JP2005238465A - Determination of amount of used ink for harmoniously realizing high density and high gloss - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that high density and high gloss are hard to realize harmoniously. <P>SOLUTION: When the limiting amount of an used ink of a specific color is determined in forming an image by combining the ink of the specific color and an alternative ink capable of being substituted for the ink of the specific color in a printer, the alternative ink is substituted for part of the ink of the specific color in accordance with predetermined rules, and a plurality of patches with different amounts of the used ink of the specific color are printed by the printer. Colorimetric values of the printed patches are acquired, and the patches are compared with one another according to the colorimetric values; the patch in which a change in density with respect to the amount of the used ink of the specific color becomes saturated is selected, and the amount of the used ink of the specific color for the selected patch is acquired, and set as a limiting amount of the used ink of the specific color. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for determining a use amount limit of a specific color ink in determining a use amount of ink in a printing apparatus.

In recent printing apparatuses, 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, it is possible to obtain a glossy printed material by selecting a predetermined glossy paper as a printing medium, or to select a preferred ink from dye-based ink and pigment-based ink according to the purpose, or dye And the pigment content is adjusted to improve glossiness and shelf life. In addition, when an image is formed by combining a plurality of inks, there are a plurality of color combinations for expressing substantially the same color. Therefore, the glossiness is also adjusted by adjusting the amount of ink used. (For example, refer to Patent Document 1).
JP 2002-327138 A

In the above prior art, it is difficult to achieve both high density and high gloss. In other words, in order to improve the quality of printed matter, the higher the color density obtained with each ink, the higher the ability to express the image and the easier it is to perform high-quality printing. It is easy to give an impression. However, the conventional technique cannot achieve both high density and high gloss. For example, in the above-mentioned Patent Document 1, composite black is mainly used when printing black on glossy paper. Although composite black can achieve high gloss, the density of black is lower than that of black using a single color black ink, and it is difficult to give depth to black expression.
The present invention has been made in view of the above problems, and provides a method for determining the amount of ink used that can achieve both high density and high gloss.

  In order to achieve the above object, the present invention prints a plurality of patches using a specific color of ink in a plurality of different usage amounts. Then, based on the colorimetric values of these patches, the ink usage amount of the specific color is obtained so that the density change of the specific color is saturated. As a result, the density of the specific color becomes as high as possible, but the minimum amount of ink used to obtain the density can be acquired. In particular, when pigment-based ink is printed on glossy paper, the gloss decreases as the ink usage increases, so the minimum ink usage that makes the density of the specific color as dark as possible is the density of the specific color. It can be said that the ink usage is selected so that the gloss is as high as possible. Therefore, by setting this usage amount as the ink usage limit value for a specific color and performing printing within this limit, printing that achieves both high density and high gloss can be performed.

  Here, as the ink of the color that can be replaced, any configuration can be adopted as long as it is an ink that can appear to be the same color as the specific color when the ink is recorded on the print medium. That is, in a four-dimensional or higher color system, colors that can substitute for other colors are generally included, and the same color can be expressed by a combination of different color component values. Therefore, for a printing apparatus that uses four or more colors of ink, it is generally possible to define an ink of a color that can substitute for a specific color of ink.

  For example, when a plurality of hue inks are combined and adhered to a minute position, they may appear as other colors to the human eye. Therefore, when a specific color can be replaced with a combination of a plurality of inks having different hues, a configuration in which these plurality of inks are used as the replacement inks can be employed. More specifically, K (black) can be expressed by combining three colors of CMY (cyan, magenta, and yellow). Therefore, K can be used as a specific color ink, and CMY three colors can be used as alternative inks. Needless to say, various configurations such as a configuration in which R (red) ink is replaced with M ink and Y ink can be employed.

  In addition, light and dark inks that have the same hue and different densities in a state where unit amount of ink is recorded on the medium due to different colorant amounts per unit weight, either becomes a specific color and the other substitutes Can be ink. In other words, such dark and light inks can be replaced by adjusting the ink discharge amount so that, for example, when the ink is recorded on the medium at a weight ratio of the light ink 2 to the dark ink 1, the ink appears to be substantially the same color. Therefore, it is possible to adopt a configuration in which light ink is used as an alternative ink when dark ink is used as a specific color ink.

  In the patch printing means, it is only necessary to print a plurality of patches having different amounts of specific color ink. However, in order to systematically evaluate the amount of specific color ink used, the use of specific color ink is used. It is preferable to follow a predetermined rule, such as increasing the amount at predetermined intervals. In addition, when only the usage amount of the specific color ink is changed, it is natural that the density and gloss change. Therefore, in the present invention, a part of the specific color ink is replaced by a predetermined rule according to a predetermined rule. Substitute with to change the amount of substitution.

  This rule is a rule for substituting for a specific color, and even if it is substituting, it is sufficient to determine the rule so that it looks almost the same color, and in fact, exact color matching is not required. For example, the rule can be determined by the above-described weight ratio or the like. That is, in order to output almost the same color as the output in the unit weight of the K ink, when each CMY ink needs a unit weight, the weight 1 of the CMY ink is substituted for the weight 1 of the K ink. Alternative rules can be defined as follows:

  As described above, when the amount of ink used in the patch is determined by substituting the specific color ink according to the predetermined rule, the amount of ink used for outputting the predetermined target color by combining the specific color ink and the alternative ink Can be determined. Of course, as described above, the output colors of a plurality of patches are not required to be strictly constant, but according to such a patch, at least a change in density with respect to a change in ink usage of a specific color is evaluated. be able to.

  The colorimetric value acquisition unit only needs to be able to acquire the colorimetric values of a plurality of printed patches, and performs various colorimetry using a predetermined colorimeter to acquire data indicating the colorimetry result. The colorimetric value can be acquired by the configuration. The colorimetric value may be any value that serves as an index for evaluating the density of the specific color. If this index can be obtained by color measurement, a patch whose density is saturated with respect to the amount of ink used for a specific color can be easily obtained by the patch selection means.

  The patch selection means only needs to be able to select a patch in which the density of a specific color is saturated. Of course, in the present invention, the colorimetric value and the data indicating the patch to be measured are associated with each other so that the colorimetric value indicating which patch is indicated can be known. With this configuration, it is possible to easily associate the density in each patch with the amount of ink used. In this case, it may be determined that the ink is saturated when the density hardly changes with respect to the ink usage, and whether or not the ink is saturated by determining a density change criterion with respect to a unit change of the ink usage. Can be determined.

  As a particularly preferable example as an object to which the present invention is applied, a configuration in which the specific color is K and the color of the alternative ink is CMY can be employed. That is, when K and CMY are in an alternative relationship, when the CMY ink and K are combined and expressed, the color based on the combination of CMY and the color based only on K are more likely to express darker black. However, when the amount of K ink used is increased, the density may be saturated and the gloss may gradually decrease. In such a situation, the minimum required amount of K ink used to obtain the maximum density of K can be defined. As a result, the usage limit of the K ink can be determined, and high density and high gloss can both be achieved by performing printing within this limit. That is, dark black can enhance the gradation expression in the dark portion, and at the same time, the glossiness can be expressed as much as possible.

  In the present invention, it is only necessary to determine the density and gloss of a specific color based on the colorimetric value, and an OD value (Optical Density) and glossiness can be adopted as the values for that purpose. That is, the OD value is defined as “−log (reflected light intensity of sample / incident light intensity)” and the glossiness is defined as “reflected light intensity of sample / reflected light intensity of standard mirror plate”. According to the OD value, the density of the printed material can be evaluated, and according to the glossiness, the gloss of the printed material can be evaluated. According to the applicant's measurement, it has been confirmed that the OD value actually saturates and the glossiness decreases as the ink usage increases. Therefore, based on these values, it is possible to easily determine the usage limit for making the density and gloss as high as possible. These values can be easily measured with a predetermined colorimeter.

  In the present invention, the density of the specific color becomes as high as possible by acquiring the amount of ink used for the specific color so that the density change of the specific color is saturated. It is sufficient if the amount can be acquired. As a specific determination method for this purpose, it is possible to employ a configuration in which a patch having a maximum density of a specific color and a gloss as large as possible is selected. That is, in a situation where the gloss gradually decreases and the density increases to a certain extent as the amount of ink used for a specific color increases, but is saturated, the maximum density can be obtained by selecting a patch with the maximum density of the specific color and a gloss that is as large as possible. It is possible to obtain the amount of ink used to obtain the density and gloss as high as possible.

  As described above, the method for defining the usage amount limitation that realizes both high density and high glossiness based on the colorimetric values is not necessarily limited to a substantial apparatus. It is also effective as a method invention. In addition, the above-described usage limit determining device may exist alone, or may be used in a state of being incorporated in a certain device. The idea of the invention includes various aspects. Further, it can be changed as appropriate, such as software or hardware.

  When the software of the usage amount limit determining device is realized as an embodiment of the idea of the invention, it naturally exists and is used on a recording medium in 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. In addition, the duplication stages such as the primary duplication product and the secondary duplication product are the same without any question. Of course, it can also be specified as a program invention like the invention described in claim 6.

  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 using a color conversion profile. As an aspect to which the present invention is applied, a color conversion profile creation apparatus, creation method, creation, and the like, as in claims 7, 8, and 9, It is also possible to specify the invention as a program. Further, as in claims 10, 11, and 12, it is possible to configure a print control apparatus, control method, and control program using the color conversion profile created as described above.

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) Maximum ink amount determination process:
(3) 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, a usage amount restriction 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 the maximum ink amount, 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 is defined so as to use K ink within a usage amount limit determined by processing to be described later. As a result, it is possible to express a dark portion with a sufficiently high density and print an image without reducing glossiness.

  The halftone processing module 21c is a module that performs halftone processing for converting the gradation value of each pixel expressed in the CMYKlclm color system and expressing it with the recording density of the ink droplets. Halftone processing is performed based on the above. 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, a maximum ink amount determination unit 25c, a patch selection unit 25d, and an LUT creation unit 25e. Patch data 15c is recorded in advance in the HDD 15 as data used in processing in the LUT creation program 25, and the LUT creation program 25 creates maximum ink amount data 15d using the patch data 15c. Further, the LUT 15b is created using the maximum ink amount data 15d.

  The patch data 15c is a patch for printing black by combining the K ink and the CMY ink, and data indicating a plurality of patches in which the usage amount of the K ink is changed stepwise. In the present embodiment, the patch data 15c is composed of data indicating the color of these patches by the CMYK gradation values. The maximum ink amount data 15d is data indicating a usage limit value of K ink. The patch printing unit 25a is a module that prints a plurality of patches based on the patch data 15c.

  That is, the patch printing unit 25a acquires the patch data 15c from the HDD 15 and transfers it to the halftone processing module 21c. As a result, halftone processing is performed on the CMYK gradation values of the patch data 15c. 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 patch data 15c 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 this embodiment, the numbers are distinguished in ascending order of the amount of K ink used.

  The patch selection unit 25d is a module that selects a patch in which a density change with respect to a change in the usage amount of K ink is saturated based on the OD value acquired by the colorimetric value acquisition unit 25b. That is, the obtained plurality of OD values are compared, and even if the usage amount of K ink is changed, it is determined that the density change is saturated when the density change is equal to or less than a predetermined threshold, and the patch is determined. select. The maximum ink amount determination unit 25c refers to the patch data of the selected patch, and acquires the K ink usage amount in the patch as the K ink usage limit value. The acquired usage amount limit value is recorded in the HDD 15 as the maximum ink amount data 15d.

  With the above processing, the use amount limit value of K ink that achieves both high density and high glossiness is grasped, and therefore the LUT creation unit 25e of the LUT creation program 25 performs the K ink within the range of the use amount restriction. The LUT 15b is created while imposing restrictions on the use of. Here, the LUT creation unit 25e prints the second patch so that the K ink is used within the usage limit, and creates the LUT 15 based on the correspondence between the colorimetric value and the color indicated by the sRGB data. To do. As a result, it is possible to create a LUT 15b that can express a dark portion with a sufficiently high density and can print an image without reducing glossiness.

(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. 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, L ^* a ^* b ^* values of colors corresponding to the representative colors of sRGB are obtained, and the correspondence between RGB data and L ^* a ^* b ^* values is defined.

  Next, in step S110, a maximum ink amount determination process is performed by the patch printing unit 25a, the colorimetric value acquisition unit 25b, the maximum ink amount determination unit 25c, and the patch selection unit 25d. In step S115, the LUT creation unit 25e performs the color separation process while limiting the usage amount of the K ink so as not to exceed the usage amount limit of the K ink determined in step S110. Here, the color separation process is a process for expressing a color with a small number of inks with a larger number of inks by performing substitution with colors having a substitution relationship.

  That is, in a situation where a large number of inks can be used, such as the printer 40, a plurality of CMYKlclm data covering the color gamut of the printer 40 are compared with the above-described sRGB data even if data is extracted at random. However, data that is preferable to the above is not extracted. The CMYKlclm data specifies the amount of ink used, but it is necessary to consider various restrictions such as the maximum ink amount determined in step S110 and the maximum ink amount (duty limit) that can be recorded on the print medium. .

  Therefore, data such as CMY that covers almost the color gamut is formed using a small number of inks, and CMYKlclm data is generated by converting the data into a larger number of inks according to a predetermined color separation rule. Of course, this separation rule includes the K ink usage limit determined in step S110. In addition, since an accurate correspondence between the color indicated by the sRGB data and the color indicated by the CMYKlclm data is ensured by subsequent colorimetry, in this separation, it is determined whether or not the colors accurately match before and after the separation. There is no need to consider. That is, the color separation process may be performed by determining the color separation rule so that the color does not change greatly before and after the color separation.

When a plurality of CMYKlclm data are obtained from the CMY three-dimensional gradation values by the separation process, patch data for outputting a patch in a color specified by each CMYKlclm data is generated. The patch data obtained here is data for printing the second patch described above. Since this patch is a colorimetric object, the number of patches is set to a realistic range (for example, 10 ³ ) in which the colorimetric work can be performed. In step S120, the second patch is printed based on the patch data. That is, the patch data is transferred to the halftone processing module 21c, and is printed by the printer 40 after being processed by the print data generation module 21d.

When the second patch is printed, 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 S125. This L ^* a ^* b ^* value is delivered to the LUT creation unit 25e.

As a result, the correspondence between the CMYKlclm data and the L ^* a ^* b ^* values of the colors printed by the CMYKlclm data is defined. As a result of the above processing, 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 is obtained, in step S130 These L ^* a ^* b ^* values are used to define the correspondence between RGB data and CMYKlclm data.

Here, the coordinate values in the L ^* a ^* b ^* space obtained in steps S105 and S125 do not always coincide with each other, but the correspondence between the two data is obtained by an interpolation operation, an optimum value search method, or the like. be able to. Even if the interpolation calculation is used, the correspondence between the sRGB data and the 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.

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

  FIG. 4 is a diagram showing an example of a patch printed as a result. In the figure, a state where rectangular patches are printed side by side on the print medium P is shown. The color of the patch shown in the figure is black, but K ink and CMY ink are used in each patch, and the usage amount of K ink and the usage amount of CMY ink are different. That is, the patches are printed so that the amount of K ink used increases from left to right and the amount of CMY ink used decreases.

  More specifically, the amount of ink used for each color is shown below the rectangular patch in the figure, and here the amount of ink used is shown as a ratio to the duty limit. That is, when recording four colors 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 set to 100%, and each patch uses four colors of ink up to the upper limit of the duedy limit. In addition, the usage amount is changed at intervals of 5% so that the usage amount of the K ink changes from 2.5% to 97.5%. Here, in order to grasp the usage amount of K ink, both the 0% and 100% ink usage amounts are unnecessary and are omitted.

  Further, in the example shown in FIG. 4, it is considered that the color is almost maintained when the CMY ink usage amount is “1” and the CMY inks are respectively used. That is, it is assumed that K ink 1 and CMY ink 1 each have an alternative relationship. Therefore, if the K ink is removed from the ink usage amount of the duty limit and the remaining usage amount is evenly allocated, the CMY ink usage amount is obtained. As shown in FIG. It varies from 5% to 0.83%. Of course, the amount of ink used in the patch is not limited to the example shown in FIG. 4, and various configurations are adopted as long as a plurality of patches with different amounts of K ink can be output by substituting K ink with CMY ink. Is possible. For example, not only the duty limit of four colors but also the duty limit when printing three or single color ink on the printing medium P may be set to 100%, or the substitution ratio is changed and the K ink is 2.5%. C ink may be 32.5%, M ink may be 35%, and Y ink may be 30%, and various configurations can be employed.

  In the patch printed as described above, since the replacement is performed as described above, the color of the patch does not always vary greatly. However, the density and gloss vary depending on the amount of K ink used. This variation greatly affects the impression of the image printed by the printer 40. That is, if the density of black is low, the blackness is poor and the expressive power of the dark part is low, and if the gloss is low, the impression of low image quality is easily given. Therefore, the present invention selects a patch that realizes both high density and high gloss from these patches.

  For this reason, 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.

  FIG. 5 is an example showing the color measurement result. In the graph shown in the figure, the horizontal axis indicates the K ink usage (%). The vertical axis represents the OD value or the glossiness, the right vertical axis represents the OD value, and the left vertical axis represents the glossiness. Also, the solid black point shown in the graph is the OD value, and the white point is the glossiness. As shown in the figure, when the amount of K ink used is small, the OD value increases as the amount of K ink used increases. However, when the amount of K ink used exceeds about 30%, the OD value changes almost. Disappears and the concentration change is saturated.

  On the other hand, as shown in FIG. 5, the glossiness decreases approximately linearly as the amount of K ink used increases. According to the above analysis, the smaller the amount of K ink used, the higher the gloss, and the higher the amount of K ink used, the higher the density. However, when the amount of ink used exceeds a certain amount, the amount of K ink used increases. It turns out that it does not contribute to. Therefore, an ink amount exceeding the certain amount of ink used does not contribute to either density or gloss. Therefore, if the amount of K ink used is limited so as not to exceed the certain amount of ink used, both high density and high gloss can be realized. Note that it is a known property that the glossiness gradually decreases due to an increase in K ink. Since this property is premised on this property, it is not necessary to measure the glossiness.

In the patch selection unit 25d, steps S230 to S260 shown in FIG. 3 are performed in order to select a patch in which the density of K is saturated. First, in step S230, a predetermined number is assigned to the OD value for each patch acquired in step S220. In this embodiment, the leftmost patch shown in FIG. 4 is defined as No. 1, and the number increases as it goes to the right. 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 difference between the OD values of adjacent patches is equal to or less than a predetermined threshold value. In this embodiment, it is determined whether “OD _{I + 1} −OD _I ” is “0.01” or less. If it is not determined in step S250 that “OD _{I + 1} −OD _I ” is equal to or less than “0.01”, the counter I is incremented in step S260, and step S250 is repeated.

When it is determined in step S250 that “OD _{I + 1} −OD _I ” is equal to or less than “0.01”, there is almost no change in density between adjacent patches, and the density change is saturated. Therefore, in step S270, the maximum ink amount determining unit 25c refers to the patch data 15c, it acquires the amount of K ink from CMYKlclm data in the I-th patches corresponding to OD _I. In step S280, data indicating the usage amount of the K ink is recorded in the HDD 15 as the maximum ink amount data 15d. With the above processing, it is possible to specify the amount of K ink that can be used to the maximum in order to achieve high density and high gloss.

(3) Other embodiments:
The above embodiment is an embodiment of the present invention. In addition to the above, as long as it is possible to acquire an ink usage amount that saturates a specific ink density in order to achieve both high density and high gloss, Various embodiments can be employed. For example, as described above, the invention is not limited to the configuration in which the use amount limiting determination device, the color conversion profile creation device, and the print control device are formed by the single computer 10, and any one or a combination thereof may be configured by a plurality of computers. .

  In the above-described embodiment, the K ink and the CMY ink are in an alternative relationship. Of course, the ink usage amount limit value may be acquired by using an alternative relationship in other inks. For example, the present invention can be applied to various situations such as a configuration in which R ink is replaced with M ink and Y ink, or one of dark and light inks is replaced.

  Furthermore, in the above-described embodiment, the patch in which the density change is saturated based on the OD value is selected, but it is also possible to determine the density change with a similar physical quantity. For example, the lightness change of the printed matter may be almost the same as the density change. In this case, the lightness may be measured by a colorimeter, and the ink usage limit may be calculated based on a patch where the lightness is saturated. .

It is a figure which shows schematic structure of a computer. It is a flowchart of a LUT creation process. It is a flowchart of a maximum ink amount determination process. It is a figure which shows the example of the patch printed. 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 ... Patch data, 15d ... Maximum 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 ... maximum ink amount determination unit, 25d ... patch selection unit, 25e ... LUT creation unit, 40 ... Printer, 50 ... Colorimeter

Claims (12)

A usage amount limitation determining device that determines a usage amount limitation of the specific color ink when an image is formed by combining a specific color ink and an alternative ink that can replace the color in a printing apparatus,
Patch printing means for causing the printing apparatus to print a plurality of patches in which the usage amount of the specific color ink is changed in each patch by substituting a part of the specific color ink with a replacement ink according to a predetermined rule;
Colorimetric value acquisition means for acquiring colorimetric values of a plurality of printed patches;
Patch selection means for comparing the plurality of patches based on the colorimetric values and selecting a patch in which density change with respect to the amount of ink used for the specific color is saturated;
A usage amount limit determining apparatus comprising: a usage amount limit value acquiring unit that acquires an ink usage amount of a specific color in a selected patch and uses the usage amount as a usage amount limit value. 2. The usage amount limitation determining apparatus according to claim 1, wherein the specific color is black and the colors of the alternative ink are cyan, magenta, and yellow. 3. The usage amount restriction determining apparatus according to claim 1, wherein the density of the specific color is determined by an OD value thereof. 4. The usage amount limit determining apparatus according to claim 1, wherein the patch selecting unit selects a patch having the highest density of the specific color and the largest possible glossiness. A usage amount limitation determining method for determining a usage amount limitation of the specific color ink when forming an image by combining a specific color ink and an alternative ink capable of substituting the color in a printing apparatus,
A patch printing step of causing the printing apparatus to print a plurality of patches in which the amount of use of the specific color ink is changed in each patch by substituting a part of the specific color ink with an alternative ink according to a predetermined rule;
A colorimetric value acquisition step of acquiring colorimetric values of a plurality of printed patches;
A patch selection step of comparing the plurality of patches based on the colorimetric value and selecting a patch in which the density change with respect to the ink usage of the specific color is saturated;
A usage limit determination method comprising: acquiring a usage amount of a specific color in a selected patch and using the usage amount as a usage limit value. A use amount restriction determination program for determining a use amount restriction of the specific color ink when an image is formed by combining a specific color ink and an alternative ink that can substitute the color in a printing apparatus,
A patch printing function for causing the printing apparatus to print a plurality of patches in which the amount of use of the specific color ink is changed in each patch by substituting a part of the specific color ink with a replacement ink according to a predetermined rule;
A colorimetric value acquisition function for acquiring colorimetric values of a plurality of printed patches;
A patch selection function for comparing the plurality of patches based on the colorimetric values and selecting a patch in which the density change with respect to the ink usage of the specific color is saturated;
A use amount restriction determination program that obtains an ink use amount of a specific color in a selected patch and causes a computer to realize a use amount limit value acquisition function that uses the use amount as a use amount limit value. A color conversion profile creation device for creating a color conversion program based on the usage amount limit determined in claim 1,
Use of a specific color ink and the alternative ink in a plurality of second patches while imposing a limit on the use amount limit value determined by the use amount limit value acquisition means on the ink use amount of the specific color A second patch printing means for specifying the amount and causing the printing apparatus to print the second patch;
Image data indicating a combination of a plurality of ink usages and a color printed by the combination based on the colorimetric values obtained by the colorimetric values of the plurality of printed second patches. And a color conversion profile creation means for creating a color conversion profile that defines a correspondence relationship between the color conversion profile and the color conversion profile creation device. A color conversion profile creation method for creating a color conversion program based on the usage limit determined in claim 5,
Use of a specific color ink and the substitute ink in a plurality of second patches while imposing a limit on the use amount of the specific color with respect to the use amount limit value determined in the use amount limit value acquisition step A second patch printing step of specifying an amount and causing the printing apparatus to print the second patch;
The colorimetric values of the plurality of printed second patches are acquired, and the correspondence between the combination of the plurality of ink usage amounts and the image data indicating the color printed by the combination is defined based on the colorimetric values A color conversion profile creation method comprising: a color conversion profile creation step of creating a color conversion profile. A color conversion profile creation program for creating a color conversion program based on the usage limit determined in claim 6,
Use of a specific color ink and the alternative ink in a plurality of second patches while imposing a limit on the use amount limit value determined by the use amount limit value acquisition function with respect to the use amount of the specific color A second patch printing function for specifying an amount and causing the printing apparatus to print the second patch;
Image data indicating the printed colorimetric values of the plurality of second patches printed by the colorimetric value acquisition function, and indicating a combination of a plurality of ink usage amounts and colors printed by the combination based on the colorimetric values 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 the computer. A print control apparatus that executes printing with reference to the color conversion profile created in claim 7,
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. A print control method for executing printing with reference to the color conversion profile created in claim 8,
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. A print control program for executing printing with reference to the color conversion profile created in claim 9,
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