JPH0823661B2 - Color processing method - Google Patents

Description

The present invention relates to a color processing method for reproducing and recording an image such as a color print image or a color television image on a photographic film, photographic paper or the like.

(Prior Art) The density of each pixel point of a color printed image is read by a scanner using three primary colors of red (hereinafter, referred to as R), green (hereinafter, referred to as G), and blue (hereinafter, referred to as B). Based on the respective density values measured separately for each of the pixels, and on the basis of each RGB signal of each pixel point of the television image, cyan (hereinafter referred to as C) and magenta (hereinafter referred to as C) which are the three primary colors of the color of the printing paper. ,
Called M. ) And yellow (hereinafter referred to as Y) densities are calculated, and by reproducing and recording the calculated CMY density values on photographic paper or the like, a hard copy of the image can be obtained conventionally. It is done from.

To convert from the point in the RGB color space of each pixel point of a color print image to the point in the CMY color space corresponding to photographic paper for hard copy, conventionally, However, (A) is a linear transformation in which conversion is performed based on the equation of the coefficient matrix, and in this linear transformation, the color reproducibility is very poor, so R ² , G ² , B ² , RG, GB, ...
Non-linear conversion including correction terms such as However, in (D), a coefficient matrix was used.

However, as described above, the color reproducibility is extremely poor in the linear conversion (Equation (1)), and the color reproducibility is still insufficient even in the non-linear conversion (Equation (2)) that corrects this. Moreover, as the number of correction terms is increased, the apparatus becomes more complicated, and a long calculation time is required.

In addition, as a method to significantly improve this color reproducibility,
Prepare a large number of standard color samples in which each density value of CMY is changed stepwise using the photographic paper used for hard copy, and use a scanner to determine the R, G, and B densities of each standard color sample. When the RGB densities of the measured image are measured using the scanner in advance, it is determined on each pixel which point in the RGB color space the pixel point corresponds to in the CMY color space. A method has been proposed in which interpolation is performed based on the correspondence between the points in the RGB color space of the standard color sample around the points in the RGB color space and the points in the CMY color space (for example, "Digital color image Color Reproduction "by Hiro Satoshi Hong, February 1988
The text "Development and commercialization trends of full-color video printers" of the seminar hosted by Japan Industrial Technology Center on the 19th
Pages 41-47 etc. ).

(Problems to be Solved by the Invention) In the method using a large number of standard color samples, since the standard color samples are created using printing paper or the like used for hard copy, the error in color reproducibility is In the space, from the CMY values corresponding to the points of the neighboring color samples, there are only minute errors that occur when the CMY values of the pixel points of the measured image are calculated by interpolation. It has the advantage of good reproducibility.

However, even if a large number of standard color samples are arranged in the CMY color space at equal intervals in the CMY color space as shown two-dimensionally in Fig. 4A, these standard color samples can be measured with a scanner. In the RGB color space obtained by the above, the measurement points (standard color coordinate points) are not significantly distorted as shown two-dimensionally in FIG. There is a problem of being lined up. Up to now, when calculating each CMY value of a point (measurement point) in the RGB space obtained by scanning each pixel of the measured image with a scanner, it was arranged in such a distorted shape in the RGB color space. However, since it is calculated from the standard color coordinate points, it requires a calculation in a distorted space, requires a very complicated calculation, and takes a long calculation time. Further, in order to reduce this calculation time, the calculation is performed. There is a problem that if the apparatus to be performed is composed of hardware, the apparatus becomes very complicated.

In addition, the color TV image itself emits light (light emission mode), and the system that observes with reflected light (reflection mode) such as a color print image or an image hard-copied on photographic paper is a color treatment. Is quite different,
A method of converting a light emission mode into a reflection mode so as to give almost the same impression to human eyes has already been proposed (Japanese Patent Application No. 63-43943, Japanese Patent Application No. 63-112163, and Japanese Patent Application No. 63163).
-11264, etc.). Therefore, by adopting the method using a large number of standard color samples, for example, it is possible to obtain a hard copy which gives an impression of almost the same color tone as the screen of a color television on photographic paper.

However, also in this case, as in the case of the color print image described above, it is necessary to interpolate each value of CMY of each pixel point of the color television image from the standard color coordinate point having a very distorted array, and the problem described above. There was exactly the same problem as.

In view of the above problems, the present invention can obtain a hard copy having very good color reproducibility by using a large number of standard color samples, shorten the calculation time, or simplify the hardware configuration. It is an object of the present invention to provide a color processing method that can be realized.

(Means for Solving the Problem) The color processing method of the present invention includes the second standard different from the first color space of a large number of standard color samples having different colors whose coordinates on the first color space are known. Of the standard color coordinate points in the color space of the first color space
When the coordinates in the first color space of a large number of grid-like coordinate points arranged in a grid in the color space are obtained by interpolation, and the coordinates in the first color space of the color to be measured are obtained, The coordinates of the measurement color in the second color space are obtained, and the coordinates in the first color space corresponding to the coordinates are obtained by interpolating from the coordinates of the grid-like coordinate points in the first color space. It is characterized by that.

Here, the above-mentioned "first color space" means, for example, the CMY color space of the conventional example described above, and the three primary colors (CMY, RGB, etc.) of a photo film or photographic paper used as a medium such as a hard copy.
Etc.) or a color space corresponding to each pigment of color printing (hereinafter referred to as “reproduction system color space”), and is an image to be hard copied (hereinafter referred to as “measured image”). The quality of color reproduction is determined by the accuracy with which each point on the first color space corresponding to each point is obtained.

Further, the "second color space" means a color space for measuring the color of each pixel point of an image to be measured, such as the RGB color space of the conventional example described above, and the three primary colors of light emitted from a color television. A color space that is determined and a color space that is obtained from these color spaces by calculation such as linear conversion (hereinafter, these color spaces are referred to as "measurement system color space"). Specifically, a color print image The color space defined by the color filter used in the scanner that measures both the standard color sample and the color print image that is the measured image, which is used in the system for obtaining the hard copy of The RGB color space determined by the scanner used to measure the standard color sample used in the system intended to obtain, or the color space obtained by linearly converting the RGB color space (the color space Is the same as the color space when the color television image (color space of the light emission mode) is converted to the reflection mode), or the color space obtained by linearly converting the RGB color space is further converted to the color space of the light emission mode. Refers to the color space.

In addition, the "many grid-like coordinate points" are "arranged in a grid".
In the color space (for example, the RGB color space), the grid means that the grid-like coordinate points are coordinate axes (for example, R
Axis, G axis, B axis) are arranged on the intersections of many straight lines parallel to each other. For example, in the two-dimensional example shown in FIG. 10, the grid-like coordinate points (● marks) are many parallel to the R axis. Straight line (-mark)
And are arranged on the intersection of a large number of straight lines (...) parallel to the G axis. It is not always necessary to line up at equal intervals in each axial direction.

(Operation) The color processing method of the present invention obtains points on the measurement system color space of a large number of standard color samples whose coordinates on the reproduction system color space are known,
From these points, the coordinates in the reproduction system color space of a large number of grid-like coordinate points in the measurement system color space arranged in a grid in the measurement system color space are obtained by interpolation, and the measurement system of the color to be measured is measured. When the coordinates in the color space are calculated, the coordinates in the reproduction system color space of the measured color are interpolated from the coordinates in the reproduction system color space of the grid-like coordinate points, so that a hard copy is created. It does not impair the advantage of the method of using standard color samples, which has very good color reproducibility, and the calculation of the mapping from the coordinate points in the measurement system color space to the coordinate points in the reproduction system color space is very easy. The calculation can be simplified, the calculation time can be greatly shortened, and the configuration of the hardware for executing the calculation can be greatly simplified.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

 FIG. 1 is a diagram showing a large number of standard color samples.

This standard color sample is made using the same photosensitive film used to obtain a hard copy of the original image described below. This photosensitive film 1 has the property of developing colors of C, M, and Y when irradiated with R, G, and B light. Correspondence between the light amounts of R, G, and B lights with which the photosensitive film 1 is irradiated and the respective C, M, and Y densities that the photosensitive film 1 develops has already been sought. This characteristic is called the characteristic curve of the photosensitive material. 30 sheets of the photosensitive film 1 are prepared, and the light amount of the B light irradiating the photosensitive film is controlled so that the photosensitive film 1 is evenly spaced in the Y-axis direction on the CMY color space of the photosensitive film. In addition, in each photosensitive film,
The light amounts of R and G irradiating the photosensitive film 1 are controlled so that they are arranged at equal intervals in the C-axis direction and the M-axis direction in the CMY color space, and a standard color sample as shown in the figure is obtained. That is, in the horizontal direction of the figure (direction of arrow C), the respective concentrations of M and Y are constant, and only the concentration of C changes stepwise, and in the vertical direction of the figure (direction of arrow M), the respective concentrations of C and Y are changed. Is constant and only the density of M is changed stepwise, and in the direction in which the number of the photosensitive film 1 is changed (direction of arrow Y), each density of C and M is constant and only the density of Y is changed stepwise. 30 × 30 × 30 = 27,000 standard color samples are obtained. These standard color samples are arranged at equal intervals in the C, M, and Y axial directions on the CMY color space, that is, the standard colors correspond to the vertices of many cubes on the CMY color space. ing.

In the present embodiment, a large number of standard colors are used at equal intervals in the respective C, M, Y axis directions.However, in the present invention, a large number of standard colors are arranged in the C, M, Y axes. It is not always necessary to line up at equal intervals in the direction, and standard samples lined up in a grid in the above definition, or even standard samples having completely randomly arranged standard colors may be used. In this embodiment, standard colors of 30 steps were prepared for each of C, M, and Y directions, but this is also just an example, and is determined based on the final color reproduction accuracy, calculation speed, and the like. Any standard color of n ₁ , n ₂ , and n ₃ colors may be prepared for each direction of M, Y.

FIG. 2 is a configuration diagram showing a schematic configuration of the scanner.

As shown in FIG. 1, the photosensitive films 1 that have developed a standard color are placed one by one on the mounting table 11. The mounting table 11 is movable in the X direction and the Y direction perpendicular to the X direction shown in the figure. The white light 13 emitted from the lamp 12 is condensed by the lens 14 and illuminates the photosensitive film 1 on the mounting table 11. The reflected light 13 'from the photosensitive film 1 carries information on the CMY color density at the irradiated position of the photosensitive film 1. The reflected light 13 'is collimated by the lens 15, divided into three optical axes by the dichroic mirrors 16 and 17, and condensed by the lenses 18, 19 and 20, respectively, and the R, G and B color filters 24,
After passing through 25 and 26, the light amounts of R, G and B lights are detected by the photodetectors 21, 22 and 23, respectively, and the respective R, G and B values at the measurement point of the photosensitive film 1 are obtained. . In this way, the mounting table 1
While moving 1 in the X and Y directions and replacing the photosensitive film 1 on the mounting table 11, the R, G, and B densities of the 27,000 standard color samples shown in FIG. 1 are measured. In an actual scanner, in order to correct the color temperature of the white light 13 and obtain a more accurate measurement value, each RGB light amount of the white light 13 before being reflected by the photosensitive film 1 is measured, and these measurements are performed. Although the values may be used to correct the RGB measurement values of the reflected light 13 'from the photosensitive film 1, this is a well-known technique and will not be mentioned here.

FIGS. 3A and 3B are diagrams showing the arrangement of standard color samples in the CMY color space and RGB color space, respectively, FIGS. 4A and 4B.
The figure is a two-dimensional schematic diagram for clearly showing the arrangement of standard color samples in the CMY color space and the RGB color space, respectively.

In the CMY color space, the standard color of 27000 is, as shown in FIG. 4A, a grid pattern (an aspect of the above-mentioned “lattice pattern”, actually C, M,
It is a three-dimensional space of Y, and these standard colors are located at each apex of a cube in which a large number of them are stacked. ) Are lined up. When the RGB densities of these standard colors are measured by the scanner shown in FIG. 2, as shown in FIGS. 3B and 4B, that is, in FIG.
Each point of A, B, C has a very distorted arrangement so as to correspond to A ', B', C'in FIG. 4B. This is the CM of the photosensitive film 1.
It means that there is no linearity between each color density of Y and the measured density of R, G, B by the scanner shown in Fig. 2, and the linear conversion of the above-mentioned formula (1) is not established and it is very difficult. It shows that there is a big error in.

FIG. 5A is a diagram showing a large number of coordinate points arranged in a grid pattern in the RGB color space, and FIG. 5B is a diagram showing a large number of points in the CMY color space corresponding to these large number of coordinate points. Is.

As described with reference to FIGS. 3A to 4B, for the same reason that many points arranged in a grid pattern in the CMY color space are distorted in the RGB color space, the RGB color space A large number of coordinate points arranged in a grid pattern above are distorted in the CMY color space.

Based on the correspondence between the points in the CMY color space of each standard color and the points in the RGB color space shown in FIGS. 3A and 3B, interpolation calculation was performed to arrange them in a grid pattern in the RGB color space. The CMY values (coordinates in the CMY color space) of the large number of equally spaced coordinate points (one aspect of the grid-shaped coordinate points of the present invention) are obtained.

FIG. 6A shows an example of the arrangement of a large number of standard color coordinate points (● marks) and evenly spaced coordinate points (○ marks) in the RGB color space.
It is a layout drawing shown dimensionally.

In this way, a number of standard color coordinate points (●) in the RGB color space that are distorted and arranged are interpolated from the C, M, and Y values of the equidistant coordinate points (marked with ○). ) Corresponding to C,
Each value of M and Y (coordinates in CMY color space) is obtained. Here, basically, certain equidistant coordinate points (marked with circles) are interpolated based on the coordinate points (marked with circles) of standard colors in four adjacent quadrangles (three-dimensionally eight cubes). It I.e.
In FIG. 6A, in order to obtain the equidistant coordinate points D, interpolation is performed based on the _five standard color coordinate points e _{1 to} e 5 in the _four quadrangles Z _{1 to} Z ₄ . In this embodiment, the RGB color space, corresponding to each of these five coordinate points e ₁ to e ₅ CM
By weighting each value of Y by the reciprocal of the distance between each of these coordinate points e _{1 to} e ₅ and the equidistant coordinate point D, each value of CMY of the equidistant coordinate point D (on the CMY color space Coordinate of) is calculated. That is, for example, C corresponding to the coordinate points e _{1 to} e ₅
When the distance between each of these coordinate points e _{1 to} e ₅ and the coordinate point D is represented by d _e1 to d _e5 , the C value C _D of the coordinate point D is expressed as C _{e1 to} C _e5. Is Is asked for. However, for example, when d _ei = 0, it is _calculated as C _D = C _ei . The same applies to M and Y. However, in reality, three-dimensional calculation is performed.

FIG. 6B is a diagram two-dimensionally showing one point J of interest among a large number of standard color coordinate points (●) and a large number of equally-spaced coordinate points (○) around this one point J. is there.

Focusing on one standard color coordinate point J, the operation of using the points e _{1 to} e ₅ in the _four quadrangles Z _{1 to} Z ₄ in order to obtain the CMY value of the point D described with reference to FIG. 6A. expressed in, (the 3-dimensional 8 points) of the point J 4 points a ₁ ~a ₄ means be used to determine the respective CMY values equally spaced coordinate point.

However, as described above, the number N of data used for interpolation included in the surrounding four quadrangles (three-dimensionally eight cubes) N (for example, points e _{1 to} e ₅ when focusing on the point D in FIG. 6A). Of five, that is, N = 5, etc., varies greatly depending on the equidistant coordinate points to be obtained, and N = 0 in the worst case (that is, N = 0).
Focusing on point D in FIG. 6A, four quadrangles surrounding Z _{1 to} Z ₄
It indicates that there is no standard color coordinate point in (three-dimensionally eight cubes). )Sometimes. in this case,
The CMY value of the equidistant coordinate points cannot be obtained,
On the finally obtained hard copy of the original image, there will be points where no color is represented (for example, if a density of 0.0 is applied as the density of the points, undesired white spots are generated in the image). .

In order to prevent such a situation from occurring, it is determined here whether or not N = 0 for each equidistant coordinate point, and N =
When there are 0 evenly spaced coordinate points, 12 quadrangles around the above four quadrilaterals Z _{1 to} Z ₄ (see FIG. 6A) (three-dimensionally, 56 radii around the above 8 cubes). CMY values of equidistant coordinate points are calculated using standard color coordinate points in a total of 16 quadrangles (64 cubes in a three-dimensional manner), including the cubes in Fig. 6B. One standard color coordinate point J shown is
Not only 4 points from a _{1 to} a ₄ but 12 points from b _{1 to} b ₁₂ (16 points in total)
It is changed to be used for the calculation of equidistant coordinate points (64 points in three dimensions). Even if this calculation method is adopted, N =
When it is 0 (that is, the CMY value of a certain equidistant coordinate point cannot be obtained), the standard color coordinate point J is used and the equidistant coordinate point C ₁ is used.
The calculation method is changed so that each point of ~ C ₂₀ is also obtained. In this way, the range of data used for interpolation is defined by the parameter α as follows.

α = a ₁ ~a _{4 (4} points) when 1 alpha = 2 〃 _{a 1 ~a 4 + b 1 ~b} 12 ( total 16 points) alpha = 3 〃 _{a 1 ~a 4 + b 1 ~b} 12 + c 1 ~ c ₁₂ (36 points in total) …………………………………… experimentally α = 4 (point J is defined by C _{1 to} C _{20 in} FIG. It has been confirmed that it is sufficient to process up to (used as the basis of calculation).

Next, a process of making a hard copy of an original image (an original image which is a basis for making a hard copy) will be described.

The RGB density of each pixel point of the original picture you want to get a hard copy is
The measurement is performed using the scanner shown in FIG. 2 used for the measurement of the standard color sample. If the characteristics of the color filters 24, 25, 26 (see Fig. 2) are different, each position of the standard color in the RGB color space will be different, so the standard color and the color of each pixel of the original image (measured color) will be accurate. In order to correspond to the above, the scanner of the same characteristic is used for the measurement of the standard color sample and the original image, and it is best to use the same scanner.

In this way, a large number of measurement points obtained from a large number of pixels of the original image are obtained in the RGB color space.

Figure 7 shows the measurement point K in the RGB color space obtained from the original image.
It is a figure showing how to calculate the value of CMY (coordinates in the CMY color space) corresponding to (x mark).

To determine the value of CMY measurement point K, the point eight values of CMY of equally spaced measuring points f ₁ ~f ₈ around the K is used, is weighted by the inverse of the distance. That is, the value of C C _f1 of each point f ₁ ~f _8, ..., expressed in C _f8, represents the distance between each point f ₁ ~f ₈ and the point K, respectively d _f1, ..., with d _f8 And C at point K
The value of D _K is Is required. However, for example, when d _fi = 0, C
_{It is calculated} as _K = C _fi . The same applies to M and Y.

In order to explain the problems that occur when the CMY values of the measurement points of the original image are obtained according to the above equation (4), the measurement points K _{1 to} K ₃ of the original image and the equidistant coordinate points g ₁ to the g ₆ illustrates a two-dimensional manner.

(4) According to the calculation method according to equation four equally spaced coordinate points g ₁ and the measurement point K ₂ as a boundary as measurement points K _1, g _2,
g _5, when in the region surrounded by Z ₅ in g _6, using the values of these four equally spaced coordinate points g _1, g _2, CMY of g _5, g ₆ (4)
The CMY value of the measurement point K ₁ is obtained according to the formula, and when it is in the area Z ₆ surrounded by the _four equally-spaced coordinate points g ₂ , g ₃ , g ₄ , g ₅ like the measurement point K ₃ , , These four equidistant coordinate points g ₂ ,
Using the CMY values of g ₃ , g ₄ , and g ₅ , measure point K according to equation (4).
A CMY value of ₃ is required. That is, when the measurement point is slightly within the area Z ₅ and slightly within the area Z ₆ with respect to the measurement point K ₂ , a considerable change may occur in the obtained CMY value. However, in this case, when a hard copy is obtained, a pseudo contour line may occur in the hard copy. Therefore, in order to solve this problem, it is preferable to use the calculation method shown below.

9A to 9C are CMs obtained from the original image and corresponding to the measurement point K (x mark) on the RGB color space, which does not cause the above problem.
It is a figure showing how to obtain the value of Y (coordinates in the CMY color space).

As shown in Fig. 9A, including measurement points K, coordinate points at equal intervals
Assuming a plane S parallel to the plane containing f ₁ , f ₂ , f ₃ , and f ₄ , equidistant coordinate points f ₁ and f ₅ , f ₂ and f ₆ , f ₃ and f ₇ , f ₄ and f The intersections of the straight line connecting ₈ and the surface S are f ₉ , f ₁₀ , f ₁₁ , f _{12 respectively.}
And the CMY values of these intersection points f ₉ , f ₁₀ , f ₁₁ , and f ₁₂ are the CMY values of f ₁ and f ₅ , f ₂ and f ₆ , f ₃ and f ₇ , f ₄ and f ₈ , respectively. Is weighted by the reciprocal of the distance and averaged. Weighting two points by the reciprocal of the distance is equivalent to the linear interpolation that is usually used.

FIG. 9B is a view showing the plane S taken out. Plane S
Assuming a straight line L passing through the measurement point K and parallel to the intersection points f ₉ and f ₁₂ , the straight line L and the intersection points f ₉ and f 12
The intersections with the straight line connecting ₁₀ and f ₁₁ and f ₁₂ are the intersections f ₁₃ and f, respectively.
₁₄ , the CMY values at these intersections f ₁₃ and f ₁₄ are obtained by weighting the CMY values at the intersections f ₉ and f ₁₀ and f ₁₁ and f ₁₂ , respectively, by the reciprocal of the distance and averaging.

FIG. 9C is a diagram showing the straight line L taken out. The CMY value at the measurement point K is obtained by weighting the CMY values at the intersections f ₁₃ and f ₁₄ by the reciprocal of the distance and averaging the values.

By such a calculation method, the CMY of the equidistant coordinate points around
By obtaining the CMY value of the measurement point K from the value of, there is no possibility that the above-mentioned pseudo contour line will occur, and the CMY value of the measurement point K can be obtained accurately.

When the CMY value of each pixel of the original image is obtained in this way, so that the CMY value of the pixel is reproduced on the photosensitive film having the same characteristics as those used to create the standard color sample,
R, G, B light is irradiated onto the photosensitive film to make a hard copy.

As described above, in the color processing method of the present invention, the CMY values of equidistant coordinate points arranged in a grid pattern in the RGB color space are obtained in advance, and when the RGB density of the original image is measured, it corresponds to the measurement points. Since the CMY values (coordinates in the CMY color space) to be calculated are obtained from eight equally spaced coordinate points in the surroundings, the calculation time is greatly shortened, and the configuration when the device that performs this calculation is configured by hardware. Is greatly simplified.

In addition, the CMY of the measurement points described with reference to FIGS. 9A to 9C are obtained by obtaining the equidistant coordinate points.
The calculation method to obtain the value of becomes possible and the discontinuous change of the CMY value at the measurement point does not occur.

Here, in the above embodiment, the reproduction system color space corresponding to the photosensitive film was the color space of the three primary colors of C, M and Y.
Are different if the characteristics of the photosensitive film are different. Also, when making a hard copy using a photosensitive film (that is, reversal film or reversal color paper etc.) that develops color on R, G, B respectively when irradiating light of R, G, B as a photosensitive film, As the reproduction system color space, the color space of the three primary colors of RGB of the photosensitive film is used. When making a hard copy by color printing, the reproduction system color space is a color space corresponding to the pigment used for the color printing. Similarly to the reproduction system color space, the measurement system color space is also variously changed according to the characteristics of the color filter of the scanner, and further, the color space corresponding to the scanner is converted by calculation, X ^OB Y ^OB Z ^OB described later. The color space, the X ^TV Y ^TV Z ^TV color space, and the like can be changed in various ways.

Next, an example in which the color processing method of the present invention is applied to obtain a hard copy of a color television image will be described.

Similar to the above embodiment, a large number of standard color samples are measured by a scanner to obtain coordinates (R, G, B) of the large number of standard colors in the RGB color space, and further the coordinates (R, G, B) are calculated. ) Is the tristimulus value (X ^OB , Y of CIE under the light source for observing hard copy).
^OB , Z ^OB ) to the formula However, (C ₁ ) is converted according to a conversion matrix, and equidistant coordinate points obtained in the RGB color space in the above embodiment are obtained in the X ^OB Y ^OB Z ^OB color space.

Color space for color TV images (X ^TV Y ^TV Z ^TV color space)
(Light emission mode) and the above X ^OB Y ^OB Z ^OB color space (reflection mode)
What is However, it has already been found that (C ₂ ) is linked by a transformation matrix (the above-mentioned Japanese Patent Application Nos. 63-43943, 63-112163, 63-112164).
No.).

Therefore, from the signal of the television image for which a hard copy is created, the point on the X ^TV Y ^TV Z ^TV color space of each pixel point of the image is obtained, and on the X ^OB Y ^OB Z ^OB color space according to the above equation (6). It is converted into a point, and the CMY value of the point is obtained from the CMY value of the equidistant coordinate points in the X ^OB Y ^OB Z ^OB color space in the same manner as in the above-mentioned embodiment.

In addition, after obtaining the coordinates of a large number of standard colors in the X ^OB Y ^OB Z ^OB color space according to the above equation (5), the inverse conversion equation of the above equation (6), that is, However, (C ₂ ′) is the coordinate of a large number of the above standard colors in the X ^TV Y ^TV Z ^TV color space according to the transformation matrix, and the equidistant coordinates arranged in a matrix in the X ^TV Y ^TV Z ^TV color space. A point is obtained, and from the point on the X ^TV Y ^TV Z ^TV color space of each pixel of the TV image that requires hard copy, C
You may make it convert directly into the point on MY color space.

As described above, the color processing method of the present invention can be widely used regardless of the emission mode or the reflection mode.

(Effects of the Invention) As described in detail above, the color processing method of the present invention is
When obtaining points in the reproduction system color space of an image that requires a hard copy, the points in the reproduction system color space of the grid-shaped coordinate points arranged in a grid in the measurement system color space should be obtained in advance. As a result, the calculation of the points on the reproduction system color space of the image is greatly simplified, the calculation time is greatly shortened, and the hardware configuration for this calculation can be greatly simplified.

Further, by obtaining the grid-like coordinate points, it is possible to employ the above-described calculation method in which pseudo contour lines do not occur on the hard copy when obtaining the coordinates in the reproduction system color space.

[Brief description of drawings]

FIG. 1 is a diagram showing a large number of standard color samples, FIG. 2 is a configuration diagram showing a schematic configuration of a scanner, and FIGS. 3A and 3B are CMY color space and RGB color of standard color samples, respectively. Figures 4A and 4B show the arrangement in space, and are schematic diagrams showing two-dimensionally the arrangement of standard color samples in the CMY color space and RGB color space, respectively. , A diagram showing a large number of evenly spaced coordinate points arranged in a matrix in the RGB color space, and FIG. 5B is a diagram showing a large number of points in the CMY color space corresponding to these many equally spaced coordinate points. , Fig. 6A is a two-dimensional layout diagram showing an example of the layout of a large number of standard color coordinate points (● marks) and evenly spaced coordinate points (○ marks) in the RGB space, and Fig. 6B shows , A point J of interest among a large number of standard color coordinate points (marked by ●) and a large number of equidistant coordinate points (marked by ○) around this point J. Dimensionally indicated figures, FIG. 7 is obtained from the original image, the measurement points on the RGB color space K
Fig. 8 shows how to obtain the CMY values (coordinates in the CMY color space) corresponding to (x). Fig. 8 shows the measurement points K _{1 to} K ₃ of the original image and the equidistant coordinate points g ₁ around them. 9A to 9C are two-dimensional diagrams of ~ g ₆ and CMY values (CMY color space) corresponding to measurement points K (x marks) on the RGB color space obtained from the original image. FIG. 10 is a diagram showing another method of obtaining the (top coordinates), and FIG. 10 is a diagram showing two-dimensionally an example of grid-shaped coordinate points. 1 ... Photosensitive film 16,17 ... Dichroic mirror 21, 22, 23 ... Photodetector

Claims (1)

[Claims] 1. A standard color coordinate point in a second color space different from the first color space of a large number of standard color samples having different colors whose coordinates on the first color space are known,
Based on the coordinates of the standard color coordinate points in the first color space, the coordinates of the first color space of a large number of grid-like coordinate points arranged in a grid in the second color space are obtained by interpolation. When obtaining the coordinates of the color to be measured on the first color space, the coordinates of the color to be measured on the second color space are obtained, and the coordinates on the first color space corresponding to the coordinates are obtained. A color processing method, wherein coordinates are obtained by interpolating from coordinates of the grid-shaped coordinate points in the first color space.