JP4496472B2 - Image processing apparatus and method, and program - Google Patents

Description

  The present invention relates to an image processing apparatus, method, and program, and more particularly, to an image processing apparatus, method, and program that adjust white balance of an image signal based on visual characteristics called human white adaptation.

  For example, a so-called white balance is adjusted for an imaging apparatus that can capture an image signal such as a digital still camera and a digital video camera, and an image output apparatus that can reproduce the image signal such as a display or a printer. It has a function.

  In the conventional white balance adjustment method, a target value for optimal white balance is set for each light source, the light source at the time of imaging is specified, and the target value of the white balance control signal of the light source at that time is calculated In some cases, the white balance correction amount is calculated so as to be directed to the calculated target value (see, for example, Patent Document 1).

JP 2001-78223 A

  When the conventional adjustment method is used, when the light source is on a black body locus, the black body locus is nonlinear as shown in FIG. 1A, and therefore it is necessary to change the pull-in direction for each color temperature or light source. It was. When the light source is a fluorescent lamp or the like and does not follow the black body locus, it is necessary to set the target value of the light source not on the black body locus as shown in FIG. There was a problem of becoming complicated.

  In addition, if the range to be pulled in to the target value is set incorrectly, there is a problem that a color difference phenomenon such as blue is applied due to excessive drawing or yellow is applied on the contrary.

  Furthermore, humans have a visual characteristic of white adaptation with a certain tolerance, and there is a problem that a method for adjusting white balance using this visual characteristic has not been established.

  The present invention has been made in view of such a situation, and it is possible to adjust the white balance more easily than in the case of drawing on a black body locus, and to suppress color difference shift due to excessive drawing. It is something that can be done.

  An image processing apparatus according to the present invention includes a determination unit that determines a color temperature of a subject based on an image signal, a determination unit that determines a reference point corresponding to the color temperature in a predetermined color space, and a reference point in the predetermined color space. A setting means for setting a white balance allowable range of a predetermined shape centered on the outer periphery of the predetermined shape based on a positional relationship between a white balance allowable range and a point before correction corresponding to an image signal in a predetermined color space The image processing apparatus includes: designation means for designating a target point; and control means for controlling white balance processing performed on the image signal in accordance with an amount of movement from the point before correction to the target point.

  The image processing apparatus of the present invention may further include an input unit that inputs the color temperature of the subject, and the determination unit is input by the color temperature determined by the determination unit or the input unit in a predetermined color space. A reference point corresponding to the color temperature can be determined.

  The setting means may set an elliptical white balance allowable range determined based on a visual experiment with a reference point as a center in a predetermined color space.

  The image processing method of the present invention includes a determination step of determining a color temperature of a subject based on an image signal, a determination step of determining a reference point corresponding to the color temperature in a predetermined color space, and a reference point in the predetermined color space A setting step for setting a white balance allowable range of a predetermined shape centering on the outer periphery of the predetermined shape based on a positional relationship between a white balance allowable range and a point before correction corresponding to an image signal in a predetermined color space It includes a designation step for designating a target point and a control step for controlling white balance processing performed on the image signal based on the amount of movement from the point before correction to the target point.

  The program of the present invention includes a determination step of determining a color temperature of an object based on an image signal, a determination step of determining a reference point corresponding to the color temperature in a predetermined color space, and a reference point in the predetermined color space. On the outer periphery of the predetermined shape based on the setting step of setting the white balance allowable range of the predetermined shape and the positional relationship between the point before correction corresponding to the image signal in the predetermined color space and the white balance allowable range It is characterized by causing a computer to execute processing including a specifying step for specifying a target point and a control step for controlling white balance processing performed on an image signal based on the amount of movement from the point before correction to the target point.

  In the image processing apparatus, method, and program of the present invention, the color temperature of the subject is determined based on the image signal, a reference point corresponding to the color temperature is determined in a predetermined color space, and the reference point is determined in the predetermined color space. A white balance allowable range having a predetermined shape centered on the center is set. Further, based on the positional relationship between the point before correction corresponding to the image signal in the predetermined color space and the white balance allowable range, a target point is designated on the outer periphery of the predetermined shape, and the point from the point before correction to the target point is specified. White balance processing performed on the image signal is controlled based on the movement amount.

  According to the present invention, it is possible to adjust the white balance more easily than in the case of drawing on a black body locus, and to suppress color difference misalignment due to excessive drawing.

  Embodiments of the present invention will be described below. Correspondences between constituent elements described in the claims and specific examples in the embodiments of the present invention are exemplified as follows. This description is to confirm that specific examples supporting the invention described in the claims are described in the embodiments of the invention. Therefore, even if there are specific examples that are described in the embodiment of the invention but are not described here as corresponding to the configuration requirements, the specific examples are not included in the configuration. It does not mean that it does not correspond to a requirement. On the contrary, even if a specific example is described here as corresponding to a configuration requirement, this means that the specific example does not correspond to a configuration requirement other than the configuration requirement. not.

  Further, this description does not mean that all the inventions corresponding to the specific examples described in the embodiments of the invention are described in the claims. In other words, this description is an invention corresponding to the specific example described in the embodiment of the invention, and the existence of an invention not described in the claims of this application, that is, in the future, a divisional application will be made. It does not deny the existence of an invention that is added by correction.

  The image processing apparatus according to claim 1 (for example, the image processing apparatus 1 in FIG. 2) includes a determination unit (for example, the color temperature determination unit 22 in FIG. 3) that determines the color temperature of the subject based on the image signal. Determination means (for example, the reference point determination unit 24 in FIG. 3) for determining a reference point corresponding to the color temperature in a predetermined color space (for example, BG, RG plane), and the reference point in the predetermined color space as the center Positioning relationship between setting means for setting a white balance allowable range of a predetermined shape (for example, allowable range setting unit 25 in FIG. 3) and a point before correction corresponding to an image signal in a predetermined color space and the white balance allowable range In accordance with the designation means for designating the target point on the outer periphery of the predetermined shape (for example, the target point degree determination unit 26 in FIG. 3), the image signal corresponding to the amount of movement from the point before correction to the target point Control white balance processing Control means (for example, the correction amount calculation unit 27 in FIG. 3).

  The image processing apparatus according to claim 2 further includes an input unit (for example, the external sensor 17 or the color temperature input unit 18 in FIG. 2) for inputting the color temperature of the subject, and the determination unit inputs in a predetermined color space. A reference point corresponding to the color temperature input by the means is determined.

  The image processing method according to claim 5 determines a color temperature of the subject based on the image signal (for example, step S1 in FIG. 8), and determines a reference point corresponding to the color temperature in a predetermined color space. A determining step (for example, step S2 in FIG. 8), a setting step (for example, step S3 in FIG. 8) for setting a white balance allowable range having a predetermined shape centered on the reference point in a predetermined color space, A designation step (for example, step S4 in FIG. 8) for designating a target point on the outer periphery of a predetermined shape based on the positional relationship between the point before correction corresponding to the image signal in the color space of the color space and the white balance allowable range; And a control step (for example, step S5 in FIG. 8) for controlling white balance processing performed on the image signal in accordance with the amount of movement from the point before correction to the target point.

  The correspondence between the configuration requirements described in the claims of the program of the present invention and the specific examples in the embodiment of the present invention is the same as that of the information processing method of the present invention described above, so that description thereof is omitted. To do.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 2 shows a configuration example of an image processing apparatus according to an embodiment of the present invention. This image processing apparatus 1 adjusts the white balance of an acquired image signal by using a visual characteristic called human white adaptation.

  A lens system 11 including a shutter, a diaphragm, a condenser lens, and the like focuses an optical image of a subject on an image sensor 12 such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor). The image sensor 12 converts the optical image focused by the lens system 11 into an analog image signal R, G, B, which is an electrical signal, by photoelectric conversion, and an analog / digital converter (A / D, S / H, AGC). ) Is output to 13. The analog / digital conversion unit 13 performs a sampling process, a gain control process, and a digital conversion process on the analog image signals R, G, and B input from the image sensor 12, and a white balance (WB) adjustment unit 14 and the correction amount determination unit 19.

  The white balance adjustment unit 14 adjusts the white balance of the image signals R, G, and B input from the analog / digital conversion unit 13 according to the control from the correction amount determination unit 19 and outputs the white balance to the gamma correction unit 15. The gamma correction unit 15 performs predetermined gamma processing on the image signals R, G, and B input from the white balance adjustment unit 14 and outputs them to the signal conversion unit 16. The signal conversion unit 16 converts the image signals R, G, B input from the gamma correction unit 15 into a luminance signal Y and color difference signals BY, RY, and outputs them to the subsequent stage.

  The external sensor 17 detects the color temperature of the subject imaged by the lens system 11 and outputs it to the correction amount determination unit 19. The color temperature input unit 18 outputs the color temperature designated by the user to the correction amount determination unit 19.

  The correction amount determination unit 19 controls the white balance correction amount in the white balance adjustment unit 14 based on the image signals R, G, and B input from the analog / digital conversion unit 13. The correction amount determination unit 19 can control the white balance correction amount in the white balance adjustment unit 14 based on the color temperature input from the external sensor 17 or the color temperature input unit 18.

  FIG. 3 shows a detailed configuration example of the correction amount determination unit 19. The achromatic color extraction unit 21 extracts achromatic color components from the image signals R, G, and B input from the analog / digital conversion unit 13 and outputs them to the color temperature determination unit 22. Based on the input from the achromatic color extraction unit 21, the color temperature determination unit 22 determines the color temperature of the subject and outputs it to the calculation unit 23. Based on the image signals R, G, B input from the analog / digital conversion unit 13 and the color temperature of the subject input from the color temperature determination unit 22, the calculation unit 23 performs white balance adjustment in the white balance adjustment unit 14. Calculate the correction amount. The white balance correction amount in the white balance adjustment unit 14 is calculated based on the color temperature input from the external sensor 17 or the color temperature input unit 18 instead of the subject color temperature input from the color temperature determination unit 22. It can also be done.

The reference point determination unit 24 of the calculation unit 23 determines a reference point S ₀ (corresponding to the conventional corrected point in FIGS. 1A and 1B) that becomes white at the input color temperature. The allowable range setting unit 25 sets an elliptical white balance allowable range centering on the reference point S ₀ (corresponding to the elliptical region shown in FIGS. 1A and 1B). The target point determination unit 26 determines the corrected target point S ₂ ′ based on the point S ₁ before correction of the image signal input from the analog / digital conversion unit 13 and the ellipse indicating the white balance allowable range. The correction amount calculation unit 27 calculates a correction amount f for correcting the uncorrected point S ₁ to the target point S ₂ ′, calculates a white balance correction amount, and outputs it to the white balance adjustment unit 14.

  Here, a method of determining an ellipse set as the white balance allowable range by the allowable range setting unit 25 will be described. As described above, this ellipse is based on a visual characteristic called white adaptation that humans have. The size of this ellipse can be obtained by the following visual experiment. First, a display capable of displaying a color corresponding to the designated color temperature is prepared. As shown in FIG. 4, a black frame 41 is provided around the display screen, and an achromatic region 42 is provided in the frame 41. The subject is prevented from seeing a color other than the color displayed in the achromatic region 42 by the subject.

  In the achromatic color region 42, in the CIELab color space having a * on the horizontal axis and b * on the vertical axis shown in FIG. The changed 961 (= 31 × 31) achromatic colors are displayed. When the subject recognizes the achromatic color displayed in the achromatic color region 42 as “achromatic color”, a mark ● is plotted at a point on the CIELab color space.

…（１） The Mahalanobis distance can be expressed by the following equation (1) by using the average values of a * and b * of the points in the CIELab color space recognized as “achromatic”.

... (1)

…（２） The reliability P indicating the ratio of the points in the CIELab color space that are recognized as “achromatic” that exist inside the ellipse can be expressed by the following equation (2).

... (2)

…（３） Therefore, in order to obtain a probability ellipse having a reliability of 95%, 0.95 is substituted for P in the equation (2), and the following equation (3) is obtained.

... (3)

If equation (1) is solved under the condition of equation (3), D ² = 5.9915 is calculated.

Here, a probability ellipse having a reliability of 95% can be expressed as a set of points in the CIELab color space with a reliability P = 0.95, that is, the inside of an ellipse having a Mahalanobis distance D ² = 5.9915. In this way, the ellipse shown in FIG. 6 is determined.

  In this case, the allowable range is calculated using the Mahalanobis distance in order to increase accuracy, but a commonly used multivariate analysis method such as a weighted Euclidean distance may be used.

  The inside of the ellipse determined as described above is determined as a range that is acceptable as the human eye is “achromatic”, and the probability ellipse formula is used as a formula for calculating the white balance allowable range. Next, the distance and angle between the center value of the ellipse and the center values of a * and b * are obtained. From the obtained a * and b *, an RGB value when the central RGB value is (255, 255, 255) is calculated. As an example, conversion equations from Lab to sRGB are shown in the following equations (4) to (13).

…（４） Conversion formula from Lab to XYZ

... (4)

…（５） When fx> 0.2069

... (5)

…（６） When fx ≤ 0.2069

... (6)

…（７） When fy> 0.2069

... (7)

…（８） When fy ≤ 0.2069

... (8)

…（９） When fz> 0.2069

... (9)

…（１０） When fz ≦ 0.2069

(10)

…（１１） Conversion formula from XYZ to RGB

... (11)

…（１２） Conversion formula from RGB to sRGB
R, G, B ≦ 0.0031308

(12)

…（１３） R, G, B> 0.0031308

... (13)

As described above, the RGB values of the short axis and the long axis of the ellipse are obtained, and based on the calculated values, the RY and BY values shown in FIG. 7 and the inclination angle θ with respect to the axis are obtained, and the white balance allowable range is determined. . For the inclination angle θ and the RY and BY values for each color temperature, the maximum and minimum values of each light source such as D ₅₅ and D ₆₅ are tabulated, and linear interpolation is performed between the color temperatures. When a more accurate white balance allowable range is required, it may be calculated from the color temperature using a calculation formula.

  Moreover, the above-described visual experiment may be performed using a color space other than the CIELab color space.

  Next, white balance adjustment processing by the image processing apparatus 1 will be described with reference to the flowchart of FIG. In this white balance adjustment processing, the optical image of the subject focused by the lens system 11 is converted into image signals R, G, and B by the image pickup device 12, and further, sampling processing, gain control processing, The process is started when the digital conversion process is performed and input to the white balance adjustment unit 14 and the correction amount determination unit 19.

  In step S <b> 1, the achromatic color extraction unit 21 of the white balance adjustment unit 14 extracts achromatic components from the image signals R, G, and B input from the analog / digital conversion unit 13 and outputs them to the color temperature determination unit 22. . The color temperature determination unit 22 determines the color temperature of the subject based on the input from the achromatic color extraction unit 21 and outputs the determined color temperature to the calculation unit 23.

In step S2, the reference point determining unit 24 of computing unit 23 determines a reference point S ₀ as a white in the input color temperature. In step S3, the allowable range setting section 25, as shown in FIG. 9, the reference point S ₀ BG, the white balance is set allowable range of elliptical shape with the center of the RG plane.

In step S4, as shown in FIG. 10, the target point determination unit 26 sets the point S ₁ (R ₁ , B ₁ ) before correction of the image signal input from the analog / digital conversion unit 13 on the BG, RG plane. Plot. When the point S ₁ (R ₁ , B ₁ ) before correction is located outside the ellipse, the following processing is performed. Processing when the point S ₁ (R ₁ , B ₁ ) before correction is located within the ellipse will be described later. As shown in FIG. 11, the point S ₁ and the ellipse are rotated so that the major and minor axes of the ellipse overlap with the axes of the BG and RG planes. This rotation angle is defined as θ. Further, the point before correction after rotation is defined as S ₁ ′. Further, as shown in FIG. 12, the target point determination unit 26 transforms the ellipse into a circle by reducing (or enlarging) the ellipse at a predetermined magnification in the vertical axis direction or the horizontal axis direction, and as shown in FIG. An intersection S ₂ between the straight line 1 connecting the point S ₁ ′ and the reference point S ₀ as the uncorrected point after rotation and the circle is calculated. Next, as shown in FIG. 14, the target point determination unit 26 performs reverse conversion when the coordinates of the intersection S ₂ are transformed from an ellipse to a circle, and further rotates it by −θ, whereby a target on the ellipse is obtained. The value S ₂ ′ (R ₂ ′, B ₂ ′) is determined.

As described above, instead of setting the intersection of the straight line l connecting the point S ₁ before correction and the reference point S ₀ and the ellipse as the target value S ₂ ′, as shown in FIG. the abscissa axis in the minor axis coordinate system likened to the longitudinal axis, when the horizontal axis coordinate before correction point S ₁ is positioned between the two focal points, and the perpendicular from the point S ₁ before correction to the horizontal axis the intersection of the ellipse and the target value S ₂ ', when the horizontal axis coordinate before correction point S ₁ is located outside of a focal point, a straight line connecting the focal point closer in terms S ₁ before correction, oval The point of intersection with may be set to the target value S ₂ ′.

Returning to FIG. In step S5, the correction amount calculation unit 27 corrects the correction amounts f _r and f for correcting the point S ₁ (R ₁ , B ₁ ) before correction to the target point S ₂ ′ (R ₂ ′, B ₂ ′). _b is calculated using the following equation (14).

…（１４）

... (14)

Further, based on the equation (14), R ₂ ′ and B ₂ ′ are calculated as shown in the following equation (15).

…（１５）

... (15)

  In step S6, the correction amount calculation unit 27 calculates the correction amount in the B / G, R / G Ratio plane shown in FIG. 1 based on the calculation result in step S5, and based on the calculated correction amount. The white balance adjustment unit 14 is controlled. Note that the details of the processing in step S6 are the same as the processing described in Japanese Patent Application No. 2003-318192 proposed by the present applicant, and thus the description thereof is omitted.

  In accordance with control from the correction amount calculation unit 27, the white balance adjustment unit 14 adjusts the white balance of the image signals R, G, and B input from the analog / digital conversion unit 13 and outputs the adjusted white balance to the gamma correction unit 15.

In step S4, when the plotted point S ₁ (R ₁ , B ₁ ) before correction is located within the ellipse, the color described in Japanese Patent Application No. 2003-090611 proposed by the present applicant. As shown in FIG. 16, a convergence method is applied and correction is performed so as to converge to the center of the circle (reference point S ₀ ).

  Specifically, as shown in FIGS. 17 and 18, the color difference signals BY and RY are corrected by setting a gain amount gain corresponding to the distance s from the center point. First, the distance s from the center point is calculated using the following equation (16).

…（１６）

... (16)

  Then, as shown in the following equation (17), the γ power of the distance s is calculated as the gain amount gain.

…（１７）

... (17)

  Further, as shown in the following equation (18) using the gain amount gain, color convergence is performed by multiplying the signals of the color difference signals BY and RY by the gain amount gain.

…（１８）

... (18)

  As for the color on the circumference, since the gain amount is 1, no correction is performed as a result, and the gain amount gain increases as it approaches the center, so that it is understood that correction that is more easily converged to the center is performed. With such a color convergence method, a signal with a different color difference located within the ellipse can be drawn into a reference point that matches the color temperature, thereby performing more accurate white balance processing.

  This is the end of the description of the white balance adjustment process performed by the image processing apparatus 1. According to this white balance adjustment processing, natural white balance control according to human visual characteristics becomes possible.

  It should be noted that the present invention is applicable not only when the light source is on a black body locus as shown in FIG. 1A but also when the light source is not on a black body locus as shown in FIG. 1B. Is possible.

  The present invention can also be applied to image pickup apparatuses such as digital still cameras and video cameras, and image output apparatuses such as displays and printers.

  Further, even in an image reproduction apparatus such as a video recorder and a DVD player, if the color temperature of a subject at the time of image recording can be fed back, the present invention is applied to correct an image signal supplied to the image output apparatus. It is possible.

  By the way, the series of processes described above by the calculation unit 23 can be executed by hardware, but can also be executed by software. When a series of processing is executed by software, a program constituting the software may execute various functions by installing a computer incorporated in dedicated hardware or various programs. For example, a general-purpose personal computer as shown in FIG. 19 is installed from the recording medium.

  The personal computer 50 includes a CPU (Central Processing Unit) 51. An input / output interface 55 is connected to the CPU 51 via the bus 54. A ROM (Read Only Memory) 52 and a RAM (Random Access Memory) 53 are connected to the bus 54.

  The input / output interface 55 includes an input unit 56 including an input device such as a keyboard and a mouse for a user to input operation commands, a CRT (Cathode Ray Tube) or an LCD (Liquid Crystal Display) for displaying a synthesized video signal, and the like. Output unit 57 composed of a display, a storage unit 58 composed of a hard disk drive for storing programs and various data, a modem, a LAN (Local Area Network) adapter, etc., and communication processing via a network represented by the Internet. A communication unit 59 to be executed is connected. Also, a magnetic disk (including a flexible disk), an optical disk (including a CD-ROM (Compact Disc-Read Only Memory), a DVD (Digital Versatile Disc)), a magneto-optical disk (including an MD (Mini Disc)), or a semiconductor A drive 60 for reading / writing data from / to a recording medium 61 such as a memory is connected.

  A program for causing the personal computer 50 to execute the above-described series of processing is supplied to the personal computer 50 while being stored in the recording medium 61, read by the drive 60, and installed in a hard disk drive built in the storage unit 58. Has been. The program installed in the storage unit 58 is loaded from the storage unit 58 to the RAM 53 and executed by a command of the CPU 51 corresponding to a command from the user input to the input unit 56.

  In this specification, the steps executed based on the program are executed in parallel or individually even if they are not necessarily processed in time series, as well as processes executed in time series according to the described order. It also includes processing.

  The program may be processed by a single computer, or may be distributedly processed by a plurality of computers. Furthermore, the program may be transferred to a remote computer and executed.

It is a figure which shows a black body locus | trajectory. It is a block diagram which shows the structural example of the image processing apparatus to which this invention is applied. It is a block diagram which shows the structural example of the correction amount determination part of FIG. It is a figure for demonstrating a visual experiment. It is a figure for demonstrating a visual experiment. It is a figure for demonstrating the determination method of the ellipse used as the white balance tolerance | permissible_range based on a visual experiment. It is a figure for demonstrating the determination method of the ellipse used as the white balance tolerance | permissible_range based on a visual experiment. It is a flowchart explaining a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a figure for demonstrating a white balance adjustment process. It is a block diagram which shows the structural example of a general purpose personal computer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Image processing apparatus, 14 White balance adjustment part, 17 External sensor, 18 Color temperature input part, 19 Correction amount determination part, 21 Achromatic color extraction part, 22 Color temperature determination part, 23 Calculation part, 24 Reference point determination part, 25 Allowable range setting unit, 26 Target point determination unit, 27 Correction amount calculation unit

Claims (6)

In an image processing apparatus that performs white balance processing on an image signal obtained by imaging a subject,
Determining means for determining a color temperature of the subject based on the image signal;
Determining means for determining a reference point corresponding to the color temperature in a predetermined color space;
Setting means for setting a white balance tolerance of a predetermined shape centered on the reference point in the predetermined color space;
Designating means for designating a target point on an outer periphery of the predetermined shape based on a positional relationship between a point before correction corresponding to the image signal in the predetermined color space and the white balance allowable range;
An image processing apparatus comprising: control means for controlling white balance processing performed on the image signal in accordance with a movement amount from the point before correction to the target point. An input means for inputting the color temperature of the subject;
2. The determination unit according to claim 1, wherein the determination unit determines a reference point corresponding to the color temperature determined by the determination unit or the color temperature input by the input unit in a predetermined color space. Image processing device. 2. The image processing according to claim 1, wherein the setting unit sets an oval-shaped white balance allowable range determined based on a visual experiment with the reference point in the predetermined color space as a center. apparatus. In the visual experiment, an achromatic color corresponding to a sampling point on a predetermined color space is presented to a subject, and a result of color recognition by the subject is plotted on the predetermined color space. The image processing apparatus according to 3. In an image processing method for performing white balance processing on an image signal obtained by imaging a subject,
A determination step of determining a color temperature of the subject based on the image signal;
A determining step for determining a reference point corresponding to the color temperature in a predetermined color space;
A setting step of setting a white balance allowable range of a predetermined shape centered on the reference point in the predetermined color space;
A designation step for designating a target point on the outer periphery of the predetermined shape based on a positional relationship between a point before correction corresponding to the image signal in the predetermined color space and the white balance allowable range;
And a control step of controlling white balance processing performed on the image signal in accordance with an amount of movement from the point before correction to the target point. A program for performing white balance processing on an image signal obtained by imaging a subject,
A determination step of determining a color temperature of the subject based on the image signal;
A determining step for determining a reference point corresponding to the color temperature in a predetermined color space;
A setting step of setting a white balance allowable range of a predetermined shape centered on the reference point in the predetermined color space;
A designation step for designating a target point on the outer periphery of the predetermined shape based on a positional relationship between a point before correction corresponding to the image signal in the predetermined color space and the white balance allowable range;
A program that causes a computer to execute processing including a control step of controlling white balance processing performed on the image signal in accordance with the amount of movement from the point before correction to the target point.

Images