JP2007267170A - Electronic camera with chroma saturation regulating function and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform image processing close to a feeling at the time of photographing according to the condition of a subject such as the strength of the sun. <P>SOLUTION: The electronic camera comprises a brightness detecting portion, an image pick-up portion, and a chroma saturation regulating portion. The brightness detecting portion detects brightness information of the field, and the image pick-up portion picks up an image of the field and generates image data. The chroma saturation regulating portion changes the chroma saturation of the image data according to a change in perception of chroma saturation corresponding to the brightness information of the field. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic camera and an image processing program.

Conventionally, a technique for extracting a specific hue area from image data and adjusting the saturation of the hue area has been known (Patent Document 1).
In addition, a technique for adjusting the saturation according to the luminance signal of the image data has been known (Patent Document 2).
JP 2002-33934 A JP 2005-295294 A

  By the way, the situation of the field actually photographed varies from a strong sunlight to a dim situation. The present inventor has realized that image data close to the impression felt by the photographer at the time of photographing can be obtained by reflecting such a difference in the field situation in the image quality adjustment of the image data.

  Usually, since an electronic camera performs exposure adjustment according to subject brightness, the intensity of sunlight described above cannot be easily estimated from the brightness signal of image data after shooting. Therefore, as in Patent Document 2, the technique for adjusting the saturation according to the luminance signal of the image data cannot sufficiently reflect the influence of the intensity of sunlight on the image data.

  Therefore, an object of the present invention is to perform image processing close to the impression at the time of shooting according to the subject situation such as the intensity of sunlight.

<< 1 >> The electronic camera of the present invention includes a brightness detection unit, an imaging unit, and a saturation adjustment unit.
The brightness detection unit detects brightness information of the object scene.
The imaging unit images the object scene and generates image data.
The saturation adjusting unit changes the saturation of the image data in accordance with a change in perception of saturation corresponding to the brightness information of the object scene.
<< 2 >> Preferably, the saturation adjusting unit increases the saturation of the image data as the object scene is brighter.
<< 3 >> Preferably, the saturation adjustment unit increases the maximum and minimum widths of the saturation gain applied to the saturation of the image data as the object scene is brighter.
<< 4 >> Preferably, the saturation adjusting unit also considers the influence of the imaging sensitivity in addition to the brightness of the object scene. That is, it is preferable that the saturation adjustment unit lowers the saturation of the low saturation region of the image data as the imaging sensitivity of the imaging unit is higher.
<< 5 >> Preferably, the saturation adjusting unit considers the age of the user in addition to the brightness of the object scene. That is, it is preferable that the saturation adjustment unit acquires or stores information on the age of the user, and increases the saturation enhancement as the age increases.
<< 6 >> Preferably, the saturation adjusting unit also considers the skin color area of the image data in addition to the brightness of the object scene. That is, it is preferable that the saturation adjusting unit suppresses the saturation enhancement of the skin color area of the image data.
<< 7 >> The image processing program of the present invention is a program for causing a computer to function as an input unit and a saturation adjustment unit.
The input unit captures image data having brightness information of the object scene.
The saturation adjusting unit changes the saturation of the image data in accordance with a change in perception of saturation corresponding to the brightness information of the object scene.

  In the present invention, the brightness of the object scene is detected, a perceptual saturation change that will occur at the brightness is estimated, and the saturation change is reflected in the saturation adjustment of the image data. For this reason, the saturation of the image data that should not be changed originally changes according to the scene situation such as the intensity of sunlight, and it is possible to obtain image data close to the visual impression at the time of shooting.

<< First Embodiment >>
(Description of configuration of the first embodiment)
FIG. 1 is a block diagram showing a configuration of the electronic camera 11.
In FIG. 1, a photographing lens 12 is attached to the electronic camera 11. In the image space of the photographic lens 12, the imaging surface of the imaging unit 13 is arranged. The imaging unit 13 is exposure controlled by the control unit 18 and generates image data. The image data generated by the imaging unit 13 is digitized via the A / D conversion unit 14 and then given to the image processing unit 15. The image processing unit 15 performs image processing such as saturation adjustment on the image data and outputs the image data to the recording unit 16. The recording unit 16 compresses and records image data after image processing.

The electronic camera 11 includes a brightness detection unit 17 that detects brightness information of the object scene.
For example, in the single-lens type electronic camera 11, a photometric sensor is mounted on the finder optical system. This photometric sensor performs TTL photometry of the object scene via the photographic lens 12 in the open aperture state. The brightness detection unit 17 can detect brightness information of the object scene based on the result of the TTL photometry and the open aperture value.
For example, in the compact type electronic camera 11, the imaging unit 13 periodically outputs a monitor image. The brightness detection unit 17 can detect brightness information of the object scene based on the luminance level of the monitor pixel and the exposure value (aperture value, shutter time, imaging sensitivity, etc.) of the monitor image.
For example, an external light type photometry unit may be provided as the brightness detection unit 17. In this case, the brightness detection unit 17 can detect brightness information of the object scene from the result of external light photometry.

(Description of operation of the first embodiment)
FIG. 2 is a flowchart for explaining the operation of the electronic camera 11. The operation will be described below according to the step numbers shown in FIG.

Step S <b> 1: The control unit 18 acquires brightness information of the object scene from the brightness detection unit 17. The control unit 18 performs an exposure calculation based on the brightness information, and determines an exposure value (aperture value, shutter time, imaging sensitivity, etc.).

Step S2: The control unit 18 controls the exposure of the imaging unit 13 according to the exposure value determined in step S1, and reads the image data.

Step S3: The image processing unit 15 performs white balance adjustment on the image data. This white balance adjustment is a preferential process preferable for accurately calculating the saturation from the image data. Furthermore, the image processing unit 15 performs color interpolation on the image data as necessary, and interpolates and generates missing color components in units of pixels. This color interpolation is a preferential process preferable for calculating the saturation in pixel units.
The image processing unit 15 calculates the saturation Cd for each pixel (or a unit of a plurality of pixels) for the image data for which such image processing has been completed.
For example, the saturation Cd is preferably calculated by substituting the color difference signals Cb and Cr in pixel units (or units of a plurality of pixels) into the following equation.
Cd = (Cb ^ 2 + Cr ^ 2) ^ 0.5
(However, ^ is an operator that indicates a power)

Step S4: The image processing unit 15 acquires brightness information of the object scene when the image data is captured from the brightness detection unit 17.
The image processing unit 15 holds a data table (see FIG. 3) indicating the correspondence between the brightness information and the saturation gain characteristic. The image processing unit 15 selects and determines the corresponding saturation gain characteristic LUTc () by referring to this data table with the acquired brightness information.
As a general tendency of this data table, a saturation gain characteristic LUTc () indicating a larger saturation gain is selected as the object scene is brighter. Further, the saturation gain characteristic LUTc () having a wider maximum / minimum saturation gain is selected and determined as the scene is brighter.
Such a general tendency can be created by obtaining a difference in color perception ability between photopic vision (cone) and scotopic vision (cone) by experiment or calculation simulation.
In addition, a saturation gain that reflects the perceived change in saturation by actually trying to adjust the saturation while following the memory of the vividness of the color that the photographer felt at the time of shooting. A characteristic may be created. By repeating this operation while changing the brightness of the object scene, the above-described data table can be created.
Note that, in the high saturation region of the image data, saturation saturation causes an adverse effect of saturation, so the saturation gain of the high saturation region is set to 1 or less so as to be common to a plurality of saturation gain characteristics shown in FIG. It is preferable to do.

Step S5: In the data table shown in FIG. 3, the saturation gain characteristic LUTc () can be selected more finely according to the imaging sensitivity when the image data is captured. Therefore, the image processing unit 15 acquires the imaging sensitivity at the time of shooting from the control unit 18, and selects the saturation gain characteristic LUTc () more finely according to the imaging sensitivity.
In this case, as shown in FIG. 3, it is preferable to lower the saturation gain in the low saturation region as the imaging sensitivity increases. With such saturation gain characteristics, it is possible to reduce color noise in a low saturation region that increases as the imaging sensitivity increases.

Step S <b> 6: The image processing unit 15 acquires from the control unit 18 the user age information that has been input and set in advance. The image processing unit 15 refers to the data table shown in FIG. 4A to determine the correction gain Gy corresponding to the user age.
This data table can be created from the experimental results of the perception sensitivity of saturation by age. This data table can also be created by conducting a questionnaire survey on the preference of saturation depending on age.
As a general tendency of this data table, it is preferable to increase the correction gain Gy monotonically as the age increases.

Step S7: The image processing unit 15 applies the saturation Cd obtained in step S3 to the saturation gain characteristic LUTc () determined in steps S4 and S5. By this processing, a saturation gain LUTc (Cd) in pixel units (or a unit of a plurality of pixels) is obtained.

Step S8: The image processing unit 15 determines whether or not the image data to be processed has been shot under shooting conditions for shooting a person (shooting mode, aperture value, color space, finish setting mode, or white balance setting). To do.
Further, the image processing unit 15 may determine whether or not the possibility of photographing a person is high by performing face recognition or person recognition on the image data.
When it is determined by such determination that the main subject of the image data is a person, the image processing unit 15 obtains the hue of the image data in units of pixels (or units of a plurality of pixels). The image processing unit 15 applies these hues to the data table shown in FIG. 4B to determine the correction gain Gs related to the skin color area of the image data.
This data table is set to suppress an excessive increase in the saturation of the skin color area in order to improve the unnaturalness of the skin color area (color noise in shaded areas, unevenness of skin, unnatural color tone), etc. The
On the other hand, when the main subject of the image data is not a person like a landscape photograph, the image processing unit 15 sets the correction gain Gs = 1.

Step S9: The image processing unit 15 obtains [saturation gain LUTc (Cd) × correction gain Gy × correction gain Gs] for each pixel (or a unit of a plurality of pixels), and obtains a corrected saturation gain. The image processing unit 15 adjusts the saturation of the image data by changing the saturation of the image data in units of pixels (or units of a plurality of pixels) according to the corrected saturation gain.

Step S10: The image data that has undergone image processing by the image processing unit 15 is sent to the recording unit 16. The recording unit 16 compresses and records this image data on a recording medium.

(Effects of the first embodiment)
In the first embodiment, attention is paid to a phenomenon in which human perception of color changes depending on the brightness of the object scene at the time of shooting. Therefore, the brightness detector 17 is provided in the electronic camera to detect the brightness information of the object scene, and the perceptual saturation change expected from the brightness of the shooting environment is used to adjust the saturation of the image data. To reflect. As a result, image data close to the impression of vividness at the time of shooting can be obtained.

  In particular, in the first embodiment, attention is paid to the phenomenon that the brighter the shooting environment is, the more vivid the image is, and the saturation of the image data is increased as the shooting environment is brighter. As a result, image data shot in a shooting environment with strong sunlight is vividly adjusted and can be made closer to the visual impression at the time of shooting.

  Furthermore, in the first embodiment, attention is also paid to the phenomenon that the change range (color depth) of color vividness increases as the shooting environment becomes brighter, and the maximum and minimum width of the saturation gain is increased as the shooting environment becomes brighter. . As a result, the image data shot in a shooting environment with strong sunlight can be brought closer to the visual impression at the time of shooting due to the rich change in saturation.

  In the first embodiment, the influence of imaging sensitivity is also taken into consideration in order to avoid a decrease in S / N accompanying saturation adjustment. That is, the higher the imaging sensitivity, the lower the saturation of the low saturation region of the image data. This processing makes it possible to reduce color noise that is conspicuous in the low saturation region.

  Furthermore, in the first embodiment, attention is also paid to a phenomenon in which color perception and preference change with age. That is, the image processing unit 15 corrects the saturation gain so as to suit the age of the user. This process enables saturation adjustment suitable for age. In particular, by enhancing the saturation enhancement as the age increases, it is possible to obtain image data with a good impression by appropriately compensating for the decrease in color perception due to aging.

  In the first embodiment, excessive saturation enhancement of the skin color area is suppressed by considering the skin color area of the image data.

<< Second Embodiment >>
FIG. 5 is a flowchart for explaining a computer operation by the image processing program. Hereinafter, this operation will be described along the step numbers shown in FIG.

Step S21: The computer captures the image data via a communication medium or a recording medium and stores it in a memory in the computer.

Step S22: The computer obtains information on the brightness of the object scene (photometric value of the object scene, exposure information at the time of photographing, etc.) from the accompanying information (EXIF information, etc.) of the image data.
For example, the photometric value of the object scene is brightness information that directly indicates the brightness of the object scene.
Further, for example, the exposure information at the time of photographing image data has the property that the exposure amount (aperture value, shutter time) is limited as the subject field becomes brighter. Therefore, the exposure information indirectly indicates the brightness of the subject field. Become.
Further, for example, the brightness level of the image data may be converted into the exposure amount indicated by the exposure information to calculate the absolute brightness of the subject in the object space (= the brightness of the subject image at the fixed exposure amount). The brightness of the subject in the object space is brightness information indicating the brightness of the object scene.

Step S23: The computer calculates the saturation Cd in pixel units (or units of a plurality of pixels) from the image data.

Steps S24 to S30: The same processing as Steps S4 to S10 of the first embodiment.
Through the above-described computer operation, it is possible to perform saturation adjustment similar to that in the first embodiment on image data after shooting.

<< Additional items of embodiment >>
In the above-described embodiment, the case where the saturation adjustment of the present invention is performed on the image data after color interpolation has been described. However, the embodiment is not limited to this. For example, the saturation adjustment of the present invention may be performed on a RAW image such as a Bayer image. In this case, a simple color interpolation process may be performed on the RAW image in order to obtain the saturation in pixel units. Alternatively, a plurality of types of color signals may be extracted from the local region of the RAW image, and the saturation may be calculated in units of a plurality of pixels based on these color signals.

  In the above-described embodiment, the saturation adjustment is changed by changing the saturation gain. However, the embodiment is not limited to this. For example, saturation adjustment may be performed according to a conversion table between saturation before adjustment and saturation after adjustment. In this case, the conversion table may be changed according to the brightness information of the object scene.

  In the above-described embodiment, the white balance adjustment is performed in advance before the saturation adjustment. By this adjustment, the color deviation of the image data is reduced, and more accurate saturation adjustment can be performed. However, the embodiment is not limited to this. It is possible to carry out the saturation adjustment of the present invention anywhere in a series of image processing.

  In the above-described embodiment, the saturation adjustment is corrected with respect to the age and skin color area. However, the embodiment is not limited to this. For example, the saturation adjustment may be corrected according to information such as sex, country, environment, or electronic camera setting.

  As described above, the present invention is a technique that can be used for an electronic camera or the like.

2 is a block diagram illustrating a configuration of an electronic camera 11. FIG. 3 is a flowchart for explaining the operation of the electronic camera 11. It is a figure which shows the data table for selecting a saturation gain characteristic. It is a figure which shows the example of a correction gain. It is a flowchart explaining the computer operation | movement by an image processing program.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Electronic camera, 12 ... Shooting lens, 13 ... Imaging part, 14 ... A / D conversion part, 15 ... Image processing part, 16 ... Recording part, 17 ... Brightness detection part, 18 ... Control part

Claims (7)

A brightness detector for detecting brightness information of the object scene;
An imaging unit for imaging the object scene and generating image data;
An electronic camera comprising: a saturation adjusting unit that changes the saturation of the image data in accordance with a perceptual change in saturation corresponding to brightness information of the object scene. The electronic camera according to claim 1,
The electronic camera according to claim 1, wherein the saturation adjusting unit increases the saturation of the image data as the object scene is brighter. The electronic camera according to claim 1,
The electronic camera according to claim 1, wherein the saturation adjustment section increases a maximum and minimum width of a saturation gain applied to the saturation of the image data as the object scene is brighter. The electronic camera according to any one of claims 1 to 3,
The electronic camera according to claim 1, wherein the saturation adjustment unit lowers the saturation of a low saturation region of the image data as the imaging sensitivity of the imaging unit is higher. The electronic camera according to any one of claims 1 to 4,
The saturation adjustment unit
An electronic camera characterized by acquiring or storing information on a user's age, and increasing saturation enhancement as the age is higher. The electronic camera according to any one of claims 1 to 5,
The electronic camera according to claim 1, wherein the saturation adjusting unit suppresses saturation enhancement of a skin color region of the image data. Computer
An input unit for capturing image data having brightness information of the object scene;
An image processing program for functioning as a saturation adjusting unit that changes the saturation of the image data in accordance with a change in perception of saturation corresponding to brightness information of the object scene.

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