JP4178788B2 - Color chart, image data generation device, profile creation method using color chart, and recording medium recording profile creation program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color chart photographed by an image data generation apparatus such as a digital camera, and an apparatus using the color chart.
[0002]
[Prior art]
In recent years, the demand for apparatuses that generate digital image data by photographing a subject (for example, a digital still camera, a digital video camera, etc.) is not limited to specialists who are involved in photography and image processing, but also general people who do not have specialized knowledge. It has spread to.
[0003]
Conventionally, among experts, when photographing a subject with the above-described image data generation device, in order to grasp the color reproduction characteristics of the image data generation device, a color chart in which color patches of a plurality of colors are arranged vertically and horizontally is used. Shooting was often done. Specifically, a color chart image obtained by photographing (for example, a color chart image printed on photo paper) is compared with the actual color chart, and the color difference of each color patch is visually confirmed. Corresponding color correction processing was performed on the photographed image of the subject to bring the color of the subject image close to the color of the actual subject. In the following description, a color difference generated between the color chart entity and the color chart image acquired by photographing the color chart, or between the subject entity and the subject image obtained by photographing the subject. The resulting color difference is referred to as “substance-image color difference ΔE”.
[0004]
A conventional example of such color correction processing is shown in Case 1 of FIG. Case 1 in FIG. 23 shows the state of color correction processing for image data when a color chart JV having color patches is photographed by the digital still camera J10 under sunlight. In FIG. 23, regarding each image data of the color chart JV (chart data JVD1, JVD2, JVDaw1, JVDaw2, JVDw1, JVDw2), an image image when each image data is embodied in the color space of the digital still camera J10 is shown. It represents.
[0005]
In Case 1, the image is taken in a state where the white balance on the digital still camera J10 side is set to “auto” (this state is represented as “AWB” in FIG. 23). In the setting of “auto”, the digital still camera J10 that detects the light at the shooting location automatically determines the color temperature of the shooting light source based on the detection result, and adjusts the white balance according to the determined color temperature. It is a setting to perform.
[0006]
In Case 1, the entity-image color difference ΔE between the color chart JV and the chart data JVD1 generated by photographing the color chart JV is a value Jcg1. The computer J90 that has received the chart data JVD1 performs color correction processing on the chart data JVD1, and outputs the data after the color correction processing to the printer J40 as chart data JVD2. In this color correction processing, the correction value Jre1 from the chart data JVD1 to the chart data JVD2 is printed by the printer J40 in consideration of the color reproduction characteristics of the printer J40 and the color space between the digital still camera J10 and the printer J40. The current color is determined to be a color approximate to the color chart JV. When the printer J40 receives the chart data JVD2 subjected to such color correction processing, the printer J40 can print a chart image JE having a color approximate to the color chart JV.
[0007]
[Problems to be solved by the invention]
However, in the above-described conventional method, when a subject having the same color as the color chart is photographed under a light source different from the light source at the time of photographing the color chart, even if the white balance is photographed, the subject substance and the image are captured. An entity-image color difference ΔE that is different from that in the case of the color chart occurs during the period of time, and the color correction processing standard (correction value Jre1 in FIG. 23) generated based on the photographing of the color chart is used as the color for the subject image. It could not be used as a standard for correction. Such difficulties will be specifically described below with reference to FIG.
[0008]
Case 2 in FIG. 23 shows a case where a color chart JV having the same color patch as Case 1 is a subject, and this subject is photographed by a digital still camera J10 under a fluorescent lamp. In Case 2, shooting is performed with the white balance on the digital still camera J10 side set to “auto”. By photographing the color chart in this setting state, chart data JVDaw1 that is image data of the color chart JV is generated. As shown in FIG. 23, the chart data JVDaw1 is different in color from the chart data JVD1 in Case 1, and the entity-image color difference ΔE between the color chart JV and the chart data JVDaw1 is different from that in Case 1. The value is a value Jcg2. Therefore, even if the correction value Jre1 defined in Case 1 is applied to the chart data JVDaw1 and the color correction processing is performed, as shown in FIG. 23, the chart data JVD2 and the chart data JVD2 when the color correction processing is Case 1 Becomes data having different color information, the printer J40 cannot print an image having the same color as the chart image JE in Case 1.
[0009]
The difference between the entity-image color difference ΔE due to the difference in the photographing light source is the state in which the white balance on the digital still camera J10 side is set to “fixed fluorescent lamp” as shown in Case 3 of FIG. 23, it is also expressed as “KWB-k”). In Case 3, the same object as Case 2 is photographed under the same fluorescent lamp as Case 2. The setting “fixed fluorescent lamp” is a setting for adjusting the white balance in accordance with a predetermined average color temperature of the fluorescent lamp. As shown in FIG. 23, the chart data JVDw1 generated by photographing in such a state set to “fixed fluorescent lamp” has a color closer to the chart data JVD1 than the chart data JVDaw1 of Case2. Also, the color is different from the chart data JVD1 of Case1, and the entity-image color difference ΔE between the color chart JV and the chart data JVDw1 becomes a value Jcg3 which is a value different from that of Case1. Therefore, even if the correction value Jre1 defined in Case 1 is applied to the chart data JVDw1 and color correction processing is performed, an image having the same color as the chart image JE in Case 1 is printed in the printer J40 for the same reason as in Case 2. Could not (see FIG. 23).
[0010]
As described above, an object to be photographed by the digital still camera J10 (hereinafter referred to as a photographing object) is one of the factors that cause an entity-image color difference ΔE different from the case 1 in the cases 2 and 3. It is conceivable that the overall color affects the degree of white balance adjustment on the digital still camera J10 side. Another possible cause is that Case 1 and Cases 2 and 3 were photographed in different exposure states. For example, when the color chart is photographed in the case 1 where the exposure is excessive or insufficient and the color chart is photographed in the cases 2 and 3 where the exposure is appropriate, the chart data JVDaw1 and JVDw1 are different in brightness from the chart data JVD1. Thus, the difference in brightness causes a difference in the entity-image color difference ΔE between the case 1 and the cases 2 and 3.
[0011]
The difference in the color chart entity-image color difference ΔE due to the difference in the photographing environment such as the light source and the exposure is particularly between the image data generating apparatus and another apparatus on the basis of the image data generated by photographing the color chart. When the profile is created and color correction processing is realized using this profile, the range of utilization of the profile is very narrowed. The profile created on the premise of the difference between the color chart entity-image color difference ΔE due to the difference in the shooting environment, after all, is reproduced in other devices of the color of the subject shot in exactly the same environment as the shooting environment of the color chart. This is because it can only be used for
[0012]
The present invention provides a color chart that solves the above-described problems and generates image data having the same color information even when a person who does not have specialized knowledge shoots under various shooting environments. The following configuration is adopted for the purpose of realizing efficient color correction processing based on image data generated by photographing a color chart.
[0013]
[Means for solving the problems and their functions and effects]
The color chart of the present invention is
Image data generated by test shooting by an image data generation device that generates image data of the target by shooting a predetermined target with white balance based on a predetermined adjustment parameter. Is a color chart used for color correction processing of image data generated by shooting other than the test shooting,
A plurality of color patches arranged in a predetermined area are provided,
The color patches are arranged so as to become achromatic when integrating each color
This is the gist.
[0014]
In the color chart of the present invention, the color patches of a plurality of colors are arranged so as to become an achromatic color when the respective colors are integrated. For this reason, when generating image data by test shooting of a color chart by the image data generation device, the hue of the color patches constituting the color chart is adjusted for white balance based on a predetermined adjustment parameter on the image data generation device side. There is little influence and it becomes easy to take white balance. Therefore, it is possible to generate image data with the same hue regardless of the type of light source that captures the color chart, and it is possible to efficiently realize color correction processing based on the generated image data. For example, when a color chart test shot is taken under a fluorescent lamp, the occurrence of color fog (green fog) due to the color chart color is prevented, so that the same shooting results as shooting under sunlight can be obtained. Can do. Therefore, when an object is photographed under a fluorescent lamp after test photographing, it is not necessary to perform a color correction process that removes the color cast.
[0015]
In the above invention, the image data generation device generates white balance, and automatically determines an exposure amount according to the surrounding environment of the target and shoots the target to generate image data of the target The achromatic color, which is the result of integrating each color of the color patch, is^*a^*b^*L representing lightness in the color system^*It is also desirable for the value of to be a color in the vicinity of 50. In this way, when the image data is generated by the color chart test shooting by the image data generation device, the brightness of the entire color chart affects the exposure amount automatically determined on the image data generation device side. Less gray and easy to balance. Therefore, even when a color chart is simply taken in a mode or setting state in which the exposure amount is automatically determined, it is possible to reliably generate image data with appropriate brightness without overexposure or underexposure. Become. For example, when generating the image data E3, it is not necessary to apply exposure correction in accordance with the brightness of the entire color chart that is the object to be photographed.
[0016]
L^*a^*b^*L representing lightness in the color system^*It is also preferable to provide a color patch having a value of 50 near the center of the chart. In the image data generating apparatus, generally, the exposure amount is automatically determined by center-weighted photometry (measuring the center portion of the effective photographing area). If the color chart is shot by such an image data generation device so that the entire color chart falls within the effective shooting area, L at the center of the chart can be obtained on the image data generation device side.^*It is possible to achieve a more accurate gray balance with reference to a color patch having a value of 50 in the vicinity, and the color patch color outside the center of the chart does not affect the gray balance. Therefore, it is possible to easily and reliably generate image data with more appropriate exposure.
[0017]
The predetermined area in which the color patches of a plurality of colors are arranged may be a substantially rectangular area, and the substantially rectangular area may be formed with substantially the same vertical and horizontal composition ratio as the photographing effective area of the image data generation device. . In this way, it is possible to reliably shoot all the color patches, and it is possible to effectively prevent failure of the color chart test shooting.
[0018]
L around a given area^*a^*b^*L representing lightness in the color system^*It is also preferable to provide an achromatic region with a value of 50 in the vicinity. In this way, when a color chart is photographed by the image data generation device, an object other than the color patch appears around the predetermined area, and the white balance adjustment degree and the exposure amount depend on the color of the reflected object. Will not adversely affect
[0019]
It is also desirable that the plurality of color patches include color patches of colors outside the sRGB color space region. In this way, it is possible to generate image data that is free from overcasting and underexposure even for colors outside the sRGB color space (for example, highly saturated colors), and color correction processing that accurately covers a wide color gamut. Can be performed.
[0020]
Information for identifying the left and right sides of a predetermined area may be provided in a format that can be recognized by the device that performs the color correction process. This makes it possible to accurately specify the position information of each color patch from the image data of the color chart when performing color correction processing, and to easily and reliably recognize the color based on the image data. Can do.
[0021]
It is also desirable that the color chart is a color chart in which image data generated by test photographing is used for profile creation between the image data generation device and another device other than the image data generation device. For example, when the configuration of the invention of claim 1 is provided, it is possible to create a profile with another device on the basis of image data with little color cast, and the accuracy of the profile can be improved. When the configuration of the invention of claim 2 is provided, it is possible to create a profile with another apparatus on the basis of image data with no excess or deficiency of exposure, and the accuracy of the profile can be further improved. For example, when a color chart including a color patch of a color outside the sRGB color space is taken as a test image, it is possible to generate image data with no color cast or over / underexposure even for a highly saturated color. A high-accuracy profile with a wide color gamut can be created based on image data. In addition, when a color chart having information that identifies the top and bottom of a predetermined area in a format that can be recognized by a device that performs color correction processing is shot by test, position information of each color patch from the image data of the color chart Can be identified and an accurate profile can be created.
[0022]
The present invention is an apparatus configured to be able to photograph the color chart, and generates image data of the color chart by photographing the color chart while taking a white balance based on a predetermined adjustment parameter. It can also be grasped as an image data generation device. In the image data generation apparatus of the present invention, image data is generated by adjusting white balance by photographing a color chart in which a plurality of color patches are integrated so that an achromatic color is obtained by integrating each color. For this reason, when the white balance is adjusted, the hue of the color patches constituting the color chart has less influence on the white balance adjustment based on the adjustment parameter defined in advance, and the white balance can be easily obtained. Therefore, with respect to the color chart, it is possible to obtain image data with less color cast due to the photographic light source color, and it is possible to generate image data with the same color regardless of the type of the photographic light source. For example, image data with less color cast can be generated even when a color chart is shot with auto white balance without specifying a light source of a place where the user takes a picture (hereinafter referred to as a shooting place light source). .
[0023]
In the above invention, it is also preferable to adopt a configuration in which the image data of the color chart is generated by automatically determining an exposure amount according to the surrounding environment of the color chart and taking a picture while taking white balance. In such an image data generation apparatus, when a plurality of color patches integrate each color, L^*a^*b^*L representing lightness in the color system^*The image data is obtained by adjusting the white balance by photographing a color chart arranged so that the value of the achromatic color is close to 50 and automatically determining the exposure amount according to the surrounding environment of the photographed color chart. Is generated. Therefore, when the exposure amount is automatically determined, the brightness of the entire color chart has less influence on the exposure amount that is automatically determined, and gray balance can be easily achieved. Accordingly, even when a color chart is simply photographed in a mode or setting state in which the exposure amount is automatically determined, it is possible to reliably generate image data with appropriate brightness without excessive or insufficient exposure. For example, it is not necessary to apply exposure correction according to the brightness of the entire color chart, which is the object to be photographed, to the generated image data.
[0024]
It is also preferable to provide storage means for storing the generated image data so that the image data can be read, since the image data of the color chart with less color cast and an appropriate exposure state can be read and used later. For example, if a profile between the image data generation device and another device is created based on the read image data, a highly accurate profile can be created.
[0025]
The present invention can also be understood as a chart image data correction apparatus that corrects image data of a color chart generated by photographing the color chart. Such a chart image data correction apparatus of the present invention includes a reference data holding unit that holds reference data that is data representing the colors of a plurality of color patches, and image data generated by referring to the reference data holding unit. Is provided with a correction value determining unit that compares the reference data with the reference data and determines the correction value of the color information of the image data. According to such a chart image data correction device, the correction value determination unit compares the image data of the color chart generated by the image data generation device with the same hue regardless of the type of photographing light source with the reference data. Thus, the correction value of the color information of the image data is determined. Therefore, with respect to one image data generation apparatus, it is possible to determine the correction value of the color information of the image data in a single manner, and the correction value determination process can be simplified. For example, the correction value of the color information of the image data of the color chart generated by one image data generation device is determined to be different for shooting under sunlight and shooting under fluorescent lighting. There is no need to perform such complicated processing.
[0026]
In the chart image data correction device of the above invention, a correction basis for holding correction basis information, which is information associating the correction value determined by the correction value determination unit with the type of the image data generation device that generated the image data of the color chart. Providing the information holding unit is also preferable in that the correction basic information can be used later.
[0027]
In the chart image data correction device according to the invention, a profile between an image data generation device that generates the image data based on a correction value determined by a correction value determination unit and a device other than the image data generation device is obtained. It is also preferable to provide a profile creation unit for creating. In this way, a profile is created based on a set correction value regardless of the type of light source at the time of shooting in the image data generation device. Therefore, it is possible to create a profile with a wide utilization range and high accuracy. For example, the created profile is not only useful when the color chart is photographed under a specific light source (for example, a fluorescent light), even when the color chart is photographed under various light sources. Thus, it is possible to provide a profile that can faithfully reproduce the color of the object photographed by the image data generation apparatus in another apparatus.
[0028]
In the chart image data correction device of the above invention, a profile information holding unit that holds profile information that is information that associates the profile created by the profile creation unit with the type of the image data generation device that generated the image data of the color chart. Providing is also preferable in that the profile information can be used later.
[0029]
The present invention receives correction basic information or profile information from the chart image data correction device described above, and corrects color information of image data generated by photographing a predetermined object based on the correction basic information or profile information. It is also possible to grasp as a color correction device. Such a color correction apparatus according to the present invention includes a data receiving unit that receives image data generated by photographing a predetermined object, and a type that determines the type of the image data generating device that has generated the image data received by the data receiving unit. A determining unit; a reading unit that reads a correction value or profile corresponding to the type of the image data generating apparatus determined by the type determining unit with reference to the correction basic information or profile information; and the reading unit Color information correcting means for correcting color information of the image data received by the data receiving means based on a correction value or a profile.
[0030]
According to such a color correction apparatus, the image data generated by photographing a predetermined object is received, the type of the image data generation apparatus that generated the received image data is determined, and the determined image data generation apparatus The correction value or profile corresponding to the type is read out with reference to the correction basic information or profile information received from the chart image data correction apparatus. The read correction value or profile is determined by the chart image data correction device regardless of the color chart light source. The color information correction unit corrects the color information of the received image data based on such a single correction value or profile. Accordingly, it is possible to simplify the color correction process of the image data generated by photographing the predetermined object. For example, the degree of correction of the color information of the generated image data and the profile to be applied differ depending on whether the predetermined object is photographed under sunlight or when photographed under a fluorescent lamp. There is no need to perform any special processing.
[0031]
The profile creation method of the present invention includes:
A method of creating a profile between an image data generation device that generates image data of a target by photographing a predetermined target while white balance is achieved, and another device other than the image data generation device. ,
Image data of the color chart is generated by photographing a color chart arranged in a predetermined region so that a color patch of a plurality of colors is achromatic when integrating each color by the image data generation device,
Based on the generated color chart image data, a profile is created between the image data generation apparatus that generated the color chart image data and another apparatus other than the image data generation apparatus.
This is the gist.
[0032]
According to the profile creation method of the present invention, when an image data generation device that generates image data of an object by photographing a predetermined object while maintaining white balance, the color patches of a plurality of colors are integrated when each color is integrated. Image data of the color chart is generated by photographing a color chart arranged in a predetermined area so as to be colored, and the image data of the color chart is generated based on the generated image data of the color chart A profile is created between the image data generation device that generated the image data and another device other than the image data generation device. With respect to the color chart, it is possible to obtain image data with little color cast due to the photographic light source color, and it is possible to generate image data with the same color regardless of the type of the photographic light source. Therefore, it is possible to create a profile with high accuracy and a wide utilization range.
[0033]
A recording medium on which the computer program of the present invention is recorded,
An image data generation device that generates image data based on image data of the color chart generated by photographing a color chart in which color patches of a plurality of colors are arranged in a predetermined region while maintaining white balance; A recording medium recording a computer program for creating a profile with another device other than the image data generating device,
A step of generating image data of the color chart by photographing the color chart arranged so that an achromatic color is obtained when the plurality of color patches are integrated with each color;
Creating the profile based on the image data of the generated color chart;
The gist of the invention is that a program for causing the computer to execute is recorded on the computer in a readable manner.
[0034]
According to the recording medium in which the computer program of the present invention is recorded, image data of the color chart is generated by photographing a color chart in which a plurality of color patches are arranged so as to become an achromatic color when each color is integrated. Based on the above, a profile is created between the image data generation device that generated the image data and another device other than the image data generation device. Therefore, it is possible to create a profile with high accuracy and a wide utilization range.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
In order to further clarify the configuration and operation of the present invention described above, embodiments of the present invention will be described in the following order.
A. Example (image data conversion system MA)
A-1. Key points of the example
A-2. Overall configuration of image data conversion system MA
A-3. White balance or exposure adjustment mechanism
A-4. Color chart structure
A-5. B. Relationship between color chart shooting environment and created profile Modified example
[0036]
A. Example
A-1. Key points of the example
FIG. 1 is an explanatory diagram showing a characteristic configuration of an image data conversion system MA according to an embodiment of the present invention. The image data conversion system MA converts image data expressed by one color space into image data expressed by a color space different from the one color space. It is a reproducible system. As shown in FIG. 1, this system includes an image data generation device that generates image data when a subject is photographed, and reference image data obtained by photographing a color chart EP having a plurality of color patches by the image data generation device. When E3 is generated, a chart image data correction device that corrects the reference image data E3, and a correction result by the chart image data correction device is used to generate the object H by the image data generation device. This is realized by a color correction device for correcting the image data H1.
[0037]
As shown in FIG. 1, the image data generation apparatus generates image data based on the sRGB color space, whereas the color correction apparatus converts the received image data into wRGB having a color reproduction area wider than the sRGB color space. The image data expressed by the color space is corrected. The chart image data correction device is an actual product of each color patch in consideration of the difference in the reference color space between the image data generation device and the color correction device and the color reproduction characteristics of the image data generation device or the color correction device. The correction value of the reference image data E3 is determined so that a color similar to the color can be reproduced by the color correction device, and a profile between the image data generation device and the color correction device is created from the determined correction value. Here, the profile means a file describing a method for reproducing a color expressed in one color space depending on a device in another color space depending on the device. Details of this profile will be described later.
[0038]
In this embodiment, as shown in FIG. 1, the image data generating device is configured by a digital still camera 10, and the chart image data correcting device and the color correcting device are configured by a printer 40 capable of color printing.
[0039]
As shown in FIG. 1, the processing performed in the image data conversion system MA is composed of two modules: a profile creation module MA1 and an image printing module MA2 that is performed after the profile creation module MA1 ends. The profile creation module MA1 generates sRGB reference image data E3 expressed by the sRGB color space that is the color space of the image data generation device by photographing the color chart EP printed on the paper P, and this sRGB reference image. Based on the data E3, processing for creating a profile between the image data generation device and the color correction device is performed. Further, in the image printing module MA2, the sRGB image data H1 generated along with the photographing of the object H is expressed by the wRGB color space, which is a color space of the color correction device, using the created profile. Conversion to the wRGB image data H4 is performed, and a process for printing an image of the object H based on the wRGB image data H4 is performed.
[0040]
As shown in FIG. 1, the sRGB reference image data E3 is generated by executing a chart image data generation program stored in the image data generation apparatus when the color chart EP is captured. In this chart image data generation program, a program for grasping an environment (hereinafter referred to as an imaging environment) where a subject including the color chart EP is captured and generating sRGB reference image data E3 based on the imaging environment is described. Yes. In this embodiment, the shooting environment of such a subject takes into account the type of light source that irradiates the subject (for example, fluorescent light, sunlight, etc.), the amount of light reflected from the subject, and the like. For example, as shown in FIG. 1, when a subject including a color chart EP is photographed under a fluorescent lamp, the white balance is automatically adjusted to match the color temperature of the fluorescent lamp, The amount of light reflected from the subject is automatically measured to determine the exposure required for shooting. When the subject including the color chart EP is photographed under sunlight, the white balance is automatically adjusted to match the color temperature of sunlight, and the amount of light reflected from the subject under sunlight is automatically adjusted. To determine the exposure required for shooting. Thereby, the sRGB reference image data E3 in which the white balance and the exposure amount are automatically adjusted is generated.
[0041]
As will be described later, in the profile creation module MA1, a color chart EP having a characteristic color patch structure is photographed by the image data generation device. Thereby, automatic adjustment of the white balance and the exposure amount in the image data generation apparatus is performed more appropriately. As a result, sRGB reference image data E3 having substantially the same color information is generated regardless of the difference in the shooting environment. For example, as shown in FIG. 1, the sRGB reference image data having substantially uniform color information and brightness information regardless of whether the color chart EP is taken under an environment of fluorescent light or sunlight. E3 is generated.
[0042]
Based on the sRGB reference image data E3, a profile creation program is executed in the chart image data correction apparatus to create a profile. By referencing the created profile by the color correction device, the color space of the sRGB image data H1 is converted to generate wRGB image data H4.
[0043]
As described above, the image data conversion system MA according to the present embodiment creates a highly accurate profile based on the sRGB reference image data E3 having substantially uniform color information regardless of the photographing environment. By performing color space conversion of image data by using it, the color of the object H can be faithfully reproduced even when the object H is photographed in various photographing environments. It is what.
[0044]
A-2. Overall configuration of image data conversion system MA
Next, the overall configuration of the image data conversion system MA of the present embodiment will be described with reference to FIGS. FIG. 2 is an explanatory diagram showing an outline of the image data conversion system MA according to the embodiment of the present invention. As shown in FIG. 2, the image data conversion system MA includes a digital still camera 10 as an image data generation device and a printer 40 as a chart image data correction device or a color correction device.
[0045]
The digital still camera 10 has a function of acquiring an image by photographing an object, and storing the acquired image as digital image data in the memory card MC. In order to execute this function, a CPU, a ROM, A control mechanism 20 composed of a RAM or the like is provided.
[0046]
As shown in FIG. 2, the digital still camera 10 is based on two color spaces that depend on the characteristics of the digital still camera 10 such as an sRGB color space and a YCbCr color space. The YCbCr color space has a wider color reproduction area than the sRGB color space.
[0047]
The control mechanism 20 of the digital still camera 10 generates image data expressed in the sRGB color space by photographing the subject, converts the generated image data into image data expressed in the YCbCr color space, and performs JPEG compression. The compressed YCbCr image data is recorded on the memory card MC. As the storage format of the image data in the memory card MC, a storage format such as the TIFF format, the GIF format, and the BMP format can be used in addition to the JPEG format.
[0048]
The printer 40 has a function of receiving image data from another digital device, converting the received image data into image data expressed in the color space of the printer, and outputting an image based on the converted image data. More specifically, it has a function of printing an image on a recording medium such as paper or cloth, a CD-R, or a printing medium such as an OHP sheet. In order to execute these functions, the printer 40 includes a control mechanism 50 constituted by a CPU, a ROM, a RAM, and the like.
[0049]
As shown in FIG. 2, the printer 40 is based on two color spaces that depend on the characteristics of the printer 40: a wRGB color space and a CMYK color space (not shown). The wRGB color space has a wider color reproduction area than the sRGB color space.
[0050]
When the printer 40 receives image data expressed in a color space other than the wRGB color space, the control mechanism 50 converts the image data into image data expressed in the wRGB color space, and the converted image data Is color-separated and converted into image data expressed in the CMYK color space. Based on the CMYK image data, the control mechanism 50 determines the discharge mode of the four colors C (cyan), M (magenta), and Y (yellow) and K (black), and based on the determined discharge mode. Instructs execution of printing.
[0051]
In the image data conversion system MA shown in FIG. 2, the digital still camera 10 and the printer 40 are not connected to each other by connection means such as a cable. The transfer of image data from the digital still camera 10 to the printer 40 is realized by inserting the memory card MC extracted from the memory card throttle 11 of the digital still camera 10 into the memory card drive 41 of the printer 40. That is, the control mechanism 50 of the printer 40 connected to the memory card drive 41 reads the YCbCr image data recorded on the memory card MC, and converts the read image data into image data expressed in the wRGB color space. .
[0052]
As described above, the image data conversion system MA includes two modules, that is, the profile creation module MA1 and the image printing module MA2. Of the series of processes performed in each of the modules MA1 and MA2, the process on the printer 40 side is a storage unit 51, a command unit 53, a color space conversion unit 68, and an L− provided in the control mechanism 50 of the printer 40. Executed by the functional units such as the w calculation unit 55, the color separation unit 56, the output unit 58, the data reception unit 60, the relationship determination unit 64, the color specification value specification unit 65, the color conversion table creation unit 66, and the color conversion table storage unit 67 (See FIG. 2). Further, the processing on the digital still camera 10 side is executed by each function unit such as a data generation unit 22, a color conversion unit 24, and a compression unit 26 provided in the control mechanism 20 of the digital still camera 10 (see FIG. 2). ).
[0053]
In this embodiment, in the profile creation module MA1, as a profile used between two devices, the digital still camera 10 and the printer 40, a wRGB color space in which the printer 40 has colors expressed in the YCbCr color space by the digital still camera 10. The profile YW describing the technique to be reproduced in is created. The processing performed by each of the functional units in the profile creation module MA1 will be specifically described with reference to FIGS. 4 to 10 as appropriate, centering on FIGS.
[0054]
In FIG. 2, the flow of processing executed by each function unit in the profile creation module MA1 is indicated by a black thin arrow. In FIG. 3, the flow of processing performed by the control mechanism 50 through the control mechanism 20 as a whole in the profile creation module MA1 is shown as a profile creation processing routine using a flowchart. In the following description, the contents of the processing executed by each functional unit will be described with a focus on FIG. 2, and the processing name also described in FIG. 3 is appended with a step name corresponding to FIG. 3 in the explanatory text. Shall.
[0055]
As shown in FIG. 2, the storage unit 51 stores in advance reference image data E0 that is information for specifying a color chart EP having a plurality of color patches. This reference image data E0 is a color space of device-independent colors L^*a^*b^*It is expressed by a color space. The reference table BT (not shown in FIG. 2) of the storage unit 51 stores the color of each color patch as L, as will be described later.^*a^*b^*Information on color values (hereinafter referred to as reference color values) expressed in a color space is stored in advance as reference color value information LQ (not shown in FIG. 2) (see FIG. 5).
[0056]
Upon receiving a color chart EP output instruction by a predetermined operation by the user, the command unit 53 sends a command to form color chart EP output data to the color space conversion unit 68. The color space conversion unit 68 that has received the command first stores the L from the storage unit 51.^*a^*b^*The reference image data E0 expressed by the color space is read (steps S200 and S210), and the reference image data E0 is converted into wRGB reference image data E1 expressed by the wRGB color space (step S220).
[0057]
The conversion from the reference image data E0 to the wRGB reference image data E1 is performed by the Lw arithmetic unit 55 in the color space conversion unit 68 in the following manner.
[0058]
In the color conversion table storage unit 67, as one content of the profile YW, an L^*a^*b^*A conversion formula from the color space to the wRGB color space is stored in advance.
[Formula 2]
Fy = (L^*+16) / 116
When Fy ≧ 0.20456, Y = Y₀・ Fy^Three
When Fy <0.20456, Y = (Y₀/7.787) ・ (L^*-16/116)
Fx = (Fy + a^*/ 500)
When Fx ≧ 0.20456, X = X₀・ Fx^Three
When Fx <0.20456, X = (X₀/7.787) ・ (Fy + a^*/ 500-16 / 116)
Fz = (Fy−b^*/ 200)
When Fz ≧ 0.20456, Z = Z₀・ Fx^Three
When Fz <0.20456, Z = (Z₀/7.787) · (Fy-b^*/ 200-16 / 116)
However, X₀, Y₀, Z₀Is the tristimulus value at the white point
(R / 255)^γ= M11 · X + m12 · Y + m13 · Z
(G / 255)^γ= M21 ・ X + m22 ・ Y + m23 ・ Z
(B / 255)^γ= M31 · X + m32 · Y + m33 · Z
However, m11 to m33 are XYZ → RGB color space conversion matrix.
[0059]
The L-w calculation unit 55 that has received a command to form the output data of the color chart EP from the color space conversion unit 68 reads the above equation 2 with reference to the color conversion table storage unit 67, and for each color patch Standard color value (L^*, A^*, B^*) Is substituted into Equation 2 above to calculate the calculation result. With such an operation, the reference color value (L) is obtained for each color patch on the color chart EP.^*, A^*, B^*) Values of wRGB colorimetric values (wR, wG, wB) corresponding to the values are obtained, and the reference image data E0 can be converted into wRGB reference image data E1.
[0060]
Note that the conversion from the reference image data E0 to the wRGB reference image data E1 can be realized without performing the calculation by the Lw calculation unit 55. Specifically, wRGB reference image data E1 expressed in the wRGB color space is stored in advance in the storage unit 51, and the color space conversion unit 68 refers to the storage unit 51 when receiving a command from the command unit 53. Thus, a configuration for reading the wRGB reference image data E1 can be considered.
[0061]
The color space conversion unit 68 temporarily stores the color values of the wRGB reference image data E1 obtained by the calculation in the reference table BT of the storage unit 51 while taking a correspondence relationship with each reference color value (see FIG. 5). In addition, the wRGB standard image data E1 is sent to the color separation unit 56. The color separation unit 56 performs color separation on the received wRGB reference image data E1 to convert it into CMYK reference image data E2 expressed in the CMYK color space (step S230), and the output unit 58 outputs the CMYK reference image data E2. To do. Thereby, the paper P on which the color chart EP is printed is discharged out of the printer 40 (step S240).
[0062]
The paper P on which the color chart EP is printed is shown in FIG. As shown in FIG. 4, the color chart EP includes a patch data area VS that is an area in which color patches of a plurality of colors are arranged. The patch data area VS has a horizontally long rectangular outline, and 240 color patches (12 vertical × 20 horizontal) having different colors are arranged in the rectangular area. Note that some of the 240 color patches (vertical 12 × 20 horizontal) may be the same color.
[0063]
The color chart EP includes a background data area BS, which is a background area of 240 color patches, around the outside of the patch data area VS. A white margin area, which is the color of the paper P, is formed around the background data area BS. The structures of the patch data area VS and the background data area BS will be described in more detail in “A-4. Color chart structure” described later. It is also possible to adopt a configuration in which the background data area BS is not provided.
[0064]
The arrangement of the color patches in the patch data area VS can be specified by arranging the color value information for each pixel of each color patch in the scanning direction of the color chart EP. Regarding the specification of such an arrangement, in the first embodiment, as shown in FIG. 4, information relating to the arrangement of color patches (hereinafter referred to as arrangement information FL) is defined by a combination of row position and column position in the color chart EP. Yes. That is, in the color chart EP, 20-digit color patches are arranged in each of the a-th to l-th rows (12 rows in total), and the arrangement of the color patches located in the first digit of the first row The information FL is represented as “a1”, and the arrangement information FL of the color patch located at the 20th digit of the 12th row is represented as “l20”.
[0065]
The color chart EP includes four identification marks Z1 to Z4 as identification data ZD for identifying the top and bottom of the color chart EP in the background data area BS. Each of the identification marks Z1 to Z4 is disposed in the vicinity of each of the four corner portions of the quadrangular patch data region VS. That is, as shown by the triangles filled with black in FIG. 4, black identification marks Z1 and black identification marks Z2 are arranged in the vicinity of the color patches whose arrangement information FL is “a1” and “a20”, respectively. ing. Among these, as shown in FIG. 4, the identification mark Z1 is above the 1-1 contour trajectory line (Y direction side shown in FIG. 4) and to the left of the 3-3 contour trajectory line (−X direction shown in FIG. 4). Side) area. Further, the identification mark Z2 is arranged in a region above the 1-1 contour locus line (Y direction side shown in FIG. 4) and on the right side of the 4-4 contour locus line (X direction side shown in FIG. 4). Yes.
[0066]
Further, as indicated by white triangles in FIG. 4, red identification marks Z3 and red identification marks Z4 are arranged in the vicinity of the color patches whose arrangement information FL is “l1” and “l20”, respectively. ing. Among these, as shown in FIG. 4, the identification mark Z3 is below the 2-2 contour trajectory line (−Y direction side shown in FIG. 4) and to the right of the 4-4 contour trajectory line (X shown in FIG. 4). (Direction side) area. Further, the identification mark Z4 is in a region below the 2-2 contour locus line (−Y direction side shown in FIG. 4) and to the left of the 3-3 contour locus line (−X direction side shown in FIG. 4). Has been placed. These four identification marks Z1 to Z4 function as information (hereinafter referred to as identification information SB) for identifying the left and right sides of the color chart EP by being read by the control mechanism 50 of the printer 40 as will be described later.
[0067]
Note that the arrangement information FL of each color patch described above indicates the color of each color patch as L^*a^*b^*Along with the reference color value information LQ expressed by the color space, it is stored in advance in the reference table BT of the storage unit 51 as reference image data E0. FIG. 5 shows a reference table BT in a state where the reference image data E0 is stored. As shown in FIG. 5, the reference table BT stores arrangement information FL from “a1” to “l20” and reference color value information LQ corresponding to each arrangement information FL.
[0068]
The reference color value information LQ is L^*a^*b^*It is expressed in the form of color values expressed by a color space. For example, as illustrated in FIG. 5, (L^*, A^*, B^*) = (M0, n0, o0) is provided. This reference color value information LQ is L^*(Brightness), a^*(Chromaticity in red / green direction), b^*Each value of (chromaticity in the direction of yellow and blue) represents m0, n0, and o0, respectively. In the reference table BT, L^*, A^*, B^*Are expressed in the form of “m + number”, “n + number”, “o + number”, but the number after “m” can take values from 0 (zero) to 100. The numbers after “n” and “o” can take values corresponding to the number of chromaticities of colors belonging to the visible region.
[0069]
The wRGB color value information WQ corresponding to the content of the reference color value information LQ is stored in the reference table BT shown in FIG. The wRGB color value information WQ is L^*a^*b^*This is information of color values when the reference color value expressed by the color space is expressed by the wRGB color space which is the color space of the printer 40. For example, as shown in FIG. 5, for a color patch whose array information FL is “a1”, (wR, wG, wB) is used as wRGB color value information corresponding to the reference color value (m0, n0, o0). WRGB color value information WQ == (p0, q0, r0). The wRGB colorimetric value information WQ has the contents that the values of wR (red in the wRGB color space), wG (green in the wRGB color space), and wB (blue in the wRGB color space) are p0, q0, and r0, respectively. It represents. In the reference table BT, the values of wR, wG, and wB are expressed in the form of “p + number”, “q + number”, “r + number”, but “p”, “q”, “r” The subsequent numbers can take values from 0 (zero) to 255 corresponding to the general number of gradations (256 gradations for each color) of each color of R, G, and B. The value of (wR, wG, wB) as the wRGB colorimetric value information WQ is received from the calculation result of the Lw calculation unit 55 in the conversion process (step S220 in FIG. 3) of the wRGB reference image data E1 described above. Is recorded by the color space conversion unit 68.
[0070]
Returning to FIG. 2 and FIG. When the color chart EP on the paper P is photographed by the digital still camera 10 based on a predetermined photographing instruction, the data generation unit 22 forms an image of the light information of the color chart EP on the CCD, thereby forming the color chart. An EP image is acquired (steps S300 and S310), and the obtained image is subjected to photoelectric conversion by a CCD and A / D conversion by an A / D converter, thereby generating sRGB reference image data E3 expressed in the sRGB color space. (Step S320). The data generation unit 22 sends the sRGB reference image data E3 to the color conversion unit 24. The color conversion unit 24 converts the received sRGB reference image data E3 into YCbCr reference image data E4 expressed in the YCbCr color space (step S330), and sends this YCbCr reference image data E4 to the compression unit 26. In order to reduce the amount of data, the compression unit 26 thins out the Cb component and the Cr component of the received YCbCr reference image data E4, and compresses the YCbCr reference image data E4 into the YCbCr reference image data E5 (step S340). The compressed YCbCr reference image data E5 is recorded on the memory card MC (step S350). If the data amount of the YCbCr reference image data E4 is small, the YCbCr reference image data E4 can be directly recorded on the memory card MC without performing the above-described compression.
[0071]
Thereafter, when the memory card MC on which the YCbCr reference image data E5 is recorded is inserted into the memory card drive 41 of the printer 40 and the printer 40 is instructed to create a profile YW, the data receiving unit 60 Reads the recorded contents of the memory card MC, receives YCbCr reference image data E5 (steps S250 and S260), and sends the YCbCr reference image data E5 to the relationship determination unit 64.
[0072]
The relationship determining unit 64 sends the YCbCr reference image data E5 to the color specification value specifying unit 65. The color specification value specifying unit 65 specifies the color specification value of the YCbCr reference image data E5 and passes the specified color specification value information to the relationship determination unit 64. The relationship determination unit 64 determines the color value and L of the received YCbCr reference image data E5.^*a^*b^*A correspondence relationship with the reference color value of the reference image data E0 expressed by the color space is determined (step S270), and based on the determined correspondence relationship, the color value of the YCbCr reference image data E5 is associated with the reference color value. However, the information is temporarily stored in the storage unit 51, and the stored information is sent to the color conversion table creation unit 66.
[0073]
FIG. 6 is a flowchart showing details of the correspondence determination processing in step S270 of FIG. 3 as a correspondence determination processing routine. This routine is started when the relationship determining unit 64 receives the YCbCr reference image data E5 in the memory card MC. When this routine is started, first, YCbCr reference image data E5 is developed as image data in a buffer (step S600), and a process for determining whether or not four identification marks Z1 to Z4 exist on this image data. Is performed (step S610). If it is determined that all of the four identification marks Z1 to Z4 are not present, it is considered that the color chart EP has not been photographed over the entire range, and a warning is given by blinking the display lamp or the like (step S690). To return to the process of step S250 of FIG.
[0074]
If it is determined that all four identification marks Z1 to Z4 are present, a process of reading the color values in the YCbCr color space of each identification mark Z1 to Z4 is performed (step S620). The above color value reading process can be realized by storing a JPEG format image data analysis program in a ROM or the like in advance.
[0075]
Next, a process for determining the top and bottom of the YCbCr reference image data E5 based on the difference in color values of the read identification marks Z1 to Z4 is performed (step S630). Specifically, the direction in which the two black identification marks Z1 and Z2 are located corresponds to the upward direction of the color chart EP, and the direction in which the two red identification marks Z3 and Z4 are located is downward in the color chart EP. Decide that it corresponds.
[0076]
After determining the top and bottom of the YCbCr reference image data E5 in this way, a process of reading the color values in the YCbCr color space is performed on the data corresponding to the color patches in the YCbCr reference image data E5 (step S640). This reading process is performed from left to right in order from the top of the image data. In the color chart EP shown in FIG. 5, the arrangement information FL is “a1”, “a2”,..., “A20”, “b1”,..., “B20”,. YCbCr colorimetric values are read in the order of "."
[0077]
Next, a process of writing the YCbCr color values in the correspondence table CT of the storage unit 51 in the reading order is performed (step S650). FIG. 7 shows the correspondence table CT in a state where the YCbCr color specification values of the YCbCr reference image data E5 are written. As shown in FIG. 7, the correspondence table CT is provided with three items of arrangement information FL of the color chart EP, YCbCr colorimetric value information YQ, and reference color value information LQ. Symbols from “a1” to “l20” corresponding to the arrangement information FL of the color chart EP are pre-filled in each column belonging to the item of arrangement information FL. Further, in each column belonging to the item of the reference color value information LQ, the value of the reference color value corresponding to the contents of the array information FL is entered in advance. The read YCbCr color specification value is written in order from the item a1 to each column belonging to the item YCbCr color specification value information YQ.
[0078]
The color value in the YCbCr color space is specified by a combination of three component values of Y (luminance), Cb (saturation), and Cr (saturation). For example, as shown in FIG. 7, in the column of YCbCr colorimetric value information YQ corresponding to the array information FL “a1”, a YCbCr colorimetric value of (Y, Cb, Cr) = (s0, t10, u20) is displayed. This YCbCr colorimetric value is written and indicates that the values of Y (luminance), Cb (saturation), and Cr (saturation) are s0, t10, and u20, respectively. In the correspondence table CT, the values of Y, Cb, and Cr are expressed in the form of “s + number”, “t + number”, “u + number”, but “s”, “t”, and “u”. The latter number can take any value in the YCbCr color space.
[0079]
When the writing of the YCbCr color values for the YCbCr reference image data E5 is completed, the correspondence table CT becomes a list describing the correspondence between the YCbCr color values and the reference color values as shown in FIG. If it is determined that the writing of YCbCr color values for all the color patches has been completed, the fact that the writing has been completed is sent to the color conversion table creation unit 66 (steps S660 and S670), and this routine is executed. finish.
[0080]
FIG. 8 is a block diagram showing how the correspondence determining process described above is performed by each function unit of the control mechanism 50. When the correspondence determination process ends, as shown in FIG. 8, two tables, the reference table BT and the correspondence table CT, have been created in the storage unit 51. By combining the storage contents of the reference table BT and the correspondence table CT, L common to both tables BT and CT is obtained.^*a^*b^*The correspondence between the wRGB color value and the YCbCr color value of each color patch can be obtained via the color value. For example, a color patch having a reference color value of (m0, n0, o0) whose array information FL is “a1” becomes a wRGB color value of (p0, q0, r0) when printed by the printer 40 (see FIG. 5), the paper P printed based on the wRGB color values is photographed by the digital still camera 10 to obtain a YCbCr color value of (s0, t10, u20) (see FIG. 7). Therefore, when image data having a YCbCr color value of (s0, t10, u20) is generated by photographing a subject with the digital still camera 10, this image data is represented by a wRGB table of (p0, q0, r0). If the color value is converted and printed by the printer 40, the photographed image can be printed in the same color as the color acquired by the digital still camera 10 during photographing.
[0081]
On the other hand, when a subject having a color other than 240 colors on the color chart EP is photographed by the digital still camera 10, image data having YCbCr color values not included in the correspondence table CT is generated. In the present embodiment, for such image data, following the above-described correspondence determination process, the digital still camera 10 can print a captured image in a color similar to the color acquired at the time of shooting. The regression calculation process (step S280 in FIG. 3) described in (1) is performed.
[0082]
As shown in FIGS. 2 to 3, the color conversion table creation unit 66 that has received the notification that the color value of the YCbCr reference image data E5 has been stored is first displayed in the table of the YCbCr reference image data E5 stored in the storage unit 51. Based on the correspondence between the color value and the reference color value, a regression calculation process described later is performed (step S280). Subsequently, a profile YW, which is a color conversion table from the YCbCr color space to the wRGB color space, is created using the calculation result of the regression calculation processing, and the profile YW is stored in the color conversion table storage unit 67. (Step S290), the profile creation processing routine (FIG. 3) is terminated. In this embodiment, the profile YW is created in the form of a conversion formula from the YCbCr color value to the wRGB color value, and this conversion formula is stored in the color conversion table storage unit 67.
[0083]
FIG. 9 is a flowchart showing details of the regression calculation processing in step S280 of FIG. 3 as a regression calculation processing routine. This routine is started after the correspondence determination process is completed. When this routine is started, first, the correspondence table CT is referred to, and processing for setting the first array information FL as an analysis target is performed (step S700). Next, a process of reading the reference color value information LQ and YCbCr color value information YQ recorded in the correspondence table CT for the array information FL set as the analysis target is performed (step S710). With the above processing, in the example shown in FIG. 7, the sequence information FL “a1” is set as an analysis target, and L (m0, n0, o0) belonging to the sequence information FL “a1” is set.^*a^*b^*The color value and the YCbCr color value of (s0, t10, u20) are read out.
[0084]
Next, the read reference color value information LQ and YCbCr colorimetric value information YQ are substituted into the following three basic arithmetic expressions JM (step S720), and each basic arithmetic expression JM after the substitution is stored in the arithmetic buffer. This is performed (step S730).
<Basic arithmetic expression JM>
L^*= (Α₁, Α₂, ... α₂₀) A
a^*= (Β₁, Β₂,… Β₂₀) A
b^*= (Γ₁, Γ₂, ... γ₂₀) A
In the above basic arithmetic expression JM, A is (1, Y, Cb, Cr, Y², Cb², Cr², Y * Cb, Y * Cr, Cb * Cr, Y^Three, Cb^Three, Cr^Three, Y²* Cb, Y²* Cr, Y * Cb², Y * Cr², Cb²* Cr, Cb * Cr², Y * Cb * Cr)^tAnd α₁, Α₂, ... α₂₀, Β₁, Β₂,… Β₂₀, Γ₁, Γ₂, ... γ₂₀Is an unknown constant. The basic arithmetic expression JM is stored in advance in a storage area in the color conversion table creation unit 66.
[0085]
Next, processing is performed to determine whether or not the next sequence information FL exists (step S740). When it is determined that the next sequence information FL exists, the next sequence information FL is set as an analysis target. (Step S750), the process returns to Step S710 and the above processing is repeated. With the above processing, in the example shown in FIG. 7, the L for each array information FL from “a1” to “l20”.^*a^*b^*The basic arithmetic expression JM into which the color value and the YCbCr color specification value are substituted is sequentially stored in the arithmetic buffer.
[0086]
If it is determined in step S740 that the next array information FL does not exist, the process of assigning the reference color value information LQ and the YCbCr colorimetric value information YQ to the basic arithmetic expression JM is completed for all the array information FL. Assuming that all equations stored in the operation buffer are read out, the regression operation is performed (step S760). Specifically, by applying the principle of the least square method to each expression after substitution, 60 unknown constants (α₁, Α₂, ... α₂₀, Β₁, Β₂,… Β₂₀, Γ₁, Γ₂, ... γ₂₀).
[0087]
Next, after performing the process of substituting the obtained regression coefficient into the above basic arithmetic expression JM (step S770), the basic arithmetic expression JM after substituting the regression coefficient is stored in the color conversion table storage unit 67 as expression 1. The storing process is performed (step S780), and this routine is terminated. Equation 1 to which the regression coefficient is substituted is the YCbCr color value and L^*a^*b^*This is a conversion formula between color values. Therefore, by substituting an arbitrary YCbCr color value (Y, Cb, Cr) into this conversion formula, L corresponding to the substituted YCbCr color value is obtained.^*a^*b^*Color value (L^*, A^*, B^*) Can be obtained.
[0088]
FIG. 10 is a block diagram showing how the above-described regression calculation processing is performed by each functional unit of the control mechanism 50. As shown in FIG. 10, when the regression calculation process is completed, the color conversion table storage unit 67 stores the LC values from the YCbCr color values.^*a^*b^*Expressions 1 and L, which are conversion expressions to color values^*a^*b^*Two formulas of Formula 2, which is a conversion formula from the color space to the wRGB color space, are stored. In the profile creation or storage process (step S290 in FIG. 3) performed after the regression calculation process, the above two formulas are combined and “YCbCr colorimetric value → L^*a^*b^*Color value → conversion formula to wRGB color space ”, which is stored in the color conversion table storage unit 67 as a profile YW for the digital still camera 10 (see FIG. 10).
[0089]
The contents of the processing performed in the profile creation module MA1 have been described above. Next, the image printing module MA2 performed after the profile creation module MA1 is finished will be described. Of the series of processing performed by the image printing module MA2, the processing on the digital still camera 10 side includes a data generation unit 22, a color conversion unit 24, and a compression unit 26 provided in the control mechanism 20 of the digital still camera 10. It is executed by the functional unit (see FIG. 2). Further, the processing on the printer 40 side includes a data receiving unit 60, a color value specifying unit 65, a color space conversion unit 68, a color conversion table storage unit 67, provided in the control mechanism 50 of the printer 40 shown in FIG. It is executed by each of the function units, that is, the Yw calculation unit 69, the color separation unit 56, and the output unit 58 (see FIG. 2).
[0090]
The processing performed by each of the above functional units in the image printing module MA2 profile will be specifically described with reference to FIG. 12 as appropriate, centering on FIG. 2 and FIG. In FIG. 2, the flow of processing executed by each functional unit in the image printing module MA2 is indicated by a black thick arrow. Further, in FIG. 11, the flow of processing performed by the control mechanism 20 to 50 as a whole in the image printing module MA2 is shown as a faithful image processing routine using a flowchart. In the following description, the contents of processing executed by each functional unit will be described with a focus on FIG. 2, and the processing names described in FIG. 11 will be denoted by step names corresponding to FIG. 11 in the explanatory text. Shall.
[0091]
When the object H as a subject is photographed by the digital still camera 10 in which the profile YW is created, as shown in FIG. 2, the data generation unit 22 forms an image of light information of the object H on the CCD. Thus, an image of the object H is acquired (steps S400 and S410), and the obtained image is subjected to photoelectric conversion by the CCD and A / D conversion by the A / D converter, and sRGB image data expressed in the sRGB color space. H1 is generated (step S420). The data generation unit 22 sends the sRGB image data H1 to the color conversion unit 24. The color conversion unit 24 converts the received sRGB image data H1 into YCbCr image data H2 expressed in the YCbCr color space (step S430), and sends this YCbCr image data H2 to the compression unit 26. The compression unit 26 reduces the data amount by thinning out the Cb component and the Cr component of the received YCbCr image data H2. As a result, the YCbCr image data H2 is compressed into YCbCr image data H3 (step S440). The first image data referred to in the claims corresponds to the YCbCr image data H3 in the first embodiment. The compressed YCbCr image data H3 is recorded on the memory card MC (step S450).
[0092]
When the memory card MC in which the YCbCr image data H3 is recorded is inserted into the memory card drive 41 of the printer 40, and the printer 40 is instructed to execute printing, the data receiving unit 60 stores the memory card MC. The recorded contents are read to receive YCbCr image data H3 (steps S500 and S510), and this YCbCr image data H3 is sent to the color value specifying unit 65. The color value specifying unit 65 specifies the color value in the YCbCr color space of the received YCbCr image data H3 (step S520), and then sends the YCbCr image data H3 to the color space conversion unit 68.
[0093]
The color space conversion unit 68 refers to the profile YW stored in the color conversion table storage unit 67, and obtains the color value of the wRGB color space corresponding to the color value of the YCbCr image data H3 (step S530). In the process of obtaining the wRGB color value corresponding to the YCbCr color value, the Y-w calculation unit 69 in the color space conversion unit 68 converts the YCbCr color value as a profile YW into a conversion formula from wCbCr color value to wRGB color value. This is realized by substituting and calculating the YCbCr color value of the image data H3. The color space conversion unit 68 converts the YCbCr image data H3 into wRGB image data H4 based on the calculation result of the Y-w calculation unit 69 (step S540), and sends the wRGB image data H4 to the color separation unit 56.
[0094]
FIG. 12 is a block diagram showing a state where the conversion process from the YCbCr color space based on the profile YW to the wRGB color space (the processes in steps S530 and S540 in FIG. 4) is performed by each functional unit of the control mechanism 50. As shown in FIG. 12, when the Yw arithmetic unit 69 in the color space conversion unit 68 receives the YCbCr color value of the YCbCr image data H3 from the (1) color specification value specifying unit 65, (2) color conversion is performed. The profile YW (Equation 1 and Equation 2) is read from the table storage unit 67, and (3) the received YCbCr colorimetric value is substituted into Equation 1 to perform an operation, whereby L corresponding to the YCbCr colorimetric value is calculated.^*a^*b^*After obtaining the color value, this L^*a^*b^*By substituting the color value into Equation 2 and performing the operation, L^*a^*b^*A wRGB color value corresponding to the color value is obtained. (4) The color space conversion unit 68 converts the YCbCr image data H3 into wRGB image data H4 based on the wRGB colorimetric values thus obtained, and sends the wRGB image data H4 to the color separation unit 56. Therefore, the image data H3 expressed by the YCbCr color space can be quickly and accurately replaced with the wRGB color space.
[0095]
Returning to FIG. 2 and FIG. The color separation unit 56 that has received the converted wRGB image data H4 performs color separation on the wRGB image data H4 to convert it into CMYK image data H5 expressed in the CMYK color space (step S540), and the CMYK image data H5 is converted to CMYK image data H5. The output unit 58 outputs (step S550). Thereby, the paper P on which the image of the object H is printed is discharged to the outside of the printer 40 (step S560).
[0096]
FIG. 13 shows the relationship between the color of the image acquired by the digital still camera 10 and the color printed by the printer 40 when the above image data conversion system MA is applied. As shown in FIG. 13, when the colorimetric value of the YCbCr image data H3 generated by photographing with the digital still camera 10 is a value on the coordinate point v1 in the YCbCr color space (a value representing red near orange). As a result of color space conversion using the profile YM on the printer 40 side that has received this YCbCr image data H3, the color value of the YCbCr image data H3 is the value on the coordinate point w1 on the xy chromaticity diagram (red closer to orange) Value). Therefore, the printer 40 prints an image based on the wRGB image data H4 having the same color value as the color acquired at the time of shooting.
[0097]
According to the image data conversion system MA described above, the color chart EP output and printed from the printer 40 is photographed by the digital still camera 10, and only the YCbCr reference image data E5 generated by photographing is input to the printer 40. A profile YW which is a color conversion table from the color space (YCbCr color space) of the digital still camera 10 to the color space (wRGB color space) of the printer 40 is created. Thereafter, by using this profile YW, the color of the subject (target object H) photographed by the digital still camera 10 can be faithfully and easily reproduced by the printer 40.
[0098]
A-3. White balance or exposure adjustment mechanism
The digital still camera 10 in the embodiment includes an adjustment mechanism for adjusting white balance or exposure. Such an adjustment mechanism will be described with reference to FIGS. 14 and 15. FIG. 14 is an explanatory diagram showing a white balance or exposure amount adjustment mechanism provided in the digital still camera 10 as a block diagram. FIG. 15 is an explanatory diagram showing items and set values that can be set as conditions relating to white balance or exposure.
[0099]
Here, before entering a specific description of a white balance or exposure adjustment mechanism, a shooting mode provided in the digital still camera 10 will be described. The digital still camera 10 has two shooting modes of “manual” and “full auto”. “Manual” is a mode in which a user manually sets setting values for setting items relating to white balance, exposure, and the like, and performs shooting. On the other hand, “full auto” is a mode in which the digital still camera 10 automatically sets the setting values for the setting items relating to white balance, exposure, etc., and performs shooting. Such a shooting mode can be set by the user operating the dial switch 15 shown in FIG. 14 to select a desired mode (either “Manual” or “Full Auto” shown in FIG. 15). . The set mode is temporarily stored in the setting management unit 28 described later.
[0100]
Next, a white balance or exposure adjustment mechanism will be specifically described. As shown in FIG. 14, the digital still camera 10 includes an exposure control unit 30, an aperture management unit 31, a shutter speed management unit 32, an exposure correction unit 33, a flash execution unit 34, and a setting management unit 28 as exposure adjustment mechanisms. A functional part is provided. In addition, as a white balance adjustment mechanism, functional units such as a WB control unit 35 and a setting management unit 28 are provided. Each of these functional units includes a CPU, a ROM, a RAM, and the like as a part of the control mechanism 20. By the operation of each of these functional units, image data (sRGB reference image data E3, sRGB image data H1) whose white balance or exposure is adjusted in the data generation unit 22 is generated.
[0101]
First, exposure adjustment will be described. Here, “exposure” refers to sending light necessary for photographing to the CCD. The amount of light sent to the CCD during shooting is hereinafter referred to as the exposure amount. The exposure amount is expressed in units of “EV (Exposure Value)”.
[0102]
As shown in FIG. 14, when the light passing through the lens 14 hits the light receiving element of the CCD, the light receiving element senses the exposure amount and generates an electric signal having a strength corresponding to the magnitude of the exposure amount. Image data is generated by the data generator 22 based on the strength of the electrical signal. Thereby, brightness information is added to the image data. The magnitude of the exposure amount is determined in principle by a combination of a shutter speed value and an aperture value, which will be described later.
[0103]
As shown in FIGS. 14 and 15, the digital still camera 10 includes setting items such as shutter speed, aperture, and exposure correction as items relating to settable exposure. In addition to these, regarding the exposure, it is possible to set items such as a flash and a photometry method, but the description of these setting items is omitted in FIGS.
[0104]
The shutter speed is a function of adjusting the exposure amount according to the light irradiation time. A value adjusted by the shutter speed is called a shutter speed value, and expressed as “1/15” or “1/30” in seconds.
[0105]
As shown in FIG. 15, in the digital still camera 10 in this embodiment, when the shooting mode is set to “manual”, the shutter speed is set to “8”, “4”, “2”, “1/2”. ”,“ 1/4 ”,“ 1/8 ”,“ 1/15 ”,“ 1/30 ”,“ 1/60 ”,“ 1/125 ”,“ 1/250 ”,“ 1/500 ” It can be set to any of the set values. The shutter speed can be set by the user operating the dial switch 15 shown in FIG. 14 to select a desired setting value.
[0106]
On the other hand, when the shooting mode is set to “full auto”, the exposure control unit 30 of the digital still camera 10 automatically determines and sets the setting value of the shutter speed (see FIGS. 14 to 15). ). The criteria for determining this set value will be described later.
[0107]
The setting value thus set is temporarily stored in the setting management unit 28. The setting management unit 28 sends the set setting value to the shutter speed management unit 32 as shown in FIG. The shutter speed management unit 32 changes the period from switching on to off of the CCD according to the received set value. As a result, the time during which light is sent to the CCD is adjusted. Note that the shutter speed may be adjusted by a method other than the software method as described above. For example, the shutter speed can also be adjusted by a mechanical method such as adjusting the time during which light passes through the lens 14 by changing the opening / closing speed of the diaphragm plate 13 which is a lens blocking curtain.
[0108]
The diaphragm is a function for adjusting the exposure amount by increasing or decreasing the cross-sectional area of light transmitted through the lens. A value adjusted by this diaphragm is called a diaphragm value (F value) and is expressed as “F4.0”, “F8.0”. Note that as the aperture value increases, the cross-sectional area of the light transmitted through the lens decreases. This is called “squeezing”. On the other hand, as the aperture value decreases, the cross-sectional area of the light transmitted through the lens increases. This is called "opening".
[0109]
As shown in FIG. 15, in the digital still camera 10 according to the present embodiment, when the photographing mode is set to “manual”, the aperture is set to “F2.0”, “F2.3”, “F2.8”. , “F4.0”, “F5.6”, and “F8.0”. Such an aperture setting can be performed by operating the dial switch 15 and selecting a desired set value, as in the case of the shutter speed.
[0110]
On the other hand, when the shooting mode is set to “full auto”, the exposure control unit 30 of the digital still camera 10 automatically determines and sets the aperture setting value (see FIGS. 14 to 15). . The criteria for determining this set value will be described later.
[0111]
The setting value thus set is temporarily stored in the setting management unit 28. The setting management unit 28 sends the set setting value to the aperture management unit 31. The aperture management unit 31 changes the aperture of the aperture plate 13 according to the received set value. Thereby, the cross-sectional area of the light transmitted through the lens 14 is adjusted.
[0112]
A method in which the exposure control unit 30 automatically determines the shutter speed and aperture setting values when the shooting mode is set to “full auto” will be described with reference to FIG. Upon receiving the setting information “full auto” from the setting management unit 28, the exposure control unit 30 commands the reflected light type exposure meter 12 to measure the light coming from the subject.
[0113]
The exposure meter 12 measures light coming from the subject and obtains an appropriate exposure by calculation based on the measurement result. Here, the proper exposure means an exposure that the photographer feels as it is seen. The calculation of the appropriate exposure is made based on the assumption that “when all the brightness and color of an average outdoor subject are mixed, it becomes 18% gray (neutral gray)”.
[0114]
The exposure control unit 30 that has received the appropriate exposure value from the exposure meter 12 determines the appropriate exposure value as the exposure amount at the time of shooting, and the optimum shutter speed value and aperture value for realizing this exposure amount. Determine the combination. Thereby, setting values relating to the shutter speed and the aperture are determined. The exposure control unit 30 sets the shutter speed and the aperture to the determined setting values, and sends information on the set setting values to the setting management unit 28.
[0115]
If the exposure control unit 30 determines that the flash 16 needs to emit light in order to realize the exposure amount at the time of shooting, the exposure control unit 30 instructs the flash execution unit 34 to that effect. The flash execution unit 34 controls light emission (light emission timing and light emission amount) of the flash 16, and automatically emits the flash at the time of shooting. As a result, the light necessary for realizing the proper exposure is automatically replenished at the time of photographing.
[0116]
Next, exposure correction settings will be described. The exposure correction is a function for correcting the brightness of an image by correcting an exposure amount determined by a combination of a shutter speed value and an aperture value. This function is used, for example, to achieve proper exposure when attempting to photograph a very bright subject or a very dark subject.
[0117]
The exposure correction function is particularly useful when the shooting mode is set to “full auto”. That is, in the case of “Full Auto”, the appropriate exposure value is automatically determined based on the assumption that “when all the brightness and color of an average outdoor subject are mixed, it becomes 18% gray”. However, the subject is not always 18% gray. If exposure correction is performed in such a case, it is possible to correct the calculated value of the exposure meter 12, so that true proper exposure can be realized.
[0118]
A value adjusted by exposure correction is referred to as an exposure correction value, and is expressed in units of EV. In the digital still camera 10 according to the present embodiment, the exposure correction is from “−2.0 EV” to “2.0 EV” regardless of whether the shooting mode is set to “auto” or “manual”. The range can be set in increments of 0.1 EV. This exposure correction is realized by the exposure correction unit 33 changing the preset aperture or shutter speed setting value according to the exposure correction value.
[0119]
Next, white balance adjustment will be described. Here, the white balance is a function for adjusting the color balance so that a white subject appears white under various light sources. The digital still camera 10 having such a white balance adjusts the RGB signal input as the subject is photographed to an output balance suitable for the light source and the color of the subject. Thereby, image data in which the color of the subject is faithfully reproduced can be generated.
[0120]
As shown in FIG. 14, such a white balance function is performed on the color information of the image data with respect to the digital image data received by the data generation unit 22 via the CCD and the A / D converter when the subject is photographed. Is realized by the WB control unit 35 correcting the above. Such corrected image data is the above-described sRGB reference image data E3 and sRGB image data H1.
[0121]
Correction of color information by the WB control unit 35 is performed as follows. That is, as shown in FIG. 14, the light that has passed through the lens 14 is separated into an R component, a G component, and a B component by passing through a CCD color filter (primary color filter using three primary colors of RGB light). The As a result, RGB signals composed of R, G, and B components are input to the A / D converter as subject color information. The A / D converter sends the RGB signal converted into the digital value to the data generation unit 22. For the RGB signal received by the data generation unit 22, the WB control unit 35 adjusts the balance of the R component, G component, and B component of the RGB signal according to the type of light source and the color of the subject.
[0122]
For example, when shooting a subject under an incandescent lamp having a low color temperature, the WB control unit 35 lowers the gain factor of the R component compared to when shooting under sunlight, and the subject under a general fluorescent lamp. In the case of photographing, the gain factor of the G component is set lower than that in photographing under sunlight. Thereby, the balance of the RGB signals is adjusted according to the type of the light source.
[0123]
Further, when shooting a subject, not only the color of the light source but also the color of the subject itself that receives light from the light source affects the shooting result. In consideration of this, the WB control unit 35 determines the component ratio of each of the R, G, and B components so that the average of the entire image acquired by shooting is achromatic (that is, R: G: B = 1: 1: 1), the RGB signal is adjusted based on the determined composition ratio. Thereby, the balance of the RGB signals is adjusted according to the color of the subject.
[0124]
As shown in FIG. 15, in the digital still camera 10 according to the present embodiment, when the shooting mode is set to “manual”, the white balance is any one of “auto”, “fixed”, and “custom”. Can be set to The white balance can be set by the user operating the dial switch 15 shown in FIG. 14 to select a desired setting.
[0125]
“Auto” is a setting used when photographing without specifying a photographing light source, and covers a color temperature in a predetermined range (4000 ° K (Kelvin) to 7000 ° K in this embodiment). The adjustment degree storage unit 36 stores in advance white balance adjustment parameters (for example, the degree of adjustment of the balance of the R component, G component, and B component) in the case of the color temperature in the above range. The WB control unit 35 refers to the storage content of the adjustment degree storage unit 36, adjusts the balance of the RGB signals, and takes a white balance.
[0126]
“Fixed” is a setting used when a photographing light source is generally designated for photographing. In the present embodiment, any one of “sunlight”, “fluorescent lamp”, “incandescent lamp”, and “cloudy sky” can be designated as the photographing light source, and “sunlight”, “fluorescent lamp”, “ "Incandescent" and "Cloudy" cover color temperatures suitable for each light source. The adjustment degree storage unit 36 stores in advance each white balance adjustment parameter (for example, the degree of adjustment of the balance between the R component, the G component, and the B component) for each color temperature described above. The WB control unit 35 refers to the storage content of the adjustment degree storage unit 36, adjusts the balance of the RGB signals, and takes a white balance.
[0127]
“Custom” is a setting used when shooting under an imaging light source that is specifically specified individually. For example, it is used when shooting in a place where sunlight and fluorescent lamps are mixed. In this “custom” setting, white balance adjustment parameters (for example, the degree of adjustment of the balance of the R component, G component, and B component) are not defined in advance in the digital still camera 10 and are not stored in advance. It is determined only by photographing white paper or the like under a specific light source. The determined parameters are subsequently stored in the adjustment degree storage unit 36 together with the name of the photographing light source when photographing white paper or the like. Thereafter, when the subject is photographed under the same light source as when white paper or the like is photographed, the white balance is set to “the parameters determined after the above” in “custom mode”. Thereby, the white balance can be accurately taken.
[0128]
On the other hand, when the shooting mode is set to “full auto”, the setting management unit 28 automatically determines the white balance setting to be “auto” (see FIGS. 14 to 15).
[0129]
A-4. Color chart structure
Next, regarding the color chart EP photographed by the digital still camera 10 provided with the white balance and exposure adjusting mechanism as described above, the arrangement relationship according to the color value of each color patch will be described with reference to FIG. . As shown in FIG. 16A, in the patch data area VS of the color chart EP, color patches having the same lightness are arranged together in one area. That is, as indicated by the encircled numbers in FIG. 16A, the reference color value L is within the area {circle around (1)} in the lower left corner of the color chart EP.^*Color patches having a (brightness) value of “around 10” are arranged together. Similarly, the region (2) to the right of the region (1) and the region (3) to the right of the region (2)^*Color patches having values of “around 20” and “around 30” are arranged together. In addition, the area {circle over (4)}, the area {circle around (5)}, and the area {circle around (6)} positioned immediately above the area {circle around (3)}, the area {circle around (2)}, and the area {circle around (1)}^*Color patches having values of “around 40”, “around 50”, and “around 60” are arranged together. Further, the areas (7), (8), and (9) located immediately above the areas (6), (5), and (4) are respectively set to L.^*Color patches having values of “around 70”, “around 80”, and “around 90” are arranged together. As described above, the color chart EP is divided into nine regions from the region (1) to the region (9) according to the value of the brightness value.
[0130]
As shown in FIG.^*Regions {circle around (1)}, {circle around (3)}, {circle around (7)}, and {circle around (9)} having values of “around 10”, “around 30”, “around 70”, and “around 90” have almost the same area. is doing. L^*Regions {circle around (4)} and {circle around (6)} having values of “around 40” and “around 60” have substantially the same area. Therefore, 240 color patches L^*The average value is “about 50”. Thus, in the color chart EP, when the color patch integrates each color, “L”^*It is arranged so that “approximate 50 achromatic colors”. In addition, “L^*“Approximately 50 achromatic colors” means “about 18% gray”.
[0131]
In the central part (the part indicated by the dotted line hatching in FIG. 16A) in the area (5) located at the central part of the color chart EP, L^*An achromatic color patch having a value of 50 is arranged.
[0132]
In the color chart EP, colors belonging to the wRGB color space, which is the color space of the printer 40, are extracted over a wide range and used as the colors of the color patches. For example, in the xy chromaticity diagram of FIG. 16B, a range D indicated by a diagonal line rising to the right indicates a range to which a highly saturated color belongs in the wRGB color space, and this range D is outside the sRGB color space. The colors are included. The color chart EP includes a color patch having a color belonging to such a range D in the area (5).
[0133]
The vertical / horizontal configuration ratio (value of mm / kk shown in FIG. 16) of the patch data area VS is substantially the same as the vertical / horizontal configuration ratio of the finder of the digital still camera. A subject belonging to the finder region is imaged on the CCD.
[0134]
Also, as shown in FIG. 16A, the background data area BS is L^*Is an achromatic color near 50.
[0135]
A-5. FIG. 17 shows the result of photographing the color chart EP printed by the printer 40 with the digital still camera 10 under different photographing environments. In FIG. 17, wRGB reference image data E1 and sRGB reference image data E3 (indicated as “E1” and “E3” in FIG. 17), which are each image data of the color chart EP, are displayed in the respective color spaces. It represents an image when embodied.
[0136]
Case (1) in FIG. 17 shows a case where the photographing mode is set to the full auto mode and the color chart EP is photographed under sunlight. In this case, the white balance is automatically set to “auto” (this white balance setting state is represented as “AWB” in FIG. 17).
[0137]
In Case (1), the entity-image color difference ΔE between the color chart EP and the sRGB reference image data E3 generated by photographing the color chart EP is a value cg1. This value cg1 is smaller than the value Jcg1 of the entity-image color difference ΔE in Case 1 (conventional example) in FIG. 23 taken under the same light source as Case (1).
[0138]
As described above, in case (1), the value of the entity-image color difference ΔE is smaller than that in the conventional case so that the color patch in the color chart EP as the subject becomes an achromatic color when the colors are integrated. This is thought to be due to the arrangement. That is, with this arrangement, the WB control unit 35 does not need to change the composition ratio of the R, G, and B components because of the color tone of the entire color chart EP, and the RGB signal according to the color of the subject. It becomes unnecessary to adjust the balance. As a result, white balance can be easily obtained. In other words, the actual color of the color chart EP can be reproduced simply by adjusting the RGB signal according to the type of light source.
[0139]
Further, in the color chart EP that is the subject, when the color patch integrates each color, L^*Arrangement so as to have an achromatic color of ≈50 is also considered to contribute to a decrease in the value of the entity-image color difference ΔE in Case (1). In other words, the color chart EP as the subject becomes 18% gray when all the brightness and color are mixed, so that it is possible to obtain an appropriate exposure only by calculation by the exposure meter 12, and exposure correction is performed in order to obtain an appropriate exposure. Therefore, it is not necessary to correct the calculation value of the exposure meter 12. The user can reproduce the actual brightness of the color chart EP simply by setting the shooting mode to the full auto mode by operating the dial switch 15 and shooting.
[0140]
Case (2) in FIG. 17 indicates a case where the photographing mode is set to the full auto mode and the color chart EP is photographed under a fluorescent lamp. In this case, the white balance is automatically set to “auto”.
[0141]
In Case (2), the entity-image color difference ΔE between the color chart EP and the sRGB reference image data E3 generated by photographing the color chart EP is substantially the same value cg1 as in Case (1). ing. This value cg1 is smaller than the value Jcg2 of the entity-image color difference ΔE in Case 2 (conventional example) in FIG. 23 taken under the same light source as Case (2).
[0142]
In the case (2), the value of the entity-image color difference ΔE is smaller than in the conventional case. In the case (1), the value of the entity-image color difference ΔE is smaller than in the conventional case. The same reason is considered.
[0143]
In the case (2), the entity-image color difference ΔE is substantially the same value cg1 as in the case (1). This is because the color patch integrates each color in the color chart EP as the subject. This is considered to be due to the arrangement of colors. That is, with this arrangement, the WB control unit 35 only needs to adjust the RGB signal according to the type of the light source, and does not need to adjust the balance of the RGB signal according to the color of the entire color chart EP. . Therefore, if the color component of the light source of the fluorescent lamp is removed, sRGB reference image data E3 having the same color information as that under sunlight can be obtained. For example, “The color component of the light source of the fluorescent lamp has been removed, but the color information of the color chart changes due to the adjustment of the balance of the RGB signals according to the color of the color chart EP as a whole. This will not cause a color cast of the light source color.
[0144]
Further, in the color chart EP that is the subject, when the color patch integrates each color, L^*Arrangement so as to have an achromatic color of ≈50 is considered to contribute to the substantially equalization of the entity-image color difference ΔE between Case (1) and Case (2). That is, the color chart EP as a subject becomes 18% gray when all of its brightness and color are mixed. Therefore, the calculation by the exposure meter 12 is also performed in the case (2) as in the case (1). A simple exposure can be obtained simply and reliably. For example, in the case of Case (2), in order to obtain an appropriate exposure, work based on specialized knowledge such as “set the exposure correction value to 1 EV by operating the dial switch 15 because the light source is dark with a fluorescent lamp” Even if it is not performed, it is possible to obtain an appropriate exposure only by setting the shooting mode to the full auto mode and leaving it to the automatic flash that emits light when necessary.
[0145]
Case 3 in FIG. 17 is a state in which the photographing mode is set to the manual mode and the white balance is set to “fixed-fluorescent lamp” (this state is represented as “KWB-k” in FIG. 17). The case where the color chart EP was image | photographed under the lamp is shown.
[0146]
In Case (3), the entity-image color difference ΔE between the color chart EP and the sRGB reference image data E3 generated by photographing the color chart EP is substantially the same as in Cases (1) and (2). The value is cg1. This value cg1 is smaller than the value Jcg3 of the entity-image color difference ΔE in Case 3 (conventional example) of FIG. 23 taken under the same light source as Case (3).
[0147]
In case (3), the value of the entity-image color difference ΔE is smaller than in the conventional case. In the case (1), the value of the entity-image color difference ΔE is smaller than in the conventional case. The same reason is considered.
[0148]
In addition, the entity-image color difference ΔE in Case (3) is substantially the same value cg1 as in Case (1) because the entity-image color difference ΔE is in Case (2) described above. , Case (1) is considered to be the same reason as having the same value cg1.
[0149]
That is, when the white balance is set to the auto mode and the color component of the fluorescent lamp as the light source is roughly removed (Case (2)), the white balance is set to “fixed fluorescent lamp” and the fluorescent light as the light source is set. When the color component of the lamp is more accurately removed (Case (3)), sRGB reference image data E3 having substantially the same color information can be obtained. This is because the integrated value of the color of each color patch is achromatic, and the balance adjustment of the RGB signal according to the color of the entire color chart EP is unnecessary, which greatly contributes to the ease and accuracy of white balance. That it is.
[0150]
As described above by comparing Case (1) to Case (3), as a result of photographing the color chart EP with the digital still camera 10, it is almost the same regardless of the type of photographing light source and the difference in white balance setting. The sRGB reference image data E3 having color information (hue information and brightness information) is generated. In the printer 40, a profile YW having substantially the same content is created based on the sRGB reference image data E3 (see profiles (1) to (3) in FIG. 17).
[0151]
In the image data conversion system MA of the present embodiment described above, the color chart EP having color patches arranged so as to become achromatic colors when the respective colors are integrated is photographed by the digital still camera 10, and the sRGB generated by this photographing is taken. A profile YW is created based on the reference image data E3. For this reason, when the sRGB reference image data E3 is generated, the hue of the color patches constituting the color chart EP affects the white balance adjustment at the time of “auto” setting or “fixed” setting on the digital still camera 10 side. It is less affected and makes it easier to achieve white balance. Therefore, it is possible to generate the sRGB reference image data E3 having the same hue regardless of the type of light source for photographing the color chart EP, and efficiently realize the profile creation process based on the generated sRGB reference image data E3. can do.
[0152]
For example, when the color chart EP is photographed under a fluorescent lamp, the occurrence of color fog (green fog) due to the color of the entire color chart is prevented, and the same photographing result (sRGB reference image) as that under sunlight is taken. Data E3) can be obtained. Therefore, when the object H is photographed under a fluorescent lamp after photographing the color chart EP, it is not necessary to perform a color correction process that removes the color cast. As described above, in the image data conversion system MA of the present embodiment, it is possible to create the profile YW based on the sRGB reference image data E3 with less color cast and the sRGB reference image data E3 with no overexposure and the accuracy of the profile YW. Can be improved.
[0153]
Further, in the image data conversion system MA of the present embodiment, the correction value (regression coefficient in the case of the present embodiment) determined in a general manner regardless of the type of light source at the time of shooting and the difference in white balance settings. Based on this, a profile YW is created. Therefore, it is possible to create a profile YW having a wide utilization range and high accuracy. For example, the created profile is not useful only when the color chart EP is photographed under a specific light source (for example, a fluorescent light), and the color chart EP is set under various light sources and white balance settings. Even when the image is photographed below, a profile YW that can reproduce the color of the photographed object H in the printer 40 can be provided.
[0154]
The color chart EP photographed by the digital still camera 10 is “L” when a plurality of color patches integrate each color.^*It is arranged so that “approximate 50 achromatic colors”. Therefore, when the sRGB reference image data E3 is generated by photographing the color chart EP, the hue and brightness of the entire color chart EP have less influence on the calculation of the necessary exposure amount, and it becomes easy to achieve gray balance. Therefore, even when the required exposure amount is automatically determined in the full auto shooting mode and the color chart is simply shot, the sRGB reference image data E3 having the appropriate brightness with no overexposure or underexposure is reliably generated. It becomes possible to make it. For example, when generating the sRGB reference image data E3, it is not necessary to add exposure correction according to the color and brightness of the entire color chart that is the object to be photographed.
[0155]
The color chart EP is L^*A color patch having a value of around 50 is provided at the center of the chart. Therefore, when the color chart EP is photographed with the digital still camera 10 that automatically determines the exposure amount by the exposure meter of the center-weighted photometry (measuring the center portion of the photographing effective area), It becomes possible to achieve a more accurate gray balance. If the entire color chart EP is photographed so that it fits in the finder, which is a photographing effective area, L at the center of the chart^*The required exposure amount is accurately determined with reference to a color patch having a value of around 50, and the color patch color outside the center of the chart does not affect the determination of the exposure amount. Therefore, the sRGB reference image data E3 with more appropriate exposure can be generated easily and reliably.
[0156]
Further, in the color chart EP, the vertical / horizontal configuration ratio of the patch data area VS is substantially the same as the vertical / horizontal configuration ratio of the finder of the digital still camera. Accordingly, when the color chart EP is photographed, it is possible to reliably photograph all the color patches without omission, and it is possible to effectively prevent photographing failure.
[0157]
The background data area BS of the color chart EP is L^*Is an achromatic color in the vicinity of 50. Therefore, when the color chart EP is photographed by the digital still camera 10, the color reflected around the patch data area VS does not adversely affect the white balance adjustment degree and the exposure amount.
[0158]
The color chart EP includes color patches of colors outside the sRGB color space. Therefore, it is possible to generate sRGB reference image data E3 that is free from over- and under-exposure of colors and colors for colors outside the sRGB color space (for example, highly saturated colors), and create a profile that accurately covers a wide color gamut. Processing can be performed.
[0159]
Further, the color chart EP includes identification marks Z1 to Z4 for identifying the top and the left of the patch data area VS in a format that can be recognized by the printer 40 that performs the profile creation process. Accordingly, when performing the profile creation process, it is possible to accurately specify the position information of each color patch from the image data of the color chart EP, and to easily and reliably recognize the color based on the image data. it can.
[0160]
B. Modified example
In the above embodiment, the image data generating device is constituted by the digital still camera 10 and the chart image data correcting device and the color correcting device are constituted by the printer 40. However, the chart image data correcting device is constituted by the computer 90, and the color correcting device. The printer 40 can also be used. Such a configuration is shown in FIG. 18 as a first modification. In this way, it is possible to efficiently create or manage profiles for a plurality of different color correction apparatuses by the computer 90, and it is possible to easily cope with model changes of the digital still camera 10 and the printer 40.
[0161]
Further, the image data generation device may be configured by the digital still camera 10, and the chart image data correction device and the color correction device may be configured by the computer 90. Such a configuration is shown in FIG. 19 as a second modification. This eliminates the need to perform profile YW creation processing and color correction processing based on the profile YW in the printer 40, and allows the printer 40 to be configured more compactly (for example, without processing received data. A printer that prints the received data as is).
[0162]
The image data generation device and the chart image data correction device may be configured by the digital still camera 10, and the color correction device may be configured by the printer 40. Such a configuration is shown in FIG. 20 as a third modification. Since the profile YW creation process is performed in the digital still camera 10 as described above, it is not necessary to input the photographing result (reference image data E3) of the color chart EP to another apparatus in order to create the profile, and it is simple. You can create a profile.
[0163]
Further, the image data generation device, the chart image data correction device, and the color correction device can be configured by the digital still camera 10. Such a configuration is shown in FIG. 21 as a fourth modification. According to such a configuration, the user who has the digital still camera 10 prints the color chart EP by the printer 40, and the profile YW is automatically generated in the digital still camera 10 only by photographing the printed color chart EP. Is created. Thereafter, when the user images the object, color correction processing based on the profile YW is automatically executed in the digital still camera 10 for the image data H1 generated by the imaging. Therefore, the user convenience can be further improved.
[0164]
In FIG. 1 and FIGS. 18 to 21, black thick arrows indicate a transfer path for correction data such as image data and profiles, but such data transfer is limited to that by a recording medium such as a memory card. Instead, it may be performed using a cable, a communication line, or the like.
[0165]
In the above embodiment, the image of the color chart EP is printed on the paper P by the printer 40, and the color chart EP on the paper P is photographed by the digital still camera 10. It is also possible to prepare in advance as a color chart EPK for test photography without outputting. As a configuration of such a color chart EPK, for example, a configuration in which each color patch is pasted on a plate body in the same arrangement as in the present embodiment, and a 18% gray frame is set around the pasting region of each color patch. Can think.
[0166]
An image data conversion system MAK when a color chart EPK for test photography is prepared in advance is shown in FIG. 22 as a fifth modification. As shown in FIG. 22, in the image data conversion system MAK, the color of each color patch is stored in the storage unit 51 as L.^*a^*b^*Information on the reference color value when expressed in the color space and information on the color value when the reference color value is expressed in the wRGB color space are stored as reference image data E0K. The reference image data E0K may be stored in the storage unit 51 in advance, or may be added to the storage unit 51 afterwards.
[0167]
Also in the case of the fifth modified example, the color chart EPK is used to obtain the LC from the YCbCr colorimetric value.^*a^*b^*Expressions 1 and L, which are conversion expressions to color values^*a^*b^*It is possible to create two formulas, Formula 2, which is a conversion formula from the color space to the wRGB color space, and by combining these two formulas, it is possible to create a profile YW similar to the above embodiment.
[0168]
As mentioned above, although the Example thru | or modification of this invention were demonstrated, this invention is not limited to such an Example etc., In the range which does not deviate from the summary of invention, it can implement in a various aspect.
[0169]
For example, the contents of the above-described processing for generating the reference image data of the color chart EP and the processing for creating a profile based on the reference image data are recorded in a computer-readable format on a recording medium such as a ROM or CD-ROM. It is good also as composition to do. According to such a recording medium, the computer reads the content recorded on the recording medium, whereby it is possible to obtain reference image data with less color cast due to the color of the photographic light source for the color chart EP. Regardless of the type or the white balance setting, reference image data having the same color can be generated. Therefore, it is possible to create a profile YW with high accuracy and a wide range of utilization. As for the configuration of the recording medium described above, a part of the process for generating the reference image data of the color chart EP and the process for creating the profile based on the reference image data is performed on a recording medium such as a ROM or a CD-ROM. It is good also as a structure which records in a computer-readable manner.
[0170]
In the above-described embodiment or modification, the sRGB reference image data E3 is used for creating the profile YW. However, the sRGB reference image data E3 can be used for purposes other than the creation of the profile. This is particularly useful when the color information of the sRGB reference image data E3 is corrected and the corrected image data is used in the digital still camera 10 or other devices. In other words, if the sRGB reference image data E3 having almost the same color information is generated by photographing the color chart EP regardless of the type of photographing light source and the difference in white balance setting, any of the sRGB reference image data E3 is used. The same correction value can be set for the shooting environment. Therefore, color correction processing can be realized uniformly and efficiently.
[0171]
The structure of the color chart EP is not limited to that shown in the above embodiment, and can be changed as appropriate. In the above embodiment, considering that the result of shooting with the auto white balance function is not only the color of the light source but also the influence of the color of the subject itself, the color of the color chart EP as the subject is changed to “average of the whole image”. Is achromatic. Therefore, when the color chart EP is photographed by the digital still camera 10 in which the white balance adjustment parameter is defined in advance and the white balance is set to the predefined adjustment parameter, the color chart EP of the digital still camera 10 is displayed. Any structure that facilitates white balance can be used.
[0172]
In the above embodiment, the image data conversion system MA between the digital still camera 10 and the printer 40 has been described. However, instead of the digital still camera 10, other image data having a reference color space different from that of the printer 40 is used. It is also possible to apply a generator. As such an image data generation device, a digital device (for example, a personal computer with a digital camera or a mobile phone with a digital camera), a scanner, a digital video camera, or the like provided with a digital still camera can be considered.
[0173]
In addition, a plurality of profiles created for different types of image data generation devices such as the digital still camera 10, scanner, and digital video camera can be stored so as to be readable by the printer 40. It is preferable in that the same image can be printed in the same color.
[0174]
The color space used in the above embodiment is merely an example, and other color spaces may be used in the image data generation device such as the digital still camera 10 or the color correction device such as the printer 40 or the computer 90. The reference color space is different between the image data generation device and the color correction device, and the image data generated in the image data generation device is generated reflecting the color space of the image data generation device If so, the present invention can be applied.
[0175]
Further, in the image data generation device or the color correction device, a color space that is a reference for generating image data may be selectable from a plurality of color spaces. Even in this case, if the reference color space is different between the image data generation device and the color correction device, the image data generation device and the color are applied by applying the image data conversion system MA of the above embodiment. A profile YW with the correction device can be created.
[0176]
In the image data conversion system MA of the above embodiment, instead of the printer 40, another device having a reference color space different from that of the image data generation device can be applied. As such other devices, monitors provided for display in various digital devices can be considered.
[0177]
In the above embodiment, the Exif format image file has been described as an example. However, the format of the image file is not limited to this, and the image data to be output by the image output apparatus and the formation of the image data are not limited thereto. Any image file including at least information on the color space used as a reference may be used. An image file including model name information is more preferable.
[0178]
The printer 40 or the computer 90 in the above embodiment is merely an example, and the configuration is not limited to the description of each embodiment. The printer 40 or the computer 90 only needs to read at least image data and create a profile YW based on the reading result.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a characteristic configuration of an image data conversion system MA according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an overview of an image data conversion system MA.
FIG. 3 is a flowchart showing a profile creation processing routine.
FIG. 4 is an explanatory diagram showing the paper P on which a color chart EP is printed.
FIG. 5 is an explanatory diagram showing a reference table BT in a state where reference image data E0 is stored.
FIG. 6 is a flowchart showing details of the correspondence determination processing in step S270 of FIG. 3 as a correspondence determination processing routine.
FIG. 7 is an explanatory view showing a correspondence table CT in a state where YCbCr color values of YCbCr reference image data E5 are written.
FIG. 8 is a block diagram illustrating a state in which correspondence determination processing is performed by each functional unit of the control mechanism 50.
FIG. 9 is a flowchart showing details of a regression calculation process in step S280 of FIG. 3 as a regression calculation process routine.
10 is a block diagram showing a state in which regression calculation processing is performed by each functional unit of the control mechanism 50. FIG.
FIG. 11 is a flowchart illustrating an image faithful print processing routine.
12 is a block diagram illustrating a state in which conversion processing from a YCbCr color space based on a profile YW to a wRGB color space is performed by each functional unit of the control mechanism 50. FIG.
13 is an explanatory diagram showing the relationship between the color of an image acquired by the digital still camera 10 and the color printed by the printer 40 when the image data conversion system MA is applied. FIG.
FIG. 14 is an explanatory diagram showing a white balance or exposure adjustment mechanism provided in the digital still camera 10 as a block diagram;
FIG. 15 is an explanatory diagram showing items and set values that can be set as conditions relating to white balance or exposure;
FIG. 16 is an explanatory diagram showing an arrangement relationship according to the color value of each color patch in the color chart EP.
FIG. 17 is an explanatory diagram illustrating a result of photographing the color chart EP printed by the printer 40 with the digital still camera 10 under different photographing environments.
FIG. 18 is an explanatory diagram showing a first modification.
FIG. 19 is an explanatory diagram showing a second modification.
FIG. 20 is an explanatory diagram showing a third modification.
FIG. 21 is an explanatory diagram showing a fourth modification.
FIG. 22 is an explanatory diagram showing a fifth modification.
FIG. 23 is an explanatory diagram showing a conventional example.
[Explanation of symbols]
10, J10 ... Digital still camera
11 ... Memory card throttle
12 ... Exposure meter
13 ... Aperture plate
14 ... Lens
15 ... Dial switch
16 ... Flash
20 ... Control mechanism
22: Data generation unit
24. Color converter
26: Compression section
28. Setting management section
30. Exposure control unit
31 ... Aperture management section
32 ... Shutter speed management unit
33 ... Exposure compensator
34 ... Flash execution part
35 ... WB control unit
36. Adjustment degree storage section
40, J40 ... Printer
41 ... Memory card drive
50 ... Control mechanism
51. Storage unit
53 ... Command section
55 ... L-w calculation unit
56. Color separation unit
58 ... Output section
60: Data receiving section
64. Relationship determination unit
65 ... Color value specifying part
66 ... Color conversion table creation section
67. Color conversion table storage unit
68. Color space conversion unit
69 ... Yw arithmetic unit
90, J90 ... computer
BS ... Background data area
BT ... reference table
CT ... correspondence table
CV ... Cable
E ... Reference image
E0: Reference image data
E1 ... wRGB reference image data
E2 ... CMYK reference image data
E3 ... sRGB standard image data
E4 ... YCbCr reference image data
E5: YCbCr reference image data
EP, EPK, JV ... Color chart
FL ... Sequence information
H ... Object
H1 ... sRGB image data
H2 ... YCbCr image data
H3 ... YCbCr image data
H4 ... wRGB image data
H5 ... CMYK image data
H6 ... sRGB image data
JM: Basic arithmetic expression
LQ ... Standard color value information
MA, MAK ... image data conversion system
MA1 ... Profile creation module
MA2 ... Image printing module
MC ... Memory card
P ... paper
SB: Identification information
VS ... Patch data area
WQ ... wRGB color value information
YQ ... YCbCr color value information
YW ... Profile
ZD: Identification data
Z1, Z2, Z3, Z4 ... Identification mark

Claims (18)

Image data generated by test shooting by an image data generation device that generates image data of the target by shooting a predetermined target while taking a white balance based on a predetermined adjustment parameter. Is a color chart used for color correction processing of image data generated by shooting other than the test shooting,
A plurality of color patches arranged in a predetermined area are provided,
A color chart in which the color patches are arranged so as to become an achromatic color when each color is integrated. The color chart according to claim 1,
The image data generation device generates the image data of the target object by taking the white balance and automatically determining the exposure amount according to the surrounding environment of the target object and photographing the target object. And
The color chart which made the achromatic color which is the result of integrating each color of the said color patch the color whose value of L ^* showing the lightness in L ^* a ^* b ^* colorimetric system is 50 vicinity. The color chart according to claim 1 or 2,
The image data generation device generates the image data of the target object by taking the white balance and automatically determining the exposure amount according to the surrounding environment of the target object and photographing the target object. And
A color chart provided with a color patch having an L ^* value of about 50 in the L ^* a ^* b ^* color system near the center of the chart. A color chart according to any one of claims 1 to 3,
The predetermined area where the color patches of the plurality of colors are arranged is a substantially rectangular area;
The color chart in which the substantially square area is formed with the same vertical and horizontal composition ratios as the photographing effective area of the image data generation device. The color chart according to any one of claims 1 to 4, further comprising an achromatic region having a value of L ^* representing lightness in the L ^* a ^* b ^* color system near 50 around the predetermined region.   The color chart according to claim 1, wherein the plurality of color patches include a color patch of a color outside the region of the sRGB color space. The color chart according to any one of claims 1 to 6, wherein information for identifying the right and left sides of the predetermined area is provided in a format that can be recognized by a device that performs the color correction process.   The color chart according to claim 1, wherein the image data generated by the test photographing is used for creating a profile between the image data generation device and another device other than the image data generation device. .   9. The color chart according to claim 1, wherein the color chart is photographable, and image data of the color chart is generated by photographing the color chart while taking a white balance based on a predetermined adjustment parameter. An image data generation device.   The image data generation device according to claim 9, wherein the image data of the color chart is generated by automatically determining and photographing an exposure amount according to a surrounding environment of the color chart while taking the white balance.   The image data generation device according to claim 9, further comprising a storage unit that stores the generated image data in a readable manner. A chart image data correction device for correcting image data of a color chart generated by photographing the color chart according to any one of claims 1 to 8,
A reference data holding unit that holds reference data that is data representing the color of each of the plurality of color patches;
A chart image data correction apparatus comprising: a correction value determining unit that refers to the reference data holding unit and compares the generated image data with the reference data and determines a correction value of color information of the image data. A correction basic information holding unit that holds correction basic information that is information that associates the correction value determined by the correction value determination unit with the color space depending on the image data generation device that generated the image data of the color chart; The chart image data correction device according to claim 12.   A profile creation unit that creates a profile between the image data generation device that has generated the image data based on the correction value determined by the correction value determination unit and another device other than the image data generation device. Item 13. The chart image data correction device according to Item 12.   The profile information holding unit that holds profile information that is information that associates the profile created by the profile creation unit with the type of the image data generation device that generated the image data of the color chart. Chart image data correction device. Based on the profile created by the chart image data correcting apparatus according to claim 14, a color correction apparatus for correcting the color information of the generated image data generated for a given object,
Correcting color information of the generated image data using the profile corresponding to the image data generating device that generated the generated image data among the profiles prepared for different types of image data generating devices. Color correction device. A method of creating a profile between an image data generation device that generates image data of a target by photographing a predetermined target while white balance is achieved, and another device other than the image data generation device. ,
Image data of the color chart is generated by photographing a color chart arranged in a predetermined region so that a color patch of a plurality of colors is achromatic when integrating each color by the image data generation device,
A profile creation method for creating a profile between an image data generation device that has generated the color chart image data and another device other than the image data generation device, based on the generated color chart image data. An image data generation device that generates image data based on image data of the color chart generated by photographing a color chart in which color patches of a plurality of colors are arranged in a predetermined region while maintaining white balance; A recording medium recording a computer program for creating a profile with another device other than the image data generating device,
A step of generating image data of the color chart by photographing the color chart arranged so that an achromatic color is obtained when the plurality of color patches are integrated with each color;
A recording medium on which is recorded a computer-readable program for causing the computer to execute the step of creating the profile based on the generated color chart image data.

Images