JP2005284521A - Printing control utilizing color transformation profile corresponding to color reproduction of multiple sorts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to perform printing by referring to a common color transformation profile even when a purpose of printing, color space to be used, or the like is different in each printing and to reduce the number of resources. <P>SOLUTION: As to a color transformation profile in which correspondence relation between data of first color space and data of second color space is regulated, a color transformation profile in which a color gamut based on the data of the first color space is defined so as to be wider than a color gamut based on the data of third color space is acquired, input image data in which a color of each of a plurality of pixels included in an image is expressed by the data of the third color space are acquired, the input image data are transformed into the data of the first color space, the transformed data of the first color space are transformed by referring to the color transformation profile, output image data in which a color of each pixel is expressed by the data of the second color space are acquired, and then a printer is allowed to perform printing on the basis of the output image data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for performing color conversion using a color conversion profile.

When printing an image, generally, color space data used in a display is color-converted into color space data used in a printer or the like with reference to a color conversion profile. In image devices such as displays and printers, the color gamut, which is the range of colors that can be expressed, is different for each machine and the color space used, so color mapping is performed to create a color conversion profile (for example, Patent Document 1).
JP 2002-359748 A

In the conventional color conversion, when the purpose of printing, the color space to be used, and the like are different, it is necessary to prepare different color conversion profiles, and it is difficult to reduce resources. For example, in order to faithfully reproduce the color indicated by the input data, a color conversion profile created without compression or expansion is required at the time of color gamut mapping, and when the printer color gamut is fully utilized. Requires a color conversion profile that has been extended during color gamut mapping so that colors in a wider area than the color gamut based on input data can be used. Further, when input data is composed of data in different color spaces and printing is performed, it is necessary to create a color conversion profile corresponding to each color space in advance and refer to an appropriate color conversion profile.
The present invention has been made in view of the above problems, and an object of the present invention is to enable printing with reference to a common color conversion profile even when the purpose of printing and the color space to be used are different. .

  In order to achieve at least one of the above objects, according to the present invention, in a color conversion profile that defines the correspondence between the data in the first color space and the data in the second color space, the color gamut based on the data in the first color space. Is defined to be wider than the color gamut based on the data in the third color space. When the input image data based on the third color space data is color-converted, the input image data is converted to the first color space data, and the converted data is converted by the color conversion profile.

  This conversion is based on the color conversion profile that defines the correspondence between the data in the first color space and the data in the second color space, and the colors in the color gamut based on the data in the third color space are converted into the data in the second color space. It is converted to express. Of course, it is possible to convert the data in the first color space into the data in the second color space based on the color conversion profile that defines the correspondence between the data in the first color space and the data in the second color space. . Accordingly, it is possible to execute printing by converting data of different color spaces in one color conversion profile.

  Here, both the data in the first color space and the data in the third color space are converted into data in the second color space by referring to the color conversion profile. Further, printing is executed by output image data based on the data of the second color space. Therefore, the first color space and the third color space are color spaces for specifying the color of the print image, and the second color space is a color space for specifying the output color in the printing apparatus. For example, as the first color space and the third color space, it is possible to adopt a color space used for expressing colors in an image device such as a display, a digital camera, or a scanner, or a device-independent color space. Of course, the image device may not be a separate body. For example, it can be said that a fax machine or a multi-function machine has a scanner and a printing device integrated, and the present invention is applied to such a fax machine or multi-function machine. Is also possible.

Specific examples of the color space include an RGB color space constituted by RGB (R: red, G: green, B: blue) color components, an L ^* a ^* b ^* space, an L ^* u ^* v ^* space, XYZ space etc. are mentioned. In the first color space and the third color space, it is necessary to define the color gamut based on the data in the first color space to be wider than the color gamut based on the data in the third color space. For example, in the RGB color space, the range of colors that can be expressed when each color component value of RGB is changed from the upper limit to the lower limit of the gradation value range is the color gamut, and the gradation value range is the same. If the meaning is defined so that the colors are different, the size of the color gamut can be adjusted.

  Therefore, if the definition of the color meaning of each color value of RGB is defined differently in the first color space and the third color space, and the range of the corresponding color when the value is changed in the former is defined wider, The color gamut based on the data in one color space can be defined to be wider than the color gamut based on the data in the third color space. As a more specific example, the third color space is a color space conforming to the sRGB standard, and the first color space is an extended RGB space such as an Adobe RGB color space (Adobe is a registered trademark of Adobe Systems). A configuration can be adopted. Note that when the first color space and the third color space are configured by the device-independent color space, the size of the color gamut can be easily adjusted by adjusting and defining the value ranges of the respective color components.

  As the second color space, it is possible to employ a color space that expresses a color with a color component value corresponding to the gradation of each ink used in the printing apparatus. This color space can be considered to increase in dimension depending on the number of ink colors. When using CMYK (C: cyan, M: magenta, Y: yellow, K: black) inks, a four-dimensional CMYK color space is used. It becomes. On the other hand, when CMYKlclm (lc: light cyan, lm: light magenta) is used, it is a 6-dimensional CMYKlclm space, and when CMYKlclmDY (DY: dark yellow) is used, it is a 7-dimensional CMYKlclmDY color space. Of course, even a printing apparatus that uses other colors such as R, G, B, and V (violet) can define a color space in the same way. In the data of the first color space to the third color space, the range of values is determined for each color component in advance, and the color range when each color component is independently changed within the range of the range is the color range of each color space. Color gamut by data.

  In the color conversion profile, it is sufficient if the correspondence relationship between the data in the first color space and the data in the second color space can be defined, and various configurations can be employed. For example, it may be color conversion table data that defines the color relationship by associating data one-to-one with respect to a plurality of representative points, or a profile that defines the color relationship by a specific function or matrix. Also good.

  The input image data acquisition means only needs to be able to acquire input image data representing an image with data in the third color space. However, according to the color conversion profile according to the present invention as described above, the input image data in the first color space can be acquired. It is naturally possible to convert the data into data in the second color space. Therefore, the input image data acquisition unit may acquire the image data representing the image with the data of the first color space as the input image data, and the color conversion unit may perform the color conversion.

  The color conversion means converts the color space before color conversion based on the color conversion profile when performing color conversion on the input image data representing the image with the data of the third color space. That is, in order to perform color conversion using the color conversion profile, it is necessary to input data in the first color space. If the input image data is data in the third color space, the data value can be converted as it is. Color management is not done. However, since the color gamut based on the data in the first color space is wider than the color gamut based on the data in the third color space, all colors that can be expressed in the data in the third color space are subject to color conversion in the color conversion profile. Includes as input color. Therefore, if the color that the data of the third color space means is expressed by the data of the first color space, it is possible to color-convert the input image data that represents the image with the data of the third color space by the color conversion profile. Become.

  When converting the input image data into the data of the first color space, it is only necessary to uniquely identify the data of the first color space from the input image data, and various configurations can be employed. For example, the conversion may be performed based on a predetermined conversion formula such as a predetermined specific function or matrix, or may be performed with reference to a predetermined profile. Note that it is preferable to perform conversion using a predetermined conversion formula such as a function or a matrix because resources can be reduced compared to the case of using a profile.

  The print execution means only needs to be able to execute printing based on the output image data, and various configurations can be employed. For example, halftone processing is performed so that the recording rate corresponds to the gradation value for each color component specified in the output image data, and print data for recording ink with the data after halftone processing is obtained. It is possible to adopt a configuration that is created and delivered to the printing apparatus.

  In the present invention, it is possible to cope with various color reproductions according to the purpose of printing by controlling the characteristics of color conversion performed by referring to the color conversion profile. As a configuration for this purpose, the correspondence relationship between the data in the first color space and the data in the second color space, which is directly defined by the color conversion profile, performs color conversion in accordance with the above-described purpose. It is required to be specified.

  For example, the data of the first color space and the data of the second color space so that the colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space are not changed before and after conversion. Stipulates the correspondence with That is, for the colors in this region, the data in the first color space and the data in the second color space are such that the color indicated by the data in the second color space is the same as the color indicated by the data in the third color space. Stipulates the correspondence with Since the color gamut based on the data in the first color space is wider than the color gamut based on the data in the third color space, it is easy to express the colors in the color gamut based on the data in the third color space with the data in the first color space. It is.

  Therefore, the color indicated by the second color space data and the color indicated by the third color space data are associated with each other so that the color indicated by the second color space data becomes the same as the color indicated by the third color space data. It is also easy to make the colors shown the same. According to such a color conversion profile, printing is performed so as to faithfully reproduce the color indicated by the input image data for the colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space. Can be executed.

  In the color conversion profile, color management is usually performed so that the color indicated by the input image data matches the color indicated by the output image data. Generally, the color gamut in the input image data and the color gamut in the output image data are Therefore, the original color is converted into a different color by color gamut mapping. However, according to the above-described configuration, it is ensured that the color within the color gamut based on the data of the second color space and the color gamut based on the data of the third color space is not converted to a color different from the color indicated by the input image data. be able to. Therefore, it is possible to execute printing in accordance with the purpose of faithful color reproduction by generating input image data limited to colors in this region and executing printing.

  Further, in the color conversion profile, the color within the color gamut based on the data of the first color space and the color outside the color gamut based on the data of the third color space is converted into the color gamut based on the data of the second color space. The correspondence relationship between the color space data and the second color space data is defined. That is, for the colors in this region, exact color matching before and after color conversion is not guaranteed. However, since it is converted to a color in the color gamut based on the data in the second color space, it is possible to output the color reliably using colors that can be output by the printing device, and printing using the color gamut of the printing device effectively. It can be performed.

  For example, when a color within the color gamut based on the data in the first color space and outside the color gamut based on the data in the third color space is outside the color gamut based on the data in the second color space, the color is reduced to the second color by the color gamut compression. Associate with spatial data. According to this configuration, even if a color outside the color gamut of the printing apparatus is specified by the input image data, it is possible to reliably output some color.

  Furthermore, when there is an area outside the color gamut based on the data of the first color space and outside the color gamut based on the data on the third color space, and an area outside the color gamut based on the data on the first color space and inside the color gamut based on the data on the second color space, The former area is associated with the latter area by color gamut expansion. According to this configuration, printing can be performed using a wider color gamut, and the image indicated by the input image data can be printed with richer colors.

  A region in the color gamut by the data in the second color space and a region in the color gamut by the data in the third color space, a region in the color gamut by the data in the first color space and a region outside the color gamut by the data in the third color space, Do not overlap. Therefore, by adopting a configuration in which the colors are surely matched in the former area and the colors are changed in the latter area, it is possible to achieve both the faithful color reproduction and the output with richer colors. . In addition, it is natural that the color space can be mapped so that the color outside the above-described region is included in the color gamut based on the data of the second color space.

  In the color conversion profile as described above, the color conversion profile may be created in any way as long as the correspondence is defined as described above. However, the correspondence as described above can be easily realized by devising the color gamut mapping when creating the color conversion profile. That is, the color gamut mapping for changing the color is not performed for the color within the color gamut based on the data of the second color space and the color gamut based on the data of the third color space, and within the color gamut based on the data of the first color space. For colors outside the color gamut based on the data of the third color space, the color is changed by color gamut compression or color gamut expansion.

  Therefore, it can be said that the technical idea of the present invention is also used in the apparatus for creating a color conversion profile in this way and the color conversion profile itself. In the present invention, the color gamuts based on the data of the first color space to the third color space are compared, and the color conversion characteristics are determined by determining which region in the color space the color to be converted belongs to. Therefore, in the color conversion profile creation device, the device-independent color space data acquisition unit acquires device-independent color space data indicating the colors of the plurality of data in the first color space to the third color space, and The gamut boundary discriminating unit discriminates the gamut boundary based on the device-independent color space data.

  If the boundary of the color gamut is to be determined, it is only necessary to acquire data in the device-independent color space only for data that is expected to be in the vicinity of the color gamut boundary, but a color conversion profile is created. For this purpose, the device-independent color space data is acquired for substantially the entire color gamut, and the correspondence between the first color space data and the second color space data is defined. Therefore, it is preferable to acquire data in the device-independent color space for colors over substantially the entire color gamut.

  Various configurations can be employed to acquire device-independent color space data corresponding to each color space data. For example, if a color is actually output by an image device that uses data in the first color space to the third color space, and the output color is measured by a predetermined colorimeter, an accurate device-independent color space Data can be acquired. In addition, if the color to be output at each gradation value is a predetermined color space such as sRGB, an arbitrary RGB value is converted into device-independent color space data by a predetermined conversion formula or the like. You may do it.

  In order to form the color gamut boundary, various configurations are adopted, such as calculating the continuous color gamut boundary by interpolating multiple device-independent color space data existing outside the color gamut. Is possible. In any case, if the boundary of the color gamut can be determined, the relationship between the color gamut can be grasped by comparing the boundary of the color gamut in each color space. Therefore, the color gamut mapping means matches colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space, and within the color gamut based on the data in the first color space and the first color. A color outside the color gamut based on the data in the three color spaces can be easily mapped into the color gamut based on the data in the second color space.

  The above configuration is a configuration for enabling color conversion for both the data of the first color space and the data of the third color space by one color conversion profile, but a method based on the same technical idea. This invention is also established. Therefore, the inventions according to claims 8 and 9 basically have the same operation as described above. In addition, the present invention may be implemented by executing a predetermined program on a computer. Therefore, the present invention can also be applied as the program, and the invention according to claims 10 and 11 basically has the same operation as described above.

  Of course, it is possible to make the configuration described in claims 2 to 4 correspond to the above-described method and program. Any storage medium can be used to provide the program. For example, a magnetic recording medium or a magneto-optical recording medium may be used, and any recording medium that will be developed in the future can be considered in the same manner. In addition, even when a part is software and a part is realized by hardware, the idea of the present invention is not completely different, and a part is recorded on a recording medium and is appropriately changed as necessary. It includes a reading form.

Here, embodiments of the present invention will be described in the following order.
(1) Outline of color conversion table creation:
(2) Apparatus and process for creating a color conversion table:
(3) Printing using the LUT created according to the present invention:
(4) Other embodiments:

(1) Outline of color conversion table creation:
FIG. 1 is an explanatory diagram schematically illustrating the steps of a color conversion table creation method according to the present invention. Since this step requires a lot of arithmetic processing, it is preferable to use a computer. Since patches are printed as will be described later, printing is preferably performed by the same printer as that using the color conversion table (LUT) created according to the present invention. It is necessary to use the same algorithm as the halftone processing adopted in the above.

In this embodiment, an LUT is created by associating eRGB data in an extended RGB space (denoted as eRGB) having a color gamut wider than the color gamut in accordance with the sRGB standard with CMYKlclm data. Incidentally, LUT is a table which defines a corresponding relationship between eRGB data and CMYKlclm data for the reference points of a finite number (e.g., 17 ^3). Although the number of data is limited, RGB data and CMYKlclm data can be associated with each other by executing interpolation processing with reference to reference points.

In the present embodiment, the sRGB data and eRGB data are data used for displaying an image on a computer display, and are 256 gradations for each color of RGB. In both sRGB data and eRGB data, colors in each gradation are predetermined. That is, it is possible to mutually convert RGB gradation values and device-independent color space values (for example, L ^* a ^* b ^* space) using a predetermined conversion formula. Furthermore, sRGB data and eRGB data can be converted into each other using a predetermined conversion formula.

  The CMYKlclm data is data for specifying the amount of ejected ink in the printer according to the present embodiment, and has 256 gradations for each color. As described above, in the present embodiment, the eRGB color space corresponds to the first color space, the sRGB color space corresponds to the third color space, and the CMYKlclm color space corresponds to the second color space.

  In order to perform printing by a printer, it is necessary to associate the eRGB data and the CMYKlclm data with the LUT. However, since the CMYKlclm data is a device-dependent color of the printer, generally when the LUT is created, the actual value in the printer is used. Measure the print result of. Then, an LUT is created by associating the colors of the eRGB data and the CMYKlclm data in the device-independent color space.

In this embodiment, the L ^* a ^* b ^* color space is adopted as the device-independent color space, and in the LUT creation process, L ^* a ^* corresponding to each of eRGB data, sRGB data, and CMYKlclm data ^. Specify the b ^* value. For eRGB data and sRGB data, L ^* a ^* b ^* values are obtained by a predetermined conversion formula as described above. In FIG. 1, a value corresponding to eRGB data is expressed as L ₁ ^* a ₁ ^* b ₁ ^*, and a value corresponding to sRGB data is expressed as L ₃ ^* a ₃ ^* b ₃ ^* .

On the other hand, the CMYKlclm data is ink value data that specifies the ink amount and is a device-dependent color. Therefore, the coordinate value in the L ^* a ^* b ^* color space is acquired by measuring the color of the actually printed patch with the colorimeter. CMYKlclm data for color measurement is prepared in advance for a plurality of colors (for example 10 ^3).

The CMYKlclm data is data that expresses an arbitrary color by appropriately combining the respective ink amounts of the six colors, and can express very similar colors by a number of combinations. Therefore, it is preferable to create CMYKlclm data for colorimetry according to a specific color separation rule in order to cover the entire color gamut and realize interpolation with high accuracy. For example, assuming that the color is expressed by three colors of CMY, a combination covering the entire color gamut can be easily extracted, so that 10 ³ colors are determined by combinations of gradation values of the three colors of CMY. To do.

Then, assuming an amount of K ink that outputs substantially the same color as the color obtained by combining the CMY color inks, a part of the CMY ink is replaced with the K ink. Similarly, a part of C ink is replaced with lc ink, and a part of M ink is replaced with lm ink. As a result, CMYKlclm data can be generated from the gradation values of the CMY three colors. In any case, when CMYKlclm data is obtained, a patch is printed with the data. That is, processing similar to halftone processing in the printer is performed, and the patch is printed by the printer. By measuring these patches with a colorimeter, L ^* a ^* b ^* values can be specified for 10 ³ patches. In FIG. 1, this value is expressed as L ₂ ^* a ₂ ^* b ₂ ^* .

  In the LUT, eRGB data and CMYKlclm data are associated with each other, but since the color gamut represented by the eRGB data is generally different from the color gamut of the printer, the color that can be represented by the printer is usually the color that can be represented by the printer. Perform gamut mapping to convert to. In the present embodiment, as described above, the color gamut (expressed as color gamut 1 in FIG. 1) that can be expressed by eRGB data is the color gamut (color in FIG. 1) that can be expressed by sRGB data. The color within the color gamut 3 is not subjected to the color gamut mapping, and the color gamut mapping is performed for the region outside the color gamut 3 and the region within the color gamut 1. The color gamut mapping is also performed for the area in the color gamut 3 and the area outside the color gamut 2 (printer color gamut). However, the area in the color gamut 3 and the area in the color gamut 2 are colored. Do not perform area mapping.

In FIG. 1, the results of the respective color gamut mapping are shown as L ₁ ^{* ′} a ₁ ^{* ′} b ₁ ^{* ′} and L ₃ ^{* ′} a ₃ ^{* ′} b ₃ ^{* ′} . L ₁ ^{* ′} a ₁ ^{* ′} b ₁ ^{* ′} obtained as described above corresponds to the original eRGB data on a one-to-one basis. The L ₃ ^{* ′} a ₃ ^{* ′} b ₃ ^{* ′} has a one-to-one correspondence with the original sRGB data, and the sRGB data can be converted into eRGB data by a conversion formula. Therefore, L ₃ ^{* ′} a ₃ ^{* ′} b ₃ ^{* ′} has a one-to-one correspondence with eRGB data. Of course, L ₂ ^* a ₂ ^* b ₂ ^* corresponds to the original CMYKlclm data on a one-to-one basis.

Therefore, eRGB data and CMYKlclm data corresponding to an arbitrary value in the L ^* a ^* b ^* space can be calculated by interpolation. When the eRGB data and the CMYKlclm data are calculated and associated with each other, a LUT is obtained. Note that when you output an image, it is often the case that the actual color such as skin color or sky blue color is output as it is rather than the actual color as it is. As for, an actual color may be converted into a memory color. That is, a specific color is associated with a memory color in the above color gamut mapping.

  In the LUT created as described above, colors existing in the color gamut of the sRGB data and in the color gamut of the printer are not subjected to color gamut mapping (color gamut compression, color gamut expansion, etc.), so the colors indicated by the sRGB data are displayed. It can be associated with CMYKlclm data that is output as it is. Therefore, color reproduction can be performed faithfully for this color.

  On the other hand, colors existing outside the sRGB data gamut and within the eRGB data gamut are subjected to gamut mapping such as gamut compression and gamut expansion, and are reproduced with colors within the printer gamut. Accordingly, even if the color is outside the color gamut of the eRGB data, if the color exists within the color gamut of the printer, it is possible to express rich gradation using the color, and the color outside the color gamut of the printer within the color gamut of the eRGB data. Can be output with colors within the color gamut of the printer by mapping.

(2) Apparatus and process for creating a color conversion table:
Next, an apparatus and a process for creating the LUT as described above will be described in detail. FIG. 2 is a block diagram showing a computer configuration for creating an LUT, and FIG. 3 is a flowchart showing a process for creating an LUT. The computer 10 includes a program execution environment including a CPU, a RAM, a ROM, and the like, and a color conversion profile creation program 11 for creating a color conversion profile can be executed by the program execution environment. The same color conversion profile creation program 11 creates an LUT by appropriately referring to data stored in the HDD 12.

  Further, it is connected to the printer 20 via an interface (not shown), and print data can be output from the computer 10 to execute printing. Further, the computer 10 can capture colorimetric data obtained by colorimetry by the colorimeter 30. The colorimetric data can be input using an input device such as a keyboard, input via a recording medium, or input by connecting and transferring data via a predetermined interface. Is possible.

  In the color conversion profile creation program 11, the LUT 12d is created using patch data 12a, sRGB data 12b, and eRGB data 12c prepared in advance. For this purpose, the color conversion profile creation program 11 includes a halftone processing unit 11a, a print data generation / output unit 11b, an sRGB data conversion unit 11c, an eRGB data conversion unit 11d, a color gamut boundary determination unit 11e, and a mapping processing unit 11f. And an LUT creation unit 11g.

  When the color conversion profile creation program 11 is executed, the halftone processing unit 11a acquires the patch data 12a (step S100) and performs halftone processing. The patch data 12a is data for printing a plurality of patches, and is data in which the color of each patch is specified by CMYKlclm data. The halftone process is a process of converting the number of gradations so that the printer 20 records the ink amount corresponding to each gradation of the CMYKlclm data with the number of gradations that can be expressed for each pixel. As the halftone processing algorithm, various algorithms such as an error diffusion method and a dither method can be adopted.

  When the halftone process is performed, the print data generation / output unit 11b generates print data for printing a patch based on the data after the halftone process, and outputs the print data to the printer 20 (step S105). That is, print data for printing patches is generated by performing processing such as rearranging the data after halftone processing in the order used by the printer 20, and outputting the print data to the printer 20. As a result, the printer 20 prints a plurality of patches.

The halftone processing unit 11a and the print data generation / output unit 11b are modules that perform the same processing as the halftone processing unit 210c and the print data generation unit 210d in the print control apparatus described later. When the patch is printed, the user sets the print result in the colorimeter 30 and measures the L ^* a ^* b ^* value for each patch. The color gamut boundary determination unit 11e of the color conversion profile creation program 11 acquires color measurement data indicating the color measurement result via an interface (not shown) or the like (step S110). The L ^* a ^* b ^* value corresponds to L ₂ ^* a ₂ ^* b ₂ ^{* shown} in FIG.

On the other hand, sRGB data 12b and eRGB data 12c are different from each other in a plurality of data obtained by changing each color component value in each RGB space, for example, each RGB value is changed independently at a constant value interval within the gradation value range. It is the data obtained by making it. The sRGB data conversion unit 11c acquires the sRGB data 12b, and converts the RGB values into L ^* a ^* b ^* values based on a predetermined conversion formula (step S115).

The color gamut boundary determination unit 11e of the color conversion profile creation program 11 acquires the L ^* a ^* b ^* value after the conversion. Incidentally, based on the sRGB data 12b L ^* a ^* b ^* value corresponds to _{^{L 3 * a 3 * b 3}} * shown in FIG. 1. The eRGB data converter 11d acquires the eRGB data 12c and converts the RGB value into an L ^* a ^* b ^* value based on a predetermined conversion formula (step S120). The color gamut boundary determination unit 11e of the color conversion profile creation program 11 acquires the L ^* a ^* b ^* value after the conversion. The L ^* a ^* b ^* value based on the eRGB data 12c corresponds to L ₁ ^* a ₁ ^* b ₁ ^{* shown} in FIG.

Through the above processing, device-independent color space data corresponding to a plurality of sRGB data, eRGB data, and CMYKlclm data is acquired by the color gamut boundary determination unit 11e. Therefore, the color gamut boundary determination unit 11e determines the boundary of the color gamut based on these L ^* a ^* b ^* values (step S125). Here, it is only necessary to determine the region where an arbitrary target color, which will be described later, is located in comparison with the boundary of the color gamut by determining the boundary of the color gamut. Can determine the boundary of the color gamut.

For example, the L ^* a ^* b ^* values in the sRGB data, eRGB data, and CMYKlclm data are plotted in the L ^* a ^* b ^* space, and the outermost L ^* a ^* b ^* values are extracted for each hue. To do. Given this L ^* a ^* b ^* values forms a boundary of the color gamut, it is possible to form the boundary of the color gamut by interpolating between the respective L ^* a ^* b ^* values. Of course, it is possible to adopt various configurations such as a configuration in which the boundary of the color gamut can be continuously grasped, and a boundary is calculated only for a portion where the boundary needs to be grasped.

The mapping processing unit 11f is a module that determines whether or not mapping is necessary for the color registered as the LUT and performs mapping as necessary. For this purpose, first, a target color is specified in the L ^* a ^* b ^* space (step S130). This target color corresponds to a plurality of reference points registered in the LUT, and is a color that covers the color gamut of the eRGB data 12c. Accordingly, each color component of the eRGB data may be changed within the gradation value range, and the eRGB data may be converted into an L ^* a ^* b ^* value by a predetermined conversion formula, or within the determined color range of the eRGB color space. Various configurations such as extracting L ^* a ^* b ^* values evenly can be adopted.

In step S130, one unprocessed target color is extracted. When the target color is extracted, the relative relationship between the target color and the boundary of the color gamut is specified in the L ^* a ^* b ^* color space (step S135). When the relative relationship between the target color and the boundary of the color gamut is grasped, it is determined whether the target color matches a predetermined mapping execution condition and mapping is necessary (step S140).

  If it is determined in step S140 that mapping is necessary, mapping is performed using a predetermined algorithm (step S145). If it is not determined in step S140 that mapping is necessary, step S145 is skipped. Then, it is determined whether or not the above processing has been completed for all target colors (step S150), and the processing from step S130 is repeated until it is determined that the processing has been completed for all target colors.

After the above processing is performed on all target colors and mapping is performed as necessary, L ^* a ^* b ^* values after mapping (in the example shown in FIG. 1, L ₁ ^{* ′} a ₁ ^{* 'b} ₁ ^*' and _{^{L 3 * 'a 3 *'}} b 3 * ') and colorimetry was _{^{L 2 * a 2 * b 2}} * and the pass to the LUT creation unit 11g.

The LUT creation unit 11g is a module that creates an LUT based on these L ^* a ^* b ^* values, and outputs the L ^* a ^* b ^* values (including values after mapping) of the target color. The CMYKlclm data is calculated by interpolation (Step S155), and the original eRGB data is associated with the calculated CMYKlclm data (Step S160). Data indicating the obtained correspondence relationship is the LUT 12d.

FIG. 4 is an explanatory diagram illustrating an example of mapping execution conditions in the processing of the mapping processing unit 11f. Figure plots the L ^* a ^* b ^* values in each of the above-described sRGB data and eRGB data and CMYKlclm data to L ^* a ^* b ^* space, showing a state taken along a certain plane including the L ^* axis ing. That is, the vertical axis is L ^* , and the horizontal axis is the saturation c ^* in a certain hue (saturation is positive in both the right and left directions on the paper).

  In the figure, the solid line indicates the boundary of the color gamut of the sRGB color space (color gamut based on sRGB data), the dashed line indicates the boundary of the color gamut of the eRGB color space (color gamut based on eRGB data), and the broken line indicates The boundary of the printer color gamut (color gamut based on CMYKlclm data) is shown. In this embodiment, the purpose of faithfully reproducing colors and the purpose of reproducing colors with rich gradations can be realized simultaneously with one color conversion profile. For this reason, the “gamut of the sRGB color space” And the color included in both of the printer color gamut and the condition that “the color is not included in the color gamut of the sRGB color space and within the color gamut of the eRGB color space. If a gamut exists, the condition that the color gamut expansion is performed is adopted.

Here, this condition will be described more specifically according to the example shown in FIG. In the example illustrated in FIG. 4, regions surrounded by the color gamut boundary and the L axis are distinguished as regions A to H. Colors included in both the color gamut of the sRGB color space and the color gamut of the printer are regions A and B. In order to determine whether or not the target color is included in this region, for example, the saturation of the target color and the color gamut boundary can be used. That is, the saturation of the target color is C _t , the saturation of the gamut boundary in the sRGB color space is C _s , the saturation of the gamut boundary in the eRGB color space is C _e , and the saturation of the gamut boundary of the printer is C _p. Whether any of the following conditions is satisfied is determined.
Condition 1: C _t <C _s and C _s <C _p
Condition 2: C _t <C _p and C _p <C _s

  That is, the target color exists in the region A if the condition 1 is satisfied, and the target color exists in the region B if the condition 2 is satisfied. If the target color is in these areas A and B, the printer 20 can output the same color as that color. Therefore, when it is determined that the target color exists in these areas A and B, the eRGB data and the CMYKlclm data are associated with each other without mapping the target color. As a result, the color indicated by the eRGB data and the color output by the CMYKlclm data are substantially the same, and faithful color reproduction is realized.

On the other hand, the regions outside the sRGB color space and within the eRGB color space are the regions E, F, and G in FIG. However, a region where the printer color gamut exists outside each region is a region G. In this way, in order to determine whether the color is included in a region outside the sRGB color space and within the color gamut of the eRGB color space, and the printer color gamut exists outside this region, for example, It is determined whether or not the following conditions are satisfied.
Condition 3: C _t ≧ C _s and C _t <C _e and C _e <C _p

  When the target color is in this region G, by outputting the color in the region H, it is possible to output a color with higher saturation without significantly changing the hue and lightness. Therefore, for the colors in the region G, the color of the region H is used by expanding the color gamut. The color gamut expansion may be performed by various algorithms as long as the colors in the region G can be associated with the colors in the region G and the region H on a one-to-one basis.

For example, the lightness and hue are not changed by mapping, and the saturation C _m after mapping is calculated as C _m = (C _t −C _s ) × (C _p −C _s ) / (C _e −C _s ). A configuration or the like can be adopted. When mapping is performed as described above and eRGB data and CMYKlclm data are associated with each other, colors having higher saturation than the color indicated by eRGB data are output by CMYKlclm data, and color reproduction with rich gradation is realized. .

  Since colors outside the printer's color gamut cannot be printed, in this embodiment, colors within the color gamut of the eRGB color space and outside the printer's color gamut are compressed into the printer's color gamut. In the present embodiment, although it is outside the color gamut of the sRGB color space, the colors within the color gamut of the eRGB color space and within the color gamut of the printer are not mapped, and faithful color reproduction can be performed. Specifically, it is determined whether the target color corresponds to the region C, D, E, or F based on the following conditions, and the necessity of mapping and its method are determined.

Condition 4: C _t ≧ C _p and C _t <C _s and C _p <C _s
Condition 5: C _t ≧ C _s and C _p <C _s
Condition 6: C _t ≧ C _s and C _t <C _p and C _p <C _e
Condition 7: C _t ≧ C _p and C _t <C _e and C _p <C _e
That is, if the condition 4 is satisfied, the target color exists in the region C. In the area C, the target color is included in the color gamuts of the sRGB color space and the eRGB color space, but is outside the printer color gamut. Therefore, color gamut compression processing is performed in order to print some color even in an image in which the target color is designated. Here, various algorithms can be adopted as an algorithm for color gamut compression processing. For example, a rule is adopted that does not change the hue but changes the lightness and saturation to become a color within the color gamut of the printer. If the condition 5 is satisfied, the target color exists in the region D. In the area D, the target color is included in the color gamut of the eRGB color space, but is outside the printer color gamut, so the color gamut compression processing is performed in the same manner as in the area C. Again, various algorithms can be employed as the algorithm for color gamut compression.

  Furthermore, if the condition 6 is satisfied, the target color exists in the region E. In region E, the target color is in the color gamut of the eRGB color space and in the color gamut of the printer. Therefore, this target color can be faithfully reproduced and mapping is not performed. Furthermore, if the condition 7 is satisfied, the target color exists in the region F. In region F, the target color is in the color gamut of the eRGB color space, but is outside the color gamut of the printer. Therefore, color gamut compression processing is performed in order to print some color even in an image in which the target color is designated. Again, various algorithms can be employed as the algorithm for color gamut compression.

  As described above, if the degree of color gamut overlap is judged based on the color gamut boundary, color conversion for different purposes (faithful color reproduction and color reproduction with rich gradations) can be performed with one LUT. It is. Also, since sRGB data can be easily converted to eRGB data, both the input image data based on sRGB data and the input image data based on eRGB data can be subjected to color conversion with a single LUT and printing can be executed. is there.

FIG. 5 is an explanatory diagram for explaining the configuration of the LUT 12d created by the above processing. In the figure, it is shown that RGB data and CMYKlclm data are associated one-to-one. As described above, the target color corresponds to a plurality of reference points registered in the LUT, and is a color that covers the color gamut of the eRGB data. Therefore, assuming that the RGB data defined in the LUT 12d is data in the eRGB color space, the color gamut compression is performed, but almost all colors (R _a1 G _a1 B _{a1 to} R _en included in the color gamut of the eRGB color space are included. G _en B _en ) can be converted to CMYKlclm data.

On the other hand, since the sRGB color space is narrower than the eRGB color space, the color gamut of the sRGB color space may be covered by a part of the RGB data (R _a1 G _a1 B _{a1 to} R _sn G _sn B _sn ) defined in the LUT 12d. it can. Accordingly, the sRGB data is converted into eRGB data (eRGB data indicating the same color as the sRGB data is calculated), and the eRGB data is converted into CMYKlclm data to output the color indicated by the sRGB data. CMYKlclm data can be acquired.

Note that a part of RGB data corresponding to the color gamut of the sRGB color space (R _a1 G _a1 B _{a1 to} R _{an Gan} B _{an in} FIG. 5) corresponds to the CMYKlclm data without mapping the color indicated by the data. It is attached. Therefore, faithful color reproduction can be performed for this RGB data. Further, RGB data indicating a color gamut of eRGB color space gamut of the sRGB color space is _{R e1 G e1 B e1 ~R en} G en B en in FIG. A part of this color is mapped outside the color gamut of the eRGB color space as described above. Therefore, rich color reproduction exceeding the expressive power of colors in the eRGB color space can be implemented.

With the above configuration, the input image data be configured within a _{R a1 G a1 B a1 ~R an} G an B an, to be carried faithful color _{reproduction, R a1 G a1 B a1 ~R} sn G sn If data corresponding to B _sn is used, printing based on data in the sRGB color space can be performed. Of course, can also be implemented printing based on data eRGB color space, wherein, With the input image data including a portion of _{R e1 G e1 B e1 ~R en} G en B en, in eRGB color space A rich color reproduction that exceeds the expressiveness of color is possible.

(3) Printing using the LUT created according to the present invention:
The LUT 12d created as described above is referred to when performing color conversion processing when the printer 20 executes printing. Therefore, it can be said that the technical idea according to the present invention is also used in a print control apparatus that executes printing with reference to the LUT 12d. A configuration for performing the printing will be described below.

  FIG. 6 is a block diagram illustrating a computer configuration example using the LUT 12d during printing. The computer 110 is a general-purpose personal computer, and a printer driver (PRTDRV) 210, an input device driver (DRV) 220, and a display driver (DRV) 230 are incorporated in the OS 200. The display DRV 230 is a driver that controls display of image data and the like on the display 180. The input device DRV 220 receives code signals from the keyboard 310 and the mouse 320 input via the serial I / F 190a and performs a predetermined input operation. It is a driver that accepts.

  The APL 250 is an application program that can execute retouching of a color image, and the user can operate the input device for operation under the execution of the APL 250 to perform an operation such as retouching, and print the color image to a printer. 20 for printing. The LUT 12d created by the present invention at the time of printing such a color image is referred to. In APL 250, image data 120a indicating a color image is created, and the color space can be selected from the sRGB color space and the eRGB color space.

  That is, in the present embodiment, the image data 120a is composed of sRGB data or eRGB data. Therefore, the image data 120a constitutes the input image data. In order to grasp this color space, the color space may be described in the header of the image data 120a, or may be specified on the property screen of the printer 20 at the time of printing.

  The PRTDRV 210 includes an image data acquisition unit 210a, a color conversion unit 210b, a halftone processing unit 210c, and a print data generation unit 210d in order to execute printing. The LUT 12d created according to the present invention is stored in the HDD 120. When the user issues a print execution instruction when executing APL 250, each module performs the following processing.

  FIG. 7 is a flowchart of the print control process. When the print control process is started, the image data 120a is acquired by the image data acquisition unit 210a. (Step S200). The image data acquisition unit 210a determines whether the number of pixels of the image data 120a is excessive or insufficient, and if there is an excess or deficiency, compensates for the excess or deficiency by interpolation calculation. The color conversion unit 210b is a module that converts RGB data into CMYKlclm data, and converts arbitrary RGB data into CMYKlclm data using reference points of the LUT 12d. The CMYKlclm data corresponds to the output image data described above.

  The color conversion unit 210b includes a color space conversion unit 210b1 and performs processing corresponding to the set color space before performing the color conversion. That is, since the RGB data described in the LUT 12d is data in the eRGB color space, when the image data 120a is data in the sRGB color space, it is necessary to convert it into data in the eRGB color space.

  Therefore, the color space conversion unit 210b1 determines the color space set for the image data 120a acquired by the image data acquisition unit 210a (step S210). If it is determined that this color space is the sRGB color space (step S220), the color space conversion unit 210b1 refers to the conversion matrix 120b recorded in the HDD 120 and converts the sRGB data into eRGB data. The conversion matrix 120b is data indicating a 3 × 3 matrix for converting sRGB data into eRGB data.

  Here, it is only necessary to be able to determine in which color space the RGB values of the input image data exist, and it may be determined for the purpose of printing. For example, it is configured to select either faithful color reproduction or rich color reproduction. If the former, it is determined that the data is in the sRGB color space, and if it is the latter, the data is in the eRGB color space. It is possible to adopt a configuration for determining. If it is not determined in step S220 that the color space is the sRGB color space, or if conversion is performed in step S230, the color space of the RGB data obtained at that time is the eRGB color space. Therefore, the color conversion unit 210b refers to the LUT 12d and converts arbitrary RGB data into CMYKlclm data by interpolation calculation (step S240).

  The color conversion unit 210b includes a color correction unit 210b2, and can perform color correction according to a user instruction or the like. That is, when printing a photograph or the like, it is often the case that a predetermined color correction, such as increasing the saturation, is performed with higher quality than faithfully reproducing the color of the actual subject or the color indicated by the image data, so that the image quality looks higher. For example, the actual color such as skin color or sky blue is not output as it is, but it looks better when converted to a color close to human memory. Therefore, the color correction unit 210b2 executes a process of extracting a specific color from the image data before or after color conversion and converting it to another color according to a user instruction or the like.

  In any case, when CMYKlclm data for each pixel is obtained by color conversion, the halftone processing unit 210c performs the same processing as the halftone processing unit 11a to obtain halftone data (step S250). The print data generation unit 210d receives the halftone data and performs a rearrangement process for rearranging in the order used by the printer 20 (step S260). After the rearrangement process, print data is generated by adding predetermined information such as image resolution, and is output to the printer 20 via the USB I / F 190b (step S270). The printer 20 prints an image based on the print data.

  FIG. 8 is an explanatory diagram illustrating printing realized by the above configuration and processing. In the present embodiment, even if the color space of the image data 120a is an sRGB color space or an eRGB color space, color conversion can be performed with one LUT 12d, and printing can be executed. However, since the data associated with the CMYKlclm data in the LUT 12d is eRGB data, when the image data 120a is data in the sRGB color space, it is necessary to convert the sRGB data into eRGB data.

When the image data 120a is data in the sRGB color space, if the image data is composed of data in a partial range (R _a1 G _a1 B _{a1 to} R _an G _an B _{an in} FIG. 5), conversion by the LUT 12d is performed. The color correction caused by the mapping is not received. Therefore, the color indicated by the sRGB data can be faithfully reproduced. Further, when the image data 120a is data covering the entire sRGB color space (R _a1 G _a1 B _{a1 to} R _sn G _sn B _{sn in} FIG. 5), part of the conversion by the LUT 12d (R _s1 G _{s1 in} FIG. 5). B _{s1 to} R _sn G _sn B _sn ) are affected by color gamut compression.

  Therefore, colors cannot be reproduced faithfully for all the sRGB data, but there are generally few colors that fall within the color gamut of the sRGB color space and outside the printer color gamut. Further, it is impossible for the printer 20 to print a color originally located outside the color gamut of the printer. Therefore, even if a color that falls within the color gamut of the sRGB color space and is outside the printer's color gamut is affected by the color gamut compression, it can be considered that the effect is minor, and a part of the color within the sRGB color space. It can be considered that faithful color reproduction is possible for these colors.

  Of course, when the image data 120a is composed of data in the sRGB color space, it may be desired to execute printing using a color outside the color gamut of the sRGB color space. In such a case, correction by the color correction unit 210b2 may be performed. For example, after the sRGB data is converted into eRGB data as shown by the broken line in FIG. 8, the color correction unit 210b2 performs conversion so as to use eRGB data indicating a color outside the sRGB color gamut. If the eRGB data obtained as a result is converted by the LUT 12d and printing is performed, an image in which rich color reproduction is performed using a color outside the color gamut of the sRGB color space can be printed.

  On the other hand, it is also possible to create image data 120a from data in which the color space is set to the eRGB color space, perform color conversion with the LUT 12d, and execute printing. In this case, a color that is in the color gamut of the eRGB color space and that can expand the saturation within the color gamut of the printer is corrected and printed so that the saturation is high. Therefore, it is possible to print an image in which rich color reproduction is performed using a color outside the color gamut of the eRGB color space. Of course, the RGB data set as being in the eRGB color space may be printed with correction by the color correction unit 210b2, or the color indicated by the eRGB data by the image data 120a limited to a part of the eRGB color space. It is also possible to perform printing that faithfully reproduces.

(4) Other embodiments:
The embodiment described above is an example, and various configurations can be adopted as long as printing can be performed with a common color conversion profile even when the purpose of printing, the color space to be used, and the like are different. For example, in the above embodiment, the RGB data has two color spaces, the sRGB color space and the eRGB color space, but three or more color spaces may be adopted.

  That is, if mapping is not performed in an area where the color gamuts of three or more color spaces overlap, colors in this area can be faithfully reproduced, and colors other than this area are appropriately mapped in the printer color gamut. If this is done, rich color reproduction using the color gamut of the printer is possible. Moreover, an image based on each RGB data using such a plurality of color spaces can be printed by one LUT, and resources can be reduced.

  Furthermore, in the LUT of the above embodiment, RGB data and CMYKlclm data are associated with each other. However, the present invention may be applied to a profile that associates device-independent color space data with RGB data or CMYKlclm data. . Furthermore, in the above embodiment, the computer 10 that creates the color conversion profile and the computer 110 that executes the print control process are separate computers. Of course, the color conversion profile is created and the print control process is performed by the same computer. Alternatively, various configurations can be employed.

It is explanatory drawing which illustrates schematically the process of the color conversion table preparation method. It is a block diagram of a computer for creating an LUT. It is a flowchart which shows the process for producing LUT. It is explanatory drawing explaining the example of mapping implementation conditions. It is explanatory drawing explaining the structure of LUT. It is a block diagram of the computer which performs printing. It is a flowchart of a printing control process. It is a schematic explanatory drawing of the printing in embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... Color conversion profile creation program, 11a ... Halftone processing part, 11b ... Print data generation / output part, 11c ... sRGB data conversion part, 11d ... eRGB data conversion part, 11e ... Color gamut boundary discrimination part, 11f ... Mapping processing unit, 11g ... LUT creation unit, 12a ... Patch data, 12b ... sRGB data, 12c ... eRGB data, 12d ... LUT, 20 ... Printer, 30 ... Colorimeter, 120a ... Image data, 120b ... Conversion matrix , 210a ... Image data acquisition unit, 210b ... Color conversion unit, 210b1 ... Color space conversion unit, 210b2 ... Color correction unit, 210c ... Halftone processing unit, 210d ... Print data generation unit

Claims (11)

A color conversion profile that defines a correspondence relationship between data in the first color space and data in the second color space, and a color gamut based on the data in the first color space is wider than a color gamut based on the data in the third color space. Color conversion profile acquisition means for acquiring a color conversion profile defined as follows:
Input image data acquisition means for acquiring input image data expressing colors for a plurality of pixels included in the image with the data of the third color space;
The input image data is converted into data of the first color space, the converted data of the first color space is converted with reference to the color conversion profile, and the color of each pixel is converted using the data of the second color space. Color conversion means for obtaining output image data expressing
A printing control apparatus comprising: a printing execution unit that causes a printing apparatus to execute printing based on the output image data. The color conversion means converts the input image data into data of the first color space based on a predetermined conversion formula for converting the data of the third color space into data of the first color space. The print control apparatus according to claim 1. In the color conversion profile, the second color space data and the second color space data and the third color space data in the color gamut are substantially the same color before and after conversion as the second color space data and the second color space data. 3. The print control apparatus according to claim 1, wherein a correspondence relationship with data in a color space is defined. In the color conversion profile, colors outside the color gamut according to the data in the first color space and outside the color gamut according to the data in the third color space are mapped into the color gamut according to the data in the second color space, and 4. The print control apparatus according to claim 1, wherein a correspondence relationship between the data and the data in the second color space is defined. A color conversion profile creation device that creates a color conversion profile that defines a correspondence relationship between data in a first color space and data in a second color space,
A plurality of data in the first color space, a plurality of data in the second color space, and a plurality of data in the third color space defined so as to have a color gamut narrower than the color gamut by the data in the first color space; Device-independent color space data acquisition means for acquiring device-independent color space data indicating colors output in
Color gamut boundary determining means for determining a color gamut boundary among the data of the first color space, the data of the second color space, and the data of the third color space from the acquired device-independent color space data;
Referring to the boundary of the determined color gamut, the first color is set so that colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space substantially match before and after conversion. The correspondence relationship between the data in the space and the data in the second color space is defined, and the color in the color gamut based on the data in the first color space and the color outside the color gamut based on the data in the third color space depends on the data in the second color space. A color conversion profile creating apparatus comprising color gamut mapping means for mapping within a color gamut and defining a correspondence relationship between the data in the first color space and the data in the second color space. A color conversion profile that defines a correspondence relationship between data in a first color space and data in a second color space,
A plurality of data in the first color space, a plurality of data in the second color space, and a plurality of data in the third color space defined so as to have a color gamut narrower than the color gamut by the data in the first color space; The device-independent color space data indicating the color output in step S1 is acquired, and the first color space data, the second color space data, and the third color space data are obtained from the acquired device-independent color space data. The color gamut boundaries in the color gamut in the color gamut of the second color space and the data in the color gamut of the third color space before and after the conversion are referred to. The correspondence relationship between the data in the first color space and the data in the second color space is defined so that they substantially coincide with each other, and within the color gamut by the data in the first color space and outside the color gamut by the data in the third color space The color is mapped in the color gamut based on the data in the second color space. Serial color conversion profile, characterized in that is created by the data of the first color space defining the correspondence between the data of the second color space. A color conversion profile that defines a correspondence relationship between data in a first color space and data in a second color space,
The color gamut based on the data in the first color space is wider than the color gamut based on the plurality of data in the third color space, and the colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space are converted. The correspondence relationship between the data in the first color space and the data in the second color space is defined so that the colors substantially match before and after, and the data is in the color gamut by the data in the first color space and by the data in the third color space. The correspondence relationship between the data in the first color space and the data in the second color space is defined so that the color outside the color gamut is converted into a color in the color gamut based on the data in the second color space. Color conversion profile. A color conversion profile that defines a correspondence relationship between data in the first color space and data in the second color space, and a color gamut based on the data in the first color space is wider than a color gamut based on the data in the third color space. A color conversion profile acquisition step for acquiring a color conversion profile defined as follows:
An input image data acquisition step of acquiring input image data representing colors of a plurality of pixels included in the image with the data of the third color space;
The input image data is converted into data of the first color space, the converted data of the first color space is converted with reference to the color conversion profile, and the color of each pixel is converted using the data of the second color space. A color conversion process for obtaining output image data expressing
A printing control method comprising: a printing execution step for causing a printing apparatus to execute printing based on the output image data. A color conversion profile creation method for creating a color conversion profile that defines a correspondence relationship between data in a first color space and data in a second color space,
A plurality of data in the first color space, a plurality of data in the second color space, and a plurality of data in the third color space defined so as to have a color gamut narrower than the color gamut by the data in the first color space; A device-independent color space data acquisition process for acquiring device-independent color space data indicating the color output in
A gamut boundary determining step of determining a gamut boundary in the first color space data, the second color space data, and the third color space data from the acquired device-independent color space data;
Referring to the boundary of the determined color gamut, the first color is set so that colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space substantially match before and after conversion. The correspondence relationship between the data in the space and the data in the second color space is defined, and the color within the color gamut according to the data in the first color space and the color outside the color gamut according to the data in the third color space depends on the data in the second color space A color conversion profile creation method comprising: a color gamut mapping step for mapping within a color gamut and defining a correspondence relationship between the data in the first color space and the data in the second color space. A color conversion profile that defines a correspondence relationship between data in the first color space and data in the second color space, and a color gamut based on the data in the first color space is wider than a color gamut based on the data in the third color space. A color conversion profile acquisition function for acquiring a color conversion profile defined as
An input image data acquisition function for acquiring input image data expressing colors of a plurality of pixels included in the image with the data of the third color space;
The input image data is converted into data of the first color space, the converted data of the first color space is converted with reference to the color conversion profile, and the color of each pixel is converted using the data of the second color space. Color conversion function to obtain output image data expressing
A print control program for causing a computer to realize a print execution function for causing a printing apparatus to execute printing based on the output image data. A color conversion profile creation program for creating a color conversion profile that defines a correspondence relationship between data in a first color space and data in a second color space,
A plurality of data in the first color space, a plurality of data in the second color space, and a plurality of data in the third color space defined so as to have a color gamut narrower than the color gamut by the data in the first color space; A device-independent color space data acquisition function for acquiring device-independent color space data indicating colors output in
A color gamut boundary determining function for determining a color gamut boundary in the first color space data, the second color space data, and the third color space data from the acquired device-independent color space data;
Referring to the boundary of the determined color gamut, the first color is set so that colors in the color gamut based on the data in the second color space and in the color gamut based on the data in the third color space substantially match before and after conversion. The correspondence relationship between the data in the space and the data in the second color space is defined, and the color in the color gamut based on the data in the first color space and the color outside the color gamut based on the data in the third color space depends on the data in the second color space. A color conversion profile creation program for causing a computer to realize a color gamut mapping function for mapping within a color gamut and defining a correspondence relationship between the data in the first color space and the data in the second color space.

Images