JP2018092350A - Image processing apparatus, image processing method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce erroneous correction on images, which is caused by color unevenness.SOLUTION: A electronic camera 100 evaluates luminance and color unevenness in an area of the face of a person appeared in a captured image, corrects a complementary color of skin color according to the evaluated luminance and color unevenness, and subtracts a value of the corrected complementary color of the skin color from a pixel value of a high luminance area.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program, and is particularly suitable for use in correcting an image captured by an imaging unit.

  An imaging device such as a digital camera takes a picture of an object after performing exposure control using an aperture and a shutter in the camera. However, even if the imaging device performs exposure control and shoots, there is a case where the face area in the captured image is lit due to the influence of the environmental light source or the strobe light. The shine means that a part of the human skin in the image becomes white due to reflection of ambient light or strobe light on the surface of the human skin. As described above, since the local high-luminance portion with respect to the skin color is present in the image, there is a possibility that an unpleasant impression as a human image is given to the user who viewed the image. Therefore, a technique for reducing the shine in the image is required.

  In response to such a demand, a technique for removing a local high-intensity part with respect to the skin color of the face region has been proposed. In Patent Document 1, a predetermined part such as a face of a subject is detected from an image captured by an imaging unit, and correction of each pixel is performed based on color information and luminance information of each pixel included in the predetermined part. Techniques for determining the ratio are disclosed.

JP-A-2005-327209

However, with the technique described in Patent Document 1, the skin color may not be correctly reproduced in the shining portion. For example, in a scene where there are a plurality of environmental light sources or a scene that emits strobe light, color unevenness may occur in the face area. In this case, with the technique described in Patent Document 1, color unevenness may be more emphasized by performing correction for reducing the shine. As a result, there is a possibility that an unnatural image unintended by the user may be obtained by correcting the shine.
The present invention has been made in view of such a problem, and an object thereof is to reduce erroneous correction of an image caused by color unevenness.

  The image processing apparatus according to the present invention corrects the pixel value of a correction target area, using a correction target area as a correction target area among areas of a human face included in an image captured by an imaging unit. An image processing apparatus that performs image processing including: an acquisition unit that acquires an evaluation value of the degree of color unevenness in at least the correction target region of the face region; and an evaluation of the degree of color unevenness in the correction target region And determining means for determining a correction amount for the pixel value in the correction target area based on the value.

  According to the present invention, it is possible to reduce erroneous image correction caused by color unevenness.

It is a figure which shows an example of a structure of an electronic camera. It is a figure which shows the structure of an image process part. It is a figure explaining a shine correction process. It is a flowchart explaining operation | movement of the electronic camera at the time of performing a shine correction. It is a figure which shows the area | region of the face detected by the face detection part. It is a flowchart explaining the 1st example of a shine correction process. It is a figure explaining strobe irradiation amount. It is a figure explaining the color nonuniformity newly generated by the shine correction. It is a figure which shows the gain characteristic at the time of calculating a shine correction amount. It is a flowchart explaining the 2nd example of a shine correction process.

  Embodiments will be described below based on the drawings. In each of the following embodiments, a case where an image processing apparatus is mounted on an electronic camera will be described as an example. The electronic camera is, for example, a digital still camera, a digital movie camera, an industrial camera, an in-vehicle camera, or a medical camera. However, as long as the apparatus has a function of performing image processing on an image captured by the imaging unit, an apparatus on which an image processing apparatus described in the following embodiments is mounted is not limited to an electronic camera. For example, an image processing apparatus described in each of the following embodiments may be mounted on an information processing apparatus such as a mobile terminal (such as a mobile phone or a tablet terminal) or a personal computer.

(First embodiment)
First, the first embodiment will be described.
FIG. 1 is a block diagram illustrating an example of the configuration of the electronic camera 100.
The lens group 101 is a zoom lens including a focus lens. The shutter 102 has an aperture function. The shutter 102 exposes the image sensor included in the imaging unit 103 in accordance with the control of the system control unit 50. The imaging unit 103 converts an optical image obtained through the lens group 101 into an electrical signal by photoelectric conversion. The imaging unit 103 includes an imaging element such as a CCD / CMOS image sensor. The A / D conversion unit 104 converts the analog signal read from the imaging unit 103 into a digital signal and outputs the image data to the image processing unit 105.

  The image processing unit 105 performs various image processing such as white balance adjustment and gamma correction on the image data output from the A / D conversion unit 104 or the image data output from the memory control unit 107. Further, the image processing unit 105 calculates a predetermined evaluation value using the result of face detection by the face detection unit 113 and the captured image data. The system control unit 50 performs exposure control and distance measurement control based on the evaluation value obtained by the image processing unit 105. As a result, the system control unit 50 performs TTL (through the lens) AF (autofocus) processing, AE (automatic consideration) processing, AWB (auto white balance) processing, and the like. Further, the image processing unit 105 corrects the shine generated in the area in the image. Details of an example of a method for correcting the shine will be described later.

  The image memory 106 temporarily stores image data when the image processing unit 105 performs various image processing. The image memory 106 stores image data read from the recording medium 112 via the recording medium interface (I / F) 111 and image data to be displayed on the display unit 109. A memory control unit 107 controls reading and writing of the image memory 106. The D / A converter 108 converts the digital signal into an analog signal. For example, the D / A converter 108 converts image display data stored in the image memory 106 into an analog signal and outputs the analog signal to the display unit 109.

  The display unit 109 includes a display device such as an LCD (Liquid Crystal Display). The display unit 109 displays an image captured by the electronic camera 100, an image read from the recording medium 112, a live view image, and the like. The display unit 109 displays a user interface for the user to perform operations on the electronic camera 100. The codec unit 110 compresses and decodes image data. The codec unit 110 encodes or decodes the image data recorded in the image memory 106 in a format conforming to a standard such as MPEG.

  The recording medium I / F 111 mechanically and electrically connects the recording medium 112 to the electronic camera 100. The recording medium 112 is a detachable recording medium such as a semiconductor memory card or a card-type hard disk. The face detection unit 113 analyzes the image data and detects a region where a face in the image is shown. The system control unit 50 includes a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The system control unit 50 executes the program stored in the non-volatile memory 121 by developing it in the work area of the system memory 122 and controls each function of the entire electronic camera 100.

  The operation unit 120 includes a touch panel as an interface displayed on the display unit 109 described above, buttons, and switches. The operation unit 120 notifies the system control unit 50 of the content of the user operation on the operation unit 120. The non-volatile memory 121 includes a non-volatile semiconductor memory that stores programs, parameters, and the like as an auxiliary storage device. Specifically, the nonvolatile memory 121 includes, for example, an EEPROM. The system memory 122 is a main storage device, and develops a program read from the nonvolatile memory 121 and stores constants and variables for operation of the system control unit 50.

Next, an example of the configuration of the image processing unit 105 and an example of processing of each unit of the image processing unit 105 will be described with reference to FIG.
The image signal generation unit 201 receives the image data output from the A / D conversion unit 104. In the present embodiment, it is assumed that the image data is RGB image data configured in a Bayer array. The image signal generation unit 201 performs synchronization processing on RGB image data configured in a Bayer array, and generates image data R, G, and B having a plurality of colors per pixel. The image signal generation unit 201 outputs the generated image data to the white balance (WB) control unit 202.

The WB control unit 202 calculates a WB correction value based on the image data information output from the image signal generation unit 201. The WB control unit 202 corrects the white balance of the image data using the calculated WB correction value.
The shine correction circuit 203 performs the shine correction process based on the image data whose white balance has been corrected by the WB control unit 202. FIG. 3 is a diagram for explaining an example of the shine correction process. For example, as shown in FIG. 3, the shine correction circuit 203 reproduces the skin color by subtracting the complementary color of the skin color from the high luminance area (the area to be corrected for shine). Details of an example of a detailed configuration of the shine correction circuit 203 and an example of a method of calculating the shine correction value will be described later.

The color conversion matrix (MTX) circuit 204 multiplies the image data by a color gain so that the image data corrected by the shine correction circuit 203 is reproduced with an optimum color, and the image data is converted into two color difference signal data R. Convert to -Y and BY.
A low-pass filter (LPF) circuit 205 limits the band of the color difference signal data RY and BY. A CSUP (Chroma Suppress) circuit 206 suppresses a false color signal in a saturated portion of the color difference signal data band-limited by the LPF circuit 205.

The image data corrected by the shine correction circuit 203 is also supplied to the luminance signal (Y) generation circuit 211. The luminance signal generation circuit 211 generates luminance signal data Y from the image data corrected by the shine correction circuit 203. The edge enhancement circuit 212 applies edge enhancement processing to the luminance signal data generated by the luminance signal generation circuit 211.
The color difference signal data RY and BY output from the CSUP circuit 206 and the luminance signal data Y output from the edge enhancement circuit 212 are converted into RGB signal data by the RGB conversion circuit 207.
A gamma (γ) correction circuit 208 performs gamma correction (gradation correction) on the RGB signal data in accordance with a predetermined gamma characteristic. The RGB signal data subjected to gamma correction is converted into YUV signal data by the color luminance conversion circuit 209, and then compressed and encoded by the JPEG compression circuit 210, and recorded as an image data file in the image memory 106 or the like.

Next, an example of the configuration and operation of the shine correction circuit 203 will be described.
An example of the operation of the electronic camera 100 when performing the shine correction will be described with reference to the flowchart of FIG.
First, the face detection unit 113 detects a human face region from the image data input to the face detection unit 113, and acquires face information for specifying the human face region in the image (S401). Subsequently, the face detection unit 113 detects organ regions such as eyes, nose, and mouth in the face region detected in S401, and acquires organ information indicating organ regions within the face region (S402). Here, the reason for acquiring the organ information is to distinguish the skin color area from the other areas.

  FIG. 5 is a diagram illustrating an example of a face area detected by the face detection unit 113. For example, the face detection unit 113 detects the area 501 as a human face area. Next, the face detection unit 113 divides the face area 501 into a plurality of blocks based on the image signal included in the face area 501 and acquires an evaluation value for each of the divided blocks. In the present embodiment, the blocks shown in FIG. 5 (each of the rectangles obtained by dividing the face area 501) are examples of divided areas. By using this evaluation value, the electronic camera 100 can determine whether or not each block is a shine correction target region (high luminance region). In the present embodiment, the face detection unit 113 acquires a block integration value as an evaluation value of a block of a region other than the organ region detected in S402 among the face regions detected in S401. The block integration value of each block is an integration value of pixel values (R, G, B) in the block.

Next, the shine correction circuit 203 performs a shine correction process based on the evaluation value acquired for each block (S404). With reference to the flowchart of FIG. 6, an example of details of the shine correction process will be described.
First, the shine correction circuit 203 acquires, for each block, face luminance information of an area excluding an area of an organ such as an eye or a mouth from the face integration value acquired in S403 of FIG. S601). The shine correction circuit 203 derives a value obtained by dividing the block integral value of the block by the number of pixels in the block as an average pixel value AveR, AveG, AveB, and average luminance from the derived average pixel values AveR, AveG, AveB The value AveY is derived. The average luminance value AveY of each block becomes the face luminance information of each block.

  Next, the shine correction circuit 203 acquires skin color average values Skin_R, Skin_G, and Skin_B of the facial region excluding the regions of organs such as eyes and mouth (S602). Subsequently, the shine correction circuit 203 determines whether or not strobe light is emitted during the main photographing (S603). In the present embodiment, the skin color average values Skin_R, Skin_G, and Skin_B acquired in S602 are examples of representative values of pixel values in the face area.

  When the strobe light is not emitted during the main photographing, the shine correction circuit 203 acquires the color evaluation value c [n] of each block (S605). The color evaluation value c [n] is used by the shine correction circuit 203 to determine whether or not each block has color unevenness. The color evaluation value c [n] is, for example, the ratio of R and B to G of each block (R / G, B / G), or an RB value normalized by luminance Y ((RB) / Y) and Mg (magenta) -G value ((R + B-G) / Y). Here, R, B, G, and Y are AveR, AveG, AveB, and AveY, respectively, described above.

  When the strobe light is emitted during the main photographing, the shine correction circuit 203 acquires the strobe irradiation amount of each block (S604). Here, an example of the strobe irradiation amount will be described with reference to FIG. The shine correction circuit 203 calculates n luminance blocks a [n] from the non-light emitting image data 701 as shown in FIG. The non-light-emitting image data 701 is obtained, for example, when the electronic camera 100 captures a subject in the same state as the main photographing without emitting the strobe light before or after the main photographing performed by emitting the strobe light. Further, the shine correction circuit 203 acquires n luminance blocks b [n] from the strobe light emission image data 702. The flash emission image data 702 is image data obtained at the time of actual photographing. Here, in FIG. 7, the entire image is divided into a plurality of blocks for convenience of explanation. However, the luminance block may be the same block as the plurality of blocks obtained by dividing the face area described above, and the information on the average luminance value AveY described above may be set in each of the luminance blocks (see FIG. 5). ). In this way, the luminance block only needs to be set for the human face area. The shine correction circuit 203 temporarily stores the luminance blocks a [n] and b [n], for example, in the system memory 122.

  When the exposure conditions are different between when the strobe light is emitted and when it is not emitted, the shine correction circuit 203 calculates a luminance block with the same exposure conditions. For example, it is assumed that the exposure conditions are aperture, shutter speed, and sensitivity. Also, let the aperture, shutter speed, and sensitivity when acquiring the luminance block a [n] be Av1, Tv1, and Sv1, respectively. Also, let the aperture, shutter speed, and sensitivity of the luminance block b [n] be Av2, Tv2, and Sv2, respectively. The shine correction circuit 203 calculates an exposure condition difference ΔEv that is a difference between these exposure conditions. The exposure condition difference ΔEv is calculated by, for example, ΔEv = 2 ^ {(Av1 + Tv1−Sv1) − (Av2 + Tv2−Sv2)}. Then, the shine correction circuit 203 multiplies the luminance block a [n] by the exposure condition difference ΔEv. Thereby, the exposure conditions of the luminance blocks a [n] and b [n] are aligned.

  The difference data (= b [n] −a [n] or b [n] −ΔEv × a [n]) between the two luminance blocks a [n] and b [n] The reflected light of the area is represented. The shine correction circuit 203 uses the difference data of the luminance blocks a [n] and b [n] as the amount of stroboscopic light irradiation on the face area, and sets the amount of stroboscopic light irradiation as an evaluation value s [n]. Get for each block. Similarly to the color evaluation value c [n], the evaluation value s [n] is also used by the shine correction circuit 203 to determine whether or not each block has color unevenness. Here, a case where the amount of strobe light applied to the face area when the strobe light is emitted is calculated as an evaluation value will be described as an example. However, the shine correction circuit 203 may calculate the color evaluation value as in the case where the strobe light is not emitted (S605).

  In S606, the shine correction circuit 203 calculates the uniformity of the evaluation values s [n] and c [n] acquired in S604 or S605. That is, the shine correction circuit 203 determines the degree of uneven illumination of the light source applied to the face area. For example, the shine correction circuit 203 calculates a dispersion value of the evaluation value c [n] or s [n], and can determine that there is uneven illumination of the light source as the dispersion value is larger. In the present embodiment, the uniformity (dispersion value) of the evaluation value c [n] or s [n] is an example of the evaluation value of the degree of color unevenness.

  Further, the shine correction circuit 203 may determine the presence or absence of uneven irradiation when the strobe light is emitted based on the non-light emission image data 701 taken before and after the strobe light emission. For example, the shine correction circuit 203 determines whether or not there is a shadow portion (bright / dark portion) in the face area in the non-light-emitting image data 701 before the strobe light emission (for example, whether or not it is in an oblique light state). For example, if the number of luminance blocks whose value (average luminance value AveY) is equal to or lower than the threshold value ThA and the number of luminance blocks whose value is equal to or higher than the threshold value ThB (> ThA) are each equal to or larger than a predetermined number, In addition, it is determined that there is a shadow portion in the face area. When there is a shadow portion in the face area, the face area is divided into a portion that is greatly irradiated with ambient light and a shadow portion. Therefore, even when the strobe light is emitted, uneven illumination occurs on the face area. This is because when the strobe light is emitted to the face area with the shadow part, the strobe light is mainly emitted to the dark part of the face area, and the light part is mixed with the strobe light and the ambient light. . When the strobe light is emitted, the shine correction circuit 203 detects a shadow portion of the face area from the non-light emitting image data 701 before and after the strobe light is emitted, and the strobe light is based on the degree of shadow of the shadow portion of the face area. The degree of irradiation unevenness at the time of light emission may be determined for each luminance block. For example, the shine correction circuit 203 stores in advance a table in which the luminance range equal to or lower than the threshold value ThA, the luminance range equal to or higher than the threshold value ThB, and the degree of shadow are associated with each other. The shine correction circuit 203 is a representative value (for example, average value or median value) of the luminance block having a value equal to or lower than the threshold value ThA, and a representative value (for example, average value) of the luminance block having a value equal to or higher than the threshold value ThB. Or median). The shine correction circuit 203 extracts the degree of shading corresponding to these representative values from the table. In this way, the degree of shadow in the face area can be determined.

  Based on the uniformity of the evaluation values s [n] and c [n], the shine correction circuit 203 detects irradiation unevenness of the light source applied to the face area. FIG. 8 is a diagram conceptually showing that new color unevenness occurs by correcting the shine of the face area. When the high brightness area 801 is generated on the face by the light source A and the light source B, if the complementary color of the skin color average value is simply subtracted from the high brightness area 801, in addition to the color unevenness existing before correcting the shine. As a result, new color unevenness 802 occurs. Therefore, in this embodiment, the shine correction circuit 203 reduces the erroneous correction by limiting the correction amount of the high luminance region 801 in such a case.

In S607, the shine correction circuit 203 is based on the uniformity of the evaluation values s [n] and c [n] calculated in S606, the face luminance information acquired in S601, and the skin color complementary color based on the skin color average value. Determine the amount of shine correction. FIG. 9 is a diagram illustrating an example of the gain characteristic when calculating the shine correction amount.
FIG. 9A shows an example of the correction gain (Gain A) for the face luminance information. As described above, in the present embodiment, the face luminance information is the average luminance value AveY of each block. The example illustrated in FIG. 9A indicates that correction is performed when the face luminance information is equal to or greater than the threshold Th1_Y. That is, in the example shown in FIG. 9A, the shine correction circuit 203 sets a larger correction gain as the luminance is higher when the face luminance information is equal to or greater than the threshold Th1_Y. Further, the shine correction circuit 203 sets the maximum correction gain when the face luminance information becomes equal to or greater than the threshold Th2_Y.

  FIG. 9B is a diagram illustrating an example of a correction gain (GainB) with respect to the uniformity of the evaluation values s [n] and c [n]. As described above, in the present embodiment, the uniformity is a dispersion value. In the example shown in FIG. 9B, the shine correction circuit 203 sets the maximum correction gain in the range where the variance values of the evaluation values s [n] and c [n] are equal to or less than the threshold value Th1_Var. Further, the shine correction circuit 203 sets a smaller correction gain as the variance value increases in the range where the variance values of the evaluation values s [n] and c [n] are in the threshold values Th1_Var to Th2_Var. That is, in the example shown in FIG. 9B, the shine correction circuit 203 causes the unevenness of the illumination of the light source applied to the face region as the variance of the evaluation values s [n] and c [n] increases. Is set to be low. Further, the shine correction circuit 203 does not perform correction when the variance of the evaluation values s [n] and c [n] is greater than or equal to the threshold Th2_Var.

The shine correction circuit 203 calculates a value obtained by multiplying Gain A and Gain B as the final correction gain α as shown in the following equation (1). The shine correction circuit 203 calculates a correction gain α for each block. In the present embodiment, the correction gain α is an example of the gain.
α = GainA × GainB (1)
Next, the shine correction circuit 203 calculates the skin color complementary colors Skin_R ′, Skin_G ′, and Skin_B ′) from the skin color average values Skin_R, Skin_G, and Skin_B acquired in S602. Then, the shine correction circuit 203 calculates the shine correction amount for each block in the high luminance area based on the complementary color of the skin color and the correction gain α. Specifically, the shine correction circuit 203 multiplies the skin color complementary colors Skin_R ′, Skin_G ′, and Skin_B ′ by the gain α to calculate a final correction amount (S607).

Next, the shine correction circuit 203 reproduces the skin color by subtracting the correction amount calculated in S607 from the pixel values R0, G0, and B0 of each pixel included in the block (S608). Note that in a region other than the high luminance region, Gain A is 0 (zero) and the gain α is 0 (zero), so that the pixel value is not corrected. In the present embodiment, for example, the second term on the right side of the equations (2) to (4) is an example of the correction amount for the pixel value in the correction target region.
R1 = R0−α × Skin_R ′ (2)
G1 = G0−α × Skin_G ′ (3)
B1 = B0−α × Skin_B ′ (4)

  As described above, in the present embodiment, the electronic camera 100 evaluates the luminance and color unevenness of the face area of the person shown in the captured image, and corrects the complementary color of the skin color according to the evaluated luminance and color unevenness. Then, the corrected complementary color value of the skin color is subtracted from the pixel value of the high luminance area. Accordingly, it is possible to reduce the case where the shine correction does not operate correctly due to the color unevenness generated by the environmental light source.

(Second Embodiment)
Next, a second embodiment will be described.
In the first embodiment, when it is determined that there is uneven illumination of the light source in the face area of the person, the complementary color of the skin color is calculated from the average value of the skin color, and the correction amount for the complementary color of the skin color is limited. The case of reducing erroneous correction due to correction has been described as an example. In contrast, in the second embodiment, when it is determined that there is uneven illumination of the light source in the face area of the person, the complementary color of the skin color is calculated in consideration of the high brightness area of the face and the uneven illumination area of the light source. As described above, the present embodiment and the first embodiment mainly differ in the method of calculating the skin color complementary color. Therefore, in the description of the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals as those in FIGS.

An example of details of the shine correction process will be described with reference to the flowchart of FIG.
Since the processing of S1001 to S1006 is the same as S601 to S606 of FIG. 6 described in the first embodiment, detailed description thereof is omitted.
In S1007, the shine correction circuit 203 determines whether or not there is uneven illumination of the light source in the face area based on the uniformity of the evaluation values s [n] and c [n] of the face area calculated in S1006. To do. In the present embodiment, as in the first embodiment, the shine correction circuit 203 converts, for example, the variance value of the evaluation value c [n] or s [n] into the evaluation value s [n] or c [n]. Calculated as an example of uniformity. For example, when the variance of the evaluation value c [n] or s [n] is larger than a threshold value (for example, the threshold value Th1_Y in FIG. 9A), the shine correction circuit 203 causes uneven illumination of the light source in the face area. If not, it is determined that there is no uneven illumination of the light source in the face area. In the present embodiment, the uniformity (dispersion value) of the evaluation value c [n] or s [n] is an example of the evaluation value of the degree of color unevenness.

  If it is determined in S1007 that the facial area has uneven illumination of the light source, the shine correction circuit 203 uses the skin color value of one or more blocks in the non-high brightness area around each block in the high brightness area. The skin color evaluation value is derived. At this time, if there is a color unevenness region in the non-high brightness region around the high brightness region, the shine correction circuit 203 derives a skin color evaluation value by excluding the block of the color unevenness region. The shine correction circuit 203 derives, for example, a distribution (for example, a histogram) of the evaluation values s [n] and c [n] of each block, and in this distribution, representative values of the evaluation values s [n] and c [n]. A block that is more than a threshold value away from (for example, the mode value) is defined as an uneven color region. Here, the non-high brightness area block around the high brightness area block is obtained, for example, according to the distance from the high brightness area block. For example, the shine correction circuit 203 extracts a predetermined number of blocks in the non-high brightness area in order from the shortest distance from the block in the high brightness area, and extracts the extracted non-high brightness area blocks in the block of the high brightness area. A block of a non-high brightness area around the.

  Then, the shine correction circuit 203 calculates a skin color complementary color in each block of the high luminance region based on the skin color evaluation value of the non-high luminance region around each block of the high luminance region (S1008). In this embodiment, one or more blocks in the non-high brightness area around the block in the high brightness area derive a correction amount for the pixel value in the correction target area (when there is uneven illumination of the light source in the face area). It is an example of the area | region used in order to do.

  Further, when the shine correction circuit 203 derives the uniformity of the evaluation value s [n] using the non-light-emitting image data 701 described above, it is determined whether the high-luminance area is a shadow area or other area. A skin color evaluation value is derived according to the region. For example, the shine correction circuit 203 acquires the non-light emitting image data 701 before the main photographing, and determines whether or not there is a shadow portion in the face area in the non-light emitting image data 701. If the result of this determination is that there is a shadow in the face area, the shine correction circuit 203 divides the face area into a shadow area and other areas. Next, the shine correction circuit 203 acquires image data (strobe light emission image data 702) obtained by actual photographing, and determines the presence / absence of a high brightness area from the strobe light emission image data 702. When the high luminance area is in the shaded area, the shine correction circuit 203 obtains skin color information in one or more blocks in the non-high luminance area around the block in the high luminance area among the blocks included in the shadow area. The skin color evaluation value in the block of the high luminance area is calculated.

  On the other hand, when the high luminance region is in a region other than the shadow portion, the shine correction circuit 203 calculates the skin color evaluation value in each block of the high luminance region as follows. That is, the shine correction circuit 203 uses the skin color information in one or more blocks in the non-high brightness area around the block in the high brightness area among the blocks included in the area other than the shaded area, and uses the high brightness The skin color evaluation value in the block of the area is calculated. As described above, in the present embodiment, the skin color evaluation value acquisition area is changed depending on whether the high-luminance area is an area where the strobe light is dominant (a shaded area) or other areas.

  The skin color evaluation value in the block of the high brightness area is, for example, the skin color average value in the block of the non-high brightness area around the block of the high brightness area. When the number of non-high brightness area blocks around the high brightness area block is one, the skin color value of the non-high brightness area block is the skin color evaluation value of the high brightness area block. . In the present embodiment, the skin color average value (or the skin color value of the non-high brightness area block) around the high brightness area block is the pixel value in the area around the correction target area. It is an example of a representative value.

  On the other hand, if it is determined in S1007 that there is no uneven illumination of the light source in the face area, the shine correction circuit 203 calculates the complementary color of the skin color of each block based on the skin color average value acquired in S1002 (S1009). . In the present embodiment, the skin color average value acquired in S1002 is an example of a representative value of pixel values in the face area. Further, in the present embodiment, the skin color average value of the area excluding the areas of the organs such as the eyes and the mouth among the face areas is calculated. Accordingly, for example, a region excluding organ regions such as eyes and mouth among the facial regions derives a correction amount for the pixel value in the correction target region (in the case where there is no uneven illumination of the light source in the facial region). This is an example of a region used for the purpose.

Next, in S1010, the shine correction circuit 203 calculates a correction gain (Gain A) based on the face luminance information acquired in S1001 (see FIG. 9A). Then, the shine correction circuit 203 calculates a value obtained by multiplying the complementary color (Skin_R ′, Skin_G ′, Skin_B ′) of skin color calculated in S1008 or S1009 by a correction gain (GainA) (S1010). This value is the amount of shine correction for each block in the high luminance region (region for shine correction).
Next, in S1011, the shine correction circuit 203 reproduces the skin color by subtracting the correction amount calculated in S1010 from the pixel value of the high luminance region (the shine correction target region).
Even if it does as mentioned above, the effect similar to the effect demonstrated in 1st Embodiment can be acquired.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  100: electronic camera, 105: image processing unit, 203: shine correction circuit

Claims (15)

Image processing for performing image processing including processing for correcting a pixel value of the correction target region, using a region whose luminance is higher than a threshold as a correction target region among human face regions included in the image captured by the imaging unit A device,
Obtaining means for obtaining an evaluation value of the degree of color unevenness in at least the correction target region of the face region;
An image processing apparatus comprising: a determination unit that determines a correction amount for a pixel value in the correction target region based on an evaluation value of a degree of color unevenness in the correction target region.   The determination means derives a correction amount for a pixel value in the correction target region based on an evaluation value of a degree of color unevenness in the correction target region and a luminance in the correction target region. The image processing apparatus according to 1.   The determination means derives a skin color complementary color in the correction target region based on a representative value of the pixel value in the face region, and evaluates the degree of color unevenness in the correction target region, and the correction target region Based on the luminance, a gain for correcting the complementary color of the skin color in the correction target region is derived, and the correction for the pixel value in the correction target region based on the complementary color of the skin color in the correction target region and the gain The image processing apparatus according to claim 2, wherein an amount is derived.   The determining unit determines an area to be used for deriving a correction amount for the pixel value in the correction target area from the face area in accordance with an evaluation value of the degree of color unevenness in the correction target area. The image processing apparatus according to claim 1, wherein a correction amount for a pixel value in the correction target area is derived based on a pixel value in the corrected area.   The determination means derives a complementary color of the skin color in the correction target region based on a representative value of the skin color in the region used for deriving a correction amount for the pixel value in the correction target region, and brightness in the correction target region Based on the above, a gain for correcting the complementary color of the skin color in the correction target region is derived, and based on the complementary color of the skin color in the correction target region and the gain, a correction amount for the pixel value in the correction target region is calculated. The image processing apparatus according to claim 4, wherein the image processing apparatus is derived. The determining means determines whether or not there is uneven illumination of a light source in the face area based on an evaluation value of the degree of uneven color in the correction target area,
When there is uneven illumination of the light source in the face area, the area used to derive the correction amount for the pixel value in the correction target area is an area around the correction target area,
6. The area used for deriving a correction amount for a pixel value in the correction target area when there is no uneven illumination of a light source in the face area is the face area. Image processing device.   The image processing apparatus according to claim 3, further comprising a derivation unit that derives a representative value of the pixel value. The acquisition means acquires an evaluation value of the degree of color unevenness in at least the correction target region of the face region for each divided region obtained by dividing the face region into a plurality of regions,
The image processing apparatus according to claim 1, wherein the determining unit determines a correction amount for a pixel value in the correction target region for each of the divided regions.   The image processing apparatus according to claim 1, wherein the obtaining unit obtains a color uniformity in the face area as an evaluation value of the degree of color unevenness.   The image processing apparatus according to claim 1, wherein the acquisition unit derives an evaluation value of the degree of color unevenness based on the image.   The acquisition unit acquires the uniformity of the amount of stroboscopic light irradiation in the face area as an evaluation value of the degree of color unevenness when the stroboscopic light is emitted and the imaging unit performs imaging. The image processing apparatus according to claim 1, wherein:   The acquisition unit is configured to acquire a degree of shading in the face area as an evaluation value of the degree of color unevenness when the strobe light is emitted and the imaging unit performs imaging. The image processing apparatus according to any one of 1 to 11.   The obtaining means emits the strobe light and captures the degree of color unevenness based on the image captured by the imaging means and the image captured by the image capturing means without emitting the strobe light. The image processing apparatus according to claim 11, wherein an evaluation value is derived. Image processing for performing image processing including processing for correcting a pixel value of the correction target region, using a region whose luminance is higher than a threshold as a correction target region among human face regions included in the image captured by the imaging unit A method,
An acquisition step of acquiring an evaluation value of the degree of color unevenness in at least the correction target region of the face region;
And a determination step of determining a correction amount for the pixel value in the correction target area based on an evaluation value of the degree of color unevenness in the correction target area.   A program that causes a computer to function as each unit of the image processing apparatus according to claim 1.