JP2008236465A - Profile creating apparatus and profile creation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To create a profile of a display device that performs superior color matching. <P>SOLUTION: A profile creating apparatus comprises a colorimeter for performing colorimetry of a screen of a display device; an evaluation image storage means, prestored with an image for evaluation defined by a control value of the display device; a profile storage means for storing a profile; a measurement data storing means for storing the measurement data of the colorimeter; a means which reads the image for evaluation and displays the read image on the display device; a means which inputs the colorimetric value of the screen of the display device measured by the colorimeter and stores the input colorimetric value into the measurement data storage means, in a state where the image for evaluation is displayed on the display device; a means which calculates the coefficient of a color reproduction model from the colorimetric value stored in the measurement data storage means; a means for calculating the error between the colorimetric value and a predictive value, obtained by the color reproduction model; a means for calculating an approximate curve for approximating the error; and a means which creates the profile defining a relationship between the device control value of the display device and the colorimetric value, on the basis of the approximate curve. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, when displaying an image on a display device such as a display or projector, the relationship between the device control value and the colorimetric value in consideration of the color reproduction characteristic of the display device so as to achieve the intended image display, the measurement conditions, etc. The present invention relates to a profile creation apparatus and a profile creation method for creating a described profile.

  When an image is displayed on a display device, color matching is generally performed so that an intended reproduction color can be displayed. What is required when performing color matching is a file that describes the relationship between device control values and colorimetric values, which are called profiles, and data such as measurement conditions. This information must be accurately described in this profile. Thus, good color matching is realized.

ここで、Ｘ_{ｒ，ｍａｘ}，Ｘ_{ｇ，ｍａｘ}，Ｘ_{ｂ，ｍａｘ}，Ｙ_{ｒ，ｍａｘ}，Ｙ_{ｇ，ｍａｘ}，Ｙ_{ｂ，ｍａｘ}，Ｚ_{ｒ，ｍａｘ}，Ｚ_{ｇ，ｍａｘ}，Ｚ_{ｂ，ｍａｘ}はＲｅｄ，Ｇｒｅｅｎ，Ｂｌｕｅチャンネルの最大発光時の三刺激値であり、Ｒ’，Ｇ’，Ｂ’はデバイス三刺激値である。 Conventionally, a CRT (CathodeRayTube) monitor has been widely used as a display device. However, in a CRT, a TRC (ToneReproductionCurve) / Matrix model (for example, see Non-Patent Document 1) or a GOG (Gain, Offset, Gamma) model (for example, By using a color reproduction model called “Non-patent Document 2”, it is possible to describe device characteristics with high accuracy. The color reproduction model in the CRT monitor is expressed by the following equation (1), where the tristimulus values of the reproduced color are X, Y, and Z.

Here, _{Xr, max} , _{Xg, max} , _{Xb, max} , _{Yr, max} , _{Yg, max} , Yb _{, max} , _{Zr, max} , _{Zg, max} , Zb _{, max} are Red, The tristimulus values at the time of maximum light emission of the Green and Blue channels are the device tristimulus values.

ここで、ｋ_ｇ，ｒ，ｋ_ｇ，ｇ，ｋ_ｇ，ｂは、Ｒｅｄ，Ｇｒｅｅｎ，Ｂｌｕｅチャンネルのゲイン値、ｋ_ｏ，ｒ，ｋ_ｏ，ｇ，ｋ_ｏ，ｂはＲｅｄ，Ｇｒｅｅｎ，Ｂｌｕｅチャンネルのオフセット値、ｎは、デバイスの表示ビット数、ｄ_ｒ，ｄ_ｇ，ｄ_ｂはデバイス制御値、γ_ｒ，γ_ｇ，γ_ｂはＲｅｄ，Ｇｒｅｅｎ，Ｂｌｕｅチャンネルのガンマ値である。 The device tristimulus values R ′, G ′, and B ′ in the equation (1) are expressed by the equation (2), and are equations that assume a nonlinear relationship with the device control value.

Here, k _{g, r} , k _{g, g} , k _{g, b} are the gain values of the Red, Green, Blue channel, and k _{o, r} , k _{o, g} , k _{o, b} are the Red, Green, Blue channel. offset value, n is the number of display bits of the _{device, d r, d g, d} b is the device control value, gamma _r, gamma _g, the gamma _b Red, Green, a gamma value of Blue channel.

  In the equation (1), tristimulus values corresponding to the maximum light emission time of each channel (device control value is 255 for 8-bit CRT) are used as matrix components. By using the tristimulus values at the maximum light emission of each channel as the matrix components, it is assumed that the chromaticity reproduced by the device control values is unchanged. Further, the tristimulus values X, Y, and Z of reproduced colors in the equation (1) are obtained from the sum of values obtained by multiplying the X, Y, and Z components of each channel and the device tristimulus values. That is, it is assumed that the additivity of each channel is established for the reproduced colors X, Y, and Z.

In the CRT, the above three assumptions hold well, and the color reproduction characteristics of the device can be satisfactorily described by a color reproduction model such as a TRC / Matrix model.
SpecificationICC.1: 2004-10 (Profileversion4.2.0.0) RS.Bernsetal., `` CRTColorimetry.PartI: TheoryandPractice '' ColorRes.Appl., 18,299-314 (1993)

  However, in other types of display devices (for example, liquid crystal displays) and display devices such as projectors, the above assumptions do not hold, and a color reproduction model that can describe the color reproduction characteristics of a CRT monitor such as a TRC / Matrix model is used. When a profile is created, there is a problem that the color reproduction characteristics of the device may not be described with sufficient accuracy.

  The present invention has been made in view of such circumstances, and a characteristic that does not satisfy the additiveity of the display when creating a profile that describes the relationship between the device control value and the colorimetric value of the display device, the measurement conditions, and the like. In view of the above, it is an object to provide a profile creation device and a creation method for improving the color reproduction characteristic description accuracy of a profile and performing better color matching.

  The present invention relates to a colorimeter that performs colorimetry on the screen of a display device for which a profile is to be created, evaluation image storage means in which an evaluation image defined by a control value of the display device is stored in advance, and stores the profile. Display control for reading out the evaluation image stored in the profile storage means, the measurement data storage means for storing the measurement data of the colorimeter, and the evaluation image storage means and displaying the evaluation image on the display device And measurement data stored in the measurement data storage means by inputting the colorimetric value of the screen of the display device measured by the colorimeter while the evaluation image is displayed on the display device Input means; model coefficient calculating means for calculating a coefficient of a color reproduction model from the colorimetric values stored in the measurement data storage means; the colorimetric values; Model error calculating means for calculating an error from a predicted value based on a reproduction model, approximate curve calculating means for calculating an approximate curve for approximating the error, and a device control value for the display device based on the approximate curve And a profile creating means for creating a profile defining the relationship between the colorimetric values.

  The present invention provides an extreme value calculation means for obtaining an extreme value of an approximate curve obtained by the approximate curve calculation means, and an evaluation image generation for generating a new evaluation image using a device control value at which the error becomes an extreme value The measurement data input means inputs a colorimetric value when the newly generated image for evaluation is displayed on the display device and measured, and the model error calculation means An error of the colorimetric value is calculated, the approximate curve calculation means calculates a new approximate curve by adding a new error, and the profile creation means creates the profile based on the new approximate curve. Features.

  The present invention relates to a colorimeter that performs colorimetry on the screen of a display device for which a profile is to be created, evaluation image storage means in which an evaluation image defined by a control value of the display device is stored in advance, and stores the profile. A profile creation method in a profile creation device comprising profile storage means and measurement data storage means for storing measurement data of the colorimeter, wherein the evaluation image stored in the evaluation image storage means is read out, A display control step for displaying the evaluation image on the display device; and a colorimetric value of the screen of the display device measured by the colorimeter in a state where the evaluation image is displayed on the display device. A measurement data input step to be stored in the measurement data storage means, and a colorimetric value stored in the measurement data storage means. A model coefficient calculating step for calculating a coefficient of a color reproduction model, a model error calculating step for calculating an error between the colorimetric value and a predicted value based on the color reproduction model, and an approximate curve for approximating the error. An approximate curve calculating step for calculating, and a profile creating step for creating a profile defining a relationship between a device control value and a colorimetric value of the display device based on the approximate curve.

  The present invention provides an extreme value calculation step for obtaining an extreme value of the approximate curve obtained by the approximate curve calculation means, and an evaluation image generation for generating a new evaluation image using a device control value at which the error becomes an extreme value The measurement data input step inputs a colorimetric value when the newly generated image for evaluation is displayed on the display device and measured, and the model error calculation step An error of a colorimetric value is calculated, the approximate curve calculating step calculates a new approximate curve by adding a new error, and the profile creating step creates the profile based on the new approximate curve It is characterized by.

  According to the present invention, when creating a profile that describes the relationship between the device control value and the colorimetric value of the display device, the measurement conditions, and the like, the color reproduction of the profile is taken into account by taking into account the characteristics that cause the additiveness of the display to fail There is an effect that it is possible to easily create a profile for realizing good color matching with improved characteristic description accuracy.

  Hereinafter, a profile creation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, reference numeral 1 denotes a control unit that controls the overall processing operation of the profile creation apparatus, and is configured from a personal computer or the like. Reference numeral 2 denotes an input unit composed of a keyboard or the like. Reference numeral 3 denotes a display device (display device) for which a profile is to be created. Reference numeral 4 is a colorimeter that measures the color of the display image of the display device 3, starts measurement by a control signal from the control unit 1, and outputs measurement data obtained as a result to the control unit 1. Reference numeral 11 denotes a coefficient calculation unit that calculates the coefficient of the color reproduction model from the measurement data (colorimetric value) of the measured evaluation image. Reference numeral 12 denotes an error calculation unit that calculates the difference between the measured colorimetric value of the evaluation image and the predicted value of the color reproduction model. Reference numeral 13 denotes an approximate curve calculation unit that calculates an approximate curve (including an approximate line) for an error in the calculated color reproduction model. Reference numeral 14 denotes an evaluation image storage unit in which evaluation image data is stored in advance. Reference numeral 15 denotes a measurement data storage unit that stores measurement data (colorimetric values) obtained by the colorimeter 4. Reference numeral 16 denotes a profile storage unit that stores the created profile data.

  Next, with reference to FIG. 2, an operation of creating a profile in consideration of characteristics that cause non-additivity of the display device in the profile creation apparatus shown in FIG. 1 will be described. First, the worker creates an evaluation image and stores it in the evaluation image storage unit 14. When creating an evaluation image, the device control value (in the range of 0 to 255 if 8-bit) is specified, but the primary color of each channel (for example, for the Red channel, dr is used for model coefficient calculation). In the range of 0 to 255, the image is changed by 15 steps, dg = db = 0), and any of the secondary colors (dr, dg, db) is 0 to verify the accuracy of the model. , Dr = dg = 0-255, changing by 15 steps, db = 0) and tertiary colors (dr, db, db are not 0), for example, dr = dg = db = 0-255 The image is created in steps of 15). When the operator operates the input unit 2 to instruct the selection of the evaluation image and the start of measurement of the colorimetric value, the control unit 1 reads predetermined evaluation image data from the evaluation image storage unit 14 (step S1). The read evaluation image data is displayed on the display device 3 (step S2).

  Next, the control unit 1 instructs the colorimeter 4 to measure the color of the evaluation image displayed on the screen of the display device 3 in a state where the evaluation image is displayed (step S3). Then, the measurement data (colorimetric value) output from the colorimeter 4 is read, and this measurement data is stored in the measurement data storage unit 15 (step S4). The control unit 1 repeats the operations of steps S1 to S4 for the number of evaluation images stored in the evaluation image storage unit 14, thereby measuring the colorimetric values for all the evaluation images and storing the measurement data. Store in unit 15. As a result, the same number of colorimetric values as the number of evaluation images stored in the evaluation image storage unit 14 are stored in the measurement data storage unit 15.

  Next, the coefficient calculation unit 11 reads out the colorimetric values stored in the measurement data storage unit 15 and calculates the coefficients of the color reproduction model from the colorimetric values using the above-described equation (1). Hold (step S5). Then, the error calculation unit 12 calculates a difference (error) between the predicted value of the color reproduction model using the previously calculated model coefficient and the colorimetric value for the secondary color and the tertiary color stored in the measurement data storage unit 15. (Step S6). For example, FIG. 4 shows an error between the predicted value of the tristimulus value Y and the measurement data of the color reproduction model in the secondary color Yellow (dr = dg, db = 0) and Black (dr = dg = db = 0). In the figure, the vertical axis represents an error of measurement data with respect to a predicted value based on the color reproduction model, and the horizontal axis represents a device control value (in the case of 8 bits). Similarly, FIGS. 5, 6, and 7 illustrate the secondary colors Cyan (dd = db, dr = 0), Magenta (dr = db, dg = 0), the tertiary color Gray (dr = dg = db), and Black, respectively. It is a figure which shows the difference | error of the predicted value of the tristimulus value Y of the color reproduction model in, and measurement data.

  Next, the approximate curve calculation part 13 calculates | requires an approximate curve based on the calculated | required error value (step S7). For example, the broken lines in FIGS. 4 to 7 are approximate curves obtained from the calculated error values. This approximate curve may be an approximate line depending on the value from which the approximate curve is obtained. Subsequently, the approximate curve calculation unit 13 calculates the maximum value, minimum value, or extreme value (maximum value, minimum value) of the obtained approximate curve (step S8).

  Next, the control unit 1 calculates data for profile creation from the calculated maximum value, minimum value, or extreme value, and device control values 0 and 255. For example, in the example shown in FIG. 4, a value that is an intermediate value between the device control value 0 and the device control value 50 is calculated based on the minimum value of the error (step S9). Then, the control unit 1 includes a device control value and a colorimetric value (sum of a colorimetric value and a predicted error in a color reproduction model obtained from the device control value) based on the obtained approximate curve, and a measurement data storage unit 15. A CLUT (Color LookUp Table) type profile is created using the device control value and the colorimetric value stored respectively in FIG. The control unit 1 stores the profile data created here in the profile storage unit 16 (step S10).

  In this way, when creating a profile that describes the relationship between the device control value and colorimetric value of the display device, the measurement conditions, etc., the color reproduction characteristic description of the profile is taken into account by taking into account the characteristics that cause non-additivity of the display. It is possible to easily create a profile for realizing good color matching with improved accuracy. In particular, since the profile is created based on the maximum value, the minimum value, or the extreme value, a highly accurate profile can be created with the minimum necessary measurement.

  Next, a modification of the profile creation operation shown in FIG. 2 will be described with reference to FIG. 3 that are the same as those shown in FIG. 2 are denoted by the same reference numerals (steps S1 to S9), and description thereof is omitted. The operation shown in FIG. 3 is different from the operation shown in FIG. 2 in that new steps S11 to S15 are provided instead of step S10. After calculating the profile creation data (approximate curve) (step S9), the control unit 1 generates a device control value image of the profile creation data based on the profile creation data (step S11). This image is displayed on the display device 3 (step S12).

  Next, the control unit 1 instructs the colorimeter 4 to measure the color of the evaluation image displayed on the screen of the display device 3 while the evaluation image is displayed (step S13). Then, the measurement data (colorimetric value) output from the colorimeter 4 is read, and this measurement data is stored in the measurement data storage unit 15 (step S14). And the control part 1 repeats the step of step S11-S14 by the number of the produced | generated images.

  Next, the control unit 1 creates a CLUT (Color LookUp Table) type profile based on the device control value and the colorimetric value stored in the measurement data storage unit 15, respectively. It memorize | stores in the memory | storage part 16 (step S15).

  Here, the details of the operation shown in FIG. 3 will be described with reference to FIG. FIG. 8 is a diagram in which error values are plotted for each device control value as shown in FIGS. In this figure, symbols P1 to P8 are error values based on the actual measurement values, and symbol C1 is an approximate curve for the error of the actual measurement values. Symbols P9 and P10 are error values based on the calculated values obtained by calculation at the extreme values of the approximate curve. The control unit 1 obtains device control values corresponding to the calculated values P9 and P10 from the approximate curve, generates an image of the device control value obtained here, and displays it on the display device 3. The error value between the actual measurement value measured by the colorimeter 4 when this image is displayed and the predicted value of the color reproduction model using the previously calculated model coefficient becomes the code P11 and the code P12. If necessary, an approximate curve C2 including these values may be created to calculate profile creation data.

  Note that, when the actual measurement value is obtained based on the extreme value obtained from the approximate curve, as shown in FIG. 9, whether or not the actual measurement value is to be obtained is determined according to the magnitude of the difference between the actual measurement value and the predicted value. It may be determined to determine whether or not to perform an actual measurement operation. That is, as shown in FIG. 9A, the difference ΔV between the measured value closest to the maximum value (here, measured value P1) and the maximum value is smaller than a predetermined threshold value (ΔV <threshold value). ), A profile is created from the approximate curve without actual measurement. On the other hand, as shown in FIG. 9B, the difference ΔV between the measured value closest to the maximum value (here, measured value P2) and the maximum value is larger than a predetermined threshold value (ΔV> threshold value). ), The actual value is measured and the maximum value is actually measured. By doing so, it is possible to omit a wasteful process of actually measuring the maximum value (or the minimum value) even though the accuracy is not improved so much, and the profile creation time can be shortened. Further, when there are two or more local maximum values or local minimum values in the approximate curve, it may be determined whether to perform actual measurement by performing determination using a threshold value for each.

  As described above, since the value obtained from the approximate curve can be corrected by the actually measured value, the accuracy of the profile data can be improved. In particular, since the extreme values are actually measured, the accuracy can be improved efficiently.

  In the above description, an example in which the prediction accuracy is corrected using the color reproduction model of equation (1) has been described. However, the present invention is not limited to this, and a color reproduction model that describes the color reproduction characteristics of other display devices. May be used. Further, although the tristimulus value Y is used for calculating the difference (error) between the predicted value of the color reproduction model and the colorimetric value of the evaluation data, the present invention is not limited thereto, and other colorimetric values may be used. Further, in calculating the difference (error) between the predicted value of the color reproduction model and the colorimetric value of the evaluation data, the secondary colors Yellow (dr = dg, db = 0), Cyan (dg = db, dr = 0), Magenta (dr = db, dg = 0) and tertiary color Gray (dr = dg = db) were used, but not limited thereto, and dr = 0, dg = 128, and only db ranges from 0 to 255. Alternatively, a secondary color that changes in the above range, a tertiary color that is constant at dr = dg = 128, and only db changes in the range of 0-255 may be used.

  Further, the profile creation process described above can be applied to creation of a profile of a display device such as a liquid crystal display, a plasma display, or a projector.

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

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

It is a block diagram which shows the structure of one Embodiment of this invention. It is a flowchart which shows operation | movement of the profile creation apparatus shown in FIG. It is a flowchart which shows operation | movement of the profile creation apparatus shown in FIG. It is an example of the error calculation of the model of the secondary color Yellow by this invention, and the calculation of an approximate line or an approximate curve. It is an example of the error calculation of the secondary color Cyan model by this invention, and the calculation of an approximate line or an approximate curve. It is an example of the error calculation of the secondary color Magenta model by this invention, and the calculation of an approximate line or an approximate curve. It is an example of the error calculation of the tertiary color Gray model by this invention, and the calculation of an approximate line or an approximate curve. It is explanatory drawing which shows the operation | movement which produces | generates profile data from an approximated curve. It is explanatory drawing which shows the operation | movement which determines whether the maximum value is calculated | required.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Control part, 11 ... Coefficient calculation part, 12 ... Error calculation part, 13 ... Approximation curve calculation part, 14 ... Evaluation image storage part, 15 ... Measurement data storage part, 16 ... Profile storage unit, 2 ... Input unit, 3 ... Display device (display device), 4 ... Colorimeter

Claims (4)

A colorimeter that performs color measurement on the screen of the display device for profile creation;
Evaluation image storage means in which an image for evaluation defined by the control value of the display device is stored in advance;
Profile storage means for storing the profile;
Measurement data storage means for storing measurement data of the colorimeter;
Display control means for reading out the evaluation image stored in the evaluation image storage means and displaying the evaluation image on the display device;
Measurement data input means for inputting the colorimetric value of the screen of the display device measured by the colorimeter and storing it in the measurement data storage means in a state where the evaluation image is displayed on the display device. ,
Model coefficient calculation means for calculating a coefficient of a color reproduction model from the colorimetric values stored in the measurement data storage means;
Model error calculating means for calculating an error between the colorimetric value and the predicted value based on the color reproduction model;
An approximate curve calculating means for calculating an approximate curve for approximating the error;
A profile creation device comprising profile creation means for creating a profile defining a relationship between a device control value and a colorimetric value of the display device based on the approximate curve. Extreme value calculation means for obtaining an extreme value of the approximate curve obtained by the approximate curve calculation means;
Evaluation image generation means for generating a new evaluation image using a device control value at which the error becomes an extreme value,
The measurement data input means inputs a colorimetric value when the newly generated image for evaluation is displayed on the display device and measured,
The model error calculation means calculates an error of a new colorimetric value,
The approximate curve calculation means calculates a new approximate curve by adding a new error,
The profile creating apparatus according to claim 1, wherein the profile creating unit creates the profile based on a new approximate curve. A colorimeter for colorimetrically measuring the screen of a display device to be profiled; an evaluation image storage means in which an evaluation image defined by a control value of the display device is stored in advance; and a profile storage means for storing the profile A profile creation method in a profile creation device comprising measurement data storage means for storing measurement data of the colorimeter,
A display control step of reading the evaluation image stored in the evaluation image storage means and displaying the evaluation image on the display device;
A measurement data input step of inputting a colorimetric value of the screen of the display device measured by the colorimeter and storing it in the measurement data storage means in a state in which the evaluation image is displayed on the display device; ,
A model coefficient calculation step for calculating a coefficient of a color reproduction model from the colorimetric values stored in the measurement data storage means;
A model error calculating step for calculating an error between the colorimetric value and a predicted value based on the color reproduction model;
An approximate curve calculating step of calculating an approximate curve for approximating the error;
A profile creation method comprising: creating a profile defining a relationship between a device control value and a colorimetric value of the display device based on the approximate curve. An extreme value calculating step for obtaining an extreme value of the approximate curve obtained by the approximate curve calculating means;
An evaluation image generation step of generating a new evaluation image using a device control value at which the error becomes an extreme value;
The measurement data input step inputs a colorimetric value when the newly generated image for evaluation is displayed on the display device and measured,
The model error calculating step calculates an error of a new colorimetric value,
In the approximate curve calculating step, an approximate curve is calculated again by adding a new error,
The profile creation method according to claim 3, wherein the profile creation step creates the profile based on a new approximate curve.

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