JP2009219006A - Apparatus, method and program for deriving spectral reflection factor - Google Patents

Abstract

A spectral reflectance of a reproduced output that matches a spectral reflectance of a reproduction target is derived.
A first decomposition processing unit that decomposes a first spectral reflectance (R1) to be reproduced into a first Fs1 and a first Mb1 using a spectral reflectance decomposition method, and a spectral reflectance estimation model. The first spectrum for calculating the second spectral reflectance (R2) that minimizes the error from the first spectral reflectance (R1) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. The reflectance calculation means, the second decomposition processing means for decomposing the second spectral reflectance (R2) into the second Fs2 and the second Mb2, and the first Fs1 and the second Mb2 are added and reproduced. Using the spectral reflectance deriving means for deriving the target third spectral reflectance (R3) and the spectral reflectance estimation model, the third target of the reproduction target can be selected from the spectral reflectances that can be reproduced on the reproduced output. A fourth spectral reflectance (R4) that minimizes an error from the spectral reflectance (R3) is calculated. And a spectral reflectance calculating means.
[Selection] Figure 1

Description

  The present invention relates to a spectral reflectance derivation device, a spectral reflectance derivation method, and a spectral reflectance derivation program.

  When color management is performed so that the reproduced output output by an image output device such as a printer has the same color as the target object to be reproduced, the current color management uses the color to be reproduced and the image output from the printer, etc. By matching colorimetric values such as XYZ tristimulus values and CIELAB with the colors of the reproduced output output by the machine, the colors of the reproduction target and the reproduced output are matched so that both colors are the same (for example, Non-patent documents 1 and 2).

  However, this reproduction method guarantees that the color of the reproduction target and the reproduction output product look the same only under a specific light source. This is because even if the tristimulus values are correct, the spectral reflectances do not coincide with each other in the condition of the same color. Conditional color here means that two objects having different spectral reflectances are perceived as the same color under a specific light source. That is, when the reproduction target and the reproduction output are observed under different light sources, there is a high possibility that both colors are perceived differently. This is a problem of conventional color management.

  One method for solving such a problem is spectral color reproduction. This spectral color reproduction is a reproduction method in which the spectral reflectance of the reproduction target is matched with the spectral reflectance of the reproduced output. However, image output devices such as printers are limited in the reproducible spectral reflectance due to limitations of ink and the like, and it is generally impossible to make the spectral reflectances coincide with each other.

As a method for solving these problems, as disclosed in Patent Document 1, the spectral reflectance of a reproduction of a certain amount of ink is estimated using a spectral printer model, and optimized using an optimization method from the estimated value and the target value. A method has been proposed in which a target and a reproduced object are spectrally and colorimetrically matched by deriving a proper ink amount. For example, a set of initial values (for example, for a CMYKOG 6-color printer, the CMYKOG value is 10% of the maximum value) is set, the spectral reflectance to be printed is estimated from the initial value, and the estimated spectral reflectance Then, the value of CMYKOG is changed so that the RMS error of the spectral reflectance of the target, ΔE94, or a combination thereof is minimized, and a spectral reflectance that matches the target spectrally and colorimetrically is derived.
Uehara Senji, “Color Management Book” 2006, pp 28-30 MD Study Group + Den Juku + DTPWorld Editorial Department, "Illustrated Color Management Practice Rule Book", 2007, p51 Special table 2005-508125 gazette

  However, the technique disclosed in Patent Document 1 has a problem that it may fall into a local solution depending on an initial value to be optimized, and it may take a long time to derive an optimal solution.

  The present invention has been made in view of such circumstances. In a printing press or the like, the color difference between a reproduction target and a reproduction output is almost zero under a specific light source, and the reproduction target and reproduction output are under a different light source. Spectral reflectance derivation device, spectral reflectance derivation method, and spectral reflectance that can quickly and accurately derive the spectral reflectance of a reproduced output that matches the target spectral reflectance as much as possible in order to reduce the color difference of the object The purpose is to provide a rate derivation program.

  The present invention is an apparatus for deriving a spectral reflectance of a reproduced output using a spectral reflectance decomposition method and a spectral reflectance estimation model, and the first spectral reflectance (R1) to be reproduced is decomposed into the spectral reflectance. Spectral reflectance that can be reproduced on the reproduced output using the first decomposition processing means that decomposes into the first Fundamental Stimuli (Fs1) and the first Metallic Black (Mb1) by the method and the spectral reflectance estimation model First spectral reflectance derivation means for calculating a second spectral reflectance (R2) that minimizes an error from the first spectral reflectance (R1) of the reproduction target, and the second spectral reflectance. A second disassembling means for decomposing the reflectance (R2) into a second Fundamental Stimuli (Fs2) and a second Metallic Black (Mb2); and the first Fun A spectral reflectance calculation unit that derives the third spectral reflectance (R3) of the reproduction target by adding the axial Stimuli (Fs1) and the second Metabolic Black (Mb2), and a spectral reflectance estimation model, A second spectrum that calculates a fourth spectral reflectance (R4) that minimizes an error from the third spectral reflectance (R3) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. And a reflectance deriving means.

  The present invention relates to a color difference calculation means for calculating a color difference under a specific light source from the fourth spectral reflectance (R4) and the first spectral reflectance (R1) to be reproduced, and whether the color difference is within an allowable range. If it is not within the allowable range, the second spectral reflectance (R2) is replaced with the third spectral reflectance (R3) of the reproduction target, and the color difference is within the allowable range. And a repeating unit that repeats the process until it becomes.

  The present invention is a method for deriving a spectral reflectance of a reproduced output using a spectral reflectance decomposition method and a spectral reflectance estimation model, and the first spectral reflectance (R1) to be reproduced is decomposed into the spectral reflectance. Spectral reflectance that can be reproduced on a reproduced output using a first reflectance processing step that is decomposed into a first Fundamental Stimuli (Fs1) and a first Metallic Black (Mb1) by a technique, and a spectral reflectance estimation model A first spectral reflectance derivation step for calculating a second spectral reflectance (R2) that minimizes an error from the first spectral reflectance (R1) of the reproduction target, and the second spectral reflectance A second decomposition processing step of decomposing the reflectance (R2) into a second Fundamental Stimuli (Fs2) and a second Metallic Black (Mb2); A spectral reflectance calculation step for deriving a third spectral reflectance (R3) of a reproduction target by adding 1 Fundamental Stimuli (Fs1) and the second Metabolic Black (Mb2), and using a spectral reflectance estimation model Then, a second spectral reflectance (R4) that minimizes an error from the third spectral reflectance (R3) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output product is calculated. And a spectral reflectance derivation step.

  The present invention includes a color difference calculation step of calculating a color difference under a specific light source from the fourth spectral reflectance (R4) and the first spectral reflectance (R1) of the reproduction target, and whether the color difference is within an allowable range. If it is not within the allowable range, the second spectral reflectance (R2) is replaced with the third spectral reflectance (R3) of the reproduction target, and the color difference is within the allowable range. And a repetition step of repeating the process until

  The present invention is a program for deriving a spectral reflectance of a reproduced output using a spectral reflectance decomposition method and a spectral reflectance estimation model, and the first spectral reflectance (R1) to be reproduced is decomposed into the spectral reflectance. Spectral reflectance that can be reproduced on a reproduced output using a first reflectance processing step that is decomposed into a first Fundamental Stimuli (Fs1) and a first Metallic Black (Mb1) by a technique, and a spectral reflectance estimation model A first spectral reflectance derivation step for calculating a second spectral reflectance (R2) that minimizes an error from the first spectral reflectance (R1) of the reproduction target, and the second spectral reflectance A second decomposition processing step for decomposing the reflectance (R2) into a second Fundamental Stimuli (Fs2) and a second Metallic Black (Mb2); Spectral reflectance calculation step for adding the first Fundamental Stimuli (Fs1) and the second Metabolic Black (Mb2) to derive the third spectral reflectance (R3) to be reproduced, and a spectral reflectance estimation model Is used to calculate the fourth spectral reflectance (R4) that minimizes the error from the third spectral reflectance (R3) of the reproduction target from among the spectral reflectances that can be reproduced on the reproduced output. And causing the computer to perform a second spectral reflectance derivation step.

  The present invention includes a color difference calculation step of calculating a color difference under a specific light source from the fourth spectral reflectance (R4) and the first spectral reflectance (R1) of the reproduction target, and whether the color difference is within an allowable range. If it is not within the allowable range, the second spectral reflectance (R2) is replaced with the third spectral reflectance (R3) of the reproduction target, and the color difference is within the allowable range. It is further characterized in that the computer is further subjected to a repetition step of repeating the process until

  According to the present invention, the color difference between the reproduction target and the reproduction output can be made substantially zero under a specific light source, and the color difference between the reproduction target and the reproduction output can be suppressed to be smaller than that of the conventional method under a different light source. The effect that it becomes possible is acquired.

  Hereinafter, a spectral reflectance derivation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. Terms used in the following description will be described. “R1” is the first spectral reflectance of the reproduction target. “R2” is the second spectral reflectance that is reproduced by printing. “R3” is the third spectral reflectance of the reproduction target. “R4” is a fourth spectral reflectance that is reproduced by printing. In FIG. 1, reference numeral 1 denotes an R1 storage unit that stores the first spectral reflectance of the reproduction target. Reference numeral 2 denotes a decomposition processing unit that decomposes a predetermined spectral reflectance into Fundamental Stimuli and Metallic Black using a spectral reflectance decomposition method. Reference numeral 3 denotes a color matching function storage unit in which the color matching functions are stored in advance. Reference numeral 4 denotes a reproduction target among the spectral reflectances that can be reproduced on the reproduction output using the spectral reflectance estimation model. The spectral reflectance derivation unit calculates a spectral reflectance that minimizes an error from the spectral reflectance. Reference numeral 5 denotes an R2 storage unit that stores the spectral reflectance (R2). Reference numeral 6 denotes a spectral reflectance calculation unit that adds Fundamental Stimuli and Metallic Black to calculate a third spectral reflectance (R3) to be reproduced. Reference numeral 7 denotes an R3 storage unit that stores the spectral reflectance (R3). Reference numeral 8 denotes an R4 storage unit that stores the spectral reflectance (R4). Reference numeral 9 denotes a color difference calculation unit that calculates a color difference under a specific light source from the spectral reflectance (R4) and the spectral reflectance (R1).

  Next, the operation of the spectral reflectance deriving device shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the spectral reflectance derivation device shown in FIG. Here, taking the case where the reproduction target is reproduced by a printing machine as an example, the specific light source (observation light source) when matching the colorimetric values is equal energy white (E), and the color matching function of the observer is the CIE 1931 standard observer. It is assumed that the color matching function is

First, the decomposition processing unit 2 reads R1 stored in the R1 storage unit 1, and uses the spectral reflectance decomposition method to calculate the spectral reflectance (R1) of the reproduction target as Fundamental Stimuli (Fs1). It decomposes | disassembles into Metallic Black (Mb1) and outputs Fundamental Stimuli (Fs1) to the spectral reflectance calculation part 6 (step S1). Here, the spectral reflectance (R1) of the reproduction target is the reflectance R1 (λ _i ) (i = 1, 2, 3,..., N, n> 3 | n) of each wavelength shown in Expression (1). It is a matrix of the sampling number of wavelengths). The spectral reflectance decomposition technique used here is a matrix A (spectral light source distribution E (λ _i ) (i = 1, 2, 3,..., N, n> 3) shown in Expression (2). | N is the sampling number of wavelengths) and color matching functions x (λ _i ), y (λ _i ), z (λ _i ) (i = 1, 2, 3,..., N, n> 3 | n is Fs1 is derived by Equation (4) from the tristimulus value T of the reproduction target calculated from the product of R1 and the matrix A shown in Equation (3). Then, Mb1 is derived from the difference between the derived Fs1 and R1 by Expression (5), and R1 is decomposed into Fs1 and Mb1. A ′ in the equations (3) and (4) represents the transposed matrix of A. Since this decomposition method is a well-known method described in the document “Hugh S. Fairman, 'Metameric Correction using Parametric Decomposition', Color Research and Application, 1987, pp261-265”, a more detailed explanation will be given. Omitted.

Fs1 = A (A ′ · A) ⁻¹ · T (4)
Mb1 = R1-Fs1 (5)

  The above Fundamental Stimuli is a spectral reflectance that gives necessary information regarding color stimulation, and the Fundamental Stimuli obtained from the spectral reflectances that are related to the conditional color matching in a specific observation light source and color matching function are all the same. Become. On the other hand, Metabolic Black is a virtual spectral reflectance at which the tristimulus value XYZ becomes zero.

  On the other hand, the spectral reflectance deriving unit 4 reads R1 stored in the R1 storage unit 1, and uses the spectral reflectance estimation model to read out the reproduction target read out from the spectral reflectance that can be reproduced by printing. The spectral reflectance (R1) and the spectral reflectance (R2) that minimizes the RMS (Root Mean Square) error are calculated and stored in the R2 storage unit 5 (step S2). The spectral reflectance estimation model used here is a model for estimating the spectral reflectance of a reproduced output from a device value, for example, a CMYK value in the case of a CMYK printer, and a previously measured CMYK value is known. It is a model that can estimate the spectral reflectance of the reproduction output of all combinations of CMYK values using a mathematical model formula from the relationship between the spectral reflectance of the reproduction output and the value of CMYK. . As an example of the spectral reflectance estimation model, a model described in “JP 2007-43286 A” or the like can be used.

  By using this model, all the spectral reflectances that can be reproduced by the printing press can be estimated. Therefore, the value of CMYK is adjusted by using a nonlinear optimization method, and an objective function, for example, the estimated spectral reflectance and R1 is calculated. The spectral reflectance (R2) that can be reproduced by printing with the smallest RMS error is calculated. As the nonlinear optimization method, any method such as sequential quadratic programming can be used.

  Next, the decomposition processing unit 2 reads the spectral reflectance (R2) stored in the R2 storage unit 5 and calculates the spectral reflectance (R2) to the Fundamental Stimulus (R2) by the same processing as the processing in Step S1 described above. Fs2) and Metallic Black (Mb2) are decomposed and Metabolic Black (Mb2) is output to the spectral reflectance calculation unit 6 (step S3).

  Next, the spectral reflectance calculation unit 6 adds Fundamental Stimuli (Fs1) and Metallic Black (Mb2) output from the decomposition processing unit 2, and the colorimetric values match the reproduction target and are reproduced by printing. A second reproduction target spectral reflectance (R3) close to the spectral reflectance that can be calculated is calculated and stored in the R3 storage unit 7 (step S4).

  Next, the spectral reflectance derivation unit 4 reads the spectral reflectance (R3) stored in the R3 storage unit 7, and the RMS error with the read spectral reflectance (R3) is the same as in step S2. A spectral reflectance (R4) that can be reproduced by printing, which is minimized, is derived and stored in the R4 storage unit 8 (step S5).

Next, the color difference calculation unit 9 reads the spectral reflectance (R1) stored in the R1 storage unit 1 and the spectral reflectance (R4) stored in the R4 storage unit 8, respectively, and reproduces the spectral target to be reproduced. Each colorimetric value under equal energy white is calculated from the reflectance (R1) and the spectral reflectance (R4) of the printed reproduction, and the color difference ΔE ^* _ab between them is calculated (step 6). Then, the color difference calculation unit 9 determines whether or not the color difference ΔE ^* _ab calculated here is within a predetermined threshold value (step S7). As a result of this determination, when the calculated color difference is outside the threshold value, the color difference calculation unit 9 instructs the separation processing unit 2 to repeat the process. At this time, the spectral reflectance (R2) stored in the R2 storage unit 5 is replaced with the spectral reflectance (R3) stored in the R3 storage unit 7, and the same operation is repeated. Then, the spectral reflectance when the color difference ΔE ^* _ab calculated by the color difference calculation unit 9 falls within the threshold value becomes the spectral reflectance of the reproduced output.

  Next, with reference to FIGS. 3 to 5, the derivation result of the spectral reflectance when the drawing paint is a reproduction target will be described. FIG. 3 is a diagram showing the spectral reflectance of the reproduced output derived by the method of the present invention and the spectral reflectance of the reproduction target. FIG. 4 is a diagram showing the spectral reflectance of the reproduced output and the spectral reflectance of the reproduction target when color matching is performed by a conventional method. As shown in FIGS. 3 and 4, it can be seen that the spectral reflectance derived by the method according to the present invention can realize a value close to the reproduction target.

3 and 4 are used to simulate the colorimetric values of the reproduction target and the reproduced output when observed under various light sources, and the color difference ΔE ^* _ab between the reproduction target and the reproduced output is calculated. The results are shown in FIG. The horizontal axis in FIG. 5 represents the light source for observation, and the vertical axis represents the color difference ΔE ^* _ab from the reproduction target at that time. In this way, the color difference between the reproduction target and the reproduction can be made almost zero under a specific light source, and the color difference between the reproduction target and the reproduction can be suppressed to be smaller than that of the conventional method even under a different light source. Become.

Although the spectral reflectance deriving device according to the present invention has been described above, other modifications such as the following are also conceivable.
(A) Although the observation light source is white with equal energy, other light sources such as D50 may be used.
(B) The color matching function of the observer is the CIE 1931 standard observer, but other color matching functions such as the CIE 1964 auxiliary standard observer may be used.
(C) Although the apparatus that outputs the reproduced output is a printing machine, an image output machine such as an ink jet printer may be used.
(D) Although the spectral reflectance estimation model described in Japanese Patent Application Laid-Open No. 2007-43286 is used as a method of estimating spectral reflectance that can be reproduced by printing, a spectral that can be reproduced by printing using other models or other methods such as LUT. The reflectance may be estimated.
(E) The RMS error is used as the objective function used in the nonlinear optimization method. For example, the weighted RMS error due to the A (A′A) ⁻¹ diagonal element, or the spectral reflectance is selected using another method. May be.
(F) Although the method used as the nonlinear optimization method is the sequential quadratic programming method, other nonlinear optimization methods such as the Simplex method may be used.
(G) Although the color difference ΔE ^* _ab is used to calculate the reproduction target and the color tone of the printed reproduction, other color difference formulas such as CIEDE2000 may be used.

  As described above, according to the spectral reflectance deriving device according to the present invention, in an image output device such as a printing press, the color difference between the reproduction target and the reproduction output under a specific light source is almost zero, and Therefore, the color difference between the reproduction target and the reproduction output can be reduced.

  Note that a program for realizing the function of the processing unit in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to derive spectral reflectance. Processing may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a flowchart which shows the spectral reflectance derivation | leading-out operation | movement in the apparatus shown in FIG. It is a figure which shows the spectral reflection factor derived | led-out using the technique of this invention, and the spectral reflectance of a reproduction target (oil paint). It is a figure which shows the spectral reflection factor of the reproduction output thing when color matching is performed by the conventional method and the spectral reflectance of the reproduction target (oil paint). It is a figure which shows the result of having simulated the color difference (DELTA ⁾ E ^* _ab of the reproduction | regeneration target when reproducing the reproduction output material color-matched by the conventional method and this method under various light sources.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... R1 memory | storage part, 2 ... Decomposition processing part, 3 ... Color matching function memory | storage part, 4 ... Spectral reflectance calculation part, 5 ... R2 memory | storage part, 6 ... Spectral reflection Rate derivation unit, 7 ... R3 storage unit, 8 ... R4 storage unit, 9 ... color difference calculation unit

Claims (6)

A spectral reflectance derivation device for a reproduced output using a spectral reflectance decomposition method and a spectral reflectance estimation model,
First decomposition processing means for decomposing the first spectral reflectance (R1) of the reproduction target into a first Fundamental Stimuli (Fs1) and a first Metallic Black (Mb1) by a spectral reflectance decomposition method;
Using a spectral reflectance estimation model, a second spectral reflectance (R1) that minimizes an error from the first spectral reflectance (R1) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. First spectral reflectance deriving means for calculating (R2);
Second decomposition processing means for decomposing the second spectral reflectance (R2) into a second Fundamental Stimuli (Fs2) and a second Metallic Black (Mb2);
Spectral reflectance calculating means for adding the first Fundamental Stimuli (Fs1) and the second Metabolic Black (Mb2) to derive the third spectral reflectance (R3) of the reproduction target;
Using a spectral reflectance estimation model, a fourth spectral reflectance (R3) that minimizes an error from the third spectral reflectance (R3) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. A spectral reflectance derivation device comprising: second spectral reflectance derivation means for calculating R4). Color difference calculation means for calculating a color difference under a specific light source from the fourth spectral reflectance (R4) and the first spectral reflectance (R1) of the reproduction target;
It is determined whether or not the color difference is within an allowable range, and when the color difference is not within the allowable range, the second spectral reflectance (R2) is replaced with the third spectral reflectance (R3) of the reproduction target, The spectral reflectance deriving device according to claim 1, further comprising: a repeating unit that repeats the process until the color difference falls within an allowable range. A method for deriving spectral reflectance of a reproduced output using a spectral reflectance decomposition technique and a spectral reflectance estimation model,
A first decomposition processing step of decomposing the first spectral reflectance (R1) of the reproduction target into a first Fundamental Stimuli (Fs1) and a first Metallic Black (Mb1) by a spectral reflectance decomposition method;
Using a spectral reflectance estimation model, a second spectral reflectance (R1) that minimizes an error from the first spectral reflectance (R1) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. A first spectral reflectance derivation step for calculating R2);
A second decomposing step of decomposing the second spectral reflectance (R2) into a second Fundamental Stimuli (Fs2) and a second Metallic Black (Mb2);
Spectral reflectance calculation step of adding the first Fundamental Stimuli (Fs1) and the second Metabolic Black (Mb2) to derive the third spectral reflectance (R3) of the reproduction target;
Using a spectral reflectance estimation model, a fourth spectral reflectance (R3) that minimizes an error from the third spectral reflectance (R3) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. A spectral reflectance derivation method comprising: a second spectral reflectance derivation step of calculating R4). A color difference calculating step of calculating a color difference under a specific light source from the fourth spectral reflectance (R4) and the first spectral reflectance (R1) of the reproduction target;
It is determined whether or not the color difference is within an allowable range, and when the color difference is not within the allowable range, the second spectral reflectance (R2) is replaced with the third spectral reflectance (R3) of the reproduction target, The spectral reflectance derivation method according to claim 3, further comprising: repeating a process until the color difference falls within an allowable range. A program for deriving the spectral reflectance of a reproduced output using a spectral reflectance decomposition method and a spectral reflectance estimation model,
A first decomposition processing step of decomposing the first spectral reflectance (R1) of the reproduction target into a first Fundamental Stimuli (Fs1) and a first Metallic Black (Mb1) by a spectral reflectance decomposition method;
Using a spectral reflectance estimation model, a second spectral reflectance (R1) that minimizes an error from the first spectral reflectance (R1) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. A first spectral reflectance derivation step for calculating R2);
A second decomposing step of decomposing the second spectral reflectance (R2) into a second Fundamental Stimuli (Fs2) and a second Metallic Black (Mb2);
Spectral reflectance calculation step of adding the first Fundamental Stimuli (Fs1) and the second Metabolic Black (Mb2) to derive the third spectral reflectance (R3) of the reproduction target;
Using a spectral reflectance estimation model, a fourth spectral reflectance (R3) that minimizes an error from the third spectral reflectance (R3) of the reproduction target among the spectral reflectances that can be reproduced on the reproduced output. A spectral reflectance derivation program that causes a computer to perform a second spectral reflectance derivation step of calculating R4). A color difference calculating step of calculating a color difference under a specific light source from the fourth spectral reflectance (R4) and the first spectral reflectance (R1) of the reproduction target;
It is determined whether or not the color difference is within an allowable range, and when the color difference is not within the allowable range, the second spectral reflectance (R2) is replaced with the third spectral reflectance (R3) of the reproduction target, The spectral reflectance derivation program according to claim 5, further causing the computer to repeat a step of repeating the process until the color difference falls within an allowable range.

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