JP5589520B2 - Color conversion profile creation apparatus, color conversion profile creation method, color conversion profile creation program, and printing apparatus - Google Patents

Description

  The present invention relates to a color conversion profile creation apparatus, a color conversion profile creation method, a color conversion profile creation program, and a printing apparatus.

  A technique for creating a color conversion profile for converting image data to be printed into information on a combination of ink amounts (ink amount sets) of a plurality of types of ink mounted on a printer has been disclosed by the applicant (Patent Document) 1). In this technique, an evaluation function for evaluating graininess, color constancy, gradation and the like based on an ink amount set initially prepared in association with a predetermined color system grid point Is used to optimize the ink amount set, and a color conversion profile is created based on the ink amount set after being optimized and determined for each grid point.

JP 2008-263579 A

  Conventionally, when optimization is performed on the ink amount set of each grid point, processing objects are sequentially processed one by one from the grid point located at the end (outer) in the color space. According to this method, when one grid point is to be processed, optimization is performed under the influence of the ink amount set for neighboring grid points. However, there are some inconveniences in the method of processing one by one from the lattice points located at the edges. For example, if a clear processing order is not determined although processing is performed one by one from the grid points located at the edges, the processing result (determined ink amount set) varies depending on the processing order. (As a result, the characteristics of the color conversion profile differ). Further, if the lattice points are processed one by one in order, it takes a lot of processing time to complete the processing for all the lattice points.

  Further, in order to improve the gradation of the ink amount in the color conversion profile, after completing the determination of the ink amount set by the above optimization for all the lattice points, the ink amount set for all the lattice points is further completed. There were times when optimization was repeated. However, repeated determination of the ink amount set by such optimization leads to further increase in processing time.

  The present invention has been made to solve at least one of the above-described problems, and a color conversion profile capable of realizing high quality in color conversion, particularly excellent gradation, in a shorter processing time than in the past. Providing technology for creating.

  One aspect of the present invention is a color conversion profile creation device that creates a color conversion profile for converting coordinate values of an input color system having a plurality of input axes into combinations of ink amounts of a plurality of types of ink. A grid point determination unit that determines a target grid point that is a target of processing for determining a combination of ink amounts from among the grid points dispersed in the input color system, and ink for the determined target grid point An ink amount determination unit that determines a combination of amounts, and a color conversion profile generation unit that generates the color conversion profile based on the determined combination of ink amounts, and the lattice point determination unit includes: After the lattice points located at the ends are determined to be the target lattice points, the lattice points that are already determined to be the target lattice points and the combinations of the ink amounts are determined approximately in the middle of the lattice points. It is constituted to repeat the processing for determining the point in the target lattice point.

  According to the present invention, first, a lattice point located at the end of each lattice point is determined as a target lattice point, a combination of ink amounts is determined for the target lattice point, and then a combination of ink amounts is determined. A process is repeated in which a lattice point located approximately in the middle between the points is newly set as a target lattice point, and a combination of ink amounts is determined. That is, when processing a certain grid point, since the combination of ink amounts has already been determined for other grid points located between the grid points, the influence of the surrounding ink amount on the grid point is affected. The amount of ink that achieves excellent gradation can be determined below. In addition, since the processing order for each grid point is clarified as compared with the prior art, fluctuations in processing results due to differences in processing order are suppressed.

  The lattice point determination unit simultaneously determines a plurality of lattice points located at the ends in the input axis direction among the lattice points as the target lattice points, and determines the lattice points located approximately in the middle as the target lattice points. The determination of the ink amount is performed by simultaneously determining the plurality of lattice points positioned approximately in the middle corresponding to the combinations of the lattice points that have already been determined as the target lattice points and the combinations of the ink amounts as the target lattice points. The unit may determine a combination of ink amounts for a plurality of target lattice points determined simultaneously by parallel processing. According to this configuration, the lattice point determination unit simultaneously determines a plurality of lattice points as target lattice points, and the ink amount determination unit performs parallel processing for determining the combination of ink amounts for the plurality of target lattice points determined simultaneously. Therefore, as compared with the conventional method in which the lattice points are processed one by one in order, the time required to complete the processing for all the lattice points can be remarkably shortened.

  When the lattice point determination unit assigns a lattice point level along the input axis direction to each lattice point, the lattice point determination unit assigns the lowest lattice point level to lattice points located at both ends in the input axis direction among the lattice points. In addition, a lattice point level that is higher than the lattice point level of the lattice point that sandwiches the lattice point is assigned to a lattice point that is located approximately in the middle between lattice points to which the lattice point level is assigned, and the lattice point level is low. The target lattice point may be determined preferentially from the point. According to this configuration, by referring to the grid point level, first, the grid point located at the end of each grid point is determined as the target grid point, and then the approximate amount between the grid points for which the combination of the ink amounts is determined. It is possible to reliably and easily proceed with the procedure for determining a lattice point in which a lattice point located in the middle is newly determined as a target lattice point.

  The ink amount determination unit determines a combination of the ink amounts by optimizing a combination of ink amounts based on an evaluation with respect to a combination of ink amounts using a predetermined evaluation function, and the evaluation function includes at least a target lattice point. An evaluation item for evaluating the gradation in the relationship between each lattice point and the target lattice point for which the combination of the ink amounts at the sandwiched positions has already been determined may be included. According to this configuration, by using the evaluation function including the evaluation items, the combination of the ink amounts determined for the target lattice point is between the surrounding lattice points for which the combination of the ink amounts has already been determined by optimization. As a result, it is possible to create a color conversion profile that realizes high quality in color conversion, particularly excellent gradation.

  The ink amount determination unit may determine the combination of ink amounts by the optimization only once for one target lattice point. According to this configuration, since the determination of the ink amount set by the above optimization for each lattice point is not repeated many times, the time required for creating the color conversion profile can be significantly shortened compared to the conventional case. it can. In other words, according to the present invention, the target grid points are determined and processed in the above-described order, so that it is sufficient if the determination of the ink amount set by the above optimization is performed once for each grid point. The amount of ink with good tonality can be determined. For this reason, it is not necessary to repeat the determination of the ink amount set by the above optimization for each lattice point as in the prior art.

  The technical idea of the present invention can be realized by devices other than the color conversion profile creation device. For example, a method (a color conversion profile creation method) having processing steps realized by each unit included in the above-described color conversion profile creation apparatus, and a program that causes a computer to execute functions realized by each unit included in the above-described color conversion profile creation apparatus ( The invention of a color conversion profile creation program) can also be grasped. In addition, the invention includes a configuration corresponding to the above-described color conversion profile creation apparatus, uses the color conversion profile for color conversion processing of image data, and controls a printer as a printing apparatus, and the print control apparatus It is possible to grasp the invention of the method and program corresponding to the above. Furthermore, it is possible to grasp the invention of a printing apparatus that incorporates the color conversion profile created as described above and uses the color conversion profile for color conversion processing of image data, and a method and program corresponding to this printing apparatus. .

It is a figure which shows the hardware constitutions and software constitution of an apparatus. It is a figure which illustrates a forward model converter and an inverse model initial stage LUT. It is a flowchart which shows the outline of a color conversion profile creation process. It is a flowchart which shows the setting process of initial LUT. FIG. 6 is a diagram illustrating an initial LUT. It is a flowchart which shows the process of object lattice point determination and optimization. It is a figure which illustrates a mode that the lattice point level was set to each input-axis direction. It is a figure which illustrates the processing order determined about each input lattice point. It is a figure which illustrates the relationship between an object lattice point and each processed lattice point. 2 is a diagram illustrating a configuration of a printer. FIG. It is a figure which shows the software structure of firmware.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1. FIG. 1 shows a hardware configuration and a software configuration of a color conversion profile creation apparatus according to the present embodiment. The main part of the apparatus is practically realized by the computer 10. Specifically, the CPU 12 included in the computer 10 reads a program stored in a memory such as a hard disk drive (HDD) 11 and executes an operation according to the program while expanding the program in the RAM 13, thereby setting the initial LUT. Each function of the unit 14, the grid point determination unit 15, the ink amount determination unit 16, the color conversion profile creation unit 17, the forward model converter FM, and the like is realized. Each of these functions will be described later.

  The HDD 11 stores the created color conversion profile 400, the inverse model initial LUT 410, and the like. The color conversion profile 400 is a color conversion for converting a coordinate value of a predetermined input color system (for example, sRGB color system) into a combination of ink amounts (ink amount set) of a plurality of types of ink used by the printer 20. It is a lookup table (color conversion LUT). In this embodiment, as an example, C (cyan) ink, M (magenta) ink, Y (yellow) ink, K (black) ink, Lc (light cyan) ink, Lm (light magenta) ink, Lk (gray) ink Assume a printer 20 that can use a plurality of inks such as LLk (light gray) ink. The ink amount set is a combination of ink amounts (tone values) of each of the plurality of inks. The inverse model initial LUT 410 will be described later.

  The computer 10 also functions as a print control device by executing calculations according to a program and controlling the printer 20 as a printing device via a USB interface (I / F) 21 or the like. In other words, the computer 10 acquires image data to be printed in which the color of each pixel is expressed by the coordinate value of the predetermined input color system, and the image data is converted into a pixel using the created color conversion profile 400. Color conversion is performed in units, and image data after color conversion (image data in which each pixel is expressed by an ink amount set) is subjected to halftone processing or microweave processing to generate print data, and the print data is converted to USB I / F 21 It is also possible to output to the printer 20 via the above. The printer 20 performs printing based on the print data. Of course, the computer 10 and the printer 20 may be connected by other interfaces such as infrared rays and wireless LAN. The computer 10 is connected to the display 30 via a video interface (I / F) 31 and is connected to an operation unit 40 such as a keyboard and a mouse via an input interface (I / F) 41.

As shown in FIG. 2A, the forward model converter FM includes a spectral printing model converter RC and a color converter CC. The forward model converter FM is a conversion model that converts an ink amount set into a color value (colorimetric value) of a device-independent color system. As shown in FIG. 2B, the inverse model initial LUT 410 is a conversion model that converts the color value of the device-independent color system into an ink amount set. In this embodiment, the CIELAB color system is used as the device-independent color system. Hereinafter, the color value of the CIELAB color system will be expressed as “L ^* a ^* b ^* ”.

The spectral printing model converter RC that forms the preceding stage of the forward model converter FM converts the ink amounts of a plurality of types of ink into spectral reflectances R (λ) of color patches that are printed according to the ink amounts. In the present specification, the term “color patch” is used in a broad sense including not only a chromatic color patch but also an achromatic color patch. The color converter CC constituting the subsequent stage of the forward model converter FM calculates the color value L ^* a ^* b ^* from the spectral reflectance R (λ) obtained by the spectral printing model converter RC. In the conversion from the ink amount set to the color value using the forward model converter FM, a light source (for example, standard light D65) or printing paper (for example, glossy paper) set in advance by the user is set as the color patch observation condition. Done. For the configuration and functions of the spectral printing model converter and the color converter, refer to JP-T-2007-511175 and JP-A-2008-263579 as appropriate.

The inverse model initial LUT 410 is obtained by, for example, dividing the L ^* a ^* b ^* space into a plurality of small cells and selecting and registering an optimum ink amount set for each small cell. This selection is performed in consideration of, for example, the image quality of the color patch printed with the ink amount set. In general, there are many ink amount sets that can reproduce one L ^* a ^* b ^* value. Therefore, in the inverse model initial LUT 410, the one that selects an optimal ink amount set from a desired viewpoint such as image quality is registered from among a large number of ink amount sets that reproduce substantially the same L ^* a ^* b ^* values. . The L ^* a ^* b ^* value that is the input value of the inverse model initial LUT 410 is a representative value of each small cell. On the other hand, the ink amount set as an output value reproduces any L ^* a ^* b ^* value in the cell. Therefore, in the inverse model initial LUT 410, the L ^* a ^* b ^* value that is the input value and the ink amount set that is the output value do not correspond exactly, and the ink amount set of the output value is converted to the forward model converter. When converted to an L ^* a ^* b ^* value by FM, a value slightly different from the input value of the inverse model initial LUT 410 is obtained. However, as the inverse model initial LUT 410, an input value and an output value that completely correspond to each other may be used. As a method of creating an inverse model initial LUT 410 by selecting an optimal ink amount set for each small cell, for example, a method described in Japanese Patent Publication No. 2007-511175 can be employed.

2. Color Conversion Profile Creation Process FIG. 3 is a flowchart showing an outline of the color conversion profile creation process executed by the computer 10 according to the program.
In step S100, an initial LUT 510 having a plurality of grid points to be determined for the ink amount set is set mainly by the function of the initial LUT setting unit 14.
FIG. 4 is a flowchart showing details of the process in step S100.
In step S110, the initial LUT setting unit 14 sets an initial value for creating the initial LUT 510 according to the operation of the operation unit 40 by the user.

  FIG. 5 shows an example of the configuration of the initial LUT 510 and its initial value setting. As an input value of the initial LUT 510, an input value in a predetermined input color system, for example, a value at substantially equal intervals predetermined as each value of RGB (red, green, blue) is set. Since one set of RGB values represents a point in the RGB color space, one set of RGB values corresponds to an input grid point in the initial LUT 510. In step S110, the initial value of the ink amount set for some small number of input grid points selected in advance from among the plurality of input grid points is input by the user. It is preferable to select at least an input grid point corresponding to a vertex of a three-dimensional color solid in the RGB color space as the input grid point to which the initial value is set. At the apex of this three-dimensional color solid, each RGB value takes the minimum value or the maximum value of the definition range. Specifically, when each RGB value is expressed by 8 bits, (R, G, B) = (0, 0, 0), (0, 0, 255), (0, 255, 0) , (255, 0, 0), (0, 255, 255), (255, 0, 255), (255, 255, 0), (255, 255, 255). The initial value of the set is set. The ink amounts for the input grid points of (R, G, B) = (255, 255, 255) are all set to zero. The initial value of the ink amount set for the other selected input grid points is arbitrary, and is set to 0, for example.

インク量Ｉ _j(R,G,B)の添え字ｊは、インク量セットを構成するインク種類毎に対応しており、本実施形態のようにインク種類がＣ，Ｍ，Ｙ，Ｋ，Ｌｃ，Ｌｍ，Ｌｋ，ＬＬｋの８種類であれば、ｊ＝１〜８である。ＲＧＢ値が０または２５５を取る入力格子点に対するインク量Ｉ _j(0,0,0)，Ｉ _j(0,0,255)…は、ステップＳ１１０においてユーザーによって予め入力された値である。（１）式および（２）式によれば、任意のＲＧＢ値におけるインク量Ｉ _j(R,G,B)を求めることが可能であり、かかるインク種類毎のインク量Ｉ _j(R,G,B)を組み合わせた情報が、当該任意のＲＧＢ値におけるインク量セットとして決定される。以下では、各インク種類Ｃ，Ｍ，Ｙ，Ｋ，Ｌｃ，Ｌｍ，Ｌｋ，ＬＬｋのインク量Ｉ_jからなるインク量セットを（Ｃ，Ｍ，Ｙ，Ｋ，Ｌｃ，Ｌｍ，Ｌｋ，ＬＬｋ）と表記する。 In step S120, the initial LUT setting unit 14 determines an ink amount set for other input grid points based on the initial value (FIG. 5) of the ink amount set. For example, the ink amount I _{j (R, G, B)} corresponding to a certain input grid point RGB is determined according to the following equations (1) and (2).

The subscript _{j of the} ink amount I _{j (R, G, B)} corresponds to each ink type constituting the ink amount set, and the ink types are C, M, Y, K, Lc as in this embodiment. , Lm, Lk, LLk, j = 1 to 8. The ink amounts I _{j (0,0,0)} , I _{j (0,0,255)} ... For the input grid points whose RGB values take 0 or 255 are values input in advance by the user in step S110. According to (1) and (2), it is possible to obtain the ink amount I _{j (R, G, B)} in any of the RGB values, the ink amount I _{j (R} in such an ink type _{basis, G , B)} is determined as an ink amount set for the arbitrary RGB value. In the following, an ink amount set composed of ink amounts I _j of the respective ink types C, M, Y, K, Lc, Lm, Lk, and LLk will be referred to as (C, M, Y, K, Lc, Lm, Lk, and LLk). write.

In step S130, the initial LUT setting unit 14 converts the ink amount set for each input grid point obtained by the processing up to step S120 into the color value L ^* a ^* b ^* using the forward model converter FM. As a result, each color value L ^* a ^* b ^* associated with each input grid point of the initial LUT 510 is obtained.

In step S140, the initial LUT setting unit 14 converts each color value L ^* a ^* b ^* obtained in step S130 into an ink amount set again using the inverse model initial LUT 410. The reason why the ink amount set is converted again using the inverse model initial LUT 410 is that the initial value of the ink amount set or the value of the ink amount set determined in step S120 reproduces the color value L ^* a ^* b ^*. It is because it is not necessarily a preferable value as a set. On the other hand, in the inverse model initial LUT 410, a preferable ink amount set in consideration of the image quality and the like is registered. If the color value L ^* a ^* b ^* is converted again into the ink amount set using this, the color value L A preferred ink amount set for realizing ^* a ^* b ^* can be obtained for each input grid point. However, step S140 may be omitted.

As a result of the processing in step S100 described above, an initial LUT 510 in which the following values are set is obtained.
Value of input grid point of initial LUT 510: (R, G, B)
Color value corresponding to each input grid point: (L ^* , a ^* , b ^* )
Ink amount set corresponding to each input grid point: (C, M, Y, K, Lc, Lm, Lk, LLk)
The ink amount set in the initial LUT 510 is optimized by processing to be described later. For this reason, the processing in step S100 is not limited to the above-described process, and if the information defining the correspondence relationship with the appropriate ink amount set corresponding to the plurality of input grid points in the predetermined input color system can be acquired as the initial LUT 510. Good.

  In step S200 (FIG. 3), the target grid point that is the target of the ink amount set determination process is selected from the input grid points of the initial LUT 510 mainly by the functions of the grid point determination unit 15 and the ink amount determination unit 16. For the determined target grid point, an ink amount set determination process is performed by optimizing the ink amount set.

FIG. 6 is a flowchart showing details of the process in step S200.
In step S <b> 210, the grid point determination unit 15 sets a grid point level for each input grid point of the initial LUT 510 along the input axis direction D for each input axis (input channel) of the initial LUT 510. In this case, if the input of the initial LUT 510 is N-dimensional, grids positioned at both ends of the input axis direction D among the input grid points in each of the input axis directions D (1), D (2),. The lowest lattice point level is assigned to the point, and the lattice point located approximately in the middle between the lattice points to which the lattice point level is assigned is higher than the lattice point level of the lattice point sandwiching the lattice point. A grid point level is assigned.

  FIG. 7 illustrates a state in which the grid point level is set in each of the input axis directions D in step S210. In the initial LUT 510 described above, the input is three-dimensional (RGB). However, in order to simplify the explanation in FIG. 7, the grid point level on the two-dimensions represented by the input axis directions D (1) and D (2). An example in which is set is shown. In FIG. 7, input grid points are indicated by white circles ◯, and grid point levels in the input axis directions D (1), D (2) are indicated by numerals 1, 2, 3,. As shown in FIG. 7, in each of the input axis directions D (1) and D (2), the grid point level = 1 is set at the grid point positions at both ends, and the grid point level = 1 is sandwiched between the grid point positions Lattice point level = 2 is set at a substantially intermediate lattice point position, and further, a lattice point level = 3 is set at a substantially intermediate lattice point position sandwiched between lattice point positions where lattice point level = 1 or 2 is set. In this way, the grid point level is set along the rule of positions of both ends → middle → further middle → further middle.

In the present embodiment, the grid point level for one input grid point is set to each grid point level GL ₁ , GL ₂ ,... GL _n in each input axis direction D (1), D (2),. (GL ₁ , GL ₂ ,... GL _n ). Accordingly, in FIG. 7, for example, the fourth input grid point from the left in the input axis direction D (1) and the third input grid point from the top in the input axis direction D (2) is the grid point level (GL ₁ , GL ₂ ) = (4, 3).

In step S220, the lattice point determination unit 15 initializes the processing level PL (sets PL = 0). The process level PL is a value indicating the number of times the processes after step S230 are executed, and the process level PL is incremented by 1 in step S270.
In step S230, the grid point determination unit 15 includes input grid points whose grid point levels are configured only by numerical values of 1 to PL + 1 (input grids whose grid point levels are configured by only some numerical values of 1 to PL + 1). Select all (including points). Therefore, if the processing level PL = 0, an input grid point having a numerical value of only 1 constituting the grid point level, that is, in the example of FIG. 7, four corners of 4 at a grid point level of (1, 1). Input grid points are selected. Similarly, if the processing level PL = 1, nine input grid points whose grid point levels are (1, 1), (1, 2), (2, 1), (2, 2) are selected. The Similarly, if the processing level PL = 2, the grid point levels are (1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3 ), (3, 1), (3, 2), (3, 3), 25 input grid points are selected.

  In step S240, the grid point determination unit 15 determines the input grid points excluding the grid points (processed grid points) that have been processed in step S250 from among the input grid points selected in step S230. The target lattice points are determined in the order according to the lattice point level. The target grid point means a grid point to be processed in step S250. Explaining based on the example of FIG. 7, if the processing level PL = 0, step S250 has never been executed, and therefore, four input lattice points at the lattice point level (1, 1) selected in step S230. Since all the target grid points are determined and there is no difference in the grid point level among these four input grid points, it is determined that the processing order is simultaneous without performing grouping (described later).

  If the processing level PL = 1, the four input lattice points whose lattice point level is (1, 1) are processed lattice points, and therefore the lattice point levels excluding them are (1, 2), (2 , 1), (2, 2), the five input grid points are divided into groups having different numerical values constituting the grid point level. In this case, a group of input grid points having a grid point level of (1, 2) and (2, 1) (a group having a grid point level of 1 and 2 and referred to as a second group), and a grid point level Are divided into (2, 2) groups (groups with a grid point level value of only 2; referred to as a third group). Then, with respect to each group thus divided, a group including a lower value at the lattice point level is preferentially determined as a target lattice point. That is, in this case, it is determined that the input lattice points of the second group are set as target lattice points first, and the processing order for the input lattice points of the second group is the same. Further, the input lattice point of the third group is determined to be the target lattice point after the second group.

  Similarly, if the processing level PL = 2, nine input lattice points whose lattice point levels are (1, 1), (1, 2), (2, 1), (2, 2) have been processed. Since it is a grid point, the grid point levels excluding those are 16 input grid points (1, 3), (3, 1), (2, 3), (3, 2), (3, 3). Divide into groups with different numerical values constituting the grid point level. In this case, a group of input lattice points (referred to as a fourth group) with lattice point levels (1, 3) and (3, 1) and lattice point levels (2, 3) and (3, 2). It is divided into a group (referred to as a fifth group) and a group (referred to as a sixth group) having a grid point level of (3, 3). In this case, it is determined that the input grid points of the fourth group are set as target grid points first, and that the processing order for the input grid points of the fourth group is the same. Further, the input grid point of the fifth group is determined to be the target grid point after the fourth group, and the processing order for each input grid point of the fifth group is determined to be simultaneous. Further, the input grid points of the sixth group are determined to be the target grid points after the fifth group, and the processing order for the input grid points of the sixth group is determined to be the same.

  FIG. 8 shows the processing order determined in step S240 for each input grid point shown in FIG. The processing order is indicated by numbers in white circles ◯ at the positions of the input grid points. As can be seen from the above description, the processing order is the first input grid point at the grid point level (1, 1) selected in step S230 when the processing level PL = 0. Similarly, in the processing order, among the input grid points selected in step S230 when the processing level PL = 1, the input grid points at the grid point levels (1, 2) and (2, 1) are the whole. The second input grid point at the grid point level (2, 2) is the third and the grid point level (1, 3) among the input grid points selected in step S230 when the processing level PL = 2. ), (3, 1) is the fourth input grid point, the grid point level (2, 3), (3, 2) is the fifth input grid point, the grid point level (3, 3) ) Is the sixth of all the input grid points.

  In step S250, the ink amount determination unit 16 executes an ink amount set determination process by optimizing the ink amount set for the target lattice point determined in step S240. If grouping of input grid points has been executed in step S240, ink amount set determination processing is executed for the input grid points of each group in accordance with the processing order determined for each group. In addition, for a plurality of input grid points (a plurality of input grid points having the same processing order illustrated in FIG. 8) determined to be the same in the processing order in step S240, the determination of the ink amount set is performed in parallel processing. Do. By repeating steps S230 and S240 in this manner, the target lattice point is preferentially determined from the input lattice point having a low lattice point level. In this case, among the input grid points as described above, first, a plurality of grid points located at the ends in the input axis directions D (1), D (2),... D (N) are simultaneously determined as target grid points. To do. After that, an input grid point positioned approximately in the middle of the processed grid points is determined as the target grid point, and at that time, a plurality of grid points positioned approximately in the middle corresponding to each combination of the processed grid points are simultaneously The target grid point is determined.

A process for optimizing an ink amount set (C, M, Y, K, Lc, Lm, Lk, LLk) associated with a certain target grid point will be described. The ink amount determination unit 16, as an example, to optimize the ink amount set by obtaining the evaluation function E _p by the following equation (3).

The evaluation function E _p calculated for a certain ink amount set indicates that the smaller the value, the higher the overall printing performance. ψ represents an ink amount set (C, M, Y, K, Lc, Lm, Lk, LLk). The first term of the formula (3) is a term having a graininess index GI representing the graininess of the printed material, and the second term is a term having a color constancy index CII representing the color constancy to the light source fluctuation of the printing color. The third term is a term having a gradation property index SI representing the gradation property (smoothness of color change) of the printed matter. The evaluation function E _p employed in the present embodiment includes at least a term relating to the gradation index SI. All terms constituting the evaluation function E _p are scalars normalized with the same size, and the smaller the value, the higher the performance. In addition, the first to third terms corresponding to each performance element are linearly combined while adjusting the weights using predetermined weighting factors w ₁ , w ₂ , and w ₃ , so that the overall printing performance can be evaluated. A function E _p is defined.

The ink amount determination unit 16, the ink amount sets which minimize the evaluation function E _p for the target lattice point (C, M, Y, K , Lc, Lm, Lk, LLk) are sequentially calculated. For example, locally moving the ink amount sets the position of the ink amount space initial ink amount set in (ink amount set associated with the input grid points in the initial LUT 510), minimizing the evaluation function E _p when the The ink amount set to be calculated is calculated. By this, the position of the ink amount set in the ink amount space is modified in a direction that minimizes the evaluation function E _p. Furthermore, likewise locally moving the ink amount sets the position of the corrected, continue to calculate the ink amount sets which minimize the evaluation function E _p at that time. By repeatedly executing the above processing (for example, 200 times), the ink amount set for the target grid point is finally optimally set to a value where the evaluation function _Ep is extremely small (overall printing performance is high). The optimized ink amount set is determined as the ink amount set for the target grid point. The above movement of the ink amount set (updated) may be completed to optimize the ink amount set with to perform a specified number of times, and the optimization with the value of the evaluation function E _p is below a predetermined threshold value It may be completed.

In this optimization process, it is necessary to calculate the evaluation function E _p for the ink amount sets (C, M, Y, K, Lc, Lm, Lk, LLk) that are sequentially updated. The graininess index GI, the color constancy index CII, and the gradation index SI corresponding to the ink amount sets that are sequentially updated are calculated, and the evaluation function _Ep is obtained. The spectral printing model converter RC and the color converter CC also predict the color value L ^* a ^* b ^* when performing optimization. In the present embodiment, the grid point optimization technique disclosed in Japanese Patent Application Laid-Open No. 2006-197080 can also be applied. In this case, a virtual force in the direction in which the evaluation function E _p is 0 is applied to each lattice point in the ink amount space, and the position of the lattice point in the ink amount space is converged to a steady state by the force. .

In the step S250, as described above, relates to a plurality of target grid points processing order is determined to be simultaneously in step S240, processing for determining the ink amount set by optimization of the ink amount sets using an evaluation function E _p is Performed in parallel. Therefore, the CPU 12 that controls the apparatus that implements the color conversion profile creation processing of the present embodiment is a processor that has the capability of performing parallel processing for determination processing for such ink amount sets at a plurality of input grid points.

  The gradation index SI employed in the present embodiment is an index for evaluating the gradation in the relationship between each processed grid point at a position sandwiching the target grid point and the target grid point. Specifically, each processed grid point sandwiching the target grid point in each of the input axis directions D (1), D (2),... D (N) from both sides, and the input axis directions D (1), D ( 2),... D (N), each processed lattice point closest to the target lattice point, and the target lattice point are respectively determined the amount of change in the ink amount or the color value, and the amount of each change is added. The value is a gradation index SI.

  FIG. 9 illustrates the relationship between the target grid point A and the processed grid points B1, B2, B3, B4 in the input axis directions D (1), D (2),... D (N), respectively. . 9 exemplifies two-dimensional lattice points represented by the input axis directions D (1) and D (2) as in FIGS. In FIG. 9, the target grid point A, the grid points C1 and C2 that are the target grid points at the same time as the target grid point A, and the processed grid points are input from the input grid points that are not yet the target grid points at that time. Are also indicated by large white circles ○, and the processed grid points B1 and B2 sandwiching the target grid point A from both sides in the input axis direction D (1) and the target grid point A on both sides in the input axis direction D (2) The processed grid points B3 and B4 sandwiched between the two are shown. There may be other input grid points between the target grid point A and each processed grid point B1, B2, B3, B4, but these other input grid points are not yet target grid points. . Therefore, the processed grid points B1 and B2 are the closest processed grid points sandwiching the target grid point A from both sides in the input axis direction D (1), and the processed grid points B3 and B4 are the input axis direction D ( In 2), the closest processed grid points sandwiching the target grid point A from both sides.

（４）式では、Ｌａｂ₁₁は、入力軸方向Ｄ（１）において対象格子点を両側から挟む最も近い各処理済格子点のうち一方の処理済格子点（処理済格子点Ｂ１）の色彩値であり、Ｌａｂ₁₂は、入力軸方向Ｄ（１）において対象格子点を両側から挟む最も近い各処理済格子点のうち他方の処理済格子点（処理済格子点Ｂ２）の色彩値である。Ｌａｂ₀は、対象格子点の色彩値である。従って、Ｌａｂ₁₁−Ｌａｂ₀、Ｌａｂ₁₂−Ｌａｂ₀はそれぞれ、ＣＩＥＬＡＢ表色系における２つの色彩値間の距離（色差）である。なお（４）式では、Ｌａｂに付す「^*」の記載を省略している。Ｘ₁−Ｘ₂は、入力軸方向Ｄ（１）において対象格子点を両側から挟む最も近い各処理済格子点のうち上記一方の処理済格子点と対象格子点との入力軸方向Ｄ（１）の距離であり、Ｘ₃−Ｘ₂は、入力軸方向Ｄ（１）において対象格子点を両側から挟む最も近い各処理済格子点のうち上記他方の処理済格子点と対象格子点との入力軸方向Ｄ（１）の距離である。処理済格子点の色彩値は、処理済格子点について最適化により決定済みのインク量セットをフォワードモデルコンバーターＦＭに入力することにより得られる。対象格子点についての色彩値も、そのとき評価関数Ｅ_pを算出するために用いられている（更新過程の）インク量セットをフォワードモデルコンバーターＦＭに入力することにより得られる。 Here, the gradation index SI can be calculated by, for example, the following equation (4) (see also FIG. 9).

In equation (4), Lab ₁₁ is the color value of one processed grid point (processed grid point B1) among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (1). Lab ₁₂ is the color value of the other processed grid point (processed grid point B2) among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (1). Lab ₀ is the color value of the target grid point. Therefore, Lab ₁₁ -Lab ₀ and Lab ₁₂ -Lab ₀ are distances (color differences) between two color values in the CIELAB color system. In the expression (4), the description of “ ^* ” attached to Lab is omitted. X ₁ -X ₂ is the input axis direction D (1) between the one processed grid point and the target grid point among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (1). ) is the distance, X ₃ -X ₂ is input axis D (1) between the other processed grid point and the target lattice point among the closest respective processed grid points sandwiching the target lattice point from both sides in This is the distance in the input axis direction D (1). The color value of the processed grid point is obtained by inputting the ink amount set determined by optimization with respect to the processed grid point to the forward model converter FM. The color value for the target grid point is also obtained by inputting the ink amount set (in the update process) used for calculating the evaluation function E _p at that time to the forward model converter FM.

Similarly, Lab ₂₁ is the color value of one processed grid point (processed grid point B3) among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (2). Lab ₂₂ is the color value of the other processed grid point (processed grid point B4) among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (2). Y ₁ -Y ₂ is the input axis direction D (2) between the one processed grid point and the target grid point among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (2). Y ₃ −Y ₂ is the distance between the other processed grid point and the target grid point among the closest processed grid points that sandwich the target grid point from both sides in the input axis direction D (2). This is the distance in the input axis direction D (2). Of course, if the input of the initial LUT 510 is three or more dimensions, a term corresponding to the input axis direction related to the increased dimension is added to the equation (4).

By optimizing the ink amount set by using an evaluation function E _p containing such gradation index SI, color change degree of between the grid points around it is smoothed (i.e. gradation The ink quantity set can be determined. Note that the target grid point located on the ridgeline of the input axis of the initial LUT 510 (in the example of FIG. 7, the grid point whose grid point level (GL ₁ , GL ₂ ) is “1”) As for the gradation index SI, a term corresponding to the input axis direction D in which the lattice point level is “1” among the terms of the equation (4) is omitted. Further, the target grid point located at the apex of the initial LUT 510 (in the example of FIG. 7, the grid point whose grid point levels (GL ₁ , GL ₂ ) are both “1”) is the most suitable first. Therefore, there is no gradation index SI.

（５）式のａ_Lは明度補正項、ＷＳ（ｕ）は画像のウイナースペクトラム、ＶＴＦは視覚の空間周波数特性、ｕは空間周波数である。粒状性指数ＧＩはカラーパッチをスキャナー等で撮像した画像データを画像平面に関してフーリエ変換することにより、画像に存在する空間波のパワースペクトルを得るとともに、当該パワースペクトルに対して視覚の空間周波数特性ＶＴＦを畳み込むことにより算出される。なお、画像データは明度の画像データを使用するのが一般的である。このように粒状性指数ＧＩは、カラーパッチ内に存在する明度の空間波の大きさを空間周波数特性ＶＴＦによる重み付けを考慮して全空間周波数に関して累積した値であるといえる。したがって、目立ちやすい粒状性を定量化することができる。なお、明度補正項ａ_Lによって全体の明度の粒状性指数ＧＩへの寄与を減殺している。粒状性指数ＧＩの算出については、Makoto Fujino,Image Quality Evaluation of Inkjet Prints, Japan Hardcopy '99, p.291-294や、特表２００７‐５１１１６１号公報や、特開２００８‐２６３５７９号公報の記載を用いる。 The graininess index GI corresponding to the ink amount set can be calculated using various graininess prediction models. For example, the graininess index GI can be calculated by the following equation (5).

In Equation (5), a _L is a brightness correction term, WS (u) is a winner spectrum of an image, VTF is a visual spatial frequency characteristic, and u is a spatial frequency. The granularity index GI obtains a power spectrum of a spatial wave existing in the image by Fourier-transforming image data obtained by imaging a color patch with a scanner or the like with respect to the image plane, and a visual spatial frequency characteristic VTF with respect to the power spectrum. Is calculated by convolving. In general, lightness image data is used as the image data. Thus, it can be said that the graininess index GI is a value obtained by accumulating the magnitude of the spatial wave of brightness existing in the color patch with respect to all the spatial frequencies in consideration of the weighting by the spatial frequency characteristic VTF. Therefore, it is possible to quantify the noticeable graininess. The contribution of the overall brightness to the graininess index GI is reduced by the brightness correction term a _L. For the calculation of the graininess index GI, the description of Makoto Fujino, Image Quality Evaluation of Inkjet Prints, Japan Hardcopy '99, p.291-294, JP-T-2007-511161 and JP-A-2008-263579 is described. Use.

（６）式のΔＬ^*は２つの異なる観察条件下（異なる光源下）におけるカラーパッチの明度差、ΔＣ^* _abは彩度差、ΔＨ^* _abは色相差を示す。色非恒常性指数ＣＩＩの計算時には、２つの異なる観察条件下でのＬ^*ａ^*ｂ^*値は、色順応変換（ＣＡＴ）を用いて標準観察条件（例えば標準の光Ｄ６５の観察下）に変換される。色恒常性指数ＣＩＩの算出については、Billmeyer and Saltzman's Principles of Color Technology， 3rd edition， John Wiley & Sons， Ｉnc， 2000， p.129， pp. 213-215や、特開２００８‐２６３５７９号公報の記載を用いる。 The color constancy index CII corresponding to the ink amount set can be calculated by, for example, the following equation (6) using a color converter CC or the like.

In the equation (6), ΔL ^* represents a lightness difference of the color patch under two different observation conditions (under different light sources), ΔC ^* _ab represents a chroma difference, and ΔH ^* _ab represents a hue difference. When calculating the color non-constant index CII, the L ^* a ^* b ^* values under two different viewing conditions are converted to standard viewing conditions (eg, under the observation of standard light D65) using chromatic adaptation transformation (CAT). Converted. The calculation of the color constancy index CII is described in Billmeyer and Saltzman's Principles of Color Technology, 3rd edition, John Wiley & Sons, Inc, 2000, p.129, pp. 213-215, and Japanese Patent Application Laid-Open No. 2008-263579. Is used.

  In step S260, the lattice point determination unit 15 determines whether or not the processing level PL + 1 has reached the highest value among the lattice point levels set in step S210, and the processing level PL + 1 has not reached the highest value. In this case, the process proceeds to step S270, the process level PL is incremented by 1, and the processes after step S230 are repeated. On the other hand, if the processing level PL + 1 has reached the maximum value, it is determined that the ink amount set determination processing has been performed using all the input grid points of the initial LUT 510 as target grid points one by one, and step S200 ends. Let

In step S300 (FIG. 3), the color conversion profile creation unit 17 creates the color conversion profile 400 based on the initial LUT 510 after the ink amount set for each input grid point is determined by optimization as described above. In this case, the color conversion profile creation unit 17 sets the color value L ^* a ^* corresponding to the optimized ink amount set (C, M, Y, K, Lc, Lm, Lk, LLk) for each input grid point ^. b ^* is calculated by the forward model converter FM. Then, an ink profile describing the correspondence between the color values L ^* a ^* b ^* and the ink amount sets (C, M, Y, K, Lc, Lm, Lk, LLk) corresponding to each other is created. Then, the color conversion profile creation unit 17 creates a color conversion profile 400 based on the ink profile.

As described above, the color conversion profile 400 is a color conversion LUT for converting, for example, the coordinate value of the sRGB color system into a combination of ink amounts (ink amount set) of a plurality of types of ink used by the printer 20. As for the sRGB color system, a correspondence relationship (sRGB profile) with the CIELAB color system is defined based on the CIE standard. Therefore, the RGB value of the sRGB color system and the ink amount set (C, M, Y, K, Lc, Lm, Lk, LLk) defined in the ink profile by the color value L ^* a ^* b ^* specified in the ink profile The color conversion profile 400 can be created by specifying and profiling the correspondence relationship with the

However, the color conversion profile 400 created in the present invention is not limited to the one describing the correspondence between the sRGB color system and the ink color system (ink amount set), but the color value L ^* a ^* b ^* and the ink table. Ink color systems and other color systems, such as those describing the relationship between color systems (the above ink profiles), and describing the correspondence between CMY color systems and CMYK color systems and ink color systems It may be a description of the relationship with the system.

3. Summary As described above, according to the present embodiment, when a target grid point is determined from among a plurality of input grid points and ink amount set determination processing is performed for the target grid point, each input grid point is first input. A grid point located at an end in the axial directions D (1), D (2)... D (N) is determined as a target grid point, an ink amount set is determined for the target grid point, and then an abbreviation of the processed grid point. The process of determining the ink amount set by newly setting the grid point located in the middle as the target grid point is repeated. Therefore, when the ink amount set is determined for a certain target grid point (excluding the above-described end grid point that is initially set as the target grid point), the input axis directions D (1), D (2). For every N), there is a processed grid point at a position sandwiching the target grid point from both sides. Referring to FIG. 8, for example, if the input grid point is at the grid point level (2, 2), the grid point level (1, 2) is already in the input axis direction D (1) at the timing when it becomes the target grid point. ) Between the two processed grid points at the grid point level (2, 1) in the input axis direction D (2).

Accordingly it relates target grid point, when determining the optimized ink amount set by the ink amount set by the evaluation function E _p including the tone index SI (step S250), the already ink amount set is optimized The gradation index SI is calculated based on the relationship with the color of surrounding grid points (processed grid points). Therefore, the ink amount set determined by optimization with respect to the target grid point realizes excellent gradation with the color associated with the surrounding grid points, resulting in high quality in color conversion, A color conversion profile 400 that realizes particularly excellent gradation is created. In addition, according to the present embodiment, the processing order for each input grid point is clarified as compared with the conventional case, so that the processing result fluctuates due to the difference in processing order (the characteristics of the color conversion profile 400 to be created differ). ) Is suppressed.

  Further, in the present embodiment, when the target grid point is determined from among the plurality of input grid points, a plurality of grid points positioned at the ends in each input axis direction D (1), D (2). The target grid points are determined simultaneously, and when there are a plurality of input grid points sandwiched between the processed grid points, the plurality of input grid points are determined simultaneously as target grid points. In addition, for a plurality of grid points determined as target grid points at the same time, the ink amount set determination process is performed in parallel. Therefore, compared to the conventional processing where the input grid points are processed one by one in order, for a plurality of grid points determined as the target grid points at the same time, all of the target grid points can be processed in parallel, The time required to complete the processing can be significantly shortened.

  In the present embodiment, as described above, when the ink amount set is optimized for the target lattice point, the ink amount set of the surrounding lattice points necessary for calculating the gradation index SI is optimized. For this reason, an ink amount set having sufficiently good gradation is determined by performing the ink amount set determination process by the optimization once for one target grid point. Therefore, after determining the ink amount set by optimization for all the input grid points as in the past, the ink amount set by optimization for all the lattice points is further determined in the same manner, starting from the latest ink amount set. It is unnecessary to repeat the process. Therefore, the time required for creating the color conversion profile 400 can be remarkably shortened compared to the conventional case.

4). The present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the scope of the invention.
FIG. 10 shows the configuration of the printer 20. In the figure, the printer 20 includes a CPU 50, a RAM 52, a ROM 51, a memory card slot 53, a bus 54 and an ASIC 55. Firmware FW for controlling the printer 20 is executed by the CPU 50 performing calculations according to the program data 15a while expanding the program data 15a stored in the ROM 51 into the RAM 52. The firmware FW generates drive data based on the print data PD stored in the memory card MC installed in the memory card slot 53. The ASIC 55 acquires drive data and generates drive signals for the paper feed mechanism 57, the carriage motor 58, and the print head 59. In the ROM 51, a color conversion profile 400 is stored. The printer 20 includes a carriage 60, and the carriage 60 includes a plurality of cartridge holders 61a to which a plurality of ink cartridges 61 can be attached. The carriage 60 includes a print head 59 that ejects ink supplied from each ink cartridge 61 from a number of nozzles.

  FIG. 11 shows a software configuration of the firmware FW. The firmware FW includes an image data acquisition unit FW1, a rendering unit FW2, a color conversion unit FW3, a halftone unit FW4, and a rasterization unit FW5. The image data acquisition unit FW1 acquires the print data PD stored in the memory card MC as a print target. The rendering unit FW2 generates input image data used for printing based on the print data PD. The input image data is composed of pixels of the number of pixels (print resolution × print actual size) corresponding to the print resolution (for example, 2880 × 2880 dpi), and each pixel conforms to the sRGB color space of 8 bits (0 to 255). The RGB values are expressed.

  The color conversion unit FW3 acquires input image data and performs color conversion on the input image data. The color conversion unit FW3 converts the RGB value into an ink amount set including the ink amount of each ink by performing an interpolation operation while referring to the color conversion profile 400. The halftone unit FW4 executes halftone processing based on the ink amount set output by the color conversion unit FW3. The rasterizing unit FW5 assigns each pixel (whether ejection is possible) of the halftone data after the halftone process to each main scan and each nozzle of the print head 59, and generates drive data. The drive data is output to the ASIC 55, and the ASIC 55 generates drive signals for the paper feed mechanism 57, the carriage motor 58, and the print head 59. As a result, printing is executed.

Regarding the grouping in step S240 (FIG. 6), the number of grid points processed in parallel in step S250 may be increased by using a rougher grouping method than the above-described mode. For example, in the above, when the processing level PL = 2, each of the grid point levels is (1, 3), (3, 1), (2, 3), (3, 2), (3, 3) When the input grid points are grouped, the input grid point group (fourth group) at the grid point levels (1, 3) and (3, 1) and the grid point levels (2, 3) and (3, 2) Group (fifth group) and the group of lattice point levels (3, 3) (sixth group), but the fourth group and the fifth group may be combined into one group. In this way, each of the grid points having the processing order of 4 and 5 illustrated in FIG. 8 is simultaneously subjected to the ink amount set determination process. In other words, in this way, for each grid point whose processing order is indicated by 5 in FIG. 8, when each of the grid points is a processing target in step S250, the grid points in some of the input axis directions However, there is a processed grid point that sandwiches each grid point from both sides in the other input axis directions. For this reason, when calculating the evaluation function E _p , the number of terms constituting the gradation index SI is reduced, but the gradation index SI cannot be obtained. With such a configuration, the number of grid points that are processed in parallel in one step S250 increases, and the time required to create the color conversion profile 400 may be further shortened.

  In the present specification, “ink” is used in a broad sense including not only liquid ink used in an ink jet printer and offset printing, but also toner used in a laser printer. As other terms having such a broad meaning of “ink”, “coloring material”, “coloring material”, and “coloring agent” can also be used.

DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... HDD, 12 ... CPU, 13 ... RAM, 14 ... Initial LUT setting part, 15 ... Lattice point determination part, 16 ... Ink amount determination part, 17 ... Color conversion profile creation part, 20 ... Printer, 400 ... color conversion profile, 410 ... inverse model initial LUT, 510 ... initial LUT, FM ... forward model converter, RC ... spectral printing model converter, CC ... color converter.

Claims (7)

A color conversion profile creation device for creating a color conversion profile for converting a coordinate value of an input color system having a multi-dimensional input axis into a combination of ink amounts of a plurality of types of inks,
A grid point determination unit that determines a target grid point that is a target of processing for determining a combination of ink amounts from each grid point dispersed in the input color system;
An ink amount determination unit for determining a combination of ink amounts for the determined target lattice points;
A color conversion profile creating unit that creates the color conversion profile based on the determined combination of ink amounts,
The lattice point determination unit determines the lattice point located at the end of each lattice point as the target lattice point, and then is determined to be approximately the middle between the lattice points that have already been determined as the target lattice point and the combination of the ink amounts has been determined. Just repeat the process for determining the grid points located in the target lattice point,
The ink amount determination unit determines a combination of the ink amounts by optimizing a combination of ink amounts based on an evaluation with respect to a combination of ink amounts using a predetermined evaluation function, and the evaluation function includes at least a target lattice point. Including an evaluation item for evaluating gradation in the relationship between each grid point and the target grid point for which the combination of the ink amounts at the sandwiched positions has already been determined,
A color conversion profile creation device characterized by that. The lattice point determination unit simultaneously determines a plurality of lattice points located at the ends in the input axis direction among the lattice points as the target lattice points, and determines the lattice points located approximately in the middle as the target lattice points. A plurality of lattice points located approximately in the middle corresponding to each combination of lattice points that have already been determined as target lattice points and for which a combination of ink amounts has been determined, are simultaneously determined as target lattice points,
2. The color conversion profile creation apparatus according to claim 1, wherein the ink amount determination unit determines a combination of ink amounts by parallel processing for a plurality of target lattice points determined simultaneously.   When the lattice point determination unit assigns a lattice point level along the input axis direction to each lattice point, the lattice point determination unit assigns the lowest lattice point level to lattice points located at both ends in the input axis direction among the lattice points. In addition, a lattice point level that is higher than the lattice point level of the lattice point that sandwiches the lattice point is assigned to a lattice point that is located approximately in the middle between lattice points to which the lattice point level is assigned, and the lattice point level is low. 3. The color conversion profile creation device according to claim 1, wherein the target grid point is determined preferentially from the point. The color conversion profile according to any one of claims 1 to 3, wherein the ink amount determination unit determines the combination of ink amounts by the optimization only once for one target lattice point. Creation device. A color conversion profile creation method for creating a color conversion profile for converting a coordinate value of an input color system having a multi-dimensional input axis into a combination of ink amounts of a plurality of types of inks,
A grid point determination step for determining a target grid point to be processed in determining a combination of ink amounts from the grid points dispersed in the input color system;
An ink amount determination step for determining a combination of ink amounts for the determined target grid points;
A color conversion profile creating step for creating the color conversion profile based on the determined combination of ink amounts,
In the lattice point determination step, after determining the lattice point located at the end of each lattice point as the target lattice point, the lattice point is determined to be approximately in the middle between the lattice points that have already been determined as the target lattice point and the combination of the ink amounts has been determined. Just repeat the process for determining the grid points located in the target lattice point,
In the ink amount determination step, the combination of the ink amounts is determined by optimizing the combination of ink amounts based on the evaluation with respect to the combination of ink amounts using a predetermined evaluation function, and the evaluation function includes at least target grid points. Including an evaluation item for evaluating gradation in the relationship between each grid point and the target grid point for which the combination of the ink amounts at the sandwiched positions has already been determined,
A color conversion profile creation method characterized by the above. A color conversion profile creation program for causing a computer to execute a process of creating a color conversion profile for converting a coordinate value of an input color system having a multi-dimensional input axis into a combination of ink amounts of a plurality of types of ink,
A grid point determination function for determining a target grid point that is a target of processing for determining a combination of ink amounts from each grid point dispersed in the input color system;
An ink amount determination function for determining a combination of ink amounts for the determined target grid points;
A color conversion profile creating function for creating the color conversion profile based on the combination of the determined ink amounts,
The grid point determination function determines the target grid point for the grid point located at the end of each grid point, and then is approximately halfway between the grid points that have already been determined as the target grid point and the combination of ink amounts has been determined. Just repeat the process for determining the grid points located in the target lattice point,
The ink amount determination function determines a combination of the ink amounts by optimizing a combination of ink amounts based on an evaluation with respect to a combination of ink amounts using a predetermined evaluation function, and the evaluation function includes at least target grid points. Including an evaluation item for evaluating gradation in the relationship between each grid point and the target grid point for which the combination of the ink amounts at the sandwiched positions has already been determined,
A color conversion profile creation program characterized by that. 6. A printing apparatus comprising a color conversion profile created by the color conversion profile creation method according to claim 5 .

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