Color conversion program, RIP device, and printing system

Abstract

To provide a color conversion program capable of more sufficiently expressing a gradation of a color near to a black point of RGB with a printer.SOLUTION: A color conversion program, which is an input ICC profile for converting an RGB value of an input image into a L*a*b* value in L*a*b* color space, includes an input ICC profile for converting a black point of an input image with any of an R value, a G value and a B value of 0 into a point Pk1 within a L*a*b* color space in which an L* value is larger than 0 and 10 or less.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a color conversion program, a RIP device, and a printing system. [Background technology]

[0002] Color profiles that convert the RGB values ​​of an input image into color values ​​in a device-independent color space have been known for some time. For example, Patent Document 1 discloses a method for converting RGB image data into device-independent L * a * b * L in color space * a * b * It is stated that it is converted to a value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-507598 Summary of the Invention [Problem to be solved by the invention]

[0004] The RGB values ​​of the input image are * a * b * When a point where the R, G, and B values ​​are all 0 (hereafter referred to as a black point) is converted by a conventional input ICC profile, the L * The value is "0". On the other hand, the printer * It is not possible to actually reproduce a color gamut with a value of "0". Depending on the printer, the minimum L * The value is about 3 to 10. Therefore, colors with RGB values ​​close to the black point (colors close to black) are not captured by the conventional input ICC profile. * a * b *If you convert the RGB values ​​to black and then print them on a printer, the color difference disappears. As a result, you cannot obtain a printed image with good gradation reproduction for colors with RGB values ​​close to the black point.

[0005] The present invention has been made in view of the above-mentioned points, and its purpose is to provide a color conversion program that enables a printer to better express the gradation of colors close to the RGB black point, as well as a RIP device in which such a color conversion program is installed, and a printing system including a RIP device and an inkjet printer. [Means for solving the problem]

[0006] The color conversion program disclosed herein converts the RGB values ​​of an input image into * a * b * L in color space * a * b * The black point of the input image where the R, G, and B values ​​are all 0 is defined as L * L with a value greater than 0 and less than or equal to 10 * a * b * Contains the input ICC profile to convert to points in color space.

[0007] According to the above color conversion program, the input ICC profile included in the color conversion program is the L of the black point after conversion. * Set the value to "greater than 0 and less than 10". This will determine the L of the black point after conversion. * The value is the minimum L that the printer can reproduce. * This allows the printer to better represent the gradations of colors that are close to the RGB black point. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating a printing system according to an embodiment. [Diagram 2] FIG. 2 is a front view showing the main part of the printer. [Diagram 3] FIG. 4 is a plan view showing the configuration of the lower surface of the carriage. [Figure 4] FIG. 1 is a schematic diagram showing the gamut of a conventional input ICC profile and the gamut of a printer. [Diagram 5] 1 is a table showing L*a*b* values ​​of representative points of a conventional input ICC profile gamut and a printer gamut. [Figure 6] 4 is a schematic diagram showing the gamut of an input ICC profile according to the embodiment. FIG. [Figure 7] 7 is a schematic diagram of the gamut of FIG. 6 viewed from a different angle. [Figure 8] 10 is a schematic diagram showing color differences near an orange point between the gamut of an input ICC profile and the gamut of a printer according to an embodiment. FIG. [Figure 9] 1 is a schematic diagram showing color differences near the emerald green point between the gamut of an input ICC profile and the gamut of a printer according to an embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a printing system according to the present invention will be described with reference to the drawings. The embodiment described here is, of course, not intended to limit the present invention in any particular way. In addition, the same reference numerals are used for members and parts that perform the same functions, and duplicated descriptions will be omitted or simplified.

[0010] [Printing system configuration] Fig. 1 is a schematic diagram showing a printing system 100 according to an embodiment. As shown in Fig. 1, the printing system 100 according to this embodiment includes a printer 10 and a computer 20 equipped with a RIP (Raster Image Processor) device 21. The RIP device 21 is a device that converts image data into raster format data that can be printed by the printer 10. The RIP device 21 is realized by the computer 20 executing RIP software. Here, the printer 10 is an inkjet printer. However, the type of printer 10 is not limited.

[0011] FIG. 2 is a front view showing a main part of the printer 10. FIG. 3 is a plan view showing the configuration of the lower surface of the carriage 1. The printer 10 includes a casing 2 and a guide rail 3 arranged in the casing 2. The guide rail 3 extends in the left-right direction (scanning direction) of FIG. 2. A carriage 1 having a recording head 15 that ejects ink is engaged with the guide rail 3. The carriage 1 reciprocates in the scanning direction along the guide rail 3 by a carriage moving mechanism 8. The carriage moving mechanism 8 has pulleys 19b and 19a arranged on both ends of the guide rail 3. A carriage motor 8a is connected to the pulley 19a. The carriage motor 8a may be connected to the pulley 19b. The pulley 19a is driven by the carriage motor 8a. An endless belt 6 is wound around each of the pulleys 19a and 19b. The carriage 1 is fixed to the belt 6. When the pulleys 19a and 19b rotate and the belt 6 runs, the carriage 1 moves left and right. The recording medium 5 is transported in a transport direction perpendicular to the scanning direction by a paper transport mechanism (not shown).

[0012] The printer 10 includes a plurality of ink cartridges 11 each containing an ink. The ink cartridges 11 store inks of different colors. Here, the printer 10 includes eight ink cartridges 11C, 11M, 11Y, 11K, 11O, 11R, 11G, and 11V, which store cyan ink, magenta ink, yellow ink, black ink, orange ink, red ink, green ink, and violet ink, respectively. Of the above inks, the cyan ink, magenta ink, yellow ink, and black ink are classified as process color inks that form an image. The orange ink, red ink, green ink, and violet ink are classified as special color inks that impart special visual effects to an image. The orange ink, red ink, green ink, and violet ink are inks for expanding the color gamut that can be expressed by the printer 10. By using these special color inks, the color gamut that can be expressed by the printer 10 is expanded compared to the case where only the cyan ink, magenta ink, yellow ink, and black ink (CMYK inks) are used. Although the inks used in printer 10 are not limited to those mentioned above, printer 10 is preferably configured to be able to use at least one of the following special color inks in addition to the process color inks: orange ink, red ink, green ink, and violet ink.

[0013] As shown in FIG. 3, the recording head 15 includes a plurality of ink heads 16. Here, the recording head 15 includes four ink heads 16. Each of the four ink heads 16 includes a plurality of nozzles 17. Each of the plurality of nozzles 17 is configured to eject ink. In one ink head 16, the plurality of nozzles 17 constitute two nozzle rows 18 arranged side by side in the scanning direction. Each nozzle row 18 is composed of a plurality of nozzles 17 arranged side by side in the transport direction. Each of the plurality of nozzle rows 18 is connected to one of the plurality of ink cartridges 11C to 11V. Hereinafter, the nozzle row connected to the ink cartridge 11C is referred to as the nozzle row 18C. Hereinafter, similarly, the nozzle rows connected to the ink cartridges 11M, 11Y, 11K, 11O, 11R, 11G, and 11V are referred to as the nozzle rows 18M, 18Y, 18K, 18O, 18R, 18G, and 18V.

[0014] The nozzle rows 18C-18V and the ink cartridges 11C-11V are connected by ink supply paths 12, respectively. The ink supply paths 12 are ink flow paths that supply ink from the ink cartridges 11C-11V to the nozzle rows 18C-18V. The ink supply paths 12 are formed of, for example, flexible tubes. The ink supply paths 12 are provided with a liquid feed pump 13. However, the liquid feed pump 13 is not necessarily required and can be omitted. A portion of the ink supply path 12 is covered by a cable protection and guide device.

[0015] The recording head 15 ejects ink toward the recording medium 5, forming dots of ink on the recording medium 5. A large number of these dots are arranged to form an image or the like on the recording medium 5. In this embodiment, the nozzles 17 constituting the nozzle row 18C eject cyan ink. The nozzles 17 constituting the nozzle row 18M eject magenta ink. The nozzles 17 constituting the nozzle row 18Y eject yellow ink. The nozzles 17 constituting the nozzle row 18K eject black ink. The nozzles 17 constituting the nozzle row 18O eject orange ink. The nozzles 17 constituting the nozzle row 18R eject red ink. The nozzles 17 constituting the nozzle row 18G eject green ink. The nozzles 17 constituting the nozzle row 18V eject violet ink.

[0016] As shown in FIG. 1, the printer 10 includes a control device 4. The control device 4 is electrically connected to a feed motor of the paper feed mechanism, a carriage motor 8a of the carriage movement mechanism 8, a liquid feed pump 13, and a recording head 15. The control device 4 controls the operations of these devices. The control device 4 is typically a computer. The control device 4 includes, for example, an interface (I / F) that receives print data and the like from an external device such as a host computer, a central processing unit (CPU) that executes instructions of a control program, a ROM that stores a program executed by the CPU, a RAM used as a working area for expanding the program, and a storage device such as a memory that stores the above program and various data. However, the configuration of the control device 4 is not particularly limited.

[0017] The RIP device 21 is a device that converts input image data into data that can be printed by the printer 10. The RIP device 21 converts device-dependent image data (e.g., RGB image data) into color values ​​in a device-independent color space (here, L * a * b *Then, the color values ​​in the device-independent color space obtained above (here, L * a * b * The printer converts the device-dependent print image data (color values) into device-dependent print image data (CMYK ink values ​​in this case). When converting device-dependent print image data into color values ​​in a device-independent color space, a conversion table (Look Up Table: LUT) called an A2B table in the color profile is used. Conversely, when converting color values ​​in a device-independent color space into device-dependent print image data, a conversion table called a B2A table in the color profile is used.

[0018] When converting input image data to color values, the input ICC profile is used. If the input image is RGB image data, the RGB values ​​are converted to L * a * b * Color value in color space (L * a * b * The input ICC profile (more precisely, the A2B table within it) is used to convert the RGB values ​​of the input image to L * a * b * Color value in color space (L * a * b * The input ICC profile for converting the CMYK values ​​of the input image into L values ​​is an input ICC profile for RGB image processing. When the input image is CMYK image data, the RIP device 21 converts the CMYK values ​​of the input image into L values ​​using an input ICC profile for CMYK. * a * b * Color value in color space (L * a * b * value).

[0019] The print image data obtained above is L * a * b *The B2A table of the output ICC profile is used to convert the values ​​into ink values ​​that printer 10 will actually print. ICC profiles include an input ICC profile that converts input print image data, and an output ICC profile that converts the converted and captured print image data into a form that is output by printer 10. The input ICC profile and the output ICC profile each include an A2B table and a B2A table.

[0020] The RIP device 21 is a computer in which a color conversion program 22 including an input ICC profile 23 invented by the inventor of the present application is installed (see FIG. 1). The input ICC profile 23 invented by the inventor of the present application converts the RGB values ​​of an input image into L * a * b * The input ICC profile is an input ICC profile that converts the input ICC profile into color values ​​in a color space. The color conversion program 22 also includes an output ICC profile. The color conversion program 22 may include an input ICC profile other than the input ICC profile 23 invented by the inventor of the present application. The computer 20 functions as a RIP device 21 by executing the installed color conversion program 22. The printer 10 prints based on data obtained by color-converting an input image by the RIP device 21. The color conversion program 22 may be read from a recording medium such as a CD or DVD. The color conversion program 22 may be downloaded via the Internet. The color conversion program 22 may be created within the computer 20. The RIP device 21 is realized here by one computer 20, but may be realized by multiple computers. The RIP device 21 may be realized by a computer on the cloud. The computer 20 may have functions other than the function as the RIP device 21, for example, a function of creating an input image.

[0021] The following describes the gamut of the input ICC profile 23 according to the invention of the present inventor, comparing it with the gamut of a conventional input ICC profile as necessary. The gamut is the range of colors that an ICC profile or a printer can express, and is expressed as L * a * b * It is expressed as a three-dimensional area in color space. Note that the following gamut diagrams are schematic diagrams, and the L * a * b * The locations of the points at which values ​​are written are not necessarily illustrated precisely.

[0022] [Gamut of conventional input ICC profile] First, the problem of the gamut of the conventional RGB input ICC profile will be described. FIG. 4 is a schematic diagram showing the gamut G0 of the conventional RGB input ICC profile and the gamut Gp of the printer 10. There have been many input ICC profiles in the past, and therefore many gamuts, and the gamut G0 shown in FIG. 4 is one example. In the example shown in FIG. 4, the gamut Gp of the printer 10 has a portion that protrudes outward from the gamut G0 of the conventional input ICC profile. The gamut Gp of the printer 10 protrudes outward from the gamut G0 of the conventional input ICC profile in the orange gamut Ro, the emerald green gamut Rg, and the red gamut Rr. The point Po in the orange gamut Ro is the orange point Po that represents the orange color of the printer 10. Here, the orange point Po is a point corresponding to the orange ink monochromatic color, and constitutes one vertex of the gamut Gp. The orange gamut Ro is a color gamut near the orange point Po, that is, a color gamut that represents an orange color close to the color of the orange ink monochromatic color.

[0023] The emerald green gamut Rg is a gamut that represents a color close to emerald green. Here, an emerald green point that represents the emerald green of the printer 10 is set in the emerald green gamut Rg and is represented by the symbol Pg (see FIG. 9). A point Pr in the red gamut Rr is a red point Pr that represents the red color of the printer 10. Here, the red point Pr is a point that corresponds to the single color of red ink and constitutes one vertex of the gamut Gp. The red gamut Rr is a gamut in the vicinity of the red point Pr, that is, a gamut that represents a red color close to the single color of red ink. Note that, if the printer 10 does not use orange ink or red ink, the orange point Po and the red point Pr may be determined appropriately. Even if the printer 10 uses orange ink or red ink, the orange point Po and the red point Pr may be determined appropriately as long as they do not deviate from the orange and red colors, respectively. The same applies to the points that represent other colors.

[0024] Figure 5 shows the L of a representative point of the gamut G0 of a conventional input ICC profile and the gamut Gp of the printer 10. * a * b * The top table in Figure 5 shows the L values ​​for representative points of the gamut G0 of a conventional input ICC profile. * a * b * The "Red", "Green", and "Blue" rows in the upper table of Fig. 5 respectively show the L values ​​of the red (R value = 255, G value = 0, B value = 0), green (R value = 0, G value = 255, B value = 0), and blue (R value = 0, G value = 0, B value = 255) of the RGB input image converted by the conventional input ICC profile. * a * b * The table at the bottom of FIG. 5 shows the L values ​​for representative points of the gamut Gp of the printer 10. * a * b * The title of each row in the table below in Fig. 5 indicates the name of the color represented by that point. * a * b *The values ​​are just examples.

[0025] As described above, the gamut Gp of the printer 10 extends beyond the gamut G0 of the conventional input ICC profile in the orange gamut Ro, the emerald green gamut Rg, and the red gamut Rr. These gamuts Ro, Rg, and Rr that extend beyond the gamut G0 of the conventional input ICC profile are not used when converting an input image using the conventional input ICC profile. In other words, when the conventional input ICC profile is used, the printer 10 is unable to fully demonstrate its color reproduction capabilities, despite the fact that its color reproduction capabilities have been expanded by using special color inks.

[0026] Although not shown in the figure, some conventional input ICC profiles have a very large gamut. By using such an input ICC profile, it is possible to fit the gamut Gp of the printer 10 within the gamut of the input ICC profile. However, if the gamut of the input ICC profile is too large, the color gradation generated by the input ICC profile is significantly compressed to fit the gamut Gp of the printer 10. This results in poor color gradation reproducibility.

[0027] Furthermore, color conversion using a conventional input ICC profile causes problems in expressing the gradation of colors close to black. This is for the following reason. When a point where the R, G, and B values ​​are all 0 (hereafter referred to as a black point) is converted using a conventional input ICC profile, the L value, which represents lightness, * The value is "0". On the other hand, the gamut Gp of the printer 10 is L * The printer 10 does not include the color gamut with a value of "0". * It is not possible to reproduce the ideal black, which has a value of "0". Depending on the printer, the minimum L value that the printer can reproduce is * The value is about 3 to 10 (for example, L in the "black dot" row in the table below in Figure 5). *For this reason, when a printer prints a color whose RGB value is close to the black point, the color difference is compressed or ignored. As a result, the gradation expression of colors close to the RGB black point becomes poor. These are the issues with conventional input ICC profiles.

[0028] [Gamut of input ICC profile according to this embodiment] Next, the gamut G1 of the input ICC profile 23 according to the invention of the present inventor will be described. FIG. 6 is a schematic diagram showing the gamut G1 of the input ICC profile 23. FIG. 7 is a schematic diagram showing the gamut G1 of FIG. 6 from a different angle. As shown in FIG. 6 and FIG. 7, the gamut G1 of the input ICC profile 23 is L * The minimum value is greater than 0. * The point Pk1 where the value is the minimum corresponds to the black point in the RGB image (the point where the R value, G value, and B value are all "0"). When the input ICC profile 23 is used, the black point of the RGB input image is converted to point Pk1 (hereinafter, this point is also referred to as black point Pk1). * The value is, for example, "3". L of the black point Pk1 of the gamut G1 * The value should be designed in the range of 0 to 10 inclusive, in accordance with the characteristics of the printer 10 (see, for example, the "black point" row in the table below FIG. 5). The input ICC profile 23 defines the black point of the RGB input image as * L with a value greater than 0 and less than or equal to 10 * a * b * Convert to black point Pk1 in the color space.

[0029] Furthermore, the input ICC profile 23 converts red (R value=255, G value=0, B value=0) in the RGB input image into L * Value is 60 to 70, a * Value is 100 to 120, b * L with a value between 85 and 105 * a * b *This point is also called the red point Pr1. * a * b * The value may be suitably designed within the above range in accordance with the characteristics of the printer 10 (for example, see the "Red" row in the table below FIG. 5). However, the L * a * b * The values ​​are merely a suitable guideline and are not limited to these. In FIG. 6 and FIG. 7, as an example, red in an RGB input image is L * Value is 65, a * Value is 110, b * The figure illustrates the case where the value is converted to point Pr1, which has a value of 95.

[0030] The input ICC profile 23 converts green (R value = 0, G value = 255, B value = 0) in the RGB input image into L * Value is 80 to 90, a * Value is between -128 and -108, b * L with a value between 80 and 100 * a * b * This point is also called the green point Pg1. * a * b * The value may be suitably designed within the above range in accordance with the characteristics of the printer 10. However, the L * a * b * The values ​​are merely a suitable guideline and are not limited to these. In FIG. 7, as an example, green in an RGB input image is L * Value is 85, a * Value is -118, b * The figure illustrates the case where the value is converted to point Pg1 of 90.

[0031] The input ICC profile 23 converts blue (R value = 0, G value = 0, B value = 255) in the RGB input image into * Value is 25 to 35, a* Value is 65 to 85, b * L with a value between -128 and -108 * a * b * This point is converted to point Pb1 in the color space. Hereinafter, this point will also be called the blue point Pb1. * a * b * The value may be suitably designed within the above range in accordance with the characteristics of the printer 10 (for example, see the "Blue" row in the table below FIG. 5). However, the L * a * b * The values ​​are merely a suitable guideline and are not limited to these. In FIG. 6 and FIG. 7, as an example, blue in an RGB input image is L * Value is 30, a * Value is 75, b * 8 and 9 show the case where the gamut G1 of the input ICC profile 23 is converted to the gamut Gp of the printer 10 by overlaying it. As shown in Fig. 8 and Fig. 9, when the RGB input image is converted using the input ICC profile 23, the red point Pr1, the green point Pg1, and the blue point Pb1, which respectively correspond to the red, green, and blue colors of the RGB input image, are located outside the gamut Gp of the printer 10.

[0032] Furthermore, the input ICC profile 23 converts the orange gamut and emerald green gamut in the RGB input image into color gamuts outside the orange gamut Ro and emerald green gamut Rg of the gamut Gp of the printer 10, respectively. FIG. 8 is a schematic diagram showing the color difference near the orange point Po between the gamut G1 of the input ICC profile 23 and the gamut Gp of the printer 10. As shown in FIG. 8, the gamut G1 of the input ICC profile 23 converts the orange gamut and emerald green gamut in the RGB input image into color gamuts outside the orange gamut Ro and emerald green gamut Rg of the gamut Gp of the printer 10. * Value=70,a * Value=64, b * value = 105, see also Figure 5). * Value=50,a * Value=0,b *If the point where the value is 0 is called the reference point Ps, the reference point Ps is located closer to the center of the gamut G1 than the orange point Po of the printer 10. Note that the reference point Ps only needs to represent the vicinity of the center of the gamut G1, and its L * a * b * The value is not limited. As shown in FIG. 8, a straight line L1 starting from the reference point Ps and connecting the reference point Ps and the orange point Po intersects with the outer surface of the gamut G1. When this intersection is the first intersection Px1, the gamut G1 is set so that the distance (color difference ΔE1) between the orange point Po of the printer 10 and the first intersection Px1 is a suitable distance. The distance (color difference ΔE1) between the orange point Po of the printer 10 and the first intersection Px1 is preferably designed to be 20 or less, more preferably 15 or less. This means that the outer surface of the gamut G1 is not too far from the orange gamut Ro of the printer 10. If the color difference ΔE1 is large, the outer surface of the gamut G1 is too far from the orange gamut Ro of the printer 10. If this happens, the color gradation of the printer 10 in the orange gamut Ro will be excessively compressed, and the gradation reproducibility will deteriorate.

[0033] The color difference ΔE1 is the L of the orange point Po * Value and L of the first intersection point Px1 * The square of the difference between the values ​​and the a of the orange point Po * Value and a of the first intersection point Px1 * The square of the difference between the values ​​and the b of the orange point Po * Value and b of the first intersection point Px1 * It is possible to obtain the square root of the sum of the square of the difference between the L value and the L value. Note that the above does not mean a method for designing gamut G1, but indicates the conditions that gamut G1 should preferably satisfy. * Value=70,a * Value=64, b *It is merely preferable that the design includes a first point having a value of 105 (which does not have to coincide with the printer's orange point, but can be a point close to the printer's orange point) and that the distance (color difference ΔE1) between the first intersection point Px1 and the first point is configured to be 20 or less; it does not have to be designed based on the reference point Ps, for example.

[0034] The same is true for the emerald green color gamut. FIG. 9 is a schematic diagram showing the color difference near the emerald green point Pg between the gamut G1 of the input ICC profile 23 and the gamut Gp of the printer 10. As shown in FIG. 9, the gamut G1 of the input ICC profile 23 is * Value=45, a * value=-85,b * The color difference ΔE2 between the emerald green point Pg of the printer 10 and the second intersection point Px2 is preferably 20 or less, and more preferably 15 or less.

[0035] The input ICC profile 23 is an input ICC profile of the look-up table (LUT) type. According to the LUT type, the RGB values ​​of an RGB image are converted into L * a * b * Therefore, the RGB black point is converted to an L value greater than 0 and less than 10. * It is easy to map values ​​and design the shape of the orange color gamut.

[0036] The gamut G1 has the following characteristics:

[0037] (1) The black point of the input RGB image is L * L with a value greater than 0 and less than or equal to 10 * a * b * This corresponds to the point Pk1 in the color space. According to this, the L* The value is greater than 0 and less than or equal to 10, and is the minimum L that the printer 10 can reproduce. * value (for example, "4", see FIG. 5). This allows the printer 10 to better express the gradation of colors close to the RGB black point.

[0038] (2) The red color in the RGB input image (R value = 255, G value = 0, B value = 0) is * Value is 60 to 70, a * Value is 100 to 120, b * L with a value between 85 and 105 * a * b * It corresponds to point Pr1 (red point Pr1) in the color space. As a result, as shown in FIG. 8, it is possible to configure a gamut G1 having a red gamut Rr1 (refers to a color gamut around the red point Pr1) in which the red point Pr of the printer 10 does not go outside the gamut of the input ICC profile, nor does the red point Pr of the printer 10 lie significantly inside the outer surface of the gamut of the input ICC profile. Therefore, it is possible to demonstrate the color reproduction capability in the red gamut Rr of the printer 10, and to suppress deterioration of color gradation reproduction. The same is true for green (R value = 0, G value = 255, B value = 0) and blue (R value = 0, G value = 0, B value = 255) in the RGB input image.

[0039] (3) The gamut G1 of the input ICC profile 23 is L * Value is 70, a * Value is 64, b *The input ICC profile 23 includes a first point (here, coincident with the orange point Po of the gamut Gp of the printer 10) whose value is 105. When the intersection point Px1 is a straight line L1 that starts from the reference point Ps and connects the reference point Ps and the first point and an outer shell surface of the gamut G1 of the gamut, the distance (color difference ΔE1) between the first point and the first intersection point Px1 is 20 or less. As a result, the orange gamut Ro1 (refers to the color gamut around the first intersection point Px1, see FIG. 8) of the gamut G1 of the input ICC profile 23 is located outside the orange gamut Ro of the gamut Gp of the printer 10. Furthermore, the orange gamut Ro1 of the gamut G1 is not too far from the orange gamut Ro of the gamut Gp of the printer 10. Therefore, it is possible to demonstrate color reproducibility in the orange gamut Ro of the printer 10, and to suppress deterioration of color gradation reproducibility. The same is true for the emerald green gamut Rg1 of gamut G1 (referring to the gamut around the second intersection point Px2, see FIG. 9).

[0040] (4) The gamut G1 of the input ICC profile 23 includes the entire gamut Gp of the printer 10. According to this input ICC profile 23, the color reproduction capability of the printer 10 can be fully utilized.

[0041] The color conversion program 22 is particularly effective when the printer uses special color inks that expand the printer's color gamut, such as orange ink, red ink, green ink, or violet ink, but the color conversion program 22 can also be effective when printing with a printer that does not use special color inks that expand the color gamut.

[0042] A preferred embodiment has been described above. However, the printing system of the present invention is not limited to the above embodiment. For example, the configuration of the printer 10 according to the above embodiment is an example, and does not limit the configuration of the printer. Unless otherwise specified, the above embodiment does not limit the present invention. [Explanation of symbols]

[0043] 10 Printers 21 RIP device 22 Color conversion program 23 Input ICC Profile 100 Printing System G0 Gamut of conventional input ICC profile G1 Gamut of input ICC profile Gp Printer Gamut Pk1 Black point of the gamut of the input ICC profile Pr1 Input ICC profile gamut red point Pg1 Green point of the gamut of the input ICC profile Pb1 Blue point of the gamut of the input ICC profile Ro1 Orange gamut of the input ICC profile Rg1 Emerald green gamut of input ICC profile Rr1 Red gamut of the input ICC profile Po Orange point (first point) of the printer gamut Pr Printer Gamut Red Point Pg Emerald green point (second point) of the printer's gamut Ro Orange area of ​​the printer gamut Rr The red gamut of the printer's gamut Emerald Green Color Gamut of RG Printer Gamut Ps Reference point Px1 1st intersection Px2 2nd intersection ΔE1 Orange gamut color difference ΔE2 emerald green gamut color difference

Claims

1. The RGB values ​​of the input image are ＊ a ＊ b ＊ L in color space ＊ a ＊ b ＊ The black point of an input image in which the R, G, and B values ​​are all 0 is defined as L ＊ L whose value is greater than 0 and less than or equal to 10 ＊ a ＊ b ＊ an input ICC profile that converts to a point in the color space; The gamut of the input ICC profile is a first point having an L* value of 70, an a* value of 64, and a b* value of 105; and a gamut in which, when a reference point having an L* value of 50, an a* value of 0, and a b* value of 0 is taken as an origin and a line connecting the reference point and the first point intersects with an outer surface of the gamut, the distance between the first point and the first intersection is 20 or less; Color conversion program.

2. An input ICC profile that converts RGB values ​​of an input image into L*a*b* values ​​in an L*a*b* color space, the input ICC profile converting a black point of the input image, where the R value, G value, and B value are all 0, into a point in the L*a*b* color space where the L* value is greater than 0 and less than or equal to 10; The gamut of the input ICC profile is L ＊ Value is 45, a ＊ Value is -85, b ＊ a second point having a value of 0; and L ＊ Value is 50, a ＊ Value is 0, b ＊ a gamut in which, when a line starting from a reference point having a value of 0 and connecting the reference point and the second point is defined as an intersection point between the reference point and the second point and an outer surface of the gamut, the distance between the second point and the second intersection is 20 or less; Color conversion program.

3. The input ICC profile defines red (R value = 255, G value = 0, B value = 0) in the input image as L ＊ Value is between 60 and 70 a ＊ Value is between 100 and 120 b ＊ Value is between 85 and 105 L ＊ a ＊ b ＊ Convert to a point in color space, 3. The color conversion program according to claim 1 or 2.

4. The input ICC profile defines the green color (R value = 0, G value = 255, B value = 0) in the input image. L ＊ Value is between 80 and 90 a ＊ Value is between -128 and -108 b ＊ Value is between 80 and 100 L ＊ a ＊ b ＊ Convert to a point in color space, The color conversion program according to any one of claims 1 to 3.

5. The input ICC profile defines blue (R value = 0, G value = 0, B value = 255) in the input image as L ＊ Value is between 25 and 35 a ＊ Value is between 65 and 85 b ＊ Value is between -128 and -108 L ＊ a ＊ b ＊ Convert to a point in color space, The color conversion program according to any one of claims 1 to 4.

6. the input ICC profile is a look-up table type input ICC profile; The color conversion program according to any one of claims 1 to 5.

7. A color conversion program according to any one of claims 1 to 6 is installed, and the program is configured to execute the installed color conversion program. RIP (Raster Image Processor) device.

8. A RIP device according to claim 7; an inkjet printer that prints based on data obtained by color-converting an input image using the RIP device; A printing system including:

9. the inkjet printer includes at least one of a nozzle for ejecting an orange ink, a nozzle for ejecting a red ink, a nozzle for ejecting a green ink, and a nozzle for ejecting a violet ink; The printing system according to claim 8.

Images