JP2002049108A - Color correction method, recording medium recording color correction program, image processing device and photographic printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the influence of the slope characteristics of a photographic light source and films on image quality and to obtain the images having good image quality by the minimum necessary correction of color balance. SOLUTION: An image processing section 2 has an image information dividing section 5 which divides the pixel values corresponding to the image data of R, G and B to plural sections, a color balance calculating section 6 which calculates the color balance of the respective sections in accordance with the pixel values of the respective sections, a color vector detecting section 10 which determines the color vectors in the R, G and B directions corresponding to the color balance by each of the respective sections on a color disks indicating the relation between saturation and hue, a component detecting section 11 which determines the components in the respective directions of the R, G and B of the respective color vectors, a color component region calculating section 12 which determines the regions between the minimum values and maximum values of the components described above as color component regions and calculates these color component regions by each of the respective sections, a correction value calculating section 7 which calculates the correction values of the respective colors in accordance with the presence or absence of the color component regions of the respective sections, and a correction section 8 which corrects the color balance in accordance with the correction values of the respective colors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing a natural color based on photometric image data obtained by reading a photographic film such as a positive film or digital image data in a PC (Personal Computer). The present invention relates to a color correction method for correcting a color balance of (blue), G (green), and R (red), a recording medium storing a color correction program, an image processing device, and a photographic printing device.

[0002]

2. Description of the Related Art Conventionally, as a printer for printing an image such as a photograph on photographic paper, an analog printer which exposes photographic paper through a negative film or a positive film on which a photographic image is recorded has been widely used. In such an analog printer, an optical member called a dimming filter unit is arranged in a region between the light source for irradiating the printing paper with light and the printing paper.

The light control filter unit has a light control filter corresponding to each color of, for example, yellow (Y), magenta (M), and cyan (C). The light emitted from the light source is dimmed by inserting these dimming filters on the optical path and adjusting the insertion amount of each dimming filter.

A light control filter unit is sometimes used to adjust a color balance when printing an image recorded on a negative film or a positive film. Such color balance adjustment may be manually performed by an operator.For example, in the case of a negative film, the color balance is automatically adjusted based on photometric data of an image recorded on the negative film. Various methods have been proposed.

One example of a method for automatically adjusting the color balance of an image recorded on a negative film is LAT.
There is a so-called D (Large Area Transmittance Density) exposure method. This LATD exposure method is an exposure method based on a theorem called Evans theory.

[0006] The Evans theory is that, when briefly described, in an image on a negative film taken of a general outdoor scenery, if all the colors recorded in this image are mixed, the image becomes almost gray. That is the theorem. That is, the LATD exposure method is an exposure method in which light transmitted from a negative film is integrated and measured, and the color and amount of light from a light source are determined so that the integrated light is reproduced in gray on a copy material.

As described above, the color balance of a negative film has conventionally been positively adjusted. This is because, in the past, photography using negative film has become widespread, and images recorded on negative film are taken by ordinary people who are not accustomed to removing the effects of light sources and the slope characteristics of film at the time of exposure. Because there are many things. Therefore, the exposure method for automatically adjusting the color balance as described above is widely used for the purpose of speeding up the processing.

The influence of the light source during the exposure is as follows. For example, a negative film photographed under a fluorescent light, an incandescent light, or under a shade of an outdoor has a magenta color, a deep blue color,
It means that the color becomes cyan and the color corresponding to the photographic light source appears on the finished print as it is. The effect of the film's slope characteristics means that the characteristics of the film, such as color and sensitivity, differ greatly from manufacturer to manufacturer, and even for images taken of the same scene, the color tone differs depending on the type of film used. To tell.

On the other hand, when printing an image recorded on a positive film, it is generally accepted that the image state on the film is printed as it is, and basically no color balance adjustment or the like is performed. . This is because users of the positive film are often advanced photographers who are familiar with photography, and the images recorded on the positive film have grasped the state of the light source at the time of exposure and the slope characteristics of the film. This is because it is often taken above.

[0010]

As described above, many photographers are skilled in photography and printing with a positive film. Therefore, when actually printing as a photograph, first perform trial printing and print. Check the condition with the photographer,
This is often done. If printing is performed without correction at this stage of trial printing, printing may be performed with a color balance slightly deviated from the image intended by the photographer. In this case, after the color balance is manually corrected so as to obtain the color balance intended by the photographer, the test printing is performed again, and the main printing is performed again after obtaining the confirmation of the photographer.

As described above, when printing an image recorded on a positive film, it may be preferable to slightly correct the color balance. However, as described above, it is assumed that no correction is performed for printing a positive film. Therefore, when correction is performed, there is no other method than manual correction by an operator. Therefore, if correction is to be performed within the range not exceeding the photographer's intention at the stage of trial printing, it is necessary for the operator to see the image on the positive film and judge whether correction should be performed or not. In addition, when performing manual correction, skill of an operator is required.

Here, LATD is used for a positive film.
Although there is a concept of applying the automatic correction according to the method, there is a case where the correction is too strong in this method and an image having a different color from an image photographed by an advanced photographer is obtained.

Further, the above-mentioned LATD exposure method has a problem that color fear may occur. The color feria is as follows. In the LATD exposure method, as described above, the correction is performed so that the average color of the entire image becomes gray. Therefore, when the image has a large area of a specific color that is not gray, Will make a correction that makes the color closer to gray. For example, when there are many red areas in an image, if the correction is performed by the LATD exposure method, the entire image will be printed with a cyan color which is a complementary color of red. Become.

As described above, it is assumed that correction is not performed on a positive film. Therefore, an optimum color correction method for a positive film has not been sufficiently developed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to eliminate the influence of a photographic light source and a slope characteristic of a film on image quality and to minimize a necessary color balance. It is an object of the present invention to provide a color correction method capable of obtaining an image with good image quality by the correction, a recording medium on which a color correction program is recorded, an image processing device, and a photographic printing device.

[0016]

According to a first aspect of the present invention, there is provided a color correction method for correcting a color balance of an image, the method comprising the steps of: A first step of dividing a pixel value obtained based on image data of different colors into a plurality of sections, and a second step of calculating a color balance for each section based on the pixel value of each section Steps, on a color disk such that the radial direction indicates saturation and the circumferential direction indicates hue, corresponding to the different colors, different radially outward from a reference point that is the center on the color disk. A third step of considering a plurality of directions heading as reference directions and obtaining color vectors of the plurality of reference directions corresponding to the color balance on the color disk for each section; of A region between the minimum value and the maximum value of the component in each of the above-described reference directions, and a color component region corresponding to the reference direction. Determining whether there is a color component area common to all sections for each of the colors corresponding to the reference direction, and calculating the correction value of each color based on the determination result. It is characterized by including a sixth step of calculating and a seventh step of correcting the color balance based on the correction value of each color.

For example, if an image recorded on a photographic film is read by a solid-state image pickup device (for example, a CCD), image data for each pixel of the image is different for each color (for example, RG
B). On the other hand, in an image captured by a digital camera or the like, digital data of each pixel of the image is obtained as image data for each different color. As the pixel value, a value obtained by, for example, logarithmic conversion of the image data of each color can be considered. By this logarithmic conversion, the subsequent processing can be performed while suppressing the scale of the image data.

The above pixel value is divided into a plurality of sections. This section may be, for example, a so-called density section in which pixel values are arranged in ascending order and divided into certain sections, or a section corresponding to each area when the original image is divided into a plurality of areas. You may. Then, the color balance is calculated for each section.

On a color disk in which the radial direction indicates the saturation and the circumferential direction indicates the hue, the RGB is shifted outward from a reference point which is the center on the color disk.
The reference direction corresponding to is defined. On this color disk, a color vector in the RGB direction corresponding to the color balance is obtained for each section. Note that this processing is the same as that when considering a position corresponding to the color balance on the color disk, a vector from the reference point to the position is decomposed into color vectors in the RGB directions. is there.

Then, for each of the RGB color vectors, a component in the RGB direction is further obtained.
A region between the minimum value and the maximum value of the component in each direction of B is defined as a component region of the color. When this color component area is calculated for each section, it is determined whether or not there is a color component area common to all the sections (hereinafter, referred to as a color component common area) for each color of RGB.

Here, when there is a color component common area,
For example, while the median value in the color component common area is the correction value for the color for which the determination was made, if there is no color component common area, for example, the correction value for the color for which the determination was made is zero. It is said. Then, the color balance is calculated again based on the calculated correction value of each color.

Since information on the light source for shooting and information on the slope characteristics of the film are reflected in all sections, as in the present invention,
By calculating a correction value for each color based on the presence or absence of a color component common area that is common to all sections, and correcting the color balance based on the correction value of each color, such a shooting light source and film slope The influence of the characteristics on the image can be removed, and an image with good image quality can be obtained.

Further, since the correction value is calculated for each color based on the presence or absence of the color component common area, for example, as described above,
By setting the correction value to the center value of the color component common area or to zero, the correction strength of the color balance can be reduced as compared with the conventional LATD method. Thereby, even if the target of the color balance correction is, for example, an image recorded on a positive film by an advanced photographer, it is not overcorrected, and from the photographer's intention with the minimum necessary correction, It is possible to obtain an image that will not be far away.

When an object having an extremely strong color exists in an image, a color component region is hardly obtained in all sections. Therefore, in this case, as described above, the color balance is corrected by excluding the color by setting the correction value for the color to, for example, zero. As a result, the method of the present invention is not affected by an object having an extremely strong color.
It can be said that the color fear is less likely to be caused as compared with the D method.

The color correction method according to the second aspect of the present invention
In order to solve the above problem, in the configuration of claim 1, in the sixth step, when it is determined that there is a color component area common to all sections, the median value in the color component common area is set to the value. It is characterized in that it is used as a correction value for the determined color.

According to the above configuration, since the correction value for correcting the color balance is set to the center value of the color component common area, the correction strength of the color balance can be reliably reduced as compared with the conventional LATD method. it can. Thereby, even if the target of the color balance correction is, for example, an image recorded on a positive film by an advanced photographer, it is not overcorrected, and from the photographer's intention with the minimum necessary correction, It is possible to obtain an image that will not be far away.

The color correcting method according to the third aspect of the present invention
In order to solve the above-mentioned problem, in the configuration according to claim 1, when it is determined in the sixth step that there is no color component area common to all sections, a correction value for the determined color is determined. Is set to zero.

When an object having an extremely strong color exists in an image, a color component region is rarely obtained in all sections. Therefore, in this case, as described above, the color balance is corrected by excluding the color by setting the correction value for the color to zero. As a result, it is not affected by an object having an extremely strong color, so that it is possible to suppress the occurrence of color fear as compared with the conventional LATD method.

A color correction method according to a fourth aspect of the present invention
In order to solve the above-described problem, in any one of the first to third aspects, the section is a density section in which the pixel values are arranged in ascending order and divided into certain sections.

Since the information on the photographic light source and the information on the slope characteristics of the film are reflected in the entire density section, each color is determined based on the presence / absence of the color component common area existing in the entire density section as in the above configuration. By calculating the correction value for each color and correcting the color balance based on the correction value of each color, it is possible to reliably remove the influence of such a photographic light source and the slope characteristics of the film on the image, thereby improving the image quality. An image can be obtained reliably.

A color correction method according to a fifth aspect of the present invention
In order to solve the above-mentioned problem, in the configuration according to any one of claims 1 to 3, the section is defined when the pixel value is divided corresponding to each divided area when the image is divided into a plurality of areas. It is characterized by a section.

Since the information on the photographic light source and the information on the slope characteristics of the film are reflected on the entire image, as in the above-described configuration, each of the sections when the pixel value is divided corresponding to each divided area of the image. By calculating a correction value for each color based on the presence or absence of a common color component common area, and correcting the color balance based on the correction value of each color, such an image of the shooting light source and film slope characteristics , The influence on the image quality can be reliably removed, and an image with good image quality can be reliably obtained.

According to a sixth aspect of the present invention, there is provided a recording medium storing a color correction program for causing a computer to execute the color correction method according to any one of the first to fifth aspects. It is characterized by recording a program.

According to the above arrangement, the computer program (for example, an image processing apparatus) executes the program, whereby the effects described in any one of claims 1 to 5 can be obtained.

An image processing apparatus according to a seventh aspect of the present invention is an image processing apparatus for correcting the color balance of an image in order to solve the above-mentioned problem. Image information dividing means for dividing a pixel value obtained based on a plurality of sections, a color balance calculating means for calculating a color balance for each section based on the pixel value of each section, On a color disk whose saturation indicates hue and whose circumferential direction indicates hue, a plurality of directions directed outward in different radial directions from a reference point, which is the center on the color disk, corresponding to the different colors, are referred to. Color vector detecting means for calculating the color vectors in the plurality of reference directions corresponding to the color balance on the color disk for each section, and for each of the color vectors, A component detecting means for determining the number of components in the reference direction, and a region between the minimum value and the maximum value of the component in each of the reference directions as a color component region corresponding to the reference direction. A color component area calculating means for calculating each section, and for each of the colors corresponding to the reference direction, determining whether or not there is a color component area common to all the sections; and correcting the respective colors based on the determination result. It is characterized by comprising correction value calculating means for calculating a value and correcting means for correcting a color balance based on the correction value of each color.

For example, if an image recorded on a photographic film is read by a solid-state image pickup device (for example, a CCD), image data for each pixel of the image is different for each color (for example, RG
B). On the other hand, in an image captured by a digital camera or the like, digital data of each pixel of the image is obtained as image data for each different color. As the pixel value, a value obtained by, for example, logarithmic conversion of the image data of each color can be considered. By this logarithmic conversion, the subsequent processing can be performed while suppressing the scale of the image data.

The above pixel value is divided into a plurality of sections by the image information dividing means. This section may be, for example, a so-called density section in which pixel values are arranged in ascending order and divided into certain sections, or a section corresponding to each area when the original image is divided into a plurality of areas. You may. Then, the color balance is calculated for each section by the color balance calculation means based on the pixel value for each section.

On a color disk in which the radial direction indicates the saturation and the circumferential direction indicates the hue, the RGB is shifted outward from a reference point which is the center of the color disk.
The reference direction corresponding to is defined. On this color disk, a color vector in the RGB direction corresponding to the color balance is obtained for each section by the color vector detection means. Note that this processing is the same as that when considering a position corresponding to the color balance on the color disk, a vector from the reference point to the position is decomposed into color vectors in the RGB directions. is there.

Then, for each of the RGB color vectors, components in the RGB direction are further obtained by the component detecting means, and the color component area calculating means calculates the difference between the minimum value and the maximum value of the components in each of the RGB directions. Are the component areas for that color. When this color component area is calculated for each section, a color component area common to all sections (hereinafter, referred to as a color component common area) for each color of RGB.
Whether or not there is is determined by the correction value calculating means.

Here, when there is a color component common area, the correction value calculating means sets, for example, the median value in the color component common area as the correction value for the determined color, If there is no area, for example, the correction value for the color for which the determination has been made is set to zero. The correction means calculates the color balance again based on the calculated correction value of each color.

Since the information on the light source for shooting and the information on the slope characteristics of the film are reflected in all sections, as in the present invention,
By calculating a correction value for each color based on the presence or absence of a color component common area that is common to all sections, and correcting the color balance based on the correction value of each color, such a shooting light source and film slope The influence of the characteristics on the image can be removed, and an image with good image quality can be obtained.

Since the correction value is calculated for each color based on the presence or absence of the color component common area, for example, as described above,
By setting the correction value to the center value of the color component common area or to zero, the correction strength of the color balance can be reduced as compared with the conventional LATD method. Thereby, even if the target of the color balance correction is, for example, an image recorded on a positive film by an advanced photographer, it is not overcorrected, and from the photographer's intention with the minimum necessary correction, It is possible to obtain an image that will not be far away.

When an object having an extremely strong color exists in an image, a color component region is hardly obtained in all sections. Therefore, in this case, as described above, the color balance is corrected by excluding the color by setting the correction value for the color to, for example, zero. As a result, it is not affected by an object having an extremely strong color, so that it is possible to reduce the possibility of causing color fear as compared with the conventional LATD method.

According to an eighth aspect of the present invention, in order to solve the above-mentioned problems, an image processing apparatus according to the seventh aspect and a color balance corrected by the image processing apparatus can be obtained. And an exposing means for exposing the photosensitive material.

The correction value of the color balance obtained by the image processing apparatus can be obtained as a correction value that can suppress the occurrence of color fear and also the effect of the type of photographic film and the photographing conditions. ing. Therefore, if the exposure means exposes the photosensitive material so as to obtain the above color balance, an image having a good color balance can be formed on the photosensitive material regardless of the color deviation in the image, the type of photographic film, and the photographing conditions. Can be burned.

The exposure by the exposure means is performed by adjusting a light control filter when the exposure means is, for example, an analog method, or by adjusting the amount of RGB light for each pixel when the exposure means is a digital method. .

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on the drawings.

The photographic printing apparatus according to the present embodiment prints an image recorded on, for example, a positive film as a photographic film on a photographic paper as a photosensitive material. As shown in FIG. Unit 1 and image processing unit 2
(Image processing apparatus) and an exposure unit 3 (exposure means). In FIG. 1, arrows passing through the image capturing unit 1 and the exposure unit 3 indicate a transport path of the positive film transported by a transport unit (not shown).

The image capturing unit 1 is a scanner that captures an image recorded on the positive film by measuring the light transmitted through the positive film, and includes, for example, a light source that irradiates the positive film with light, and RGB color filters. And a CCD (Charge Coupled Device) camera (hereinafter simply referred to as CCD).
The rotation filter is rotated so that the light of each color of RGB sequentially reaches the CCD, and the light transmitted through the positive film is converted to RGB.
The CCD sends an electric signal corresponding to the amount of received light to the image processing unit 2 for each of R, G, and B.
As a result, image data corresponding to the density of each pixel of the image recorded on the positive film is obtained for each of RGB. When the CCD is constituted by a three-plate CCD, the above-mentioned rotary filter is unnecessary.

The image data obtained by the CCD is, for example, 4096 gradations (12 bits) from 0 to 4095.
, But 256 tones from 0 to 255
The present invention can be applied to each gradation (8 bits). In any of the above cases, a smaller value indicates a higher density, and a larger value indicates a lower density.

The image processing section 2 performs processing for correcting the color balance of an image (for example, one frame of a positive film). Specifically, the image processing unit 2 includes the image capturing unit 1
A correction value of the exposure amount is calculated for each of the RGB based on the image data for each of the RGB sent from the printer, and the information is sent to the exposure unit 3. The detailed configuration of the image processing unit 2 will be described later. The image processing unit 2 includes a microprocessor and / or a DSP (Digit) incorporated in the photographic printing device.
al Signal Processor) or a PC (Personal Computer) provided outside the device.
May be configured. Further, the image processing unit 2 includes a memory (not shown) for temporarily storing image data from the image capturing unit 1.

The exposure unit 3 exposes the photographic paper through a positive film so as to obtain a color balance based on the RGB correction values calculated by the image processing unit 2, and converts the image recorded on the positive film. It is to be printed on photographic paper,
For example, it is constituted by a light source, a light control filter unit, a film disposing means, a printing lens, and the like.

The light source is, for example, a halogen lamp. The dimming filter unit is configured with filters of each color of yellow (Y), magenta (M), and cyan (C), and performs dimming by a color reduction method. Each of these color filters consists of two filters, and the two filters are arranged so as to sandwich the optical path of the light emitted from the light source. By changing the amount of each color filter inserted in the optical path, it is possible to adjust the RGB exposure amount, that is, the color balance of the printed image.

The film arranging means has a function of moving an image to be printed on the positive film conveyed into the exposure section 3 to an exposure position and shielding the periphery of the image from light. Auto N
ega-Mask). A printing lens is an optical member for emitting light from a light source, temporarily collecting light transmitted through a positive film, and projecting the light on photographic paper.

Next, the image processing section 2 will be described. As shown in FIG. 1, the image processing unit 2 includes a conversion unit 4, an image information division unit 5, a color analysis unit 6, a correction value calculation unit 7, and a correction unit 8.

The conversion unit 4 performs logarithmic conversion of image data for each RGB obtained by each pixel of the CCD of the image capturing unit 1 by taking a natural logarithm thereof. Therefore, 0
The conversion unit 4 converts the image data 4095 to 0 to 8.3.
It is converted to a logarithmic value of 17. As a result, the scale of the image data is suppressed. In the present embodiment, this logarithmic value is used as a pixel value in the subsequent processing.

Image information dividing section 5 (image information dividing means)
Divides the above pixel value obtained based on the RGB image data of each pixel in the image into a plurality of density sections. The density section refers to a section when the density information of the positive film is divided into a plurality of sections with an appropriate width, that is, a section when pixel values are arranged in ascending order and divided into certain sections. The width of each density section is, for example, 0.25
Then, since the pixel values are obtained in the range of 0 to 8.317, there are approximately 33 density sections. The width of each density section depends on the experiment, experience,
The setting can be changed as appropriate according to the accuracy of input data (scanning data) and the like.

The color analyzer 6 detects the color bias for each density section, and thereby detects the color bias of the entire image, and constitutes the most characteristic part of the present invention. The color analyzer 6 includes a color balance calculator 9, a color vector detector 10, a component detector 11, and a color component region calculator 12.

The color balance calculation section 9 (color balance calculation means) calculates a color balance for each density section based on the pixel value for each density section.

The color vector detecting section 10 (color vector detecting means) is provided on a color disk in which the radial direction indicates saturation and the circumferential direction indicates hue. When considering a plurality of directions going outward in different radial directions from the center reference point as reference directions, color vectors of the plurality of reference directions corresponding to the color balance are obtained for each density section on the color disk. .

The component detecting section 11 (component detecting means) obtains the components in the plurality of reference directions for each of the RGB color vectors.

The color component area calculation section 12 (color component area calculation means) sets the area between the minimum value and the maximum value of the component in each reference direction as a color component area corresponding to the reference direction. The color component area is calculated for each density section.

The correction value calculation section 7 (correction value calculation means) determines whether or not there is a color component area common to all density sections in each of the RGB directions corresponding to the reference direction. Is used to calculate the correction value of each color.

The correction section 8 (correction means) corrects the color balance based on the correction value of each color.

Hereinafter, the details of each of the above components will be described together with the operation of the photographic printing apparatus.

First, when a positive film is inserted into the image capturing unit 1, the CCD of the image capturing unit 1 measures light from a light source passing through a predetermined frame of the positive film, and is recorded on the frame. The captured image is captured, and RGB image data of each pixel of the captured image is sent to the image processing unit 2 (FIG. 3;
S1). In the image processing unit 2, the conversion unit 4 converts the RGB image data from the image capturing unit 1 into a logarithmic value (pixel value). The RGB pixel values of all the frames of the positive film are
It is stored in a memory (not shown). On the other hand, the positive film for which the photometry of all frames in the image capturing unit 1 has been completed is transported to the exposure unit 3 by a transport unit (not shown).

The image information dividing unit 5 divides the pixel value into predetermined density sections (for example, every 0.25) (S5).
2) The color analysis unit 6 analyzes whether or not there is a color bias for each density section (S3). Here, the color analysis processing will be described in more detail based on the flowchart of FIG.

First, the color balance calculation section 9 of the color analysis section 6 calculates a color balance in an arbitrary density section (for example, a density section from 0 to 0.25) in the density section based on the pixel value (S3). -1). More specifically, the color balance calculation unit 9 obtains an average value R _AVE of R, an average value G _AVE of G, and an average value B _{AVE of} B in the density section, and calculates these average values R _AVE , G _AVE. The color balance by the LATD method is calculated based on B _AVE .

For example, when it is assumed that there are three pixel values in the density section, the average value R _AVE in the density section is set.
G _AVE and B _AVE are respectively R _AVE = (R ₁ + R ₂ + R ₃ ) / 3 G _AVE = (G ₁ + G ₂ + G ₃ ) / 3 B _AVE = (B ₁ + B ₂ + B ₃ ) / 3. Therefore, the color balance D _AVE in this case is obtained by D _AVE = (R _AVE + G _AVE + B _AVE ) / 3 (A).

Next, when the color disk shown in FIG. 5 is considered, the color vector detection unit 10 determines the color vector (r) · R in the RGB direction corresponding to the color balance on the color disk.
(G) and (b) are obtained (S3-2).

Here, the above-mentioned color disk indicates a two-dimensional space in which the radial direction indicates saturation and the circumferential direction indicates hue. On this color disk, directions that are directed radially outward from the reference point O, which is the center of the color disk, and differ by a central angle of 120 ° from each other correspond to the respective RGB directions (reference directions). I have. And the reference point O
The directions exactly opposite to the directions of RGB correspond to the directions of Y (yellow), M (magenta), and C (cyan), which are complementary colors of RGB. That is, the directions of R, Y, G, C, B, and M are counterclockwise starting from the reference point O in this order so that the angle between the reference point O and the two adjacent directions is 60 °. Lined up.

The size R _balance , G _balance, and B _balance of the color vectors (r), (g), and (b) in the RGB direction corresponding to the color balance D _AVE are as follows: R _balance = R _AVE −D _AVE G _balance = G _AVE −D _AVE B _balance = B _AVE −D _AVE Therefore, _assuming that the coordinates of the position (p) corresponding to the color balance D _AVE on the color disk are (x, y), the coordinates (x, y) are the vector size R
_{Using balance} / G _balance / B _balance ,
It looks like an expression.

[0073]

(Equation 1)

However, the angle in the expression (1) indicates an angle in a counterclockwise direction around the reference point O with respect to the R direction. That is, the R direction is 0 ° and the G direction is 120 °.
° (the angle between the R direction and the G direction is 120 °), and the B direction is 240 ° (the angle between the R direction and the B direction is 240 °).

The respective color vectors (r), (g),
To find (b) means to find a position (p) on the color disk corresponding to the color balance D _AVE , consider a vector from the reference point O to the position (p), and convert this position vector in the RGB direction. Color vector (r)
This is the same as decomposing into (g) and (b).

Subsequently, the component detecting section 11 performs RG processing on each of the above color vectors (r), (g), and (b).
A component in the B direction is obtained (S3-3). Specifically, it is as follows.

As shown in FIG. 6, consider an axis parallel to the CR, MG, and YB directions on the color disk. In addition, for convenience of the following description, these axes are sequentially referred to as an R axis and a G axis.
Axis, B axis.

For example, each color vector (r), (g),
When obtaining the component in the R direction in (b), first, a perpendicular line is drawn from the reference point O to the R axis, and the intersection with the R axis is set as the reference position (0). Then, each color vector (r) · (g)
From the end point of · (b) (the tip of the arrow) down the vertical line to the R axis, the intersection of the R-axis and the r ₁ · g ₁ · b _1, respectively.
On the R axis, the direction corresponding to the OR direction on the color disk is considered as a positive direction, and the opposite direction is considered as a negative direction. In the example of FIG. 6, since r ₁ > g ₁ > b ₁ , the color vector (r) ·
When (g) and (b) are arranged in descending order of the component in the R direction, they become color vectors (r), (g) and (b).

Note that r ₁ , g ₁ , and b ₁ can be obtained by the following equations.

R₁= R_balance× cos0 ° g₁= G_balance× cos120 ° b₁= B_balance× cos240 ° The remaining G in each color vector (r) · (g) · (b)
The same applies to the case where the components in the direction and the B direction are obtained. Toes
G direction in each color vector (r) / (g) / (b)
When determining the direction component, first, the reference point O is perpendicular to the G axis.
The line is lowered, and the intersection with the G axis is set as the reference position (0). So
Then, from the end point of each color vector (r) / (g) / (b)
Also drop a perpendicular to the G axis, and set the intersection with the G axis to r_Two・
g_Two・ B _TwoAnd On G axis, OG direction on color disk
The direction corresponding to is considered the positive direction, and the opposite direction is considered the negative direction.
I can. In the example of FIG._Two> R_Two> G_TwoSo the color
Vectors (r), (g), and (b) have many components in the G direction
When arranged in order, the color vectors are (b), (r), and (g).
You.

Note that r ₂ , g ₂ , and b ₂ can be obtained by the following equations.

R ₂ = R _balance × cos 240 ° g ₂ = G _balance × cos 0 ° b ₂ = B _balance × cos 120 ° Also, B in each color vector (r) · (g) · (b)
When obtaining the direction component, first, a perpendicular line is drawn from the reference point O to the B axis, and the intersection with the B axis is set as the reference position (0).
Then, a perpendicular line is drawn from the end point of each of the color vectors (r), (g), and (b) to the B-axis, and the intersection with the B-axis is r ₃
・ G ₃・ b ₃ On the B axis, the direction corresponding to the OB direction on the color disk is considered as a positive direction, and the opposite direction is considered as a negative direction. In the example of FIG. 6, since g ₃ > b ₃ > r ₃ ,
When the color vectors (r), (g), and (b) are arranged in descending order of components in the B direction, they become color vectors (g), (b), and (r).

Note that r ₃ , g ₃ , and b ₃ can be obtained by the following equations.

R ₃ = R _balance × cos 120 ° g ₃ = G _balance × cos 240 ° b ₃ = B _balance × cos 0 ° Next, the color component area calculation unit 12 calculates the color vector (r) · (g The area between the minimum value and the maximum value of the components in each of the RGB directions in (b) is defined as the component area of each color in the RGB direction (3-4).

Here, the minimum value and the maximum value of the component in the R direction are R _min and R _max , the minimum value and the maximum value of the component in the G direction are G _min and G _max , respectively, and the minimum value and the component of the component in the B direction are respectively. Maximum values are B _min and B respectively
When _{max, R min, R ma x} , G min, G max, B
_min and B _max are represented by the following equations, respectively.

R _min = min (r ₁ , g ₁ , b ₁ ) R _max = max (r ₁ , g ₁ , b ₁ ) G _min = min (r ₂ , g ₂ , b ₂ ) G _max = max ( r ₂ , g ₂ , b ₂ ) B _min = min (r ₃ , g ₃ , b ₃ ) B _max = max (r ₃ , g ₃ , b ₃ ) For example, in FIG. 6, the minimum value of the component in the R direction is shown. Is b ₁
And the maximum value is r ₁ . Therefore, the color component area calculation unit 12 sets the area between b ₁ and r ₁ as the color component area in the R direction. Similarly, for the G direction,
Since the minimum value of the component is g ₂ and the maximum value is b ₂ ,
The color component region calculation unit 12 calculates g ₂ and b for the G direction.
The region between the _two is a color component region. Also, in the B direction, the minimum value of the component is r ₃ and the maximum value is g ₃ , so that the color component region calculation unit 12 calculates
An area between r ₃ and g ₃ is defined as a color component area. FIG.
Each of the R axis, the G axis, and the B axis shows the range of such a color component region.

By examining the range of each color component area in this way, it is possible to automatically determine the color bias in that section. That is, the color component area for R is R
If the color exists in the positive direction, the color is biased toward R in the density section, and if the color is biased in the negative direction of R, it is determined that the color is biased to C in the density section. can do.

The color analyzer 6 performs the above processing until the processing is completed for all the density sections (S3-5).

When the color component areas in the RGB directions are obtained for all the density sections as described above, the correction value calculating section 7
Determines whether there is a color component area common to all density sections for each of RGB. By considering such a color component common area, it is possible to determine the color bias for the entire density section, that is, for the entire image. Then, the correction value calculation unit 7 calculates the correction value of each color based on the determination result (S4).

More specifically, the correction value calculation section 7 calculates the RGB values
When it is determined that there is a color component area common to all density sections for each color, a median value in a common color component area (hereinafter, referred to as a color component common area) is used as a correction value for the color for which the determination is made. On the other hand, if it is determined that there is no color component area common to all density sections, the correction value for the color for which the determination has been made is set to zero.

Then, the correction unit 8 replaces the RGB correction values obtained by the correction value calculation unit 7 with R _AVE , G _AVE , and B _{AVE of} the above-described equation (A), and re-balances the color. Calculate the color correction value.

The color balance (exposure correction value) obtained in S4 is output from the correction unit 8 to the exposure unit 3 (S4).
5). Then, the exposure unit 3 adjusts the dimming filter unit so that each of the RGB exposure amounts corresponding to the color balance is obtained, and a predetermined frame of the positive film conveyed from the image capturing unit 1 receives a predetermined frame from the light source. The image of the frame is printed on the photographic paper by irradiating light (S6).

Next, a specific example of the correction in the correction value calculating section 7 will be described with reference to FIGS. 8 (a) to 8 (c). Here, the calculation of the correction value in the R-axis direction will be described as an example. It is also assumed that there are three density sections, for example, and that the color component areas obtained in each density section are all on the positive side (R side instead of C side) from the reference position 0. I do. in this case,
The color balance of each density section is all red (cyan)
It is not a system.

(Specific Example A) As shown in FIG. 8A, the minimum values of the components are 5, 6, and 7, respectively, and the maximum values are 6, 7, and 8, respectively, in each of the density sections. Case.

In this example, the color component areas are 5-6, 5-7, 5-8
Becomes In this case, the color component common areas common to all of the density sections are 5 to 6.

Therefore, the correction value calculation unit 7 sets the median value 5.5 of the color component common areas 5 to 6 as the correction value for R.

Incidentally, when the correction value is calculated by the conventional LATD method, (6 + 7 + 8) / 3 = 7.

That is, when the minimum value of the component area in each density section is constant as in this specific example, when the correction value is obtained by the method of the present embodiment, the correction value (7) obtained by the conventional LATD is obtained. As a result, a value (5.5) close to the minimum value is obtained as a correction value, and the correction strength of R is more reliably reduced than in the related art.

(Specific Example B) As shown in FIG. 8B, in each of the density sections 区間, the minimum value of the component is 2, 3, 4 respectively, and the maximum value is 5, 5, 5 respectively. Case.

In this example, the color component areas are 2-5, 3-5, 4-5
Becomes In this case, the color component common areas common to all of the density sections are 4 to 5.

Therefore, the correction value calculation section 7 sets the median value 4.5 of the color component common areas 4 to 5 as the correction value for R.

Incidentally, when the correction value is calculated by the conventional LATD method, (5 + 5 + 5) / 3 = 5.

That is, when the maximum value of the component area in each density section is constant as in this specific example, when the correction value is obtained by the method of the present embodiment, the correction value (5) obtained by the conventional LATD is obtained. Is small (4.5), and the correction strength is weaker than in the prior art, as in the specific example A. However, in this specific example, correction close to the conventional LATD is performed.

(Specific Example C) As shown in FIG. 8 (c), in each of the density sections 〜, the minimum value of the component is 5, 5, 2, and the maximum value is 9, 9, 3, respectively. Case.

In this example, the color component areas are 5-9, 5-9, 2-3
Becomes In this case, there is no color component common region common to all of the density sections to.

Therefore, in this case, the correction value calculating section 7
Sets the correction value for R to 0.

Incidentally, when the correction value is calculated by the conventional LATD method, (9 + 9 + 3) / 3 = 7.

That is, as in this specific example, when the intensity (chroma) of the component region of the entire density section is too different even if it exists in red, the method of the present invention is significantly different from the conventional LATD. , Different correction values are obtained. This allows
It is possible to correct the entire color balance by excluding only objects having strong colors.

As described above, in the present invention, a color component common region common to all density sections is obtained, and a correction value is calculated based on the presence or absence of this color component common tone range. When the original image contains information on the photographic light source and information on the slope characteristics of the film, such information is reflected in the entire density section of the image, and the color balance of the entire image tends to be biased. As described above, a correction value is calculated for each color based on the presence or absence of a color component common area that is present in common in all density sections, and a color balance is corrected based on the correction value of each color, so that a shooting light source can be obtained from the entire image. And the effect of the slope characteristics of the film can be removed, and an image with good image quality can be obtained.

Further, since a correction value is obtained by automatic calculation from the pixel value of the image, the bias of the color balance in the entire image is automatically determined, and the color balance is corrected, so that even a non-skilled person can easily perform the color correction. It can be carried out.

Also, since the correction value is calculated for each color based on the presence or absence of the color component common area, for example,
By setting the correction value to the median value of the color component common area as in B, or setting the correction value to zero as in the specific example C, the color balance of the conventional LATD method is improved. The correction strength can be reduced. Thus, even if the target for which the color balance is to be corrected is, for example, an image recorded on a positive film by an expert photographer, it is possible to perform correction that does not involve much manipulation of the actual image. That is, the method of the present invention is particularly suitable for correcting the color balance of an image recorded on a positive film.

In particular, when an object having an extremely strong color exists in an image as in the specific example C, a color component region is hardly obtained in all sections.
Therefore, in this case, the color balance is corrected by excluding the color by setting the correction value for that color to, for example, zero. As a result, it is not affected by an object having an extremely strong color.
The generation of color feria can be suppressed as compared with the method.

That is, conventionally, in a scene (image) in which a strong color object or the like exists, most of the divided sections are occupied by the object in many cases, and even if the other sections are near achromatic colors, Since the detection result reflects the influence of the strong color object, color feria has occurred. Moreover, it has been very difficult to calculate the entire correction value excluding only objects having strong colors.

However, according to the present invention, the correction value is detected and corrected on the basis of the color component areas which exist uniformly in all the density sections, that is, the areas where the vector areas of each density section overlap in the entire density section. Therefore, even if there is an object with extremely strong color, it will not be affected as in the past,
The occurrence of color feria can be suppressed.

In the present embodiment, a case has been described in which pixel values are divided into predetermined density sections and correction values are obtained for each density section. However, each image area when an image is divided into a plurality of areas is described. The same effect as in the present embodiment can be obtained by dividing the pixel value in accordance with the above and obtaining a correction value for each image region. Whether the pixel value is divided by the density section or the image area can be appropriately set, for example, depending on the image to be corrected.

As can be seen from the above description, the present invention is designed to remove the influence of the photographic light source and the influence of the slope characteristic of the film, so as to detect a color biased in the entire image. Image area),
The point is that a special color analysis is performed for each section.

In the color correction of the present invention, the correction accuracy is improved or reduced depending on the number of sections (the number of divisions) of the density section or the section corresponding to the divided area of the image. Experiments have shown that in a scene with rich colors, the smaller the number of divisions is, the better the correction accuracy is. Therefore, by setting the number of divisions according to the image to be corrected, correction accuracy suitable for the image can be obtained.

In the case of a positive film, a photographer often shoots after grasping the color balance, so that a large correction is not preferred. However, it is meaningless to make only a small correction to a scene that requires correction, so it is necessary to check an appropriate number of divisions according to the environment.

In addition, the correction accuracy varies depending on the number of sections for obtaining a color component common area, such as obtaining a common color component area only for some sections. In this case, if it is only a part of the section, a monotonous image (image with poor color change)
Therefore, there is a risk that incorrect correction may be made, so that it is necessary to set the number of sections when obtaining the color component common region according to the scene.

In the present embodiment, the central value in the color component common area is used as the correction value for the color.
It is not limited to this median. For example, in the color component common region, a value according to the degree of color change of the scene to be handled (a little closer to R or closer to C from the median) may be used as the correction value. For example, the R axis shown in FIGS. 6 and 7 represents the intensity from R to C, and an area exists near R in a certain section, and an area exists near C in another section. Therefore, it is safer to use the median value of the color component common area as the correction value as in the present embodiment.

The above processing in the present embodiment can be realized by a program. This program is stored in a computer-readable recording medium.
In the present invention, the recording medium may be a memory (not shown) (not shown) necessary for the image processing unit 2 to perform processing, or a program (not shown) may be used as an external storage device. It may be a program medium provided with a reading device and readable by inserting a recording medium therein.

In any of the above cases, the stored program may be configured to be executed by accessing a microprocessor (not shown), or the stored program may be read and the read program may be distributed. The server and the receiving server may be configured to execute the program by downloading to a program storage area (not shown). In this case, it is assumed that the download program is stored in the main device in advance.

Here, the program medium is a recording medium configured to be separable from the main body, and is a tape system such as a magnetic tape or a cassette tape, a floppy (registered trademark).
Magnetic disk and CD-R such as disk and hard disk
Disk system of optical disk such as OM / MO / MD / DVD, card system such as IC card (including memory card) / optical card, or mask ROM, EPROM, EEP
It may be a medium that fixedly carries a program including a semiconductor memory such as a ROM or a flash ROM.

Further, in the present invention, since the system configuration is connectable to a communication network including the Internet, the medium may carry the program in a fluid manner so that the program is downloaded from the communication network. When the program is downloaded from the communication network, the download program may be stored in the main device in advance or may be installed from another recording medium.

The content stored in the recording medium is not limited to a program, but may be data.

In the above description, the exposure unit 3 irradiates light to the positive film to print the image of each frame of the positive film on photographic paper. The present invention can be applied even when the digital camera 3 is configured to perform digital exposure. In the case of digital exposure, the exposure unit 3 has a configuration including a light modulation element that modulates irradiation light onto photographic paper based on RGB digital image data. And send the RGB correction values
What is necessary is just to make each pixel perform exposure based on the said exposure correction value. Examples of the light modulation element include a PLZT exposure head, a DMD (digital micromirror device), an LCD (liquid crystal display), an LCS (liquid crystal shutter), an LED panel, a laser, a FOCRT.
(Fiber Optic Cathode Ray Tube) and CRT.

In the above description, the method of adjusting the color balance when a photograph is printed by the photographic printing apparatus has been described. For example, based on the RGB image data obtained by reading the image of each frame of the positive film,
The present invention can also be applied to a case where a plurality of frame images are displayed on a monitor and the color balance is adjusted on the monitor, and a case where the color balance of a positive image captured by a digital camera or digital video is adjusted on a PC monitor. . Further, the color balance adjusting method of the present invention can be applied to a case where an image is displayed by projecting RGB light onto a screen like a liquid crystal projector.

In the above description, in the photographic printing apparatus,
Although the case where the color balance is adjusted using a positive film has been described, the present invention can be similarly applied to a case where a negative film is used.

[0129]

As described above, the color correction method according to the first aspect of the present invention is a color correction method for correcting the color balance of an image, which is based on image data for each different color of each pixel in the image. A first step of dividing a pixel value obtained by the above into a plurality of sections, and a second step of calculating a color balance for each section based on the pixel value of each section.
And on a color disk in which the radial direction indicates saturation and the circumferential direction indicates hue, corresponding to the different colors, different radial outer sides from a reference point which is the center on the color disk The third step of considering the plurality of directions toward the reference direction as the reference directions and obtaining the color vectors of the plurality of reference directions corresponding to the color balance on the color disk for each section, A fourth step of obtaining components in a plurality of reference directions, and a region between the minimum value and the maximum value of the components in each of the reference directions is defined as a component region of a color corresponding to the reference direction. A fifth step of calculating for each section, and for each of the colors corresponding to the reference direction, determining whether or not there is a color component area common to all the sections; and correcting the respective colors based on the determination result. The value to be calculated And step is a configuration and a seventh step of correcting the color balance based on the correction value of each color.

Therefore, since the information of the photographing light source and the information of the slope characteristic of the film are reflected in all the sections, the present invention is based on the presence or absence of the color component common area existing in all the sections as in the present invention. By calculating the correction value for each color and correcting the color balance based on the correction value of each color, it is possible to remove the influence of such shooting light sources and the slope characteristics of the film on the image, resulting in images with good image quality. Can be obtained.

Also, since the correction value is calculated for each color based on the presence or absence of the color component common area, for example, as described above,
By setting the correction value to the center value of the color component common area or to zero, the correction strength of the color balance can be reduced as compared with the conventional LATD method. Thereby, even if the target of the color balance correction is, for example, an image recorded on a positive film by an advanced photographer, it is not overcorrected, and from the photographer's intention with the minimum necessary correction, It is possible to obtain an image that will not be far away.

When an object having an extremely strong color exists in an image, a color component area is hardly obtained in all sections. Therefore, in this case, as described above, the color balance is corrected by excluding the color by setting the correction value for the color to, for example, zero. As a result, it is not affected by an object having an extremely strong color, so that the effect of suppressing the occurrence of color feria can be achieved as compared with the conventional LATD method.

The color correction method according to the second aspect of the present invention
As described above, in the configuration of claim 1, in the sixth step, when it is determined that there is a color component area common to all sections, the median value in the color component common area is determined. The configuration is a correction value for color.

Therefore, since the correction value for correcting the color balance is the median value of the color component common area, the correction strength of the color balance can be reliably reduced as compared with the conventional LATD method. Thereby, even if the target of the color balance correction is, for example, an image recorded on a positive film by an advanced photographer, it is not overcorrected, and from the photographer's intention with the minimum necessary correction, This has the effect that an image that is not far apart can be obtained.

The color correction method according to the third aspect of the present invention
As described above, in the configuration of claim 1, when it is determined in the sixth step that there is no color component area common to all the sections, the correction value for the determined color is set to zero. Configuration.

Therefore, when an object having an extremely strong color exists in an image, a color component area is hardly obtained in common in all sections, and the correction value for that color is set to zero. As a result, the color balance is corrected by excluding the color. As a result, there is no effect of an object having an extremely strong color, so that there is an effect that generation of color fear can be suppressed as compared with the conventional LATD method.

The color correction method according to the fourth aspect of the present invention
As described above, in any one of the first to third aspects, the section is a density section in which the pixel values are arranged in ascending order and divided into certain sections.

Therefore, since the information of the photographing light source and the information of the slope characteristic of the film are reflected in all the density sections, the correction for each color is performed based on the presence or absence of the color component common area which is common to all the density sections. By calculating the values and correcting the color balance based on the correction values for each color, it is possible to reliably remove the influence of such light sources and the slope characteristics of the film on the image, and to ensure an image with good image quality. The effect that it can obtain is produced.

The color correction method according to the fifth aspect of the present invention
As described above, in the configuration according to any one of claims 1 to 3, the section is a section when the pixel value is divided corresponding to each divided area when the image is divided into a plurality of areas. It is.

Therefore, since the information of the photographing light source and the information of the slope characteristic of the film are reflected on the entire image, they are common to each section when the pixel value is divided corresponding to each divided area of the image. Correction values are calculated for each color based on the presence or absence of the existing color component common area, and the color balance is corrected based on the correction values for each color. Can be reliably removed, and an image having good image quality can be reliably obtained.

According to a sixth aspect of the present invention, there is provided a recording medium on which is recorded a program for causing a computer to execute the color correction method according to any one of the first to fifth aspects. It is a configuration consisting of

Therefore, when the computer (for example, an image processing device) executes the above-mentioned program, the effect described in any one of claims 1 to 5 can be obtained.

An image processing apparatus according to a seventh aspect of the present invention is an image processing apparatus for correcting a color balance of an image as described above, and obtains the image data based on image data for each color of each pixel in the image. Image information dividing means for dividing a pixel value to be divided into a plurality of sections, color balance calculating means for calculating a color balance for each section based on the pixel value for each section, and indicating the saturation in the radial direction. On a color disk whose circumferential direction indicates hue, corresponding to the different colors, a plurality of directions from the reference point, which is the center on the color disk, toward different radial directions outward are considered as reference directions, Color vector detecting means for obtaining, in each section, color vectors in the plurality of reference directions corresponding to the color balance on the color disk, and the plurality of reference directions for each of the color vectors. A component detecting means for obtaining a component, and a region between the minimum value and the maximum value of the component in each of the reference directions is set as a color component region corresponding to the reference direction, and this color component region is calculated for each section. A color component area calculating means for determining whether or not there is a color component area common to all sections for each of the colors corresponding to the reference direction, and calculating a correction value for each of the colors based on the determination result; The configuration includes a value calculation unit and a correction unit that corrects the color balance based on the correction value of each color.

Therefore, since the information of the photographing light source and the information of the slope characteristic of the film are reflected in all sections, the present invention is based on the presence or absence of the color component common area existing in all sections as in the present invention. By calculating the correction value for each color and correcting the color balance based on the correction value of each color, it is possible to remove the influence of such shooting light sources and the slope characteristics of the film on the image, resulting in images with good image quality. Can be obtained.

Since the correction value is calculated for each color based on the presence or absence of the color component common area, for example, as described above,
By setting the correction value to the center value of the color component common area or to zero, the correction strength of the color balance can be reduced as compared with the conventional LATD method. Thereby, even if the target of the color balance correction is, for example, an image recorded on a positive film by an advanced photographer, it is not overcorrected, and from the photographer's intention with the minimum necessary correction, It is possible to obtain an image that will not be far away.

When an object having an extremely strong color exists in an image, a color component region is hardly obtained in all sections. Therefore, in this case, as described above, the color balance is corrected by excluding the color by setting the correction value for the color to, for example, zero. As a result, since an object having an extremely strong color is not affected, a color fear can be hardly caused as compared with the conventional LATD method.

As described above, the photographic printing apparatus according to the eighth aspect of the present invention uses the image processing apparatus according to the seventh aspect and the photographic material so that the color balance corrected by the image processing apparatus can be obtained. And an exposure unit for exposing.

Therefore, the correction value of the color balance obtained by the image processing apparatus is a correction value that can suppress the occurrence of color fear and the effect of the type of photographic film and the photographing conditions. Has been obtained as. Therefore, if the exposure means exposes the photosensitive material so as to obtain the above color balance, regardless of the color bias in the image and the type of photographic film and shooting conditions,
There is an effect that an image having a good color balance can be printed on the photosensitive material.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration mainly of an image processing unit of a photographic printing apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration of the entire photographic printing apparatus.

FIG. 3 is a flowchart showing a flow of an operation in the photo printing apparatus.

FIG. 4 is a flowchart showing details of a color analysis process in the flowchart of FIG. 3;

FIG. 5 is an explanatory diagram showing a color disk used in the color correction method according to the present invention and color vectors in the RGB direction corresponding to the color balance in an arbitrary density section on the color disk.

FIG. 6 is an explanatory diagram showing a technique for obtaining respective components of the respective color vectors in the RGB direction.

FIG. 7 is an explanatory diagram showing color component regions in each of RGB directions.

FIGS. 8A to 8C are explanatory diagrams showing specific examples of correction value calculation in a correction value calculation unit of the image processing unit.

[Explanation of symbols]

2 Image processing unit (computer) 3 Exposure unit (exposure unit) 5 Image information division unit (image information division unit) 7 Correction value calculation unit (correction value calculation unit) 8 Correction unit (correction unit) 9 Color balance calculation unit (color) Balance calculating means) 10 color vector detecting section (color vector detecting means) 11 component detecting section (component detecting means) 12 color component area calculating section (color component area calculating means)

Continued on the front page F term (reference) 2H106 AB04 BA27 2H110 BA15 BA18 CB31 CB41 CB76 CE03 5B057 CA01 CA08 CB01 CB08 CE17 DA08 5C077 MP08 PP28 PP32 PP37 PP46 PP58 PP65 TT09 5C079 HB01 HB06 LA00 LA01 LA02 LA10 LA11

Claims (8)

[Claims] 1. A color correction method for correcting a color balance of an image, the method comprising: dividing a pixel value obtained based on image data for each different color of each pixel in the image into a plurality of sections. A second step of calculating a color balance for each section based on a pixel value for each section; and a color disk in which the radial direction indicates saturation and the circumferential direction indicates hue. In correspondence with the different colors, a plurality of directions directed outward in different radial directions from a reference point that is a center on the color disk are considered as reference directions, and the plurality of references corresponding to the color balance on the color disk are considered. A third step of obtaining a color vector in each direction for each section; a fourth step of obtaining components of the plurality of reference directions for each of the color vectors; a minimum value and a maximum value of the components in each of the reference directions And the fifth step of calculating the color component area for each section in each section, and setting a color component area corresponding to the reference direction in each section. A sixth step of determining whether or not there is a color component region to be corrected and calculating a correction value of each color based on the determination result; and a seventh step of correcting a color balance based on the correction value of each color. And a color correction method comprising: 2. In the sixth step, when it is determined that there is a color component area common to all sections, a median value in the color component common area is set as a correction value for the color for which the determination has been made. The color correction method according to claim 1, wherein: 3. In the sixth step, when it is determined that there is no color component area common to all sections, a correction value for the determined color is set to zero. 2. The color correction method according to 1. 4. The color correction method according to claim 1, wherein said section is a density section in which said pixel values are arranged in ascending order and divided into predetermined sections. 5. The section according to claim 1, wherein said section is a section when said pixel value is divided corresponding to each divided area when an image is divided into a plurality of areas. Color correction method described in 1. 6. A recording medium on which a color correction program is recorded, wherein a program for causing a computer to execute the color correction method according to claim 1 is recorded. 7. An image processing apparatus for correcting a color balance of an image, wherein an image information division unit divides a pixel value obtained based on image data for each different color of each pixel in the image into a plurality of sections. Means, a color balance calculating means for calculating a color balance for each section based on a pixel value for each section, and a color disk in which the radial direction indicates saturation and the circumferential direction indicates hue, In correspondence with the different colors, a plurality of directions directed outward in different radial directions from a reference point that is a center on the color disk are considered as reference directions, and the plurality of references corresponding to the color balance on the color disk are considered. Color vector detecting means for obtaining a color vector in each direction for each section; component detecting means for obtaining the components in the plurality of reference directions for each of the color vectors; A region between the minimum value and the maximum value of the component to be used as a color component region corresponding to the reference direction, and a color component region calculating means for calculating the color component region for each section; Correction value calculation means for determining whether or not there is a color component region common to all sections for each of the colors to be calculated, and calculating a correction value for each color based on the determination result; and An image processing apparatus comprising: a correction unit configured to correct a color balance by using a correction unit. 8. A photographic apparatus comprising: the image processing apparatus according to claim 7; and an exposure means for exposing a photosensitive material so as to obtain a color balance corrected by the image processing apparatus. Printing equipment.