JP4574533B2 - Color processing method, program, and light source estimation device - Google Patents

Description

  The present invention relates to a method for estimating a light source using a user's visual result.

  Conventionally, when an input image is faithfully color-matched using an output device such as a printer, colorimetric color reproduction has been performed. Colorimetric color reproduction is a human visual characteristic (hereinafter referred to as the same color) of two objects that have the same spectral reflectance, even if the spectral reflectance characteristics of the two objects are different. This is a color reproduction method using “metamerism”.

  Hereinafter, the colorimetric color reproduction will be described in detail.

  As shown in FIG. 12, the light emitted from the light source enters the object, and the reflected light enters the human eye. The incident light is converted into a color signal by cells called three spindles existing on the retina of the human eye. Humans perceive color by the strength of these color signals. These color signals are called tristimulus values. The tristimulus values XYZ represent the spectral distribution of the illumination light source as s (λ), the spectral reflectance of the object as o (λ), and the spectral sensitivity characteristics of the human eye as CIE (International When the color matching function is determined by the Lighting Committee), it can be expressed by the following equation.

  Here, the integration range is 380 to 730 nm in the visible light region, and k is a normalization coefficient.

  That is, in colorimetric color reproduction, color matching is performed by matching the XYZ value of the original color calculated by the above equation with the XYZ value of the reproduced color. However, as indicated by the above equation, the XYZ values depend on the illumination light source. Therefore, even if the XYZ values of the original color and the reproduced color match under a certain illumination light source, the XYZ values do not always match under a different illumination light source. That is, in colorimetric color reproduction, color reproduction accuracy is guaranteed only under a specific illumination light source. Therefore, in the field of printing such as a printer, the standard auxiliary light source D50 defined by the CIE is used as a reference illumination light source. In the field of display output such as a display, the illumination light source is used as the standard light source D65. Color design is done by unifying.

  Here, the light source of the CIE standard light source D65 and the light source of the CIE standard auxiliary light source D50 used for color design are light sources that approximate sunlight, and cannot be completely reproduced by an artificial light source such as a fluorescent lamp. In order to cope with this, a technique called color rendering is used. Color rendering is to artificially create a light source that is close to the light sources of the CIE standard light source D65 and the CIE standard auxiliary light source D50. Currently, fluorescent lamps that are generally used as illumination light sources include a high color rendering type, a three-wavelength type, and a normal type.

  The high color rendering type is high in color rendering by approximating spectral information to the target light source, but is expensive. On the other hand, the three-wavelength type is not so high in color rendering by approximating only the chromaticity with respect to the target light source, but is inexpensive and widely used in general households. Although this high color rendering type and three wavelength type fluorescent lamps are rendering the same target light source, when color reproduction is performed under each light source, especially at the target light source and three wavelengths with low color rendering, There was a problem that color reproduction with high accuracy was not possible. In other words, in order for the user to perform color reproduction with high accuracy, the lighting environment must be the same as at the time of design as much as possible. For example, in order to reproduce a printed matter with high accuracy, it is necessary to use a high color rendering type daylight white fluorescent lamp exhibiting high color rendering properties as the CIE standard auxiliary light source D50, which is a heavy burden on the user.

Therefore, the color reproduction method disclosed in Patent Document 1 prepares an optimal color reproduction method for a plurality of types of illumination light sources, and the user selects a color reproduction method corresponding to the illumination light source that performs color reproduction. Provide a color reproduction method that is optimal for the environment in which images are observed.
JP-A-11-232444

  However, in the color reproduction method of Patent Document 1, there is a burden that the user needs to know in advance the type of illumination light source for performing color reproduction.

  An object of the present invention is to make it possible to easily estimate a light source by visually evaluating a light source estimation check pattern.

In order to achieve the above object, a color processing method according to claim 1 is a color processing method for estimating a light source using a light source estimation check pattern including a reference patch and a sample patch corresponding to each of a plurality of light sources. The light source check pattern information in which the types of the plurality of light sources corresponding to the included sample patch information are different depending on the category is held corresponding to each of the plurality of categories, and the plurality of held light source check patterns From the information, light source check pattern information corresponding to a user instruction to select a category is selected, the light source check pattern information is output using an image output device using the selected light source check pattern information, and based on the user instruction Identify the type of perceived sample patch that is close in color to the reference patch and identify Said light source is estimated from the type of the sample patches, and performing a color processing according to the estimated light source.
In order to achieve the above object, a light source estimation apparatus according to claim 8 is a light source estimation apparatus that estimates a light source using a light source estimation check pattern including a reference patch and a sample patch corresponding to each of a plurality of light sources. Te, a plurality of types of the plurality of light sources information containing Murrell sample patch to correspondence being the source check pattern information different depending on the category, a holding means for holding in association with each of a plurality of categories, the holding The light source check pattern information is selected from the light source check pattern information according to a user instruction to select a category, and the light source check pattern information is output using an image output device using the selected light source check pattern information. Based on the output means to output and user instructions, the color was perceived close to the reference patch And having identification means for identifying the type of Npurupatchi, and a light source estimation means for estimating a light source from the identified type of the sample patch.

  According to the present invention, a light source can be easily estimated by visually evaluating a light source estimation check pattern.

  Hereinafter, an example of the embodiment will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of a system including a color matching processing device according to the first embodiment.

  In FIG. 1, a personal computer 5 displays a user interface and the like on a color matching processing device 1, an image output unit 3 for outputting an image, an image storage unit 11 storing image data, and a display device 7 to be described later. A UI display unit 8 is provided.

  The color matching processing device 1 includes a color profile database 9, a light source estimation check pattern data storage unit 2, an image input unit 12, a color profile selection unit 10, and a color conversion unit 13. The color profile database 9 stores color profile data optimized under various light sources. The light source estimation check pattern data storage unit 2 stores light source estimation check pattern data (FIG. 4). The color conversion unit 13 performs color conversion on the image data using the color profile selected by the color profile selection unit 10.

  A display device 7 is connected to the UI display unit 8. A PC operating device 6 such as a mouse or a keyboard for operating the personal computer 5 is connected to the UI display unit 8 and the color profile selection unit 10. The image output unit 3 is connected to an image output device 4 such as an ink jet printer.

<Overall processing flow>
FIG. 2 is a flowchart showing a procedure of color matching processing executed by the color matching processing device 1 in FIG.

  First, the UI display unit 8 displays the user interface shown in FIG. 3 on the display device 7 (step S201). FIG. 3 is a diagram illustrating a user interface.

  The thumbnail display unit 401 displays check pattern thumbnails. The evaluation check box 402 has a check box for indicating a result of evaluation of the check pattern by the user. A check pattern output button 403 is a button for instructing output of a light source estimation check pattern. The determination button 404 is a button for determining the result of the evaluation check box 402. In the present embodiment, as the image output device 4, an ink jet printer equipped with six color inks of cyan (C), magenta (M), yellow (Y), black (K), red (R), and green (G). Is used. The image output apparatus is not limited to this, and may be another printer such as an electrophotographic printer.

  Returning to FIG. 2, when the check pattern output button 403 is pressed for light source estimation in the UI of FIG. 3 (YES in step S <b> 202), the light source estimation check pattern of FIG. 4 is output using the image output device 4. (Step S203). The user evaluates the output light source estimation check pattern and instructs the evaluation result using the evaluation check box 402 (step S204).

  When the determination button 404 is pressed (YES in step S205), illumination light source estimation described later is performed based on the result evaluated in step S204. Then, the color profile selection unit 10 selects a color profile corresponding to the estimated illumination light source from the color profile database 9 (step S206).

  The color conversion unit 13 performs color conversion on the image data using the color profile selected in step S206 (step S207). The image is output by outputting the image data subjected to color conversion in step S207 to the image output device 4 via the image output unit 3 (step S208).

  According to the process of FIG. 2, the light source can be easily estimated using the light source estimation check pattern. Since color conversion is performed using a color profile corresponding to the estimated light source, color conversion suitable for an actual light source can be performed, and a high-quality output image can be obtained.

<Light source estimation check pattern>
FIG. 4 is a diagram for explaining an example of the light source estimation check pattern output in step S203 of FIG.

  In FIG. 4, the light source estimation check pattern 301 includes a reference patch 302 and a sample patch 303. Regions 1 to 4 (304 to 307) indicate pairs of reference patches and sample patches. FIG. 5 is a diagram for explaining the color difference between the reference patch and the sample patch in regions 1 to 4 in FIG. FIG. 5 shows a change in color difference between the reference patch and the sample patch in regions 1 to 4 in FIG. 4 when the illumination light source is different from the high color rendering day white light source, the three-wavelength day white light source, the A light source, and the C light source. . Ink amount combination data indicating such a change is stored in the light source estimation check pattern data storage unit 2, and is output by the image output unit 3 using the image output device 4 in step S203.

  When the area 1 is selected by the user, it is estimated that the light source is a high color rendering daylight white. Similarly, the light source is estimated to be a three-wavelength daylight white color when the region 2 is selected, an A light source when the region 3 is selected, and a C light source when the region 4 is selected. FIG. 6 is a diagram for explaining a method of creating the light source estimation check pattern of FIG.

  The light source estimation check pattern in FIG. 4 is created using metamerism. When comparing the original patch with the reproduced patch, the same color appears under a specific illumination light source due to metamerism, but appears different under other illumination light sources.

  FIG. 6 shows the spectral reflectance of the six color inks C, M, Y, K, R, and G used in the image output apparatus 4. Here, when these six color inks are combined in 256 gradations, there are 256 combinations of inks in the sixth power. (However, since there is a limit on the amount of ink that can be ejected onto paper, not all combinations can be realized in practice.) At this time, combinations of inks having the same CIE-L * a * b * value under the D50 light source There are multiple. However, even if the same CIE-L * a * b * is indicated, the spectral reflectances are different due to different ink combinations. Therefore, even if they match under the D50 light source, the CIE-L * a * b * values do not always match under other light sources. That is, it is not always perceived as the same color.

  An example of this phenomenon will be described. Macbeth color checker Black is an original color, and one ink combination with CIE-L * a * b * is obtained under a D50 light source, and the change in color difference in each light source is shown in FIG.

  As shown in FIG. 7, the color difference is 1.0 or less under a high color rendering day white fluorescent lamp, while the color difference is 3.0 or more under other illumination light sources. Generally, when the color difference between two colors is 3.0 or more, a person can clearly perceive the difference between the two colors. That is, in the combination of inks shown in FIG. 7, when the original color and the reproduced color are compared with each other under a high color rendering type daylight white fluorescent lamp, they appear to be the same color due to metamerism, but are viewed with other light sources. Appear as different colors.

  The light source estimation check pattern is created by using a combination of inks in which the original color and the reproduced color look the same only with a specific light source and otherwise look different.

  In this embodiment, ΔE94 is used for calculating the color difference. Furthermore, the color difference that appears equal is ΔE94≈1, and the color difference that appears different is ΔE94> 3.0.

<Illumination source estimation>
The illumination light source estimation method is as follows. In FIG. 4, the light source estimation check pattern output using the image output device 4 is visually checked, and the closest color among the reference patch 302 and the sample patch 303 in the regions 1 to 4 (303 to 307). This is done by selecting the pair that appears as.

  When a user who is under an arbitrary illumination light source views the light source estimation pattern described above, if the color difference between the reference patch and the sample patch in the regions 1 to 4 is large, it is perceived as a different color. When the color difference is small, it is perceived as the same color. That is, the evaluation check button 402 on the above-described user interface is checked for the combination in which the colors of the reference patch and the sample patch are the closest.

For example, let us consider a case where the color difference due to the illumination light source change between the reference patch and the sample patch changes as shown in FIG. 5, and the light source estimation check pattern is observed under a high color rendering type daylight white fluorescent lamp. At this time, the reference patch and the sample patch are perceived as the same color only in the region 1, and the regions 2 to 4 are perceived as different from the reference patch and the sample patch. Therefore, it can be estimated that the illumination light source is a high color rendering type daylight white fluorescent lamp corresponding to the region 1.
Thus, the illumination light source from which the user observes the image can be estimated by visually evaluating the light source estimation check pattern under an arbitrary illumination light source.

(Second Embodiment)
FIG. 8 is a block diagram illustrating a configuration of a system including a color matching processing device according to the second embodiment.

  The present embodiment relates to a configuration that enables the above-described light source estimation check pattern data and color profile selection processing to be processed on the server side via a network.

  In the system of FIG. 8, a server 601 (external device) and a personal computer (PC) 609 are connected via a network. Connected to the personal computer (PC) 609 are an image output device 610 such as an ink jet printer, an image input device 611 such as a digital camera or a scanner, a PC operation device 612 such as a mouse or a keyboard, and a display device 613 such as a display. Yes.

  The server 601 includes a color matching processing device 602 and a communication unit 607. The color matching device 602 includes a color profile database 604 (storage means) that stores color profiles optimized for each light source, a color profile selection unit 603, and a light source estimation check pattern data storage unit that stores light source estimation check pattern data. 605 and a light source selection check pattern selection unit 606. The color profile selection unit 603 and the light source selection check pattern selection unit 606 are connected to the communication unit 607, respectively.

<Overall processing flow>
FIG. 9 is a flowchart illustrating a procedure of color matching processing executed by the color matching processing device 602 in FIG.

  The user interface of FIG. 10 is displayed on the display device 612 (step S701).

  FIG. 10 is a diagram illustrating an example of a user interface displayed on display device 612 in FIG.

  The user interface (UI) of FIG. 10 is almost the same as that of FIG. 3, and the difference is that a light source category selection unit 803 for selecting a predetermined light source category from a plurality of light source categories shown in FIG. 11 is added. It is a point.

  As shown in FIG. 11, these light source categories are roughly divided into indoor, outdoor, and art museums as illumination light sources for the user. The light source estimation check pattern selection unit 606 selects a light source estimation check pattern corresponding to the category selected using the light source category selection unit 803 from the light source estimation check patterns stored in the light source estimation check pattern database 605.

  In the UI of FIG. 10, when the category selection 803 is selected (YES in step S702) and the check pattern output button is pressed (YES in step S703), the light source category information selected in S702 is displayed on the data communication network 608. To the server 601 (step S704). Based on the transmitted light source category information, the light source estimation check pattern selection unit 606 selects light source estimation check pattern data from the light source estimation check pattern data storage unit 605 (step S705). The selected light source estimation check pattern is transmitted by the communication unit 607 via the data communication network 608 (step S706). The PC 609 receives this light source estimation check pattern (step S707), and outputs the received light source estimation check pattern using the image output device 610 (step S708). By identifying the evaluation check box checked by the user, the user evaluation based on the output light source estimation check pattern is acquired (step S709).

  When the enter button 805 is pressed (YES in step S710), light source estimation is performed based on the result evaluated in the PC 609 in step S709, and the estimated light source information is transmitted to the server 601. In the server 601, the color profile selection unit 603 selects a color profile corresponding to the estimated light source from the color profile database 604. Then, the server 601 transmits the color profile to the PC 609 via the data communication network 602 (step S711).

  The PC 609 inputs image data from the image input device 611 (step S712), and performs color conversion using the color profile selected in step S711 (step S713). The color-converted image data is output using the image output device 610 (step S714).

  According to the process of FIG. 9, it is possible to eliminate the need for preparing an enormous color profile in the PC 609. Just by specifying a simple category, the user can output a light source estimation check pattern for each light source category from an enormous color profile, and the user can perform color evaluation with higher accuracy simply by visual evaluation under an illumination light source that observes the image. It can be carried out.

(Other embodiments)
<Output equipment>
In the above embodiment, an inkjet printer having six colors C, M, Y, K, R, and G is used as an output device. However, the present invention is not limited to this, and the original color can be changed by changing the illumination light source. The output device is not limited to this as long as it can output an output pattern that causes a color change of the reproduced color.

<Light source estimation check pattern>
In the above embodiment, the reference patch and the sample patch are output to the same medium. However, the present invention is not limited to this, and the reference patch is prepared in advance, and the sample patch may be output and compared for evaluation. The reference patch may be displayed on an output device such as a monitor and evaluated by comparing with a sample chart.

  In the above embodiment, estimation examples such as a high color rendering type daylight white fluorescent lamp, a three-wavelength type daylight white fluorescent lamp, an A light source, and a C light source are shown as typical light sources. It does not matter.

<Light source estimation check pattern threshold setting>
In the above embodiment, ΔE94 is used as the color difference, but it goes without saying that the present invention is not limited to this. For example, CIE-ΔE2000 may be used.

<Light source estimation method>
In the above embodiment, the combination of the reference patch and the sample patch in which the colors of the reference patch and the sample patch are equal is selected. Conversely, a combination in which the colors of the original patch and the sample patch are different may be selected. . Also, a plurality of sets may be selected instead of selecting the same (different) group. That is, the embodiment is not limited to the above-described embodiment as long as the reference patch and the sample patch are distinguished using metamerism.

<Image data>
In the above embodiment, the image is acquired by the digital camera or scanner of the image input device. However, the present invention is not limited to this, and may be an image acquired by an external storage device such as HD, CD, DVD, or graphic I do not care. That is, the image data is not limited to this.

<Storage medium>
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), and a device (for example, a copier, a facsimile device, etc.) including a single device. You may apply to.

  Another object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the embodiments to a system or apparatus, and the computer (or CPU, MPU, etc.) of the system or apparatus stores the storage medium. It is also achieved by reading out and executing the program code stored in.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, and a DVD. -RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM, etc. can be used. Alternatively, the program code may be downloaded via a network.

Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) running on the computer based on the instruction of the program code. This includes a case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes a case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

1 is a block diagram schematically illustrating a configuration of a personal computer including a color matching processing device according to a first embodiment. It is a flowchart which shows the procedure of the color matching process performed by the color matching processing apparatus in FIG. It is a figure explaining the user interface displayed on the display apparatus in FIG. It is a figure explaining an example of the light source estimation check pattern output by step S203 of FIG. It is a figure explaining the color difference of the reference patch and sample patch in the area | regions 1-4 of FIG. It is a figure explaining the preparation method of the light source estimation check pattern of FIG. It is a figure explaining the color difference change of an original color and reproduction color when changing an illumination light source (High color rendering type daylight white fluorescent lamp, three wavelength type daylight white fluorescent lamp, A light source, C light source). It is a block diagram which shows the structure of a system provided with the color matching processing apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the color matching process performed by the color matching processing apparatus in FIG. It is a figure explaining an example of the user interface displayed on the display apparatus in FIG. It is a figure explaining the several light source category which should be selected by the light source selection part in FIG. It is a figure explaining colorimetric color expression.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,602 Color matching processing apparatus 2 Light source estimation check pattern data storage part 4,610 Image output device 5,609 Personal computer (PC)
7,613 Display device 8 UI display unit 9,604 Color profile database 10,603 Color profile selection unit 401 Thumbnail display unit 402 Evaluation check box 403 Check pattern output button 404 Decision button 605 Light source estimation check pattern storage unit 606 Light source estimation check pattern Selection unit 607 communication unit

Claims (8)

A color processing method for estimating a light source using a light source estimation check pattern including a reference patch and a sample patch corresponding to each of a plurality of light sources,
The light source check pattern information in which the types of the plurality of light sources corresponding to the included sample patch information are different depending on the category is held corresponding to each of the plurality of categories,
From the plurality of held light source check pattern information, select light source check pattern information according to a user instruction to select a category,
Using the selected light source check pattern information, outputting the light source check pattern using an image output device,
Based on user instructions, identify the type of perceived sample patch that is close in color to the reference patch,
Estimating a light source from the identified type of the sample patch;
A color processing method comprising performing color processing according to the estimated light source.   The color difference between the reference patch and the sample patch is approximately 1 or less under a light source to which the sample patch corresponds, and is 3 or more under a light source other than the light source to which the sample patch corresponds. The color processing method according to claim 1. The light source estimation check pattern is output using an image output device,
3. The color processing method according to claim 1, wherein color data for causing the image output apparatus to output the sample patch corresponding to the image output apparatus is held.   The color processing method according to claim 1, wherein a plurality of color processing conditions corresponding to each of the plurality of light sources are held.   5. The color according to claim 1, wherein the sample patch is created using a metamerism that has a color matching relationship with a reference patch only under a specific illumination light source. Processing method.   The color processing method according to claim 3, wherein the image output apparatus outputs an image using C, M, Y, K, and other types of color materials.   The program for implement | achieving the color processing method of any one of Claim 1 thru | or 6 recorded on the recording medium so that a computer could read. A light source estimation device that estimates a light source using a light source estimation check pattern including a reference patch and a sample patch corresponding to each of a plurality of light sources,
A holding means for the type of the plurality of light sources information containing Murrell sample patch corresponds is the source check pattern information different depending on the category, held in association with each of a plurality of categories,
A selection unit that selects light source check pattern information according to a user instruction to select a category from the plurality of light source check pattern information held;
Using the selected light source check pattern information, an output means for outputting the light source check pattern using an image output device;
Identification means for identifying a perceived sample patch type close in color to the reference patch based on user instructions;
A light source estimation unit for estimating a light source from the identified type of the sample patch.

Images