparatus is configured by the computer 10, but the print control process according to the present invention can be implemented by the program execution environment installed in the printer 40, and the printer 40 is directly connected to the printer 40. Image data may be acquired from a digital camera connected to the printer and the print control process may be performed. Of course, the print control process may be performed with a digital camera in the same configuration, and various other configurations such as performing the print control process according to the present invention by a distributed process may be employed. The print control processing according to the present invention may be performed in a so-called multi-function machine in which a scanner for capturing an image and a printer for printing an image are integrated.

  In the computer 10 according to the present embodiment, a printer driver (PRTDRV) 21, an input device driver (DRV) 22, and a display driver (DRV) 23 are incorporated in the OS 20. The display DRV 23 is a driver that controls the display of image data and the like on the display 18, and the input device DRV 22 receives a code signal from the keyboard 31 and mouse 32 input via the serial communication I / O 19a and receives a predetermined signal. A driver that accepts input operations.

  In the present embodiment, an image can be printed on the printer 40 by an application program (not shown). The application program is, for example, an application program that can execute retouching of a color image, and the user operates the input device for operation and causes the printer 40 to print the color image under the execution of the application program. Can do.

  In the present embodiment, image data 15 a indicating an image to be printed is recorded in the HDD 15. The image data 15a is dot matrix data in which each color component of RGB (red, green, blue) is expressed in gradation to define the color of each pixel. In this embodiment, each color has 256 gradations and the sRGB standard. The image data adopts a color system according to the above. In the present embodiment, the image data 15a will be described as an example, but various data such as JPEG image data using the YCbCr color system and image data using the CMYK color system can be used. Of course, the present invention is applied to data conforming to the Exif 2.2 standard (Exif is a registered trademark of the Japan Electronics and Information Technology Industries Association), data corresponding to Print Image Matching (PIM: PIM is a registered trademark of Seiko Epson Corporation), etc. It can also be applied.

(1-2) Printer driver configuration:
When a printing instruction is given by the application program or the like, the PRTDRV 21 is driven, and the PRTDRV 21 sends data to the display DRV 23 to input information indicating printing conditions such as a printing medium, image quality, and printing speed (not shown). Is displayed. When the user inputs information necessary for printing through the UI by operating the keyboard 31, mouse 32, etc., each module of the PRTDRV 21 is activated and print data is generated. The generated print data is output to the printer 40 via the USB I / O 19b, and the printer 40 executes printing based on the print data.

  More specifically, the PRTDRV 21 includes an image data acquisition module 21a, a color conversion module 21b, a halftone processing module 21c, and a print data generation module 21d in order to execute printing. When an instruction to execute printing of the image indicated by the image data 15a is given by the application program, the PRTDRV 21 is activated. The image data acquisition module 21a acquires image data 15a indicating an image for which a print execution instruction has been given by the application program. At this time, if there is an excess or deficiency in the number of pixels of the image data 15a, resolution conversion processing is performed as appropriate in order to secure the pixels necessary for printing.

  The color conversion module 21b is a module that converts the color system indicating the color of each pixel. The printer 40 refers to the LUT (color conversion table) 15b recorded in the HDD 15 as appropriate, and the printer 40 converts the sRGB color system of the image data 15a. Conversion is made to the CMYKlclm color system that uses the mounted ink (CMYKlclm) as a component. The LUT 15b is a table that expresses colors by using the sRGB color system and the CMYKlclm color system, associates the colors, and describes the correspondence between a plurality of colors. Accordingly, with respect to an arbitrary color expressed in the sRGB color system, the colors of the CMYKlclm color system corresponding to the arbitrary color can be obtained by interpolation calculation by referring to the surrounding color and the sRGB color defined in the LUT 15b. And color conversion can be performed.

  Note that the LUT 15b in the present embodiment is an LUT created by the LUT creation program 25 that can be executed by the computer 10, and details of the processing will be described later. In the LUT 15b created by the LUT creation program 25, CMYKlclm data for outputting the highest density black and surrounding colors (colors having a small color difference) with reference to the ink amount data determined by the processing described later. Is defined. As a result, it is possible to output a darker black as compared with the case of printing with a single color of K ink.

  The halftone processing module 21c converts the gradation value of each pixel expressed in the CMYKlclm color system, and realizes recording with an ink amount corresponding to the gradation value with a smaller number of gradations. This module performs processing, and performs halftone processing based on the data after color conversion. That is, ejection / non-ejection of ink droplets is determined for each pixel of the printer 40. Further, the print data generation module 21 d receives the data after the halftone process, and rearranges the data in the order used by the printer 40.

  That is, in the printer 40, an ejection nozzle row is mounted as an ink ejection device, and a plurality of ejection nozzles are arranged in parallel in the sub-scanning direction in the nozzle row. used. Therefore, the data to be used at the same time among the data arranged in the main scanning direction is rearranged in order so that the printer 40 can simultaneously buffer the data. The print data generation module 21d generates print data by adding predetermined information such as image resolution to the rearranged data, and outputs the print data to the printer 40 via the USB I / O 19b. As a result, an image is formed on the print medium by the printer 40.

(1-3) Configuration of LUT creation program:
Next, the configuration of the LUT creation program 25 will be described. As shown in FIG. 1, the LUT creation program 25 includes a patch printing unit 25a, a colorimetric value acquisition unit 25b, an ink amount data determination unit 25c, a patch selection unit 25d, and an LUT creation unit 25e. Black patch data 15c and composite patch data 15d are recorded in advance in the HDD 15 as data used in processing in the LUT creation program 25, and the LUT creation program 25 uses the black patch data 15c and composite patch data 15d. Ink amount data 15e is created. Further, the LUT 15b is created using the ink amount data 15e.

  The black patch data 15c is data for recording a patch with the highest density black using only K ink. In the present embodiment, the ink having the highest black density when one type of ink is recorded up to the upper limit value on the printing medium is used. Accordingly, in the black patch data 15c, the components other than the K component of the CMYKlclm data are “0”, and the K component is a gradation value indicating the upper limit value of the ink amount that can record one kind of ink on the printing medium.

  The combined patch data 15d is data for recording patches by combining K ink and other inks. In this embodiment, the recording amount of K ink is the upper limit value of the one kind of ink. The recording amounts of other inks are a plurality of recording amounts of 20% or less, and the number of other inks is one or two colors. That is, the upper limit value when recording two or more types of ink on the print medium is about the upper limit value + 20% when recording one type of ink.

  Therefore, when recording other inks, the upper limit value for recording one kind of ink is set to 20% or less so as not to exceed the upper limit of the amount of ink that can be recorded on the print medium when a plurality of inks are combined. I have to. Also in the composite patch data 15d, the components other than the K component of the CMYKlclm data and the other ink components are "0", and the K component indicates the upper limit of the ink amount that can record one type of ink on the print medium. The other inks are gradation values corresponding to 20% or less of the upper limit of the amount of ink that can record one type of ink on the printing medium. The ink amount data 15e is data indicating a combination of ink amounts that are darker than the highest density black that can be output with a single K ink color, and the ink amount (tone value) for each color.

  The patch printing unit 25a is a module that prints a plurality of patches based on the black patch data 15c and the composite patch data 15d. That is, the patch printing unit 25a acquires the black patch data 15c composite patch data 15d from the HDD 15 and transfers it to the halftone processing module 21c. As a result, halftone processing is executed on the CMYKlclm tone values of the black patch data 15c and the composite patch data 15d. The data after the halftone process is converted into print data by the process of the print data generation module 21 d and output to the printer 40. With this process, the plurality of patches described above are printed.

The colorimetric value acquisition unit 25b is a module that acquires colorimetric data by the colorimeter 50, and can acquire both the OD value and the L ^* a ^* b ^* value. The OD value of the patch printed based on the black patch data 15c and the composite patch data 15d is acquired. In other words, after a plurality of patches are printed by the printer 40, the user operates the colorimeter 50 to measure its OD value and inputs it to the computer 10. When the OD value is input to the computer 10, the colorimetric value acquisition unit 25b acquires data indicating the OD value, and stores each patch in association with the OD. In the present embodiment, a patch printed based on the black patch data 15c is set to No. 0, and other inks are distinguished by assigning numbers in the order of measurement.

  Based on the OD value acquired by the colorimetric value acquisition unit 25b, the patch selection unit 25d compares the patch printed based on the black patch data 15c with the patch printed based on the composite patch data 15d. , A module that selects a patch that has a darker density than black in the K ink single color and has the highest density among them. The ink amount data determination unit 25c refers to the data of the selected patch, and records, in the HDD 15, gradation values indicating the usage amount of K ink and the usage amount of other ink in the patch as ink amount data 15e.

  With the above processing, the combination of ink amounts that are darker than the highest density black that can be output with a single K ink color and the ink amount for each color are grasped, so the LUT creation unit 25e of the LUT creation program 25 Creates the LUT 15b while reflecting the ink amount data 15e in the CMYKlclm data for printing a dark black.

  The LUT creation unit 25e includes a color separation processing unit 25e1. The color separation processing unit 25e1 makes provisional determination in a low-dimensional (three-dimensional in this embodiment) space less than the number of inks, and determines the gradation value of the provisionally determined color component based on a predetermined color separation rule. This is a module for converting to gradation values in a multidimensional space. In the present embodiment, a process of reflecting the ink amount data 15e is performed in the process of the color separation process. As a result, it is possible to create a LUT 15b that can express a dark portion with a sufficiently high density and print an image.

(2) LUT creation processing:
Next, processing in the LUT creation program 25 will be described in detail based on the flowchart shown in FIG. In the LUT 15b of this embodiment, RGB data is defined so as to cover the entire space in the sRGB color space, and the LUT 15b is created by associating the RGB data with the CMYKlclm data. For this purpose, tone values in the sRGB color system used in the display 18 and the CMYKlclm color system corresponding to the ink used in the printer 40 are converted into coordinate values in the L ^* a ^* b ^* space, and the L ^* The RGB data and the CMYKlclm data are associated with each other in the a ^* b ^* space.

Therefore, LUT creation unit 25e, first plurality of RGB data to cover the color gamut of the display 18 at step S100 (e.g., 17 ³⁾ are selected and determined as the representative color of the display 18. In step S105, the determined RGB data is converted into coordinate values in the L ^* a ^* b ^* space. Note that image data compliant with the sRGB standard can be converted into coordinate values in the L ^* a ^* b ^* space by a known conversion formula. Of course, the output color corresponding to the RGB data may be measured by a colorimeter or the like to obtain the L ^* a ^* b ^* value. As a result, the L ^* a ^* b ^* value of the color corresponding to the representative color of sRGB is obtained, and the correspondence between the RGB data and the L ^* a ^* b ^* value is defined.

  In step S110, the patch printing unit 25a, the colorimetric value acquisition unit 25b, the ink amount data determination unit 25c, and the patch selection unit 25d of the LUT creation program 25 determine the ink amount data 15e. This process will be described in detail later. When the ink amount data 15e is determined, the color separation processing unit 25e1 of the LUT creation unit 25e temporarily determines CMYKlclm data indicating the color of the color measurement target patch in steps S115 to S125.

  First, in step S115, a predetermined number (for example, 1000) of data (CMY data) is determined in a CMY color space lower than the six dimensions of CMYKlclm. At this time, each CMY tone value range in the CMY color space is defined as the same value range as CMY in the CMYKlclm data, and the tone value range is divided into nine equal parts, and the obtained ten tone values are arbitrarily combined. Generate data.

  In step S120, CMYK data is generated from the CMY data by the undercolor removal process. In other words, since a predetermined amount of the three CMY colors is combined, it is perceived as an achromatic color, so that it can be considered that the predetermined amount of CMY ink and the predetermined amount of K ink are equivalent. Therefore, a part of the CMY data is set as K data by using this equivalent conversion. As a result, CMY data can be converted into CMYK data. In the undercolor removal processing, equivalent conversion of the maximum amount that can be converted may be performed, conditions for suppressing graininess may be imposed, and various methods can be employed.

  In step S125, CMYKlclm data is generated from the CMYK data by multicolor separation processing. That is, since the C ink and the lc ink have substantially the same hue and different densities, it is possible to perform printing of substantially equivalent colors by recording more lc ink than the C ink. Similarly, printing of substantially equivalent colors can be performed for M ink and lm ink by recording more lm ink than M ink.

  Therefore, the amount of lc ink for outputting a color equivalent to a predetermined amount of C ink is determined in advance, and equivalent conversion is performed in which part of the C ink is replaced with lc ink. In addition, an amount of lm ink for outputting a color equivalent to a predetermined amount of M ink is determined in advance, and equivalent conversion is performed in which part of the M ink is replaced with lm ink. As a result, CMYK data can be converted into CMYKlclm data. It should be noted that various methods can be employed for multi-color separation processing, and conditions for not exceeding the upper limit that can be recorded on the printing medium, conditions for smoothing the brightness change, and for suppressing graininess Conditions may be imposed.

  In the processing up to step S125, CMYKlclm data is provisionally determined without reflecting the ink amount data 15e. Therefore, in order to reflect the ink amount data 15e in the temporarily determined CMYKlclm data, the ink amount data 15e is acquired from the HDD 15 in step S130. Then, the color separation processing unit 25e1 executes a maximum density securing process in step S135.

  The maximum density ensuring process is a process for converting CMYKlclm data for outputting at least the highest density black so that it is not a single color of K ink but an amount reflecting the ink amount indicated by the ink amount data 15e. In this case, the ink amount is gradually changed in the other CMYKlclm data. That is, in the CMYKlclm data provisionally determined in step S125, the CMYKlclm data for outputting the highest density black is limited to only the K ink single color and the upper limit value (the ink that can record one kind of ink on the printing medium). The upper limit of the amount).

  Therefore, the usage amount of the K ink is rewritten to the usage amount indicated by the ink amount data 15e, and the usage amount of the other ink is rewritten to the usage amount indicated by the ink amount data 15e. Further, in the CMYKlclm data provisionally determined in step S125, the gradation value of K ink gradually decreases and the gradation values of other inks gradually increase as the color changes from the darkest black to the light color. Therefore, in order to suppress a sudden change in the ink usage, the CMYKlclm data provisionally determined so that the usage of the other ink gradually changes as the color changes from the darkest black to the lighter color can be changed. It is.

  It should be noted that at least if the ink amount data 15e is reflected in the CMYKlclm data for outputting the highest density black, the object of the present invention can be achieved, but a rapid change in the amount of ink used can be achieved as in the present embodiment. By suppressing, it can be set as more useful LUT15b. Of course, various conditions can be taken into consideration in the maximum density securing process in step S135. For example, it is possible to impose conditions that do not exceed the upper limit that can be recorded on the print medium, conditions that suppress graininess, and the like.

  In the above-described maximum density securing process, the temporarily determined CMYKlclm data is changed. At this time, the equivalent color conversion is not performed by the reverse process of the undercolor removal process. That is, in the present invention, other ink is combined with the K ink in order to output a darker black than the highest density black that can be output with a single K ink color. Therefore, the hue and lightness may fluctuate as compared with the highest density black, but such a change in hue and lightness is allowed, and priority is given to outputting dark black. Further, according to the experiment by the applicant of the present application, as described later, the other inks to be combined with the K ink are one color or two colors.

  Therefore, the technical idea is different from the invention in which equivalent color conversion is performed by three color components such as under color removal, and the process in step S135 is not the reverse process of the under color removal process. As described above, the hue and lightness variation due to the combination of K ink with another ink is allowed, but this variation does not have a great influence on the LUT 15b. That is, the highest density black is originally very dark in color, and even if the hue slightly changes, the change can hardly be perceived. Further, in the LUT 15b, sRGB data indicating the same color and CMYKlclm data are associated with each other by the process described later. Therefore, when sRGB data is converted into CMYKlclm data with reference to the LUT 15b, a color that is significantly different from the color indicated by the sRGB data is not output.

When the CMYKlclm data is determined in step S135, the color separation processing unit 25e1 passes the CMYKlclm data to the halftone processing module 21c in step S140 and prints the patch. This patch is a colorimetric patch, and the printed patch is measured by the colorimeter 50. That is, the user operates the colorimeter 50 to measure its L ^* a ^* b ^* value and inputs it to the computer 10. When the L ^* a ^* b ^* value is input to the computer 10, the colorimetric value acquisition unit 25b acquires the L ^* a ^* b ^* in step S145. This L ^* a ^* b ^* value is delivered to the LUT creation unit 25e.

Through the above processing, the CMYKlclm data determined in step S135 and the L ^* a ^* b ^* values of the colors printed by the CMYKlclm data are associated with each other. As a result, the color of the L ^* a ^* b ^* value corresponding to the sRGB representative color, the L ^* a ^* b ^* values of the color to be printed by the CMYKlclm data will be obtained, in step S150 These L ^* a ^* b ^* values are used to define the correspondence between RGB data and CMYKlclm data.

Here, although the coordinate values in the L ^* a ^* b ^* space acquired in steps S105 and S145 are not necessarily coincident with each other, an interpolation operation or an optimum value is based on each L ^* a ^* b ^* value. If a search method or the like is performed, the correspondence between sRGB data and CMYKlclm data can be obtained. Even if interpolation calculation is used, the correspondence between sRGB data and CMYKlclm data can be accurately defined by printing a large number of the patches and obtaining L ^* a ^* b ^* values for a large number of colors. it can.

(2-1) Ink amount data determination process:
Next, the ink amount data determination process in step S110 will be described in detail. FIG. 3 is a flowchart of the ink amount data determination process. In this process, the patch printing unit 25a first acquires the black patch data 15c and the composite patch data 15d from the HDD 15 in step S200, and in step S210, the black patch data 15c and the composite patch data are sent to the halftone processing module 21c. Deliver 15d.

  FIG. 4 is a diagram showing an example of a patch printed as a result. In the figure, the patch is indicated by a rectangle, a black patch is printed at the right end, and a combined patch is printed side by side. The main ink used in each patch is K ink, and the color is black, but in the composite patch, CMYlclm ink is used in combination with K ink, and the density differs in each patch. ing.

  In addition, the amount of ink used in the patch is shown as a percentage below the rectangular patch in the figure. Here, the upper limit value of the ink amount that can record one type of ink on the print medium is 100%. That is, when recording one type of ink within a predetermined area of the print medium P, the upper limit usage amount that does not cause bleeding or the like is 100%. In the printing medium P and the ink set in the present embodiment, the upper limit value when recording two or more types of ink exceeds the above-mentioned 100%, and other inks can be recorded from the state of 100% K ink. it can.

  Therefore, in the composite patch, K ink is fixed to 100% and CMYlclm is added by 10% each. Of course, the purpose of the composite patch is to grasp the combination of inks whose density is high, and the amount of CMYlclm used is not necessarily 10%. For example, patches of 5%, 15%, and 20% for each color may be printed, or a plurality of CMYlclm colors may be combined. In any case, after printing the black patch and the composite patch, in step S220, the colorimetric value acquisition unit 25b acquires the OD value. That is, when the user measures the color of the patch printed by the printer 40 using the colorimeter 50 and inputs the color measurement result to the computer 10. The OD value is acquired by the colorimetric value acquisition unit 25b.

The patch selection unit 25d performs steps S230 to S260 shown in FIG. 3 in order to select a composite patch that outputs the highest density. First, in step S230, a predetermined number is assigned to the OD value for each patch acquired in step S220. In the present embodiment, the black patch at the right end shown in FIG. 4 is defined as 0, the second composite patch from the right is defined as 1, and the number increases as it goes to the left. The number is Imax. In this specification, the n-th OD value is expressed as OD _n.

In step S240, the counter I is initialized to “1”, and in step S250, it is determined whether or not the OD value (OD _I ) of the composite patch is larger than the OD value (OD ₀ ) of the black patch. If it is not determined in step S250 that the OD value of the composite patch is greater than the OD value of the black patch, the counter I is incremented in step S260, and step S250 is repeated. If it is determined in step S250 that the OD value of the composite patch is larger than the OD value of the black patch, black having a darker density than the black patch can be expressed by the composite patch to be determined.

Therefore, in step S252, the OD value (OD _I ) of the composite patch determined to be larger than the OD value of the black patch is temporarily stored in RAM or the like, and whether the counter I reaches the maximum value (Imax) in step S254. Determine whether or not. If it is not determined in step S254 that the counter I has reached the maximum value (Imax), step S260 is performed, and the processes in and after step S250 are repeated.

When it is determined in step S254 that the counter I has reached the maximum value, the ink amount data determination unit 25c refers to the RAM in step S270, and the maximum OD value (maxOD _n ) from the temporarily stored OD value. , And the ink usage amount is acquired by referring to the combined patch data of the corresponding patch. In step S280, the acquired ink use amount is recorded in the HDD 15 as ink amount data 15e. With the above processing, it is possible to specify the combination of ink and the amount of use for outputting higher density black recorded with a single K ink color.

(3) Example:
FIG. 5 is a graph showing the OD value measured by the applicant. In the figure, the OD value measured by printing a K ink only patch and a patch obtained by adding one color of CMYlclm to K ink in a certain ink set is shown. Here, the patch is printed by increasing the amount of K ink used in each patch. In FIG. 5, the amount of CMYlclm ink used is constant, and is 10% or 0% for each color. Therefore, the horizontal axis of the graph is the K ink gradation value, and the vertical axis is the OD value. In this graph, patches having the same amount of CMYlclm ink used are indicated by the same symbol.

  The straight line parallel to the vertical axis shown in the graph of FIG. 5 corresponds to the upper limit of the ink amount that can record one type of ink on the print medium. When the gradation value of K ink is set to 0 in each patch, the OD value becomes about 0 to 0.5, and the OD value gradually increases as the gradation value of K ink increases. However, when the gradation value of K ink approaches the upper limit value, the increasing tendency of the OD value gradually weakens, and almost no increase in the OD value is observed when the upper limit value is exceeded. However, in the ink set shown in FIG. 5, the increase is almost monotonously toward the upper limit value, and it is considered that the OD value of each patch takes the maximum value at the upper limit value.

  Therefore, if the OD value larger than the K ink single color can be obtained by recording the K ink up to the upper limit value of the printing medium and further adding other ink, the preferred ink combination and use in the above-described ink amount determination device It becomes possible to specify the quantity. In fact, as shown in FIG. 5, in the above upper limit value, the patch combining the K ink and the C ink and the patch combining the K ink and the lc ink have an OD value larger than that of the K ink single color patch.

  For this reason, assuming that a patch in which at least 10% of each color of CMYlclm is added to K ink is assumed as the composite patch, and processing by the above-described ink amount determination device is performed, it is obtained using only K ink. It is possible to determine the amount of ink that outputs darker black than the highest density black. If a color conversion profile is created using this ink amount, the color for obtaining CMYKlclm data for recording black at a density higher than the highest density black obtained using only K ink by color conversion. It becomes a conversion profile. Furthermore, by referring to the color conversion profile by the print control device, it is possible to control the print device so that black is recorded at a density higher than the highest density black obtained using only K ink.

(4) Other embodiments:
The above embodiment is an embodiment of the present invention, and other than the above, as long as the amount of ink used for outputting a darker color can be obtained as compared with the case where a specific color ink is used alone. Various embodiments can also be employed. For example, the present invention is not limited to the configuration in which the ink amount determination device, the color conversion profile creation device, and the print control device are formed by the single computer 10 as described above, and any one or a combination thereof may be configured by a plurality of computers.

  In the above-described embodiment, other ink is combined with K ink to output the highest density black. However, cyan or magenta or the like is used to output a dark color in other colors such as cyan or magenta. May be output as a patch of a specific color, and a combined patch in which other ink is combined with the specific color may be output for comparison. As a result, it is possible to obtain a higher density output with a limited ink set, and it is possible to execute printing while reliably using colors in the color gamut of the ink set.

  Further, in the above embodiment, the amount of K ink used is fixed in the composite patch to be compared with the black patch, but the density of K ink may be changed. That is, if the density of K ink is made smaller than the upper limit value, the amount of other ink used can be increased, and the number of combinations of K ink and other ink can be increased. Accordingly, it is possible to determine the ink combination and the ink usage amount for outputting high density black from among many options.

  When the gradation value of K ink is smaller than the upper limit value, the gradation value for which the usage amount of K ink is smaller than the upper limit value is used as data for outputting the highest density black in the maximum density securing process in step S135. Will be set. In the ink set shown in FIG. 5, the density does not increase by reducing the amount of K ink used. Therefore, in the case of such an ink set, it is preferable to create a composite patch by fixing the amount of K ink used to the upper limit.

  However, depending on the ink, the tendency of change in density may be reversed by reducing the K ink, and the upper limit value when recording multiple types of ink is the same as the upper limit value when recording one type of ink. Or it may be close. In such a case, it is preferable not to fix the usage amount of K ink to the above upper limit value, but to create a composite patch including patches whose usage amount of K ink is smaller than the upper limit value.

  Furthermore, in the above embodiment, the maximum density securing process is performed after the undercolor removal process shown in step S120 and the multicolor separation process shown in step S125. However, the order of the processes may be changed. For example, the maximum density securing process may be performed after the undercolor removal process, and the multi-color separation process may be performed thereafter. In this case, it is preferable that the data for outputting the specific color with the highest density is not changed or greatly changed in the multi-color separation process.

  Furthermore, the composition patch is not limited to the configuration in which one chromatic color ink is added to the K ink, and a configuration in which two colors of ink or achromatic color ink is added may be employed. FIG. 6 is a graph showing an OD value obtained by measuring a patch obtained by adding an achromatic color ink or a plurality of inks to K ink in a certain ink set. This ink set is composed of CMYKlclm colors and light black ink (lk).

  In the figure, a patch containing only K ink, a patch obtained by adding one color of lk ink to K ink, a patch obtained by combining CMYlclmlk with K ink and changing the amount of each ink used, is printed. The measured OD value is shown. In this case as well, patches are printed by increasing the amount of K ink used in each patch, with the horizontal axis representing the K ink gradation value and the vertical axis representing the OD value. Also, patches having the same amount of CMYlclmlk ink used are indicated by the same symbol.

  The straight line parallel to the vertical axis shown in the graph of FIG. 6 corresponds to the upper limit of the amount of ink that can be recorded on one type of ink on the print medium. In the ink set shown in FIG. Increasing the tone value also increases the OD value. However, as the K ink tone value approaches the upper limit, the OD value tends to increase gradually, and when the upper limit is exceeded, the increase in the OD value is hardly observed. It becomes impossible. When comparing the OD value of each color at the upper limit value, a patch obtained by adding 10% lk ink to a K ink, a patch obtained by adding 20% lk ink, a patch obtained by adding 5% each of C ink and lk ink, C ink, The OD value is larger than the OD value for the K single color, with a total of four types of patches including 10% lk ink.

  For this reason, assuming the patch including any of the above four types of patches as the composite patch, and performing the processing by the above-described ink amount determination device, the highest density black that can be obtained using only K ink. It is possible to determine the amount of ink that outputs darker black. Further, it is possible to perform color conversion so that dark black is output according to the color conversion profile. Furthermore, the printing apparatus can be controlled to output dark black. Of course, the combination of the ink set and the amount of ink used shown in FIG. 6 is also an example, and a synthetic patch containing the colorless ink using another ink, for example, an ink set containing a colorless ink for adjusting glossiness and image quality. May be printed for comparison.

It is a figure which shows schematic structure of a computer. It is a flowchart of a LUT creation process. 5 is a flowchart of ink amount data determination processing. It is a figure which shows the example of the patch printed. It is a figure which shows the colorimetric value of a patch. It is a figure which shows the colorimetric value of a patch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Computer, 15 ... HDD, 15a ... Image data, 15b ... LUT, 15c ... Black patch data, 15d ... Composite patch data, 15e ... Ink amount data, 21 ... PRTDRV, 21a ... Image data acquisition module, 21b ... Color conversion Module, 21c ... Halftone processing module, 21d ... Print data generation module, 25 ... LUT creation program, 25a ... Patch printing unit, 25b ... Colorimetric value acquisition unit, 25c ... Ink amount data determination unit, 25d ... Patch selection unit, 25e ... LUT creation unit, 25e1 ... color separation processing unit, 40 ... printer, 50 ... colorimeter

Claims (14)

A colorimetric value acquisition means for acquiring a colorimetric value of a specific color patch recorded so as to have the highest density of a specific color ink and a plurality of composite patches recorded by combining the specific color ink and another ink; ,
Patch selecting means for comparing the density of the patch based on the colorimetric value and selecting a composite patch having a higher density than the specific color patch;
And an ink amount data determination unit that uses data indicating the amount of the other ink used and the amount of the specific color ink used in the selected composite patch as ink amount data for outputting the specific color having the highest density. An ink amount determining apparatus. 2. The ink amount determining apparatus according to claim 1, wherein the specific color ink is black. 3. The ink amount determination apparatus according to claim 1, wherein the specific color ink and the other ink are inks that are simultaneously mounted on a predetermined printing apparatus. 4. The ink amount determination apparatus according to claim 1, wherein the composite patch is a plurality of patches obtained by varying the amount of the other ink used. 5. The ink amount determining apparatus according to claim 1, wherein the other ink used in the synthetic patch is one color or two colors. An ink amount determination method for determining ink amount data for outputting a specific color at a maximum density,
A colorimetric value acquisition step of acquiring colorimetric values of a specific color patch recorded so as to obtain the highest density of a specific color ink and a plurality of composite patches recorded by combining the specific color ink and another ink; ,
A patch selection step of comparing the density of the patch based on the colorimetric value and selecting a composite patch having a higher density than the specific color patch;
An ink amount determination method comprising: an ink amount data determination step using the ink amount data as data indicating the use amount of the other ink and the use amount of a specific color ink in the selected composite patch . An ink amount determination program for determining ink amount data for outputting a specific color at the highest density,
A colorimetric value acquisition function that acquires the colorimetric values of a specific color patch recorded to achieve the highest density of a specific color ink and multiple composite patches recorded by combining a specific color ink and another ink; and ,
A patch selection function for comparing patches based on the colorimetric values and selecting a composite patch having a higher density than the specific color patch;
An ink amount that causes a computer to realize an ink amount data determination function that uses the ink amount data as data indicating the amount of other ink used and the amount of specific color ink used in the selected composite patch Decision program. In the color conversion profile creation device for creating a color conversion profile based on the ink amount data determined in claim 1,
A plurality of pieces of patch data specifying the amount used for each of a plurality of inks used in the printing apparatus, and the amount of ink used between the specific color ink and the other ink in the patch for outputting the specific color having the highest density Patch data acquisition means for acquiring patch data designated by the ink amount data;
A colorimetric patch printing means for printing a colorimetric patch on the printing device based on the patch data;
The colorimetric values of the printed plurality of colorimetric patches are acquired by the colorimetric value acquisition unit, and correspond to colors printed with an arbitrary ink usage amount and the ink usage amount based on the colorimetric value. A color conversion profile creation device comprising color conversion profile creation means for creating a color conversion profile that defines a correspondence relationship with image data. The patch data is to determine the usage amount of each ink by tentatively determining the usage amount of a plurality of inks according to a predetermined rule and then distributing a part of the specific color ink after the temporary determination to the other ink. 9. The color conversion profile creation apparatus according to claim 8, wherein In the color conversion profile creation method for creating a color conversion profile based on the ink amount data determined in claim 6,
A plurality of pieces of patch data specifying the amount used for each of a plurality of inks used in the printing apparatus, and the amount of ink used between the specific color ink and the other ink in the patch for outputting the specific color having the highest density A patch data acquisition step of acquiring patch data specified by the ink amount data;
A colorimetric patch printing step for causing the printing apparatus to print a colorimetric patch based on the patch data;
The colorimetric values of the printed plurality of colorimetric patches are acquired, and a correspondence relationship between an arbitrary ink usage amount and image data corresponding to a color printed with the ink usage amount is obtained based on the colorimetric value. A color conversion profile creation method comprising: a color conversion profile creation step of creating a prescribed color conversion profile. In a color conversion profile creation program for creating a color conversion profile based on the ink amount data determined in claim 7,
A plurality of pieces of patch data specifying the amount used for each of a plurality of inks used in the printing apparatus, and the amount of ink used between the specific color ink and the other ink in the patch for outputting the specific color having the highest density A patch data acquisition function for acquiring the patch data specified by the ink amount data,
A colorimetric patch printing function for causing the printing device to print a colorimetric patch based on the patch data;
The colorimetric values of the printed plurality of colorimetric patches are acquired by the colorimetric value acquisition function, and correspond to colors printed with an arbitrary ink usage amount and the ink usage amount based on the colorimetric value. A color conversion profile creation program that causes a computer to realize a color conversion profile creation function for creating a color conversion profile that defines a correspondence relationship with image data. In the print control apparatus for executing printing with reference to the color conversion profile created in claim 8,
Image data acquisition means for acquiring image data in which a color for each pixel in an image to be printed is expressed in a predetermined color system;
Color conversion that converts the color system of the acquired image data with reference to the color conversion profile created by the color conversion profile creation means into an ink color system that expresses the color of the pixel by gradation for each ink color Means,
A printing control apparatus comprising: a printing unit that specifies an amount of ink used according to a gradation for each ink color after color conversion and causes the printing apparatus to form an image. In the printing control method for executing printing with reference to the color conversion profile created in claim 10,
An image data acquisition step of acquiring image data expressing a color for each pixel in an image to be printed in a predetermined color system;
Color conversion that converts the color system of the acquired image data with reference to the color conversion profile created in the color conversion profile creation step into an ink color system that expresses the color of the pixel by gradation for each ink color Process,
A printing control method comprising: a printing step of specifying an ink use amount by gradation for each ink color after color conversion and causing the printing apparatus to form an image. In a print control program for executing printing with reference to the color conversion profile created in claim 11,
An image data acquisition function for acquiring image data in which a color for each pixel in an image to be printed is expressed in a predetermined color system;
Color conversion that converts the color system of the acquired image data with reference to the color conversion profile created by the color conversion profile creation function into an ink color system that expresses the color of the pixel by gradation for each ink color Function and
A printing control program for causing a computer to realize a printing function for specifying an ink usage amount by gradation for each ink color after color conversion and causing the printing apparatus to form an image.

Images