JP3070827B2 - Method and apparatus for obtaining color gamut - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for obtaining a color gamut, and more particularly to a color management system for realizing color reproduction of a color image between different color image input / output devices such as a color scanner, a color display and a color printer. The present invention relates to a color gamut obtaining method for obtaining a color gamut of a color image recording device such as a color printer used in a printer, and an apparatus therefor.

[0002]

2. Description of the Related Art Color scanners, color displays,
In order to realize color reproduction of a color image between different color image input / output devices such as a color printer, detailed color characteristic data of each color image input / output device is required. Currently, the format of a profile describing the color characteristics of a color image input / output device is being standardized,
A color management system using a color characteristic profile of a color image input / output device has been developed and is being incorporated into an operating system of a personal computer.
In order to support such a color management system, the vendor of each color image input / output device needs to simultaneously create and supply a new color profile describing its color characteristics in addition to the hardware and driver software. Is growing.

In the case of a color image input device or a color image display device based on the R (red), G (green), B (blue) color system such as a color scanner and a color display, the device values R, G, The relationship between the color created by B and the tristimulus values X, Y, and Z (defined by the CIE (International Commission on Illumination)) of the color can be expressed by Equation 1.

[0004]

(Equation 1)

The element a _ij of the 3 × 3 matrix in _{Equation 1} is R,
If the tristimulus values X, Y, and Z of the G and B tricolor phosphors and the white color are given, the calculation can be performed. Therefore, the tristimulus values X, Y, and Z of only the total of four colors of the three color phosphors of R, G, and B set in the color image input / output device and white are calculated as
Just by measuring with a spectrophotometer or the like, it is possible to obtain the color characteristics of the color image input / output device, that is, the color reproduction range that the color image input / output device can handle.

On the other hand, like a color printer, a color image recording for reproducing colors by subtractive color mixing or juxtaposed color mixing using a plurality of color inks such as C (cyan), M (magenta), Y (yellow), and K (black). In the case of a device, the color characteristics to be reproduced are complicated, and a linear equation using only color data obtained by colorimetry of several color patches, such as a color image display device, accurately determines the color reproduction range. It cannot be represented. In order to obtain an accurate color reproduction range of such a color image recording device, hundreds to thousands of color patches are actually output, and the colors are measured by a measuring device such as a spectrophotometer. The correspondence between the ink density and the tristimulus values X, Y, Z at that time must be determined.
(Document "New Algorithm for UCR"
UsingDirect Color Mappin
g ", M. Tsukada et. al., SPIE,
Vol. 2413 (1995)).

[0007]

In the above-mentioned prior art, the color reproduction range of a color image recording apparatus such as a color printer which reproduces colors by using a plurality of C, M, Y, and K color inks is more accurate. In order to obtain a proper color gamut, the number of color patches to be measured must be increased, and the colorimetric work requires a large number of man-hours (labor), an advanced colorimetric technique and a measurement environment. Had become. In addition, every time specifications such as ink, printing method and paper are changed,
There was a problem that the measurement work had to be restarted from the beginning. In addition, since there is a problem of individual differences (variations) between color image recording apparatuses, it is basically desirable to measure color characteristics and create profiles for each color image recording apparatus. Assuming that hundreds to thousands of colors are measured for the number,
It took a lot of man-hours, making it virtually impossible.

Therefore, when a profile describing the color characteristics is not supplied, or when a standard profile is supplied but it is desired to absorb individual differences, the task of measuring the color is left to the general user. Will be done. However, in order for general users to measure the color characteristics of a color image recording device such as a color printer, an expensive measuring device such as a spectrophotometer must be prepared, the colorimetric technology must be mastered, and the measurement environment must be prepared. Problems such as not becoming a big hindrance are actually difficult.

An object of the present invention is to provide a color image system to which a color scanner, a color display, a color printer and the like are connected in order to realize color reproduction of a color image between these different color image input / output devices. Of the color characteristic data of the color image input / output device, the color gamut of the color image recording device in which the measuring operation is the most complicated and requires the most man-hours is determined by the tristimulus values X and Y of the color patches output by the color image recording device. , Z without the need for expensive spectrophotometers or color measurement techniques, as long as the spectral sensitivity characteristics of the imaging system of the color image input device connected to the color image system and the spectral distribution characteristics of the illumination can be obtained. The color patch original output from the image recording device is read by a color image input device whose color characteristics are known, so that the spectral response of each color patch is Provided is a color gamut acquisition method and apparatus capable of acquiring a color gamut of a color image recording device by restoring characteristics and calculating tristimulus values X, Y, and Z under arbitrary reference illumination. Is to do.

[0010]

According to the present invention, there is provided a color gamut acquiring method for acquiring a color gamut of a color image recording apparatus using multi-color ink. A plurality of color patches that cover the color gamut, a color patch image composed of the plurality of color patches is created, and the color patch image is output by the color image recording device to obtain a color patch document. The color patch document is read by a color image input device provided with a spectral distribution characteristic of illumination and a spectral sensitivity characteristic of an imaging system to obtain a color patch image, and each color patch in the color patch document is unknown. An unknown spectral reflection characteristic is created by expressing the spectral reflection characteristic by a weighted sum of a finite number of known basis functions, and is obtained from each color patch area in the color patch image. From the three primary color signals, the spectral distribution characteristic of the illumination, the spectral sensitivity characteristic of the imaging system, and the unknown spectral reflection characteristic, an observation equation relating to the unknown spectral reflection characteristic is created and solved to solve all the colors in the color patch document. By restoring the spectral reflection characteristics of the patches and calculating the tristimulus values of all the color patches from the spectral reflection characteristics of all the color patches and the spectral distribution characteristics of any reference illumination, the color reproduction of the color image recording device It is characterized by obtaining an area.

Further, in the color gamut obtaining method according to the present invention, the number of basis functions for modeling the spectral reflection characteristics of a color patch is obtained by using a color image input device having a plurality of illuminations having different spectral distribution characteristics. It is characterized by increasing.

Further, according to the present invention, there is provided a color gamut acquiring apparatus comprising: a color image input means for inputting a color patch image from a color patch document composed of a plurality of color patches; Color signal reading means for reading three primary color signals in a color patch area of a color patch image; three primary color signals read by the color signal reading means; spectral sensitivity characteristics of an imaging system; spectral distribution characteristics of illumination; Observation equation creation means for creating an observation equation from the equation, unknown characteristic parameter analysis means for solving the observation equation created by the observation equation creation means to obtain a spectral reflection characteristic parameter, and spectroscopy obtained by the unknown characteristic parameter analysis means From the reflection characteristic parameter and the spectral reflection characteristic modeling basis function Spectral reflection characteristic restoration means for restoring light reflection characteristics, tristimulus value calculation means for calculating tristimulus values from the spectral reflection characteristics restored by the spectral reflection characteristic restoration means and the spectral distribution characteristics of reference illumination, and the tristimulus Means for storing the tristimulus values calculated by the value calculation means in the color gamut table by referring to the detailed image information to obtain a color gamut, and for restoring in the color patch image Loop control means for returning control to the color signal reading means when a color patch to be left remains.

Still further, in the color gamut acquiring apparatus according to the present invention, the color image input means has a plurality of illuminations having different spectral distribution characteristics.

On the other hand, the color image system of the present invention performs color reproduction using a multicolor ink and a color image input device provided with the spectral distribution characteristics of illumination and the spectral sensitivity characteristics of the imaging system, but the color reproduction range is unknown. A color image recording device;
In a color image system including a color image display device, the color image input device, the color image recording device, and a computer connected to the color image display device, a color reproduction range that the color image recording device can reproduce is covered. A color patch image creating means for creating a color patch image composed of a plurality of color patches, and outputting the color patch image created by the color patch image creating means by the color image recording device to form a color patch document. A color signal reading means for reading three primary color signals of a color patch area of a color patch image read by the color image input device from the color patch document; a three primary color signal read by the color signal reading means; and a spectral distribution of the illumination. From the color characteristics and the spectral sensitivity characteristics of the imaging system. A spectral reflection characteristic analyzing means for restoring the spectral reflection characteristics of each color patch in the original document; and a tristimulus value calculation for calculating tristimulus values of each color patch from the spectral reflection characteristics of each color patch in the color patch original document. Means for storing the tristimulus values calculated by the tristimulus value calculation means in the color gamut table by referring to the detailed image information to obtain the color gamut, and storing means in the color gamut table; And a loop control unit for returning control to the color signal reading unit when a color patch to be restored remains in the color patch image.

Further, the color image system according to the present invention is characterized in that the color image input device has a plurality of illuminations having different spectral distribution characteristics.

Further, the color image system according to the present invention comprises:
An observation equation for creating an observation equation from the three primary color signals read by the color signal reading means, the spectral sensitivity characteristic of the imaging system, the spectral distribution characteristic of the illumination, and the spectral reflection characteristic modeling basis function; Creating means; unknown characteristic parameter analyzing means for solving the observation equation created by the observation equation creating means to obtain a spectral reflection characteristic parameter; spectral reflectance characteristic parameters determined by the unknown characteristic parameter analyzing means; A spectral reflection characteristic restoring means for restoring the spectral reflection characteristic from the modeling basis function.

[0017]

Next, the present invention will be described in detail with reference to the drawings.

First, the outline of the color gamut obtaining method and the device thereof according to the present invention will be described. Note that, here, the color image input device uses the three primary color signals R,
A color scanner for obtaining G and B, a color image display device is a color display having three color phosphors of R, G and B,
The case where the color image recording apparatus is a color printer capable of printing with three color inks C, M, Y or four color inks C, M, Y, K will be described.

FIG. 4 shows the color information of the color patch document 58 when the color patch document 58 is read by using the general color scanner 40, that is, the three primary color signals R, G,
The input process until B is obtained will be described. First, the illuminating light emitted from the illumination (lamp) 41 of the color scanner 40 passes through the glass 42 of the color scanner 40, hits the surface of the color patch document 58, and is reflected to be reflected light.
The reflected light again passes through the glass 42 and the lens 43 of the color scanner 40, is reflected by a mirror 44 built in the color scanner 40, and is further decomposed into three primary colors of red, green and blue by a three-color spectral filter 45. Is done. Then, each of the three primary color lights is converted into a CCD (Charge).
The signal is converted into an electric signal by an image pickup device 46 such as a coupled device, amplified, amplified, and output into three primary color signals R,
G and B.

Now, the spectral distribution characteristic of the illumination 41 is I
(Λ), the spectral transmission characteristic of the glass 42 is G (λ), the spectral transmission characteristic of the lens 43 is L (λ), the spectral reflection characteristic of the mirror 44 is M (λ), and the spectral characteristic of the three-color spectral filter 45 is S.
r (λ), Sg (λ), Sb (λ), and image sensor 4
Assuming that the spectral sensitivity characteristic of C.6 is C (λ), when a color patch in a color patch document 58 whose spectral reflection characteristic is R (λ) is read using the color scanner 40, the three primary colors of this color patch are read. Signals R, G, and B are given by Equation 2.
It is represented as

[0021]

(Equation 2)

Here, λ represents the wavelength, and the integration range is in the visible light region.

Now, the color characteristics of the color scanner 40 are represented by the spectral distribution characteristics I (λ) of the illumination and the spectral sensitivity characteristics T of the imaging system.
r (λ), Tg (λ), and Tb (λ).
Spectral sensitivity characteristics of imaging system Tr (λ), Tg (λ), Tb
(Λ) is the spectral transmission characteristic G (λ) of the glass 42, the spectral transmission characteristic L (λ) of the lens 43, the spectral reflection characteristic M (λ) of the mirror 44, and the spectral characteristic Sr of the three-color spectral filter 45.
(Λ), Sg (λ), Sb (λ), and image sensor 46
Is represented by the product of the spectral sensitivity characteristics C (λ). Then, the spectral sensitivity characteristics Tr (λ), Tg (λ), Tb (λ) of the imaging system
Can be combined into one function for each of the three primary color signals R, G, B as shown in Equation 3.

[0024]

(Equation 3)

From equation (3), equation (2) is represented as equation (4).

[0026]

(Equation 4)

The three primary color signals R, G, B on the left side in Equation 4
Are obtained from the color scanner 40, and the spectral distribution characteristics I (λ) of the illumination and the spectral sensitivity characteristics Tr (λ) and Tg of the imaging system are obtained.
Since (λ) and Tb (λ) are known, Equation 4 is an observation equation relating to the spectral reflection characteristic R (λ) of the color patch. In Expression 4, if the spectral reflection characteristic R (λ) is obtained, the tristimulus values X, Y, and Z of the color patch under an arbitrary reference illumination Is (λ) can be calculated by Expression 5.

[0028]

(Equation 5)

Here,

[Outside 1] (Λ),

[Outside 2] (Λ),

[Outside 3] (Λ) represents a color matching function, and k is a proportionality constant calculated by Equation 6, which is all known.

[0030]

(Equation 6)

In order to solve the spectral reflection characteristic R (λ) of the color patch, which is an unknown function of the wavelength λ, from the observation equation of Expression 4, the spectral reflection characteristic R (λ) is converted into a finite number of spectral reflection characteristic modeling basis functions. It is modeled as in Equation 7 with a weighted sum of r _i (λ).

[0032]

(Equation 7)

Here, r _i (λ) is an n-dimensional basis function relating to the spectral reflection characteristic R (λ) of the color patch, and is known. For a basis function (vector) that matches the spectral reflection characteristics of an object, see the document “Dependency”.
of the spectral reflector
nce curves of the munsell
co1or chips ", J. Cohen, Psyc
HonicalScience, Vol. 1, p
p. 369-370 (1964),
Other basis functions can be used, such as the basic waveform of a cosine wave as shown in FIG. The weighting coefficient a _i in Equation 7 is a spectral reflection characteristic parameter representing color information of the spectral reflection characteristic R (λ) of the color patch.

Substituting the spectral reflection characteristic R (λ) of the color patch modeled by the weighted sum of the n-dimensional spectral reflection characteristic modeling basis function r _i (λ) into Expression 4 as shown in Expression 7. As a result, an n-ary simultaneous linear equation relating to the spectral reflection characteristic parameter a _i representing the spectral reflection characteristic R (λ) of the color patch is obtained as shown in Expression 8.

[0035]

(Equation 8)

In Equation 8, the spectral reflection characteristic modeling basis function r _i (λ), the spectral distribution characteristic I (λ) of illumination of the color scanner 40, and the spectral sensitivity characteristic Tr of the imaging system
Since (λ), Tg (λ), and Tb (λ) are known and invariant, the product terms can be integrated in advance. That is, ∫r _i (λ) I (λ) Tr (λ) dλ, ∫r
_{i (λ) I (λ)} Tg (λ) dλ, ∫r i (λ) I
(Λ) Tb (λ) dλ is a constant coefficient, which is represented by Kr
Assuming that _i , Kg _i , and Kb _i , Equation 8 becomes the observation equation of Equation 9 regarding the unknown spectral reflection characteristic parameter a _i .

[0037]

(Equation 9)

In the problem of solving the unknown spectral reflection characteristic parameter a _i of the equation (9), (number of unknowns) ≦
From the relationship of (number of equations), the dimension n of the spectral reflection characteristic modeling basis function r _i (λ) that can be used for modeling the spectral reflection characteristic R (λ) of the color patch is inevitably determined. In the case of the equation (9), three become the maximum. Therefore, the observation equation of Equation 9 becomes a ternary linear simultaneous equation of Equation 10, and the unknown spectral reflection characteristic parameters a ₁ ,
a ₂ and a ₃ can be solved.

[0039]

(Equation 10)

In order to improve the restoration accuracy of the spectral reflection characteristic R (λ) of the color patch, a spectral reflection characteristic modeling basis function r used for modeling the spectral reflection characteristic R (λ)
_When the dimension n of _i (λ) is set to four or more, a color scanner 40 having a plurality of illuminations 41 having different spectral distribution characteristics I (λ) is prepared, and the same color patch is scanned by different illuminations 41. Thus, a plurality of sets of three primary color signals R, G, B are obtained.

Here, two different spectral distribution characteristics R
Using the color scanner 40 having the illumination 41 indicating (λ), the dimension n of the spectral reflection characteristic modeling basis function r _i (λ) used for modeling the spectral reflection characteristic R (λ) is reduced to four. A description will be given of the case in which this is done. In this case, the spectral distribution characteristics I (λ) of the illumination 41 of the color scanner 40 and the spectral sensitivity characteristics Tr (λ), T
The constant coefficients Kr _i , Kg _i , and Kb _i obtained by calculating the integral term of the product of g (λ), Tb (λ) and the spectral reflection characteristic modeling basis function r _i (λ) are calculated for each illumination 41. For each spectral distribution characteristic I (λ). These _{(Kr i, Kg i, Kb} i) and (KR _i,
KG _i , KB _i ), the observation equation of Expression 11 is obtained. However, when the color patch is read by the two illuminations 41, the three primary color signals are R, G, B and R ', G', B '.
And

[0042]

[Equation 11]

By obtaining the six observation equations of Equation 11, four unknown spectral reflection characteristic parameters a _i (i = 1 to 4) can be solved.

By substituting the spectral reflection characteristic parameter a _i obtained from the observation equation (10) or (11) into the equation 7, the spectral reflection characteristic R of the color patch is obtained.
(Λ) can be restored. Further, the tristimulus values X, Y, and Z of the color patches can be calculated by substituting the restored spectral reflection characteristics R (λ) into Equation 5.

In order to obtain the color reproduction range of the color image recording apparatus, as shown in FIG. 6, a plurality of color patches are printed on a color patch document 58 while controlling the amount of color ink, and all of them are printed. By restoring the spectral reflection characteristic R (λ) of the color patch and calculating the tristimulus values X, Y, and Z, a color reproduction range that can be expressed by the color image recording apparatus can be obtained.

[0046]

FIG. 1 shows a color gamut acquiring apparatus 2 for acquiring a color gamut of a color image recording apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a 00. The color gamut acquiring apparatus 200 of the present embodiment includes a color image input unit 1, a color signal reading unit 3, an observation equation creating unit 5, an unknown characteristic parameter analyzing unit 7, a spectral reflection characteristic restoring unit 9,
The tristimulus value calculation means 11, the storage means 13 for storing in the color gamut table, and the loop control means 14 constitute a main part thereof. In FIG. 1, reference numeral 2 denotes three primary color signals R,
The color patch image 4 composed of G and B has an average three primary color signals R, G and B (represented by the same symbols as the three primary color signals).
The same applies to the following), 6 is an observation equation of Expression 10, 8 is a spectral reflection characteristic parameter a _i , 10 is a spectral reflection characteristic R (λ), 12
Represents tristimulus values X, Y, Z, 38 represents detailed image information, and 50 represents spectral sensitivity characteristics Tr (λ), Tg (λ), Tb of the imaging system.
(Λ) and 51 are spectral distribution characteristics I (λ) of illumination, 52 is a spectral reflection characteristic modeling basis function r _i (λ), and 53 is a reference illumination storing spectral distribution characteristics Is (λ) of a plurality of reference illuminations. Memory 54, a color reproduction area table 54;
Indicates a color patch document.

FIG. 6 is a diagram showing an example of the color patch document 58. In the color patch document 58, a plurality of color patches, each having a slightly different C in the horizontal direction and a slightly different M in the vertical direction, are recorded side by side in a tile shape, and furthermore, Y and K for each sheet are recorded. Are set to be different.

FIG. 7 is a diagram showing an example of the color gamut table 54. The color gamut table 54 includes C, M,
The ink amounts of Y and K and the three primary color signals of X, Y and Z are stored for each color patch.

FIG. 8 is a diagram showing an example of the detailed image information 38. The detailed image information 38 stores a color patch number, a start position of the color patch, the number of pages of the color patch document, and the ink amounts of C, M, Y, and K for each color patch. Note that the size of one color patch is also stored.

Next, the operation of the color gamut obtaining apparatus 200 according to the first embodiment thus configured will be described together with the color gamut obtaining method.

First, the spectral sensitivity characteristics Tr (λ) of the imaging system,
Tg (λ), Tb (λ) and spectral distribution characteristics I (λ) of illumination
The color image input unit 1 given the color patch image 58 reads the color patch document 58 as shown in FIG. 6 and creates the color patch image 2 composed of the three primary color signals R, G, and B.

Next, the color signal reading means 3 calculates the average value of the three primary color signals R, G, and B in the color patch area for restoring the spectral reflection characteristic R (λ) in the color patch image 2 for each of the color patch originals 58. A color patch for obtaining the spectral reflection characteristic R (λ) in the color patch image 58, obtained in accordance with the detailed image information 38 as shown in FIG. The average three primary color signals R, G, and B (hereinafter, referred to as target color patches) are obtained.

Subsequently, the observation equation creating means 5 provides the spectral sensitivity characteristics Tr (λ), T of the image pickup system of the color image input means 1.
g (λ), Tb (λ), and spectral distribution characteristics I (λ) of illumination
A spectral reflection characteristic modeling basis function r _i (λ) used to model the spectral reflection characteristic R (λ) of the color patch area of the color patch document 58;
From G and B, an observation equation 6 relating to the spectral reflection characteristic parameter a _i of Formula 10 is created.

Next, the unknown characteristic parameter analysis means 7
By solving the observation equation 6 relating to the spectral reflection characteristic parameter a _i of Expression 10, the spectral reflection characteristic parameter a _i (i = 1 to
Obtain 3).

Subsequently, the spectral reflection characteristic restoring means 9 substitutes the spectral reflection characteristic parameter a _i (i = 1 to 3) into Equation 7 to obtain the spectral reflection characteristic R in the target color patch in the color patch document 58. (Λ) is restored.

Next, the tristimulus value calculating means 11 calculates the restored spectral reflection characteristic R (λ) and the spectral distribution characteristic Is (λ) of the reference illumination desired by the user in the spectral distribution characteristic memory 53 of the reference illumination. From the above, color patch manuscript 5 according to Equation 5
The tristimulus values X, Y, and Z for the target color patch in 8 are calculated.

Subsequently, storage means 1 for storing in the color gamut table
Reference numeral 3 denotes the amount of ink constituting the target color patch is obtained from the detailed image information 38, and the amount of ink of the color patch and the tristimulus values X, Y, and Z are expressed in the color format shown in FIG. It is stored in the reproduction area table 54. here,
The color gamut table 54 may have a format other than that shown in FIG.

Finally, the loop control means 14 returns the control to the color signal reading means 3 when the color patch image 2 still has a color patch area for restoring the spectral reflection characteristic R (λ). The processing is repeated until the spectral reflection characteristic R
If there is no color patch area for which (λ) should be restored, the process ends.

FIG. 2 shows two illuminations A and B for obtaining a color reproduction range of the color image recording apparatus according to the second embodiment of the present invention.
1 is a block diagram illustrating a configuration of a color gamut acquisition device 201 having The color gamut acquisition device 201 having two illuminations A and B according to the present embodiment includes a color image input unit 1, a color signal reading unit 3, an observation equation creating unit 5, an unknown characteristic parameter analyzing unit 7, Reflection characteristic restoring means 9;
Tristimulus value calculating means 11, storing means 13 for storing a color gamut table, loop control means 14, lighting switching means 15
Thus, the main part is constituted. In FIG. 2,
Symbols 2a and 2b are color patch images composed of three primary color signals R, G and B, and 4 is an average three primary color signals R, G and
B and 6 are observation equations of Formula 11, 8 is a spectral reflection characteristic parameter a _i , 10 is a spectral reflection characteristic R (λ), 12 is tristimulus values X, Y, and Z, 38 is detailed image information, and 50 is an imaging system. Spectral sensitivity characteristics Tr (λ), Tg (λ), Tb (λ), 52
Is a spectral reflection characteristic modeling basis function r _i (λ), 53 is a spectral distribution characteristic memory of reference illumination that stores spectral distribution characteristics Is (λ) of a plurality of reference illuminations, 54 is a color reproduction area table,
55 is the spectral distribution characteristic Ia (λ) of the illumination A, 56 is the illumination B
The spectral distribution characteristics Ib (λ) 58 of the color patch document respectively.

Next, the operation of the color gamut obtaining apparatus 201 according to the second embodiment thus configured will be described together with the color gamut obtaining method.

First, the spectral sensitivity characteristics Tr (λ) of the imaging system,
The color image input means 1 having Tg (λ) and Tb (λ) and two kinds of illuminations A and B having different spectral distribution characteristics Ia (λ) and Ib (λ) switched by the illumination switching means 15 is a color image input means. The color patch image 2a input under the spectral distribution characteristic Ia (λ) of the illumination A of the patch document 58 and the color patch image 2b input under the spectral distribution characteristic Ib (λ) of the illumination B are obtained.

Next, the color signal reading means 3 transmits the detailed image information 38 as shown in FIG. 8 describing the position information of each color patch of the color patch document 58 and the amount of ink constituting each color patch. With reference to each of the two color patch images 2a and 2b, the average value of the three primary color signals R, G, B and R ', G', B 'in the same color patch area is obtained, and the average three primary color signals in the target color patch are obtained. Obtain R, G, B and R ', G', B '.

Subsequently, the observation equation creating means 5 determines the spectral sensitivity characteristics Tr (λ), T of the imaging system of the color image input means 1.
g (λ), Tb (λ), and spectral distribution characteristics Ia of illumination A
(Λ), the spectral distribution characteristic Ib (λ) of the illumination B, the spectral reflection characteristic modeling basis function r _i (λ) used for modeling the spectral reflection characteristic R (λ), and the average three primary color signals R,
From G, B, and R ′, G ′, B ′, an observation equation 6 relating to the spectral reflection characteristic parameter a _{i in} Expression 11 is created.

Next, the unknown characteristic parameter analysis means 7
By solving the observation equation 6 regarding the spectral reflection characteristic parameter a _{i in} Expression 11, the spectral reflection characteristic parameter a _i (i = 1 to
Obtain 4).

Subsequently, the spectral reflection characteristic restoring means 9 substitutes the spectral reflection characteristic parameter a _i into Equation 7 to obtain
The spectral reflection characteristic R (λ) of the target color patch in the color patch document 58 is restored.

Next, the tristimulus value calculating means 11 calculates the restored spectral reflection characteristic R (λ) and the spectral distribution characteristic Is (λ) of the reference illumination desired by the user in the spectral distribution characteristic memory 53 of the reference illumination. From the above, color patch manuscript 5 according to Equation 5
Calculate the triangular values X, Y, and Z in the target color patch in 8.

Subsequently, storage means 1 for storing in the color gamut table
Reference numeral 3 denotes a color reproduction area in a format as shown in FIG. 7 in which the amount of ink constituting the target color patch is obtained from the detailed image information 38, and the amount of ink of the color patch and the tristimulus values X, Y, and Z are represented. It is stored in the table 54. Here, the color gamut table 54 may be in a format other than FIG.

Finally, if the color patch area of the spectral reflection characteristic R (λ) to be restored remains in the two color patch images 2a and 2b, the loop control means 14 sets the color signal reading means 3 And the process is repeated, and when there is no color patch area of the spectral reflection characteristic R (λ) to be restored, the process is terminated.

FIG. 3 is a block diagram showing a configuration of a color image system 202 for acquiring a color reproduction range of a color image recording apparatus according to a third embodiment of the present invention. The color image system 202 of the present embodiment includes the color image input device 30.
, Color image display device 31, and color image recording device 3
2 and a computer 34 equipped with a memory 33.

The memory 33 stores the color image recording device 3
A color patch document creating means 39 for creating a color patch document 58 used for measuring the color reproduction area 2;
Color gamut estimating means 40 for calculating the color gamut and a color gamut table 54 are provided.

The color patch document creating means 39 includes: an ink amount generating means 35; a color patch image creating means 36;
It is configured to include detailed image information 38 and printer information 57.

FIG. 9 is a diagram showing an example of the printer information 57. The printer information 57 includes a printer name, resolution information, a color system, a printing method, and the number of effective gradations.

The color gamut estimating means 40 includes a color signal reading means 3, a spectral reflection characteristic analyzing means 60, a tristimulus value calculating means 11, a storing means 13 for a color gamut table, a loop control means 14, , The spectral sensitivity characteristics Tr of the imaging system
(Λ), Tg (λ), Tb (λ) 50, illumination spectral distribution characteristic I (λ) 51, spectral reflection characteristic modeling basis function r _i (λ) 52, and spectral distribution of a plurality of reference illuminations Characteristic Is
And a reference illumination spectral distribution characteristic memory 53 for storing (λ).

The spectral reflection characteristic analyzing means 60 includes the observation equation creating means 5 and the unknown characteristic parameter analyzing means 7 in the color gamut obtaining apparatus 200 according to the first embodiment shown in FIG.
And the spectral reflection characteristic restoring means 9.

In FIG. 3, reference numeral 2 denotes a color patch image, 4 denotes average three primary color signals R, G, B, 10 denotes spectral reflection characteristics R (λ), 12 denotes tristimulus values X, Y, Z, and 37 denotes Each shows a color patch image.

Next, the operation of the color image system 202 for obtaining the color gamut of the color image recording apparatus of the third embodiment configured as described above will be described together with the color gamut obtaining method.

First, in the color patch document creating means 39, the ink amount generating means 35 is connected to the color image recording device 3 described in the printer information 57 as shown in FIG.
The number of color patches and the amount of color ink forming each color patch are determined in accordance with the color system of No. 2 and the number of effective gradations.

Next, the color patch image creating means 36
Color image recording device 32 described in printer information 57
From the resolution information, how to arrange a plurality of color patches on the color patch document 58 is determined, and the color patch image 37, the position information of the color patches of the color patch image 37, and the ink amount are described. And the detailed image information 38 as shown in FIG. Then, the created color patch image 37 is stored in the color image recording device 32.
, And becomes a color patch document 58.

When the color patch document 58 created in this way is input by the color image input device 30, the color signal reading device 3 in the color gamut estimating device 40 outputs the color patch document 58 to the color image input device 30. The average three primary color signals R, G, and B in the target color patch area in the color patch image 2 are obtained from the captured color patch image 2 with reference to the image detailed information 38.

Next, the spectral reflection characteristic analyzing means 60 obtains the obtained average three primary color signals R, G, B and the spectral sensitivity characteristics Tr (λ), Tg (λ), Tg (λ) of the image pickup system of the color image input device 30.
From Tb (λ), the spectral distribution characteristic I (λ) of the illumination, and the spectral reflection characteristic modeling basis function r _i (λ), an observation equation of Formula 10 is created, and the spectral reflection of the color patch is calculated from the observation equation. The characteristic parameter a _i is derived to restore the spectral reflection characteristic R (λ) of the target color patch.

Subsequently, the three-slice numerical value calculating means 11 calculates the spectral distribution characteristic Is (λ) of the reference illumination desired by the user in the spectral distribution characteristic memory 53 of the reference illumination by using the restored spectral reflection characteristic R (λ). To convert them into tristimulus values X, Y, and Z.

Next, storage means 13 for storing in the color gamut table
Obtains the amount of ink constituting the target color patch from the detailed image information 38, and calculates the amount of ink of the color patch and the tristimulus values X, Y, and Z in a color reproduction area table 54 in a format as shown in FIG. To be stored. Here, the color gamut table 54 may be in a format other than FIG.

Lastly, if there is a color patch area to be restored in the color patch image 2, the loop control means 14 returns control to the color signal reading means 3 and repeats the process to repeat the color to be restored. If no patch area remains, the process ends.

[0084]

As described above, according to the color gamut obtaining method and apparatus of the present invention, if there is only a color image input device whose spectral sensitivity characteristics of an imaging system and spectral distribution characteristics of illumination are known. A color patch original composed of color patches of a plurality of colors output by a color image recording device is read, and the spectral reflection characteristics of all the color patches are automatically restored to obtain the color reproduction range of the color image recording device. Therefore, there is an effect that the measurement of the color gamut of a color image recording apparatus which conventionally requires a large number of man-hours, advanced measurement techniques and expensive color measuring equipment can be performed by ordinary users.

Further, according to the color gamut acquisition method and apparatus of the present invention, since the color gamut can be measured for each color image recording device, an accurate color gamut can be obtained for each individual, and a more accurate color gamut can be obtained. There is an effect that color printing can be realized.

Further, according to the color image system of the present invention, as long as there is only a color image input device whose spectral sensitivity characteristics of the image pickup system and the spectral distribution characteristics of the illumination are known, the color patch created by the color patch document creating means can be used. Reads a color patch document composed of multiple color patches whose images have been output by a color image recording device and automatically restores the spectral reflection characteristics of all color patches to obtain the color reproduction range of the color image recording device Therefore, there is an effect that a general user can measure the color gamut of a color image recording apparatus which conventionally requires a large number of man-hours, advanced measurement techniques, and expensive color measuring equipment.

Further, according to the color image system of the present invention, since the color gamut can be measured for each color image recording device, an accurate color gamut can be obtained for each individual, and more accurate color printing can be realized. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a color gamut acquisition apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a color gamut acquisition apparatus having two illuminations according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a color image system for realizing a color gamut of a color image recording apparatus according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a process of inputting a color patch document in the color image input device.

FIG. 5 is a diagram exemplifying a spectral reflection characteristic modeling basis function for modeling a spectral reflection characteristic of a color patch document;

FIG. 6 is a diagram illustrating a color patch document of a color patch image created by controlling the amount of color ink so as to cover the color reproduction range of the color image recording apparatus.

FIG. 7 is a diagram showing an example of a color gamut table in FIG. 1;

FIG. 8 is a diagram illustrating an example of image detailed information in FIG. 1;

FIG. 9 is a diagram illustrating an example of printer information in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Color image input means 2 Color patch image 3 Color signal reading means 4 Average three primary color signals 5 Observation equation creation means 6 Observation equation 7 Unknown characteristic parameter analysis means 8 Spectral reflection characteristic parameter 9 Spectral reflection characteristic restoration hand throw 10 Spectral reflection characteristic 11 3 Stimulus value calculation means 12 Tristimulus values 13 Storage means in color gamut table 14 Loop control means 15 Illumination switching means 30 Color image input device 31 Color image display device 32 Color image recording device 33 Memory 34 Computer 35 Ink amount generation means 36 Color patch image creation means 37 Color patch image 38 Detailed image information 40 Color scanner 41 Illumination 42 Glass 43 Lens 44 Mirror 45 Trichromatic spectral filter 46 Image sensor 50 Spectral sensitivity characteristic of imaging system 51 Spectral distribution characteristic of illumination 52 Spectral reflection characteristic Modeling basis function 53 Spectral distribution characteristic memory of reference illumination 54 Color reproduction area table 55 Spectral distribution characteristic of illumination A 56 Spectral distribution characteristic of illumination B 57 Printer information 58 Color patch document 60 Spectral reflection characteristic analysis means 200 Color reproduction area acquisition device 201 Color gamut acquisition device having two illuminations 202 Color image system for acquiring color gamut of color image recording device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (7)

(57) [Claims] 1. A color gamut obtaining method for obtaining a color gamut of a color image recording apparatus using multi-color ink, comprising: creating a plurality of color patches covering a color gamut reproducible by the color image recording apparatus. Creating a color patch image composed of the plurality of color patches, outputting the color patch image by the color image recording device to obtain a color patch document, the color patch document, the spectral distribution characteristics of illumination and A color patch image is read by a color image input device provided with a spectral sensitivity characteristic of an imaging system, and the unknown spectral reflection characteristic of each color patch in the color patch document is weighted sum of a finite number of known basis functions. An unknown spectral reflection characteristic represented by the following formula is created, three primary color signals obtained from each color patch area in the color patch image, the spectral distribution characteristic of the illumination, From the spectral sensitivity characteristics of the imaging system and the unknown spectral reflection characteristics, an observation equation for the unknown spectral reflection characteristics is created, and this is solved to restore the spectral reflection characteristics of all the color patches in the color patch document. Obtaining a color reproduction range of the color image recording apparatus by calculating tristimulus values of all color patches from a spectral reflection characteristic of a color patch and a spectral distribution characteristic of an arbitrary reference illumination. Method. 2. A method according to claim 1, wherein a color image input device having a plurality of illuminations having different spectral distribution characteristics is used to obtain a basis function for modeling a spectral reflection characteristic of a color patch. A color gamut acquisition method characterized by increasing the number. 3. A color image input means for inputting a color patch image from a color patch document composed of a plurality of color patches, and three primary color signals of a color patch area of the color patch image input by the color image input means. Color signal reading means for reading an image, and an observation equation creating means for creating an observation equation from the three primary color signals read by the color signal reading means, the spectral sensitivity characteristics of the imaging system, the spectral distribution characteristics of illumination, and the spectral reflection characteristic modeling basis function. An unknown characteristic parameter analyzing means for solving the observation equation created by the observation equation creating means to obtain a spectral reflection characteristic parameter; and a spectral reflection characteristic parameter obtained by the unknown characteristic parameter analyzing means and the spectral reflection characteristic modeling. Spectral reflection characteristics that restore spectral reflection characteristics from basis functions Restoring means; tristimulus value calculating means for calculating tristimulus values from the spectral reflection characteristics restored by the spectral reflection characteristic restoring means and the spectral distribution characteristics of the reference illumination; and the tristimulus calculated by the tristimulus value calculating means. Means for storing a value in a color gamut table to obtain a color gamut by storing values in a color gamut table with reference to the image detailed information; and when a color patch to be restored remains in the color patch image. A color control unit that returns control to the color signal reading unit. 4. A color gamut acquiring apparatus according to claim 3, wherein said color image input means has a plurality of illuminations having different spectral distribution characteristics. 5. A color image input apparatus provided with a spectral distribution characteristic of illumination and a spectral sensitivity characteristic of an image pickup system, a color image recording apparatus which performs color reproduction with multi-color inks, but has an unknown color reproduction range, In a color image system including an image display device, the color image input device, the color image recording device, and a computer connected to the color image display device, a plurality of color reproduction regions covering the color reproduction range reproducible by the color image recording device are provided. A color patch image creating means for creating a color patch image composed of color patches of colors, and the color patch image created by the color patch image creating means is output by the color image recording apparatus to obtain a color patch document. The color patch image of the color patch image read by the color image input device. A color signal reading means for reading the three primary color signals; and a spectral reflection of each color patch in the color patch document based on the three primary color signals read by the color signal reading means, the spectral distribution characteristics of the illumination, and the spectral sensitivity characteristics of the imaging system. Spectral reflection characteristic analyzing means for restoring characteristics; tristimulus value calculating means for calculating tristimulus values of each color patch from spectral reflection characteristics of each color patch in the color patch document; Means for storing the calculated tristimulus values in the color gamut table by referring to the detailed image information to obtain a color gamut; and a color patch to be restored in the color patch image. And a loop control unit that returns control to the color signal reading unit when the image data remains. 6. The color image system according to claim 5, wherein said color image input device has a plurality of illuminations having different spectral distribution characteristics. 7. The color image system according to claim 5, wherein said spectral reflection characteristic analyzing means includes: a three primary color signal read by said color signal reading means; a spectral sensitivity characteristic of said imaging system; a spectral distribution characteristic of said illumination; An observation equation creating means for creating an observation equation from the spectral reflection characteristic modeling basis function, an unknown characteristic parameter analyzing means for solving the observation equation created by the observation equation creating means to obtain a spectral reflection characteristic parameter, and an unknown characteristic parameter A color image system comprising: a spectral reflection characteristic restoring unit that restores a spectral reflection characteristic from the spectral reflection characteristic parameter obtained by the analysis unit and the spectral reflection characteristic modeling basis function.