JP2001309392A - Device and method for correcting color in color image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for correcting colors in a color image, by which a sample color is correctly photographed in an image by suppressing the influence of the reflection, etc., of light effectively in the case of photographing the color sample into the color image with an object. SOLUTION: In the device for color correction which is provided with a hollow main body having the opening part of a prescribed shape and size, the inner surface of at least a wall part opposing the opening part of the main body is set to be black and the peripheral part of the opening part or its neighborhood is formed with a white part. The device is imaged together with the object in a state where its opening part faces the camera and after that, color correction is performed with the prescribed color, which is set on the inner surface of the wall part opposing the opening part of the device, as reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for correcting a color of a printed image.

[0002]

2. Description of the Related Art As is well known, a subject such as a so-called digital camera captures a subject as a color image and, for example, compares the color of an image obtained by output with an output device such as a printer with the actual color of the subject. In this case, a certain difference is inevitably generated between the two. In order to make the color of the color image captured and printed by such a camera and the actual color of the subject as close as possible and have no difference, color correction (so-called color matching) is performed on the captured color image. ) Is known, and various techniques have been devised for this purpose. For example, image data of a color image captured by a camera is taken into a personal computer (hereinafter, referred to as a PC), and a specific part (highlight part or It is conventionally known that a correction process is performed on the basis of a shadow portion).

In order to perform such color correction with higher accuracy, a color sample of a predetermined color (preferably, a plurality of colors) is prepared, and the color sample is also attached to an edge of an image when an object is imaged. To perform color correction on the basis of this sample color. As such a color sample, for example, a combination of black or a combination of black and white, and further a combination of gray and the like can be considered. For any color, for example, a characteristic value such as brightness is set to a predetermined value in advance. The one set is used.

[0004] Then, for a color image on which the above-mentioned color sample is imprinted, the image data is taken into a PC, and the color data is designated on the basis of each color of the sample, and then corrected by predetermined color correction software. Do. In this case, since the correction is performed based on the color sample captured together with the subject (that is, under the same conditions), when performing standard color correction based on a specific portion included in the subject, In comparison, it can be expected that correction with higher accuracy can be performed.

[0005]

When a color sample as described above is manufactured, generally, the color of the sample is set on the surface of a flat main body (or mount) of an appropriate size. It is the easiest to manufacture and convenient to use. However, in the case where the color sample is a flat plate and the sample color is set on the surface in this way, depending on the state of light at the shooting site, when the color sample is projected in a color image together with the subject, There has been a problem that reflection of light causes reflection on the surface of the color sample, so that the sample color cannot be correctly reflected in the image.

Accordingly, the present invention provides a color correction method for a color image, in which the influence of light reflection and the like can be effectively suppressed when a sample image is projected in a color image together with a subject. It is intended to provide a device and a color correction method.

[0007]

According to a first aspect of the present invention, there is provided a color correcting device used for color correction of a color image, comprising a hollow main body having an opening having a predetermined shape and size. At least the inner surface of the wall of the main body facing the opening is set to a predetermined color, and the body is imaged together with the subject with the opening facing the camera.

The invention according to claim 2 of the present application is the invention according to claim 1, wherein the predetermined color is black.

Further, the invention according to a third aspect of the present invention is the invention according to the second aspect, characterized in that a white portion is set at a peripheral portion of the opening or in the vicinity thereof.

Further, the invention according to claim 4 of the present application is a color correction method for performing color correction by capturing a color image, wherein the color correction method according to any one of claims 1 to 3 above. The device for color correction is imaged together with the subject with its opening facing the camera, and then the predetermined color set on the inner surface of the wall of the device for color correction facing the opening. The color correction is performed based on

Further, according to a fifth aspect of the present invention, in the fourth aspect of the present invention, the predetermined color in the captured color image is set to a predetermined brightness. It is characterized by performing color correction.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a state of photographing by an electronic still camera (hereinafter, referred to as a digital camera) using a device for color correction according to an embodiment of the present invention. The present invention relates to a digital camera 10
When the image photographed by the above is output by an output device such as a printer or a display device, the color correction is performed to realize the color matching between the color of the output image and the actual color of the subject. In order to perform such color correction, at the time of shooting, a color correction device 20 having an area set to a predetermined color serving as a sample color is imaged together with a subject in a shooting range of the digital camera 10.
In the state shown in FIG. 1, when photographing with the digital camera 10, the color correction device 20 is imaged together with the subject 17, and the color correction device 20 falls within the photographing range on the liquid crystal display 3 provided on the back side of the camera body. Is displayed.

In this embodiment, a digital camera 10
A support member 12 extending forward from the main body is mounted on the main body of the device, and the color correction device 20 is mounted on a distal end portion of the support member 12. The support member 12 is
The color correction device 20 is supported in the vicinity of the optical axis P of the optical system in the digital camera 10 so that the color correction device 20 is included in the photographing range (preferably at a corner or an end of the photographing range). For this purpose, the position and the shape are set to predetermined values.

FIG. 2 is a perspective view of the color correction device 20. The color correction device 20 includes a substantially rectangular parallelepiped hollow main body, and a front wall portion 21 of the main body has approximately 1 mm.
An opening 22 having a square shape of 0 mm square is provided. The inner surface of the rear wall 23 facing the front wall 21 of the main body in which the opening 22 is formed is set to black. In addition, the outer surface of the front wall portion 21 has a region set to white in the periphery of the opening 22 and in the vicinity thereof.
(Hereinafter referred to as white area) 24 and gray area
(Hereinafter, referred to as a gray area) 25. The white region 24 is further composed of a glossy region 24a and a dull region 24b. In this embodiment, the glossy area 24a on the outer surface of the front wall portion 21 is formed by attaching glossy paper such as a commercially available Kodak gray card with its back side up. On the other hand, the dull area 24b is formed by sticking a very white paper among various types of dull paper, such as inkjet print paper. On the other hand,
The gray area 25 on the outer surface of the front wall portion 21 is formed by attaching gray paper such as a commercially available Kodak gray card, for example.

As will be described in detail later, when the color correction device 20 performs color correction on an image captured together with a subject, the black, white, and gray colors appearing in the area in the opening 22, the white area 24, and the gray area 25 are determined. ,Respectively,
The darkest color, the brightest color, and the above black and white colors in the image are extracted as colors for visually determining the brightness, and are used as reference colors.

FIG. 3 shows an image taken by the digital camera 10 when the color correction device 20 is applied to a general subject such as landscape. In the lower left corner of the photographed image 30, the color correction device 20 is photographed with its opening 22 facing the camera 10. In this embodiment, the color correction device 20 is used.
Is provided with the configuration of the main body and each color as described above, so that when the color correction device 20 is photographed together with the subject in the photographed image 30, the rear surface is opposed to the front wall portion 21 provided with the opening 22. Light can be suppressed from reaching the inner surface of the rear wall portion 23 located at the position (i.e., the inner surface of the wall portion where black is set). According to this, even when the light may be reflected on the front wall 21, the light is suppressed from reaching the inner surface of the rear wall 23. As a result, in an image captured with the opening 22 of the color correction device 20 facing the camera 10, the area inside the opening 22 is always suitable as a reference color in the subsequent color correction processing. Appears to have a black color.

Next, referring to a flowchart of FIG. 4, all steps of a color matching process between the color of the subject and the color of the color print image using the above-described color correction device 20 will be schematically described. First, in step S10, the digital camera 10 captures an image of a subject in a state where the color correction device 20 is captured at a corner of the shooting range. Thereby, imaging data including the color correction device 20 such as the captured image 30 shown in FIG. 3 is obtained. The imaging data is 8-bit RGB color image data. S
At 20, the digital camera 10 captures image data stored in a computer-readable recording medium (not shown) such as a compact flash memory or a smart media into a personal computer (hereinafter, referred to as a PC), and performs color matching processing. Open with predetermined application software to perform In this embodiment, Photoshop (Photoshop) of Adobe Systems Incorporated is used as the application software. S
In the 30, the magnification, rotation,
Performs various processes such as noise removal and unnecessary object removal,
Arbitrarily process the imaging data.

In S40, a basic correction process before color matching (to be described later in detail with reference to FIG. 5) is performed. At this time, the black color appearing in the area within the opening 20 of the color correction device 20 and the white color appearing in the white area 24 are extracted and set as reference colors. In S50,
In the same manner as a conventionally known color matching method, a device profile for the digital camera 10 is converted into a device profile for a color printer (hereinafter, referred to as a profile) to which image data is output. In this step, different color tones and saturations are corrected between the digital camera 10 and the color printer for each pixel constituting the image data via a predetermined color management function set on the application software. . In this embodiment, as the color management function, a color sink (C
colorSync) is set. This color sink employs the “Lab color space” as a reference for the color space, and in order to cope with this, the device profiles for the digital camera 10 and the color printer are respectively set to the color space of each device. The relationship between a color value and a color value in a Lab color space as a common word between the two devices is described. By the step in S50, the final image data output to the color printer is obtained.

In S60, the color printer prints out the image data. For this print output, driver software that allows the PC to control the printer
(A so-called printer driver) is called, but in this color matching process, the color correction by the printer driver is set to off. Thus, the color matching processing ends.

The basic correction process (S40 in FIG. 4) before color matching will be described with reference to FIG. In this correction processing, first, in S41, a sharpness effect is added to the image data by increasing the contrast between pixels constituting the image data. next,
In S42, exposure and white balance error correction are performed. In this step, black and white appearing in each region of the color correction device 20 are extracted as the blackest and whitest colors in the color image, respectively, and each numerical value related to RGB is set to a predetermined reference value (floor). (The upper limit of the key or a value near the upper limit and the lower limit or its value). For example, when handling image data of 256 gradations for each of RGB, each numerical value for RGB of the whitest color is set to “245”.
, And each numerical value related to the RGB of the blackest color is set to “5”. This step causes the image to have a natural tint. After the processing in S42, the process returns to the main routine shown in FIG. In this correction process, in order to eliminate so-called "quantization error" as much as possible, for example, after the process in S41, the image data of 8 bits for each color of RGB is converted into image data of 16 bits for each color of RGB, and thereafter, May be performed.

In the above-described color matching processing, after the profile conversion in S50 of FIG. 4 is executed, the display device displays an image having an extremely different color from the image before the conversion (that is, an image different from the actual color). ) May be displayed. This is because the color space of the display device is smaller than that of the printer, and colors included in the color space of the printer but not included in the color space of the display device are displayed with low saturation. . In connection with this, the following method can be considered as one of the methods for realizing the color matching between the color of the subject and the color of the print image and avoiding the color change in the display device.

First, before the captured image is opened by application software for performing color matching processing, the color space of the display device and the printer is set as the RGB color space used when editing the RGB image on the application software. A color space having a wide color gamut (for example, Adobe RGB) is set to include the color space. Also,
The setting is performed so that the colors of the color space are displayed within the range that the display device can display. Further, on the application software, before opening the captured image, a setting is made to invalidate the color matching which is usually automatically performed for display on the display device. Under these settings, the captured image is opened with the application software, and the above-described basic correction processing before color matching (FIG. 4)
S40) is performed.

Further, after the basic correction processing before the color matching, a profile for a digital camera is converted into a profile for a color space having a wide color gamut. Then, after this conversion step, print output is executed. In this method, the image data before performing the profile conversion is printed out according to a predetermined output setting on a printer driver that can control the printer. At this time, on the printer driver, a profile for the printer is set as a color space of the image data to be output, and a setting for disabling color correction by the printer driver is performed. By printing and outputting under such settings, color matching is performed according to the printer at the stage when the application software sends out the image data, and it is printed without color correction as it is. As a result, it is possible to match the color of the image displayed on the display device with the color of the subject while realizing color matching between the color of the subject and the color of the print image.

When performing color matching between the color of the image displayed on the display device and the color of the subject, it is necessary to standardize the ambient light at the time of photographing and to set the hardware of the display device itself. It is necessary to perform a simple adjustment of (black shadow = brightness adjustment and color tone adjustment of black and white points) and software adjustment such as color sync and Adobe gamma. For more information on these prerequisites,
For example, it is disclosed in "Complete Manual for Color Matching" published in the April 1999 issue of Nikkei Mac (registered trademark).

FIGS. 6A and 6B are perspective views each showing a modification of the color correction device 10 according to the above embodiment. The device 40 for color correction shown in FIG.
Has an octagonal prism-shaped hollow body,
An opening 42 having a predetermined shape and dimensions is formed at a corner formed by the two side walls 44 and 45. The outer surface of one side wall portion 44 is set to white, and the outer surface of the other side wall portion 45 is set to gray. Further, the inner surface of the side wall constituting the main body of the color correction device 40 is set to black.

On the other hand, the color correction device 50 shown in FIG. 6B has a substantially spherical (soccer ball) hollow main body, and the angle formed by two adjacent wall portions 54 and 55. An opening 52 having a predetermined shape and size is formed in the portion. The outer surface of one side wall portion 54 is set to white, and the outer surface of the other wall portion 55 is set to gray. Further, the inner surface of the wall constituting the main body of the color correction device 50 is set to black. In the color correction device 50, the hollow main body is a rod-shaped shaft member 57 fixed vertically to the base member 58 on the installation surface.
And is supported at a predetermined height.

These color correction devices 40 and 50 are:
As in the case of the rectangular parallelepiped color correction device 20 described above, with the openings 42 and 52 facing the camera,
The image is taken together with the subject. The color correction device 4
According to 0 and 50, at the time of imaging, it is possible to suppress light from reaching the inner surface of the wall constituting the main body (that is, the inner surface of the wall where black is set). Thereby, especially the opening 4
Even in the case where light may be reflected on the peripheral portion of the walls 2 and 52 or on the outer surface of the wall in the vicinity thereof, the light is suppressed from reaching the inner surface of the wall. As a result, the areas in the openings 42 and 52 always appear on the captured image so as to have a black color suitable for a reference in the later color matching processing.

The present invention is not limited to the illustrated embodiment, and it goes without saying that various improvements and design changes can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, as the application software for performing the color matching process, Photoshop of Adobe Systems Incorporated was used. However, the present invention is not limited to this.
Any software that can execute the color matching processing described with reference to FIG. 5 and FIG. 5 may be used. Further, the entire area of the inner surface of the wall constituting the main body of the color correction device is set to black. However, if an effect in which the area in the opening appears sufficiently black is achieved, the inner surface of the wall is at least opened. It may be set to black only at the part facing the part.

[0029]

According to the color correcting device according to the first aspect of the present invention, at least the inner surface of the wall of the hollow body having the opening facing the opening is set to have a predetermined color. Is imaged together with the subject with the camera facing the camera, so even if the reflection of light may occur when the image is taken together with the subject in a color image, the light is reflected by the wall provided with the opening, and It is possible to prevent the inner surface of the wall portion located at the back facing the wall portion (that is, the inner surface of the wall portion set with a predetermined color (sample color)) from being reached. That is, even if reflection occurs on the surface of the correction device due to light reflection during imaging, the influence of the reflection can be suppressed, and the sample color can be correctly captured in the image.

According to the second aspect of the present invention, basically, the same effects as those of the first aspect can be obtained. In particular, since the predetermined color is black, even when the shadow of the wall provided with the opening is displayed together with the “predetermined color” when the image is captured together with the subject in the color image, there is no particular problem. It is easy to handle, and it is possible to perform more accurate color correction.

Further, according to the third aspect of the present invention, basically the same effects as those of the second aspect can be obtained. In particular, since a white portion is set at or near the periphery of the opening, two achromatic colors of black and white can be used as a reference, and color correction with even higher accuracy can be performed. .

Further, according to the fourth invention of the present application,
A color correction method for capturing a color image and correcting the color,
The device for color correction according to any one of the first to third inventions is imaged together with a subject in a state where the opening is directed to a camera, and thereafter, the device is mounted on the opening of the device for color correction. Since the color correction is performed based on the predetermined color set on the inner surface of the opposing wall, even if reflection of light may occur when the image is taken together with the subject in the color image, the light is transmitted through the opening. It is possible to prevent the light from being reflected by the provided wall portion and reaching the inner wall surface (that is, the inner wall surface in which a predetermined color (sample color) is set) located in the back and facing the wall portion, thereby achieving higher accuracy. Color correction can be performed.

Further, according to the fifth invention of the present application,
Basically, the same effects as those of the fourth aspect can be obtained. In addition, color correction is performed for the predetermined color in the captured color image after setting the color to a predetermined lightness, so that, for example, two achromatic colors of black and white are used as a reference. The color correction can be performed with higher accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a state of shooting by a digital camera using a color correction device according to an embodiment of the present invention.

FIG. 2 is a perspective view of the color correction device.

FIG. 3 is an image captured by a digital camera when the device for color correction is applied to a general subject.

FIG. 4 is a flowchart illustrating all steps of a color matching process between a subject color and a color print image using the color correction device.

FIG. 5 is a flowchart of a basic correction process (S40 in FIG. 4) before color matching in the color matching process.

FIG. 6A is a perspective view showing a modification of the color correction device according to the embodiment. (b) It is a perspective view showing another modification of the device for color correction concerning the above-mentioned embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Digital camera 20, 40, 50 ... Color correction device 22, 42, 52 ... Opening 24, 44, 54 ... White area 25, 45, 55 ... Gray area 30 ... Photographed image

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/79 H04N 101: 00 5C066 // H04N 101: 00 9/79 H (72) Inventor: Satoshi Kasai Kyoto 653, Tenjincho, Horikawa-dori, Kamigyo-ku, Kyoto-shi 653 Tenjincho, Excel 1102 Horikawa F-term (reference) 2G020 AA08 DA02 DA04 DA16 DA43 DA65 5B047 AA30 AB04 BA02 BB10 BC14 BC30 DC20 5C022 AA13 AB68 AC76 AC80 5C055 A06 BA06 BA08 HA31 HA37 5C065 AA03 BB01 CC01 CC08 HH04 5C066 AA01 AA05 AA15 CA05 CA17 EA07 EB01 EC01 EC06 HA02 JA01

Claims (5)

[Claims] 1. A color correction device used for color correction of a color image, comprising: a hollow main body having an opening having a predetermined shape and size; and a wall portion facing at least the opening of the main body. A color correction device, wherein an inner surface is set to a predetermined color, and an image is taken together with a subject with the opening facing the camera. 2. The device according to claim 1, wherein the predetermined color is black. 3. The color correction device according to claim 2, wherein a white portion is set at a peripheral portion of the opening or in the vicinity thereof. 4. A color correction method for capturing a color image and correcting the color, wherein the color correction device according to claim 1 is directed to a camera. Capturing an image of the subject together with the subject in a state, and then performing color correction based on the predetermined color set on the inner surface of the wall facing the opening of the color correction device. . 5. The color correction method according to claim 4, wherein the predetermined color in the captured color image is subjected to color correction by setting the color to a predetermined brightness.