JP2014204174A - Color processing apparatus and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a profile for agreement in apparent color by preventing picture quality degradation which is caused by error in a brightness direction in isochromatic experiment.SOLUTION: A brightness/color information acquisition unit 304 acquires brightness information of reference color, brightness information of adjustment color, and color information. A personal profile generating unit 305 corrects the brightness information of adjustment color by using the brightness information of reference color, and calculates, from the brightness information of adjustment color that has been corrected and the color information of adjustment color that has been acquired, a colorimetric value after correction of adjustment color. Then, based on a first color signal and a second color signal, a colorimetric value of reference color, and the colorimetric value after correction of adjustment color, a personal profile 210 for agreement in apparent color at first and second image output apparatuses is generated.

Description

  The present invention relates to color processing for generating a profile for matching color appearance.

  Human visual sensitivity to color appearance is standardized as a color matching function by the International Commission on Illumination (CIE). This CIE color matching function is used for color matching that numerically matches the color of a matching target device (such as a monitor or a printer) and matches it numerically.

  The tristimulus values XYZ calculated by the CIE color matching function are average values of the color matching experiment results by a plurality of subjects. On the other hand, the human visual sensitivity to the color appearance varies depending on the individual, and even if the tristimulus values XYZ are matched using the CIE color matching function, the color appearance does not always match in the individual.

  Patent Document 1 proposes color conversion that takes into account the characteristics of the user's color appearance. According to Patent Document 1, an experiment for comparing a plurality of color charts with display colors on a corresponding display is performed to acquire user characteristics. Based on the characteristics obtained in the experiment, a look-up table (LUT) that converts the display display color corresponding to the user is created, and color conversion of the image using the LUT realizes color management that absorbs individual differences. To do.

  However, color comparison experiments include observer adjustment errors. Human vision has a characteristic that it is difficult to discriminate the difference in luminance as the luminance increases, and it is not possible to discriminate subtle contrast in the brightness direction. If color conversion is performed based on an experimental result including an error in the brightness direction, there is a possibility that gradation degradation occurs such that the brightness is reversed in an extreme case.

JP 2006-203622 A

  It is an object of the present invention to generate a profile for matching color appearance by preventing image quality deterioration due to an error in the brightness direction in a color matching experiment.

  The present invention has the following configuration as one means for achieving the above object.

  The color processing according to the present invention is color processing of a color processing device that generates a profile for matching the appearance of colors, and the reference color output by the first image output device based on the first color signal and the first color output. Color measurement of the first color signal, the second color signal, and the reference color when the user determines that the adjustment color output from the second image output device is the same color based on the second color signal The brightness information of the reference color is obtained from the colorimetric value of the reference color, and the brightness information of the reference color is obtained from the colorimetric value of the adjustment color. Brightness information and color information are acquired, the brightness information of the adjustment color is corrected using the brightness information of the reference color, and the brightness information of the corrected adjustment color and the color information of the acquired adjustment color are used. Calculating a colorimetric value after correction of the adjustment color, and calculating the first color signal and the second color signal. , The reference color of colorimetric values, and, and generating the profile from colorimetric values after the correction of the adjustment color.

  According to the present invention, it is possible to generate a profile for matching color appearance while preventing image quality deterioration due to an error in the brightness direction in a color matching experiment.

FIG. 3 is a block diagram illustrating an example of the configuration of an information processing apparatus used as a color processing apparatus according to an embodiment. The figure explaining a user color matching experiment. The figure explaining the structural example of the color processing apparatus which produces | generates a personal profile. The flowchart explaining a personal profile production | generation process. The figure which shows the example of a table in which the color signal and colorimetric value after a correction process were recorded. FIG. 4 is a block diagram illustrating an example of the configuration of a color processing apparatus according to a second embodiment. 9 is a flowchart for explaining personal profile generation processing according to the second embodiment. The flowchart explaining the evaluation process of a gradation evaluation part.

  Hereinafter, color processing according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Device configuration]
A configuration example of an information processing apparatus used as the color processing apparatus of the embodiment will be described with reference to the block diagram of FIG.

  The CPU 101 executes a program stored in the ROM 111 or the hard disk drive (HDD) 103 using the main memory 102 such as a RAM as a work memory, and controls a configuration to be described later via the system bus 106. Note that the ROM 111 and the HDD 103 store programs and various data for realizing color processing described later.

  An instruction input unit 107, an external storage device 108, a colorimeter 109, and the like are connected to a general-purpose interface (I / F) 104 such as USB or IEEE1394. The instruction input unit 107 is a keyboard or a mouse. The external storage device 108 is a USB memory, a memory card, an optical disk drive, a hard disk drive, or the like. The colorimeter 109 is a sensor, a digital camera, a spectral radiance meter, or the like.

  On the monitor 110 of the display device connected to the video card (VC) 105 that provides an interface such as HDMI (registered trademark), the CPU 101 displays information indicating the user interface (UI), processing progress, and processing results. Is done.

  For example, the CPU 101 loads an application program (AP) stored in the ROM 111, HDD 103 or external storage device 108 into a predetermined area of the main memory 102 in accordance with a user instruction input via the instruction input unit 107. Then, the AP is executed, and the UI is displayed on the monitor 110 according to the AP.

  Next, the CPU 101 loads various data stored in the HDD 103 or the external storage device 108 into a predetermined area of the main memory 102 in accordance with the UI operation by the user. Then, predetermined arithmetic processing is performed on various data loaded into the main memory 102 in accordance with the AP. The CPU 101 displays the calculation processing result on the monitor 110 according to the UI operation by the user, or stores it in the HDD 103 or the external storage device 108.

  The CPU 101 can also exchange programs, data, and arithmetic processing results with a server device on the network via a network I / F (not shown) connected to the system bus 106. Further, if the Internet is used as a network, it is possible to download programs and various data from a specific home page or obtain programs and various data in the form of an attached file to an e-mail.

[Color matching experiment]
In this embodiment, a personal profile is generated based on the result of a color matching experiment previously performed by the user. The user color matching experiment will be described with reference to FIG.

  FIG. 2 shows an outline of a color matching experiment using two image output devices. The first image output apparatus 201 displays a color chart (hereinafter referred to as a reference color chart) 203 that serves as a color reference by a color signal 208. The second image output device 202 is a target of color conversion processing, and displays a color chart (hereinafter referred to as an adjustment color chart) 204 as a color adjustment target by a color signal 209. The color signal adjusting device 205 is a device that adjusts the color signal 209 supplied to the second image output device 202, and includes an instruction input device 206 such as a mouse or a keyboard for adjusting the color signal 209.

  The first and second image output apparatuses are arbitrary devices that output images based on color signals, such as monitors, printers, and projectors. Further, the first image output device and the second image output device may be the same type of device or different types of devices. For example, the color chart of the printed material is used as the reference color chart 203, and the color of the adjustment color chart 204 displayed on the monitor is adjusted.

  The user adjusts the color signal 209 using the UI provided by the color signal adjustment device 205 so that the color appearance of the adjustment color chart 204 approaches the color appearance of the reference color chart 203. When it is determined that the color of the adjustment color chart 204 is equivalent to the color of the reference color chart 203, for example, a color matching button provided by the UI of the color signal adjustment device 205 for indicating that the color matching is obtained is displayed. click. When the color matching button is clicked, the color signal 208 (first color signal) and the corresponding color signal 209 (second color signal) are stored in the storage device 207 (including the HDD 103 and the external storage device 108). .

  The above color matching experiment is repeatedly performed for an arbitrary number of colors of one or more colors, and the storage device 207 stores the same number of color matching data (correspondence between the first color signal and the second color signal).

Generate profile
A configuration example of the color processing apparatus 301 that generates a personal profile will be described with reference to FIG. Note that the configuration shown in FIG. 3 is realized by the CPU 101 executing the color processing AP.

  The brightness / color information acquisition unit 304 acquires brightness information and color information in the user observation environment corresponding to the first color signal 208 and the second color signal 209 obtained in the color matching experiment. The brightness information and the color information are the first color signal 208, the second color, as the colorimetric values measured by the colorimeter 109 using the reference color chart 203 and the adjustment color chart 204 when the color matching button is clicked. Corresponding to each signal 209, it is stored in the storage device 207.

  The brightness information and the color information are displayed in advance in a color matching experiment environment (user observation environment) by displaying a reference color chart 203 and an adjustment color chart 204 corresponding to a plurality of color signals, and using them as a colorimeter 109. Is stored in the storage device 207 as a colorimetric value measured by the above. Then, the brightness / color information acquisition unit 304 may interpolate brightness information and color information corresponding to the first color signal 208 and the second color signal 209 from these colorimetric values.

  In the following description, the brightness information is assumed to be luminance Lv and the color information is assumed to be xy chromaticity. However, any colorimetric values such as L * a * b *, Luv, Jab, etc. in which brightness and color are separated may be used.

  The personal profile generation unit 305 generates a personal profile from the luminance Lv and the xy chromaticity obtained by the brightness / color information acquisition unit 304, details of which will be described later. The storage unit 306 stores the generated personal profile 210 in the storage device 207 in association with the user identification information. The color conversion unit 307 corrects the input color signal using the personal profile 210 corresponding to the user identification information stored in the storage device 207 by the storage unit 306, and converts the corrected color signal into the second image. This is supplied to the output device 202.

  The personal profile generation process will be described with reference to the flowchart of FIG. The personal profile generation process is executed by the personal profile generation unit 305 of the color processing apparatus 301.

The personal profile generation unit 305 sets an identification number (i = 1) for selecting the first color chart from the target color chart group (S401), refers to the storage device 207, and sets the identification The luminance Lv and xy chromaticity of the color chart corresponding to the number i are acquired (S402). For the i-th color chart, the luminance Lv and xy chromaticity of the reference color chart 203 output by the first image output device 201 are represented as Lv _1i , x _1i , and y _1i . Also, the user-adjusted luminance Lv and xy chromaticity of the adjustment color chart 204 output by the second image output device 202 are represented as Lv _2i , x _2i , and y _2i .

Next, the personal profile generation unit 305 sets the value of the weight coefficient k _i of the luminance Lv _1i of the reference color chart 203 for correcting Lv _2i that is the luminance of the adjusted color chart 204 after user adjustment (S403). ). The weighting factor k is 0 ≦ k _i ≦ 1. Then, to correct the Lv _2i to Lv _2i 'by the addition processing shown in Equation (1) (S404).
Lv _2i '= k _i × Lv _1i + (1-k _i ) × Lv _2i … (1)

In Expression (1), when the weighting factor k _i is increased, the ratio of Lv _1i of the reference color chart 203 in Lv _2i ′ increases, and the ratio of the luminance Lv _2i of the adjustment color chart 204 after user adjustment decreases. That is, it is equivalent to reducing the influence of the error accompanying the user adjustment. When the weight coefficient k _i = 1, the second term of the equation (1) is 0, which is equivalent to replacing Lv _2i with Lv _1i .

Although the above is an example in which the weight coefficient k _i is set for each color chart, the same weight coefficient k may be applied to all the color charts. Further, the average gain ΣLv _2i / ΣLv _1i of the brightness of the adjustment color chart 204 after the user adjustment with respect to the brightness of the reference color chart 203 from all color charts may be used for correction. Expression (2) is an expression for performing correction using a common weighting factor k and average gain.
Lv _2i '= k × Lv _1i + (1-k) × ΣLv _2i / ΣLv _1i … (2)

  Next, the personal profile generation unit 305 determines whether or not correction processing has been performed for all color charts (S405). If it has not been completed, the identification number i is incremented (S406), and the process returns to step S402. When the correction process for all color charts is completed, the process proceeds to step S407.

When the correction process for all color charts is completed, the personal profile generation unit 305 _converts the first color signal to the second color based on the correspondence between Lv _1i , x _1i , y _1i and Lv _2i ′, x _2i , y _2i . A three-dimensional LUT is generated as a personal profile for conversion to a color signal (S407).

FIG. 5 shows an example of a table in which color signals and colorimetric values after correction processing are recorded. The table includes the first color signal, the color measurement value of the reference color chart 203, the color measurement value of the adjustment color chart 204 after user adjustment and correction, and the second color signal corresponding to the color measurement value after correction. Including. The first color signal is a signal value of the reference color chart 203 and is known. When the colorimetric value of the reference color chart 203 measured by the colorimeter 109 is not an XYZ value, for example, X _1i Y _1i Z _1i is calculated from Lv _1i , x _1i , y _1i . The colorimetric value of the corrected color chart 204 after correction is calculated by the equation (3).
X _2i = Lv _2i '× x _2i / y _2i
Y _2i = Lv _2i '
Z _2i = Lv _2i '× (1-x _2i -y _2i ) / y _2i … (3)

Then, based on the known RGB-XYZ characteristics of the second image output device 202, X _2i Y _2i Z _2i is converted into a second color signal.

Further, based on the relationship between the colorimetric values X _1i Y _1i Z _{1i of} the reference color chart 203 and the corresponding X _2i Y _2i Z _2i , for example, the first color signal and the second color at a 9 × 9 × 9 RGB grid point 3DLUT is generated by calculating the correspondence of the color signal. Expression (4) is used for conversion from X ₁ 'Y ₁ ' Z ₁ 'corresponding to the interpolation value of the first color signal to X ₂ ' Y ₂ 'Z ₂ '.
X ₂ '= Σ (X _2i / X _1i ) × X ₁ ' / n
Y ₂ '= Σ (Y _2i / Y _1i ) × Y ₁ ' / n
Z ₂ '= Σ (Z _2i / Z _1i ) × Z ₁ ' / n (4)
Here, n is the number of color charts for which color matching experiments were performed.

In Equation (4), the average value of the ratio of the set of colorimetric values (X _1i Y _1i Z _1i and X _2i Y _2i Z _2i ) obtained by the color matching experiment is calculated, and X ₁ 'Y ₁ Multiply 'Z ₁ '. Then, as described above, 3DLUT is generated by converting X ₂ 'Y ₂ ' Z ₂ 'into the second color signal based on the known RGB-XYZ characteristics.

  The personal profile format is not limited to 3DLUT. For example, a gamma coefficient or matrix for converting the first color signal RGB to the second color signal R'G'B ', a conversion formula such as a gain coefficient for RGB is calculated. It may be a personal profile.

  In this way, the brightness value of the adjustment color chart 204 after the user adjustment is corrected using the brightness value of the reference color chart 203 with respect to the color matching experiment result. For this reason, it is possible to reduce the influence of errors included in the user adjustment, and it is possible to preferentially correct color information having a large characteristic difference between individuals (for example, color information of a color chart having a high luminance). As a result, it is possible to suppress image quality degradation such as gradation inversion caused by an error included in the user adjustment.

  As a result, it is possible to generate a profile for matching the color appearance while preventing image quality deterioration due to an error in the brightness direction in the color matching experiment. In other words, it is possible to reduce the influence of the adjustment error in the color matching experiment and generate a personal profile for performing color conversion that matches the visual characteristics of each individual.

  Further, when the weight coefficient value is k = 1, the brightness information of the reference color chart 203 is used as the brightness information, and only the color information is stored for each user while maintaining the brightness of the reference color chart 203. It becomes possible to correct.

  The color processing according to the second embodiment of the present invention will be described below. Note that the same reference numerals in the second embodiment denote the same parts as in the first embodiment, and a detailed description thereof will be omitted.

In the first embodiment, the brightness Lv _2i of the adjustment color chart 204 of the user color matching experiment result is corrected to Lv _2i ′ using the weighting coefficient k and the brightness Lv _1i of the reference color chart 203. In the second embodiment, an example will be described in which gradation degradation is evaluated when the user color matching experiment result is applied as it is, and the luminance Lv _2i of the adjustment color chart 204 is corrected according to the evaluation result.

  A configuration example of the color processing apparatus 301 of the second embodiment will be described with reference to the block diagram of FIG. The color processing apparatus 301 according to the second embodiment is different from the color processing apparatus 301 according to the first embodiment illustrated in FIG. 3 in that it includes a gradation evaluation unit 309 that evaluates gradation deterioration. The gradation evaluation unit 309 evaluates gradation deterioration when the personal profile generation unit 305 generates a personal profile. The personal profile generation unit 305 determines the weighting coefficient k based on the evaluation result of the gradation evaluation unit 309 so as to suppress gradation deterioration.

  The personal profile generation process according to the second embodiment will be described with reference to the flowchart of FIG. In the personal profile generation process of the second embodiment, the gradation evaluation unit 309 evaluates gradation deterioration (S411), and based on the evaluation result, the personal profile generation unit 305 determines the weighting factor k (S412), This is the same as the processing of the first embodiment shown in FIG.

  The evaluation process of the gradation evaluation unit 309 will be described with reference to the flowchart of FIG.

The gradation evaluation unit 309 interpolates the luminance Lv _2i of the adjustment color chart 204 after user adjustment, and calculates luminance values for all gradations (S801). In other words, the tone evaluation unit 309 calculates the luminance Y _i of the second color signal from the signal value of the adjusted color chart 204 after the user adjustment, for example, using equation (5).
Ri '= (Ri / 255) ^2.2 ;
Gi '= (Gi / 255) ^2.2
Bi '= (Bi / 255) ^2.2 ;
Y _i = 0.299R _i + 0.587G _i + 0.114B _i ;… (5)

For example, assuming that the luminance Y is represented by 8 bits, the gradation evaluation unit 309 converts 256 luminance values L _j (j = 0-255) corresponding to the range of Y = 0-255 to Y _i And Lv _2i are interpolated. Any interpolation method such as bilinear, bicubic, or spline may be used as the interpolation method.

Next, the gradation evaluation unit 309 sets the initial value 0 to the evaluation value E for evaluating gradation degradation (S802), sets the initial value 0 to the counter j (S803), and degrades between gradations. D is calculated by equation (6) (S804).
ΔL = L _{j + 1} -L _j ;
D = | ΔL |;… (6)

Then, the gradation evaluation unit 309 compares the degradation D with a predetermined threshold value x (S805), and determines that the degradation D is visually identified if D> x, and increments the evaluation value E ( S806). The threshold value x may be determined experimentally. Further, the threshold value x may be changed according to the target luminance Lj. For example, considering the characteristic that human vision is more difficult to discriminate brightness differences as brightness increases, use brightness L _j and coefficient m (value from 0 to 1), and use mL _j instead of threshold x May be.

  Next, the gradation evaluation unit 309 increments the counter j (S807), compares the value of the counter j with a predetermined value (255 in this example) (S808), and if j <predetermined value, the process is performed. Return to S804. If the value of the counter j reaches a predetermined value, the evaluation value E is output (S809), and the evaluation process is terminated.

The evaluation value E represents the number of gradations where deterioration (gradation reversal or gradation step) is visually identified, and the larger the value, the greater the gradation deterioration. The personal profile generation unit 305 brings the weight coefficient k closer to “1” as the evaluation value E is larger, and decreases the contribution of the luminance Lv _2i of the adjustment color chart 204 after the user adjustment. Also, when the evaluation value E is small, the weight coefficient is brought close to “0” to increase the contribution degree of the user adjustment result.

  In this way, the weight coefficient k is controlled according to the evaluation result of the gradation evaluation unit 309, and the contribution degree of the user adjustment result is changed. In other words, the degree of correction by the weight coefficient k can be controlled in accordance with the degree of image quality degradation caused by user adjustment.

[Other Examples]
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (11)

A color processing device for generating a profile for matching color appearance,
When the user determines that the reference color output from the first image output device based on the first color signal and the adjustment color output from the second image output device based on the second color signal are the same color, the first The reference color is obtained from the colorimetric value of the reference color with reference to a storage device that stores the one color signal and the second color signal, and the colorimetric value of the reference color and the colorimetric value of the adjustment color. Acquisition means for acquiring brightness information of the adjustment color and color information from the colorimetric value of the adjustment color;
The brightness information of the adjustment color is corrected using the brightness information of the reference color, and the color measurement after correction of the adjustment color is performed from the corrected brightness information of the adjustment color and the acquired color information of the adjustment color. A correction means for calculating the value;
From the first color signal and the second color signal, the colorimetric value of the reference color, and the colorimetric value after correction of the adjustment color, the color appearance in the first and second image output devices A color processing apparatus comprising: generating means for generating a profile for matching the two.   The correction means sets a weighting factor, and the result of adding the brightness information of the reference color and the brightness information of the adjustment color at a ratio according to the weighting factor is used as the brightness information of the corrected adjustment color. 2. The color processing apparatus according to claim 1, wherein And an evaluation means for evaluating gradation deterioration from the brightness information of the adjustment color,
3. The color processing apparatus according to claim 2, wherein the correction unit sets the weighting coefficient according to the evaluation result.   4. The correction means according to claim 3, wherein the weighting factor is set so that the ratio of the brightness information of the reference color increases as the evaluation result indicates that the gradation deterioration is larger. Color processing device.   2. The color processing apparatus according to claim 1, wherein the correction unit performs the correction by replacing brightness information of the adjustment color with brightness information of the reference color.   6. The color processing apparatus according to claim 1, further comprising storage means for storing the generated profile in association with user identification information in the storage device.   7. The color according to claim 1, further comprising color conversion means for color-converting a color signal supplied to the second image output device using the profile. Processing equipment.   8. The color processing apparatus according to claim 7, wherein the color conversion unit performs the color conversion using a profile related to user identification information.   2. The profile according to claim 1, wherein the profile is for matching an individual's color appearance in the second image output device with an appearance of the individual color in the first image output device. The color processing apparatus according to claim 8. A color processing method of a color processing apparatus that includes an acquisition unit, a correction unit, and a generation unit, and generates a profile for matching the appearance of colors,
When the user determines that the reference color output from the first image output device based on the first color signal and the adjustment color output from the second image output device based on the second color signal are the same color, the first The acquisition means for referring to a storage device that stores one color signal and the second color signal, and the colorimetric value of the reference color and the colorimetric value of the adjustment color, from the colorimetric value of the reference color Obtaining brightness information of the reference color, obtaining brightness information and color information of the adjustment color from a colorimetric value of the adjustment color,
The correction means corrects the brightness information of the adjustment color using the brightness information of the reference color, and from the brightness information of the corrected adjustment color and the acquired color information of the adjustment color, Calculate the colorimetric value after correction,
The generation unit generates the profile from the first color signal and the second color signal, the colorimetric value of the reference color, and the colorimetric value after correction of the adjustment color. Color processing method.   10. A program for causing a computer to function as each unit of the color processing device according to claim 1.

Images