JP2008306391A - Color processing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare color correction data in which a calculated value and an apparent color match. <P>SOLUTION: The image data of a color patch are output to a display device (S202), and the measured value of the spectral radiance of the color patch displayed by the display device is input (S203). Then, a colorimetric value is calculated from the measured value using a color-matching function (S206), a correction color-matching function is calculated (S207) and the colorimetric value is corrected using the correction color-matching function (S209). Then, the color correction data are prepared using the image data of the color patch and the corrected colorimetric value (S212). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to color processing for creating color correction data.

  In recent years, liquid crystal displays, liquid crystal projectors, and plasma displays have been widely used as display devices in place of CRT displays.

  These displays are used not only for screens as color television receivers, but also for business use such as presentations, and the opportunity to display image data edited on a computer device (PC) has increased.

  The CRT display has a huge glass tube. An electron gun is disposed at the rear end of the vacuum tube, and a phosphor that emits light by collision of electrons is applied to the inside of the front surface of the vacuum tube. This is a mechanism in which an electron beam is generated by applying a high voltage of tens of thousands of volts to an electron gun, and electrons are collided with a phosphor to emit light. In particular, in the case of a color CRT, a color image is displayed using three electron guns corresponding to red (R) light, green (G) light, and blue (B) light.

  In a plasma display, two glass plates attached with electrodes are stacked in parallel, and a rare gas is injected into the gap between the glass plates. Thousands of small chambers (cells) are formed on the rear glass plate by partitions, and phosphors of R, G, and B are respectively applied to the cells. When a voltage is applied to this small cell, gas discharge occurs between the electrodes, and ultraviolet rays are generated. The ultraviolet rays are irradiated to the phosphors R, G, and B of the cell, and the phosphors emit light in the visible light range.

  The structure of the liquid crystal projector varies, but for example, the light from the lamp for the light source is split into R light, G light, and B light and then incident on the polarizing plate. The light that has passed through the polarizing plate is incident on each of the R, G, and B liquid crystal panels. Then, by adjusting the output light amount of each of R, G, and B according to the primary color video signal by the polarization action of each liquid crystal panel, and expanding and projecting the combined light of these lights onto the screen, a color image is displayed on the screen. Form.

  Any of the above display devices is a system that displays a desired color by changing the ratio of R light, G light, and B light to mix colors.

  Luminance is an important index representing the specifications of these display devices. Each manufacturer has made various efforts to improve the luminance. For example, since G has the spectral wavelength that most affects the luminance of RGB, the luminance is improved by enhancing G emission of RGB.

  However, if G light emission is enhanced to obtain high brightness, the color reproduction of the display device shifts in the G direction as a whole on the device-independent colorimetric values, which may cause inconveniences in color management. is there. For example, like a uniform color space such as Lab, the method of converting the entire color reproduction information into a psychophysical quantity based on the white color having the brightest value of the device, the color of the dark part from the middle is more in the R direction than it looks. Will be converted to a value. Therefore, when color reproduction is managed using a normal colorimetric value and a color management system (CMS) of a display device, there is a problem that the calculated value does not match the apparent color.

  In order to avoid this problem, appearance models such as CIECAM02 have been proposed in which human visual adaptation is modeled. However, in order to use the appearance model, it is necessary to prepare a plurality of parameters such as the environment representing the adaptation state, the adaptation brightness of the usage state, and the background color, and complex color processing using a mathematical model is required. In other words, color management using an appearance model can only be performed by a color manager who has a deep knowledge of color adaptation and color reproduction, and is virtually impossible for consumers who do not have such knowledge. I can say that.

  The problem that the calculated color does not match the apparent color is caused by using a constant color matching function without considering the human adaptation state when calculating the colorimetric value. Therefore, in order to solve the above problem, a technique for easily correcting the colorimetric values based on the human adaptation state is required.

JP 2000-050086 JP

  An object of the present invention is to create color correction data in which a calculated value matches an apparent color.

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

  The color processing according to the present invention outputs image data of a color patch to a display device, inputs a measurement value of spectral radiance of the color patch displayed by the display device, and uses the color matching function to calculate the color patch from the measurement value. Calculate a colorimetric value, calculate a corrected color matching function, correct the colorimetric value using the corrected color matching function, and use the image data of the color patch and the corrected colorimetric value, Color correction data is created.

  According to the present invention, it is possible to create color correction data in which the calculated value matches the apparent color.

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

[Device configuration]
FIG. 1 is a block diagram illustrating a configuration example of the color processing apparatus 100 according to the first embodiment.

  The CPU 101 executes an operating system (OS) and various software stored in the ROM 108 and the hard disk drive (HDD) 105 using the RAM 102 as a work memory. Then, the configuration described later is controlled via the system bus 112, and color processing described later is executed.

  A serial ATA (SATA) interface (I / F) 103 is an interface connecting the HDD 105 and the system bus 112. The network I / F 104 is an interface that connects the network 113 and the system bus 112. The graphic accelerator 106 is an interface that connects the display 107 and the system bus 112. The USB (universal serial bus) I / F 109 is an interface that connects the system bus 112 to devices such as a keyboard 110, a mouse 111, and a measuring instrument 114 such as a spectral radiance meter connected to the serial bus.

[Color processing]
When the OS is started by the CPU 101, a user interface (UI) is displayed on the display 107. The user operates the keyboard 110 and the mouse 111 to instruct execution of the measurement application program (AP) stored in the HDD 105 via the UI. The OS that has input this user instruction causes the CPU 101 to activate the measurement AP specified by the user.

  Further, the user operates the measuring instrument 114 to enable measurement of the color patch image displayed on the display 107.

  FIG. 2 is a flowchart showing an example of measurement processing by the measurement AP.

  In this embodiment, RGB single color signals held in the HDD 105 or the like are sequentially displayed on the display 107 and measured, and brightness correction is performed according to the measurement result. Then, color correction data (for example, a color correction profile) is created based on the brightness corrected measurement value.

  The measurement AP displays a UI, which will be described later, and receives designation of a measurement color file and an output file from the user (S200). Then, RGB data of a plurality of RGB single color patches (hereinafter referred to as patch data) is loaded into a predetermined area of the RAM 102 from the measurement color file stored in the HDD 105 (S201). The patch data may be acquired from a server connected to the network 113 or a server on the Internet.

  When instructed to create color correction data, the measurement AP supplies one piece of patch data stored in the RAM 102 to the graphic accelerator 106 (S202). The graphic accelerator 106 transmits patch data (or an analog video signal obtained by D / A conversion) to the display 107, and causes the display 107 to display a color patch image.

  The measurement AP instructs the measurement device 114 to measure the color patch image, inputs the measurement value (spectral radiance data) output from the measurement device 114, stores it in the HDD 105 (S203), and terminates the measurement from the measurement device 114. Step S203 is repeated until the indicated signal is received. When a signal indicating the end of measurement is received from the measuring instrument 114 (S204), it is determined whether or not the measurement corresponding to all patch data has been completed (S205). If the measurement has not been completed, the process returns to step S202, and steps S202 to S204 are repeated until the measurement corresponding to all patch data is completed.

When the measurement is completed, the measurement AP calculates an XYZ value for each patch data from the measurement value stored in the HDD 105 according to the equation (1) (S206).
Xi = K∫Ei (λ) x (λ) dλ
Yi = K∫Ei (λ) y (λ) dλ (1)
Zi = K∫Ei (λ) z (λ) dλ
Where Ei (λ) is the spectral radiance data for the i-th patch data,
x (λ) y (λ) z (λ) is the color matching function,
λ is wavelength,
K = 683 (constant),
Integration range is λ = 400 ~ 700nm

Next, a corrected color matching function y ′ (λ) of y (λ) is calculated from equation (2) (S207). Here, the luminance value of the G single color patch is G.
y '(λ) = {1-log (G / 255)} ^1/3 × y (λ)… (2)

Next, the measurement AP calculates a correction Y value Yi ′ using the correction color matching function y ′ (λ) (S208).
Yi '= K∫Ei (λ) y' (λ) dλ (3)

Next, the measurement AP performs luminance correction according to equation (4) (S209).
Xi "= Xi ・ Yi / Yi '
Yi "= Yi… (4)
Zi "= Zi ・ Yi / Yi '

  The measurement AP determines whether or not the processing of steps S206 to S209 has been completed for all patch data (S210). If the process has not been completed, the process returns to step S206, and steps S206 to S209 are repeated until the process corresponding to all patch data is completed.

  When the calculation of the brightness correction value X "Y" Z "of all patch data is completed, the measurement AP calculates color correction data (for example, color correction) from the RGB value of the patch data and the corresponding brightness correction value X" Y "Z". Profile) is created (S211). Then, the color correction data with the output file name designated by the user is stored in a predetermined area such as the HDD 105 (S212), and the process is terminated. Thereafter, the color processing apparatus 100 or an apparatus that displays an image on the display 107 uses the color correction data created in step S211 to perform color correction on the image data to be output to the display 107, thereby reproducing the color of the display 107. to manage.

  When the display 107 is enhanced in G emission to obtain high brightness, the color reproduction of the display 107 is generally shifted in the green (G) direction on the device-independent measurement. Therefore, a correction color matching function is calculated by correcting the appearance amount of the visual G component, and the XYZ values (colorimetric values) of the color patches are corrected. That is, the colorimetric value near the high luminance is corrected, and the colorimetric value can be adjusted to the actual appearance. As a result, the above-described problem that the calculated value (colorimetric value) does not match the apparent color can be solved by using a color matching function that takes into account the human adaptation state when calculating the colorimetric value. .

● UI
FIG. 3 is a diagram illustrating an example of a UI displayed by the measurement AP in step S200.

  The user presses the measurement color file designation button 303 to designate a file in which the RGB values of the color patches are described. In response to this designation, the measurement AP reads the measurement color file and displays a list of measurement value Nos and RGB values of the color patches in the window 301.

  When the user operates the scroll bar 302 to scroll the list display of the window 301 and selects any measurement color No, the display of the measurement color No is reversed. When the user presses the measurement color edit button 304 with the measurement color No selected, the dialog shown in FIG. 4 is displayed. The user can operate the dialog shown in FIG. 4 to add or delete color patches, and correct RGB values.

  The user presses an output file specification button 305 to specify the storage destination, path name, file name, and the like of the color correction data created by the measurement AP.

  Further, when the user presses the profile creation button 306, the measurement AP passes through the processing from step S201. The end button 307 is a button for ending the measurement AP.

  FIG. 5 is a state transition diagram illustrating the operation of the measurement AP.

  When activated, the measurement AP performs initial processing such as displaying the UI shown in FIG. 3 (S501), and enters a user operation waiting state (S502).

  When the user presses the measurement color file designation button 303, the measurement AP performs measurement color file designation processing (S504), reads the measurement color file (step S201 processing), and returns to the operation waiting state (S502).

  When the user operates the scroll bar 302, the measurement AP performs display scroll processing (S503), scrolls the list display of the window 301, and returns to the operation waiting state (S502).

  When the user presses the measurement color edit button 304, the measurement AP performs setting update processing (S506), displays the dialog shown in FIG. 4, and accepts the addition, deletion, and correction of RGB values of color patches. Then, the process returns to the operation waiting state (S502).

  When the user presses the output file designation button 305, the measurement AP performs output file designation processing (S505) and returns to the operation waiting state (S502).

  When the user presses the profile creation button 306, the measurement AP performs the measurement process (S508) from step S202 to S212 shown in FIG. 2, and returns to the operation waiting state (S502).

  When the user presses the end button 307, the measurement AP performs end processing (S505).

  Thus, by correcting the color matching function according to the luminance value and calculating the tristimulus value (colorimetric value) from the corrected color matching function, it is possible to match the calculated value with the apparent color. Become. In other words, the color matching function y (λ) is corrected based on the color displayed with a relatively strong light quantity in RGB, for example, the green component value (G value) having the strongest correlation with the color matching function y (λ). Thus, it becomes possible to match the measured value with the actual appearance relatively easily by correcting the measured value near the high brightness.

[Modification]
Correction of color matching function In the above description, the example of correcting the color matching function using the logarithm (2) has been described. However, correction may be performed using gamma conversion or a one-dimensional lookup table (1DLUT) in addition to the logarithm. It is also possible to combine various operations such as higher order functions.

● Color to be measured In the above, an example was described in which RGB color patches were measured and the luminance values of G color patches were used. As a modification, however, it is also possible to perform correction conversion using the brightness value of the brightest value of each RGB color patch and gamma conversion.

[Other embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a computer, an interface device, a reader, a printer, etc.), but an apparatus (for example, a copier, a facsimile machine, a control device) including a single device. Etc.).

  Another object of the present invention is to supply a storage medium storing a computer program for realizing the functions of the above embodiments to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus executes the computer program. But it is achieved. In this case, the software read from the storage medium itself realizes the functions of the above embodiments, and the computer program and the computer-readable storage medium storing the computer program constitute the present invention. .

  Further, the above functions are not only realized by the execution of the computer program. That is, according to the instruction of the computer program, the operating system (OS) running on the computer and / or the first, second, third,... This includes the case where the above function is realized.

  The computer program may be written in a memory of a device such as a function expansion card or unit connected to the computer. That is, it includes the case where the CPU of the first, second, third,... Device performs part or all of the actual processing according to the instructions of the computer program, thereby realizing the above functions.

  When the present invention is applied to the storage medium, the storage medium stores a computer program corresponding to or related to the flowchart described above.

A block diagram showing a configuration example of a color processing apparatus of an embodiment, A flowchart showing an example of measurement processing by the measurement AP, A diagram showing an example of a UI displayed by a measurement AP, Figure showing an example of dialog for measurement color editing. It is a state transition diagram explaining the operation of the measurement AP.

Claims (7)

Output means for outputting color patch image data to a display device;
Input means for inputting a spectral radiance measurement value of a color patch displayed by the display device;
A calculation means for calculating a colorimetric value from the measurement value using a color matching function;
A calculation means for calculating a correction color matching function;
Correction means for correcting the colorimetric value using the correction color matching function;
A color processing apparatus comprising: a creation unit that creates color correction data using the image data of the color patch and the corrected colorimetric value.   2. The color processing apparatus according to claim 1, wherein the calculation unit calculates the corrected color matching function based on a green component value of the measurement value.   3. The correction unit according to claim 1, wherein the correction unit corrects the X and Z values of the tristimulus value based on a Y value of the tristimulus value calculated using the correction color matching function. Color processing device.   The color according to any one of claims 1 to 3, further comprising color correction means for color correcting image data to be output to the display device using the color correction data. Processing equipment. Output color patch image data to a display device,
Input a spectral radiance measurement value of the color patch displayed by the display device,
Using a color matching function, a colorimetric value is calculated from the measured value,
Calculate the correction color matching function,
Using the correction color matching function, the colorimetric value is corrected,
A color processing method, wherein color correction data is created using image data of the color patch and the corrected colorimetric value.   5. A computer program for controlling a computer device to function as each unit of the color processing device according to claim 1.   7. A computer-readable storage medium in which the computer program according to claim 6 is recorded.

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