JP5915242B2 - Image processing apparatus, image processing method, image processing program, and recording medium recording the image processing program on a computer - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing method, an image processing program, and a recording medium on which the image processing program is recorded so as to be executable on a computer.

  Regarding a digital image taken by an imaging device using a CCD (Charge Coupled Device) image sensor or the like as an imaging device, the color change of the output signal of the CCD due to the color temperature of the light source is unnatural to human eyes. White balance correction that corrects the image so that it does not feel is an essential function.

  In white balance correction, the optimum white balance according to the shooting scene (simply referred to as the scene) is determined by judging the shooting scene (that is, the light source) such as outdoors (sunny), cloudy (shade), incandescent, and fluorescent. A technique for determining the gain and executing white balance correction is known. For example, brightness (illuminance) and color distribution in a shaded (cloudy) green scene and an indoor fluorescent lamp scene Are known to be difficult to identify.

  Therefore, the shooting scene is mistakenly determined as a scene under fluorescent light for a scene with green outdoors, and white balance correction is performed for a scene with green outdoors. Sometimes became magenta.

  As described above, in the conventional white balance correction technique, determination (outdoor determination) between a scene with outdoor green (outdoor) and a scene under the fluorescent light (indoor) fails, and the determination is performed based on the determination. In some cases, white balance correction cannot be performed with high accuracy.

  To deal with such a problem, for example, Patent Document 1 discloses a white balance correction device that estimates a light source based on information (frequency component and edge amount component) on a subject pattern and performs white balance correction. ing.

  Further, Patent Document 2 defines an identification boundary in a multidimensional space based on feature information such as illuminance information and color temperature information, performs outdoor determination based on the identification boundary, and performs white balance correction according to the determination result. An image processing apparatus to be executed is disclosed.

  Patent Document 3 discloses a digital camera that obtains a regression line from the distribution of hue data by the least square method, determines whether the scene is green based on the slope of the regression line, and performs white balance correction. Has been.

  However, as described in the above patent document, the detection method of the edge amount component or the like for performing the white balance correction increases the processing amount, increases the processing time, and increases the cost (increasing CPU performance, memory capacity, etc.) )).

  In addition, the outdoor boundary between a scene with outdoor greenery (outdoor) and a scene under fluorescent light (indoors) is uniformly determined based on an identification boundary based on feature information and a regression line based on a least-squares method based on the distribution of hue data. This is difficult depending on the subject, and it may be difficult to accurately perform outdoor determination and perform appropriate white balance correction.

  Therefore, the present invention records an image processing apparatus, an image processing method, an image processing program, and an image processing program that can perform outdoor determination of a shooting scene with low processing load, high accuracy, and stability in an executable manner on a computer. An object is to provide a recording medium.

In order to achieve this object, the image processing apparatus according to the present invention preliminarily includes a first area including an area outside the white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed. First area setting means for setting, and second area setting for presetting a plurality of second areas corresponding to white extraction ranges in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed A white balance evaluation value acquisition means for acquiring a white balance evaluation value from the digital image; and determining whether the white balance evaluation value acquired by the white balance evaluation value acquisition means is within a white extraction range; First white balance correction for calculating a first white balance correction coefficient based on the white balance evaluation value determined to be within the range The number calculating means, the number of the white white balance evaluation value acquired by the balance evaluation value acquisition means determines whether or not distributed to the first area, the white balance evaluation value distributed to the first area First area determination means to be acquired and whether or not the white balance evaluation value is distributed in any of the plurality of second areas, and each second area of the plurality of second areas is determined. Second area determination means for obtaining the number of distributed white balance evaluation values, and the first area determination means and the second area determination among the first area and the plurality of second areas. an upper area determining means for determining an area number is often higher multiple of the obtained white balance evaluation value by means, a plurality of upper determined by the upper area determining means A white balance evaluation value distributed to the rear, based on the first white balance correction coefficient, and a second white balance correction coefficient calculation means for calculating a second white balance correction coefficient, wherein the upper area determining On the basis of the number of white balance evaluation values distributed in each of the upper plurality of areas obtained by the means, outdoor information relating to whether or not the digital image corresponds to an outdoor scene is obtained.

  According to the present invention, it is possible to perform outdoor determination of a shooting scene with a low processing load and high accuracy and stability.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the external view of the digital camera which is one Embodiment of the image processing apparatus which concerns on this invention, (a) is a top view, (b) is a front view, (c) shows a back view. It is an example of the functional block diagram of a digital camera. It is a schematic diagram of the control block of CPU which concerns on white balance control. It is a flowchart (1st Embodiment) of a white balance process. It is explanatory drawing of the white detection frame and green evaluation value determination in the two-dimensional color coordinate which makes G / R x-axis and G / B is y-axis. It is explanatory drawing of the fluorescent lamp evaluation value determination in the two-dimensional color coordinate which makes G / R x-axis and G / B is y-axis. It is a flowchart (2nd Embodiment) of a white balance process.

  Hereinafter, a configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

[First Embodiment]
The image processing apparatus according to the present embodiment presets a first area (green area) including an area outside the white extraction range in which white balance evaluation values corresponding to an outdoor green subject on a digital image are distributed. A first area setting unit (green area setting unit 211) and a second area (fluorescent lamp area) corresponding to a white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed. Second area setting means (fluorescent lamp area setting means 212) for presetting a plurality of values, white balance evaluation value acquisition means (white balance evaluation value acquisition means 203) for acquiring a white balance evaluation value from a digital image, white balance It is determined whether the white balance evaluation value acquired by the evaluation value acquisition means is distributed in the first area, and is distributed in the first area. First area determining means (green evaluation value determining means 206) for acquiring the number of white balance evaluation values, determining whether the white balance evaluation values are distributed in any of a plurality of second areas, Second area determination means (fluorescent lamp evaluation value determination means 207) for respectively acquiring the number of white balance evaluation values distributed in each second area of the second area, the first area, and a plurality of second areas An upper area determining means (upper area determining means 208) for obtaining a plurality of upper areas having a large number of white balance evaluation values acquired by the first area determining means and the second area determining means, The digital image corresponds to an outdoor scene based on the number of white balance evaluation values distributed in each of the upper multiple areas obtained by the upper area determination means And requests the outdoor information about whether Luke (outside weight rate calculation unit 209). Note that the parentheses indicate correspondence with the words in the embodiment.

  In the present embodiment, an imaging apparatus (digital camera) will be described as an example of an image processing apparatus. However, the image processing apparatus according to the present invention is not limited to this, and a mobile phone, a personal computer, a printer, and the like. The present invention can be applied to electronic devices such as image forming apparatuses. That is, it is only necessary to be an electronic device that can input a digital image (RAW-RGB data) and execute white balance correction control to be described later.

(Configuration of imaging device)
FIG. 1 shows an external view of a digital camera, (a) shows a top view of the camera, (b) shows a front view of the camera, and (c) shows a rear view of the camera.

  As shown in FIG. 1A, the digital camera has a sub LCD 1, a release shutter 2 (SW1), and a mode dial 4 (SW2) on the upper surface.

  As shown in FIG. 1B, the digital camera has a strobe light emitting unit 3, a distance measuring unit 5, a remote control light receiving unit 6, a lens unit 7, and an optical viewfinder (front) 11 on the front. Have. A memory card throttle 23 indicates a throttle for inserting a memory card 34 such as an SD card, and is provided on the side of the camera.

  As shown in FIG. 1C, the digital camera has an AFLED (autofocus LED) 8, a strobe LED 9, an LCD monitor (display means) 10, an optical viewfinder (back surface) 11, and a zoom on the back surface. It has a button (zoom lever) TELE12 (SW4), a power switch 13 (SW13), a zoom button (zoom lever) WIDE14 (SW3), and a self-timer / deletion switch 15 (SW6).

  Furthermore, the menu switch 16 (SW5), the OK switch 17 (SW12), the left / image confirmation switch 18 (SW11), the down / macro switch 19 (SW10), the up / strobe switch 20 (SW7), the right A switch 21 (SW8) and a display switch 22 (SW9) for displaying an image are provided.

  FIG. 2 is a functional block diagram of a control system of the digital camera shown in FIG. The system configuration inside the digital camera will be described below.

  As shown in FIG. 2, in this digital camera, a CCD 121 serving as a solid-state imaging device, on which a subject image incident through a photographing lens system installed in the lens unit 7 forms an image on a light receiving surface, is output from the CCD 121. Front-end IC (F / E) 120 that processes signals (analog RGB image signals) into digital signals, signal-processing IC 110 that processes digital signals output from front-end IC (F / E) 120, and data temporarily An SDRAM 33 to be stored, a ROM 30 in which a control program and the like are stored, a motor driver 32 and the like are provided.

  The lens unit 7 includes a zoom lens, a focus lens, a mechanical shutter, and the like, and is driven by a motor driver 32. The motor driver 32 is controlled by a microcomputer (CPU, control unit) 111 included in the signal processing IC 110.

  The CCD 121 is a solid-state imaging device for photoelectrically converting an optical image, and an RGB primary color filter as a color separation filter is arranged on a plurality of pixels constituting the CCD, and an electrical signal (analogue) corresponding to RGB three primary colors. RGB image signal) is output.

  A front-end IC (F / E) 120 is a CDS 122 that performs sampling hold (correlated double sampling) on the CCD output electrical signal (analog image data), and an AGC (Auto Gain Control) 123 that adjusts the gain of the sampled data. A vertical synchronization signal (VD) and a horizontal synchronization signal (HD) are supplied from an A / D converter (A / D) 124 that performs digital signal conversion and a CCD I / F 112, and drive timing signals for the CCD 121 and the F / E 120 are supplied. A TG (timing generator: control signal generator) 125 is generated.

  The oscillator (clock generator) supplies a clock to the system clock of the signal processing IC 110 including the CPU 111, the TG 125, and the like. The TG 125 receives the oscillator clock and supplies a pixel clock for pixel synchronization to the CCD I / F 112 in the signal processing IC 110.

  A digital signal input from the F / E 120 to the signal processing IC 110 is temporarily stored as RGB data (RAW-RGB) in the SDRAM 33 by the memory controller 115 via the CCD I / F 112.

  The signal processing IC 110 includes a CPU 111 that performs system control, a CCD I / F 112, a resizing processing unit 113, a memory controller 115, a display output control unit 116, a compression / expansion unit 117, a media I / F unit 118, a YUV conversion unit 119, and the like. ing.

  The CCD I / F 112 outputs a vertical synchronizing signal (VD) and a horizontal synchronizing signal (HD), takes in a digital (RGB) signal input from the A / D 124 in accordance with the synchronizing signal, and passes through the memory controller 115. RGB data is written to the SDRAM 33.

  The display output control unit 116 sends the display data written in the SDRAM 33 to the display unit, and displays the captured image. The display output control unit 116 can display on the LCD monitor 10 built in the digital camera, or output it as a TV video signal and display it on an external device.

  The display data here is OSD (on-screen display) data for displaying a natural image YCbCr, a shooting mode icon, etc., and the memory controller 115 reads and displays the data placed on the SDRAM 33. The data is sent to the output control unit 116, and the data synthesized by the display output control unit 116 is output as video data.

  The compression / decompression unit 117 compresses the YCbCr data written in the SDRAM 33 during recording and outputs JPEG-encoded data. During reproduction, the compression / decompression unit 117 decompresses the read JPEG-encoded data into YCbCr data and outputs the YCbCr data.

  The media I / F 118 reads data in the memory card 34 to the SDRAM 33 or writes data on the SDRAM 33 to the memory card 34 in accordance with an instruction from the CPU 111.

  The YUV conversion unit 119 converts the RGB data temporarily stored in the SDRAM 33 into luminance Y and color difference CbCr data (YUV data) based on the image development processing parameters set by the CPU 111, and writes back to the SDRAM 33.

  The resizing processing unit 113 reads out YUV data and performs size conversion to a size necessary for recording, size conversion to a thumbnail image, size conversion to a size suitable for display, and the like.

  In addition, the CPU 111 which is a control unit that controls the overall operation loads a control program and control data for controlling the camera stored in the ROM 30 at the time of startup into, for example, the SDRAM 33, and performs the overall operation based on the program code. Control.

  The CPU 111 performs imaging operation control, setting of image development processing parameters, in accordance with an instruction by a button key of the operation unit 31, an external operation instruction from a remote controller (not shown), or a communication operation instruction by communication from an external terminal such as a personal computer. Performs memory control and display control.

  The operation unit 31 is used by the photographer to instruct the operation of the digital camera, and a predetermined operation instruction signal is input to the control unit by the operation of the photographer. For example, as shown in FIG. 1, various button keys such as a two-stage (half-pressed and fully-pressed) release shutter 2 for instructing shooting, zoom buttons 12 and 14 for setting an optical zoom and an electronic zoom magnification are provided.

  When the operation unit 31 detects that the power key of the digital camera is turned on, the CPU 111 performs a predetermined setting for each block. With this setting, an image received by the CCD 121 via the lens unit 7 is converted into a digital video signal and input to the signal processing IC 110.

  The digital signal input to the signal processing IC 110 is input to the CCD I / F 112. The CCD I / F 112 performs processing such as black level adjustment on the photoelectrically converted analog signal and temporarily stores it in the SDRAM 33. The RAW-RGB image data stored in the SDRAM 33 is read by the YUV conversion unit 119, and subjected to gamma conversion processing, white balance processing, edge enhancement processing, and YUV conversion processing, and is written back to the SDRAM 33 as YUV image data. .

  The YUV image data is read by the display output control unit 116. For example, if the output destination is an NTSC system TV, the resizing processing unit 113 performs horizontal / vertical scaling processing according to the system, and Is output. By performing this process for each VD, monitoring which is a display for confirmation before still photographing is performed.

(Operation of imaging device)
Next, the monitoring operation and still image shooting operation of the digital camera will be described. This digital camera performs a still image shooting operation while performing a monitoring operation as described below in the still image shooting mode.

  First, when the photographer turns on the power switch 13 and sets the mode dial 4 to the photographing mode (still image photographing mode), the digital camera is activated in the recording mode. When the CPU 111 detects this, the CPU 111 outputs a control signal to the motor driver 32 to move the lens unit 7 to a photographing position, and the CCD 121, F / E 120, signal processing IC 110, SDRAM 33, ROM 30, LCD monitor 10 And so on.

  Then, by directing the photographic lens system of the lens unit 7 toward the subject, a subject image incident through the photographic lens system is formed on the light receiving surface of each pixel of the CCD 121. An electrical signal (analog RGB image signal) corresponding to the subject image output from the CCD 121 is input to the A / D 124 via the CDS 122 and AGC 123, and converted into 12-bit RAW-RGB data by the A / D 124.

  This RAW-RGB data is taken into the CCD I / F 112 of the signal processing IC 110 and stored in the SDRAM 33 via the memory controller 115. The RAW-RGB data read from the SDRAM 33 is input to the YUV conversion unit 119 and converted into YUV data that can be displayed, and then the YUV data is stored in the SDRAM 33 via the memory controller 115. .

  The YUV data read from the SDRAM 33 via the memory controller 115 is sent to the LCD monitor 10 via the display output control unit 116, and a captured image (moving image) is displayed. At the time of monitoring in which a photographed image is displayed on the LCD monitor 10, one frame is read out in a time of 1/30 seconds by thinning out the number of pixels by the CCD I / F 112.

  In this monitoring operation, the photographed image (moving image) is only displayed on the LCD monitor 10 functioning as an electronic viewfinder, and the release button 2 is not yet pressed (including half-pressed).

  By displaying the photographed image on the LCD monitor 10, the composition for photographing a still image can be confirmed. In addition, it can output as a TV video signal from the display output control part 116, and a picked-up image (moving image) can also be displayed on external TV (television) via a video cable.

  Then, the CCD I / F 112 of the signal processing IC 110 determines an AF (automatic focus) evaluation value, an AE (automatic exposure) evaluation value, an AWB (auto white balance) evaluation value (WB evaluation value) from the captured RAW-RGB data. (Also referred to as AWB evaluation value).

  The AF evaluation value is calculated by, for example, the output integrated value of the high frequency component extraction filter or the integrated value of the luminance difference between adjacent pixels. When in the in-focus state, the edge portion of the subject is clear, so the high frequency component is the highest. By using this, at the time of AF operation (focus detection operation), AF evaluation values at each focus lens position in the photographing lens system are acquired, and AF operation is performed with the maximum point as the focus detection position. Is executed.

  The AE evaluation value and the WB evaluation value are calculated from the integrated values of the RGB values in the RAW-RGB data. For example, the screen (image area) corresponding to the light receiving surface of all the pixels of the CCD 121 is equally divided into 256 blocks (areas) (horizontal 16 divisions and vertical 16 divisions), and the RGB integration of each block is calculated. The number of block divisions is merely an example, and the present invention is not limited to this.

  Then, the control unit reads the calculated RGB integrated value, and in the AE process, calculates the luminance of each area (block) of the screen and determines an appropriate exposure amount from the luminance distribution. Based on the determined exposure amount, exposure conditions (the number of electronic shutters of the CCD 121, the aperture value of the aperture unit, the insertion and removal of the ND filter, etc.) are set. In the AWB process, an AWB control value that matches the color of the light source of the subject is determined from the RGB distribution (described later). By this AWB process, white balance is adjusted when the YUV conversion unit 119 performs conversion processing to YUV data. Note that the AE process and the AWB process are continuously performed during monitoring.

  Then, when a still image shooting operation in which the release button is pressed (half-pressed to fully pressed) is started during the monitoring operation, an AF operation that is a focus position detection operation and a still image recording process are performed.

  That is, when the release button is pressed (half to full), the focus lens of the photographing lens system is moved by a drive command from the control unit to the motor driver 32. For example, contrast evaluation called so-called hill-climbing AF is performed. The AF operation of the method is executed.

  When the AF (focusing) target range is the entire region from infinity to close, the focus lens of the taking lens system moves to each focus position from close to infinity or from infinity to close, and the CCD I / F 112 The control unit reads the AF evaluation value at each focus position calculated in step (1). Then, the focus lens is moved to the in-focus position with the point where the AF evaluation value at each focus position is maximized as the in-focus position, and in-focus.

  Then, AE processing is performed, and when the exposure is completed, the mechanical shutter unit is closed by a drive command from the control unit to the motor driver 32, and an analog RGB image signal for a still image is output from the CCD 121. Then, as in the monitoring, the data is converted into RAW-RGB data by the A / D 124 of the F / E 120.

  The RAW-RGB data is taken into the CCD I / F 112 of the signal processing IC 110, converted into YUV data by the YUV conversion unit 119, and stored in the SDRAM 33 via the memory controller 115. The YUV data is read from the SDRAM 33, converted into a size corresponding to the number of recording pixels by the resizing processing unit 113, and compressed to image data in the JPEG format or the like by the compression / decompression unit 117. The compressed image data such as JPEG format is written back to the SDRAM 33, read from the SDRAM 33 via the memory controller 115, and stored in the memory card 34 via the media I / F 118.

(White balance control)
FIG. 3 is an explanatory diagram of a control block of the CPU 111 related to white balance control. The white balance control executed by each control block of the CPU 111 will be described with reference to the processing flowchart shown in FIG.

  It should be noted that the block dividing means 201, RGB integrating means 202, white balance evaluation value acquiring means 203, white extracting means 204, white balance correction coefficient calculating means (1) 205 (first white balance correction coefficient calculating means) shown in FIG. , Green evaluation value determination means 206 (first area determination means), fluorescent lamp evaluation value determination means 207 (second area determination means), upper area determination means 208, outdoor weighting rate calculation means 209, white balance correction coefficient calculation Means (2) 210 (second white balance correction coefficient calculating means), green area setting means 211 (first area setting means), fluorescent lamp area setting means 212 (second area setting means), weighting means 213, Each unit of the white balance correction unit 214 captures software (imaging program) executed by the CPU 111. Can be configured by executing the apparatus, the data necessary for its execution, for example, is loaded into SDRAM 33.

  First, as described above, the RGB accumulating unit 202 corresponds to the image area (corresponding to the light receiving surfaces of all the pixels of the CCD 121) after the RAW-RGB is taken into the CCD I / F 112 and then equally divided into 256 blocks by the block dividing unit 201. Screen) for each block, R values, G values, and B values (also simply referred to as R, G, and B, collectively referred to as RGB), integrated values (R integrated values, G integrated values, and B integrated values). (S101: RGB integrated value acquisition process). The R value, the G value, and the B value are expressed by, for example, 8 bits, but the quantification method is not particularly limited.

Next, the white balance evaluation value acquisition unit 203 is also referred to as an RGB average value per pixel (also referred to as an R average value, a G average value, or a B average value from the acquired RGB integrated values of each block. Is calculated), and the WB evaluation value (G / R, G / B) and the AE evaluation value (Y) are calculated (S102: WB evaluation value, AE evaluation value generation process). Here, the calculation of the WB evaluation value (G / R, G / B) and the AE evaluation value (Y) can be calculated by, for example, the following equations (1) to (3).
G / R = (G average value × 100) / R average value (1)
G / B = (G average value × 100) / B average value (2)
Y = (R average value × 3 + G average value × 6 + B average value) / 10 (3)
Note that the calculation method of the WB evaluation value (G / R, G / B) and the AE evaluation value (Y) is not limited to the above example, but may be other known or new calculation methods. good.

  Further, the white extraction unit 204 stores a white extraction block (white block) based on the WB evaluation value (G / R, G / B) as long as it is within a preset white extraction range (S103: white). Extraction process). The specific processing method of the white extraction processing is not particularly limited, and a known or new white block extraction method may be used. For example, as shown in FIG. White detection of a plurality of ellipse or rectangular frames along a blackbody radiation characteristic curve (blackbody radiation curve) (indicated by reference numeral c in FIG. 5) on a two-dimensional color coordinate with G / B as the y-axis It may be set as a frame, and when the WB evaluation value is included in the white detection frame, it may be detected as a white extraction block. In the example of FIG. 5, the white detection range is indicated by a plurality of ellipse frames, and each ellipse frame corresponds to a white detection frame corresponding to the white detection range of each light source.

Next, the white balance correction coefficient calculation means (1) 205 determines whether or not the number of white extraction blocks extracted in the white extraction process (S103) is equal to or greater than a predetermined number. Then, the WB evaluation value (G / R, G / B) of each white extraction block is weighted by the AE evaluation value (Y) of the corresponding block, and then integrated to obtain G / R, G per pixel. / B (first white balance correction coefficient) is calculated (S104: high luminance weighting process).

  If there are no more than a certain number of white extraction blocks, the WB evaluation values (G / R, G / B) of all the blocks are integrated to calculate G / R and G / B per pixel. Then, the average of the obtained G / R and G / B per pixel is set as the WB correction coefficients Rgain and Bgain, and the process proceeds to the white balance correction coefficient multiplication process (S109).

  Next, the green evaluation value determination unit 206 performs green area determination based on the WB evaluation values (G / R, G / B) (S105: green evaluation value determination processing). In the green evaluation value determination process, a predetermined threshold is provided for each of the WB evaluation values G / R and G / B, and an evaluation value in which both exceed the threshold is determined as a green evaluation value (the number is acquired). The area determined as the green evaluation value is set in advance by the green area setting unit 211.

  For example, as shown in FIG. 5, the values of both G / R and G / B are large (predetermined threshold values X, G, B) on a two-dimensional color coordinate having G / R as the x axis and G / B as the y axis. The evaluation value in the region (exceeding Y) (the green area that is the hatched portion indicated by A in FIG. 5) is determined as the green evaluation value. The judgment formulas are G / R ≧ X and G / B ≧ Y.

Next, the fluorescent lamp evaluation value determination means 207 performs fluorescent lamp area determination based on the WB evaluation values (G / R, G / B) (S106: fluorescent lamp evaluation value determination processing). FIG. 6 shows a schematic diagram of the fluorescent lamp area. In FIG. 6, the hatched portion indicated by B is the white fluorescent lamp area, and the shaded portion indicated by C is the daylight white fluorescent lamp area, and the evaluation value located in this portion is determined as the fluorescent lamp evaluation value (the number is acquired). . The determination formula for white fluorescent lamp determination is expressed by Formula 2, and the determination formula for day white fluorescent lamp determination is expressed by Formula 3. The area determined as the fluorescent lamp evaluation value is set in advance by the fluorescent lamp area setting means 212.

Next, the upper area determination means 208 has two upper areas (the first selection area and the second selection area) that have a large number of determined evaluation values among the three areas of the green area A and the fluorescent lamp areas B and C. ) Is selected. Also, the outdoor weighting factor calculation means 209 calculates the outdoor weighting factor by Equation 4 based on the number of evaluation values of the selected area (S107: upper area determination, outdoor weighting factor calculation process). The outdoor weighting factor is a value for approaching an outdoor white balance target (white balance setting conditions suitable for shooting outdoors in fine weather), and the optimal WB for outdoor use is set as the outdoor weighting factor increases. It is what is done.

  Formula 4 will be described. Statistically, WB evaluation values are concentrated in one fluorescent lamp area under fluorescent lamps, but when shooting green such as trees and flowers outdoors, the green area and the fluorescent lamp area span multiple areas. Since WB evaluation values are distributed (WB evaluation values corresponding to green are dispersed in both the green area and the fluorescent lamp area), when the evaluation values are widely distributed in the upper two areas in Equation 4, outdoor weighting is performed. The maximum rate is set. For example, the adjustment coefficient k can be set to 25 so that the ratio of the top two area evaluation values is 50% and the outdoor weighting rate is maximized. In addition, by multiplying the ratio of the upper two area evaluation values, when the number of evaluation values in one area is small (when the establishment of a green scene outdoors is low), the outdoor weighting rate is made low.

  More specifically, from the area A determined as the green area and the areas B and C determined as the fluorescent lamp area, the top two areas with the largest number of WB evaluation values are selected, so that the shooting scene is outdoors. Even when green is photographed, at least one of the top two areas includes the green area A, and the WB evaluation value corresponding to the green that has been distributed in the fluorescent lamp areas B or C Since it is used to obtain the WB correction coefficient, it can be prevented from becoming a WB correction coefficient corresponding to the indoor fluorescent lamp, and the WB correction coefficient corresponding to the outdoor green scene can be accurately obtained. It is.

  If only the top one area is selected, the WB evaluation value corresponding to green distributed in the area that has not been selected cannot be picked up, leading to a decrease in the outdoor weighting rate. By selecting the top two areas, this problem can be avoided.

  In addition, in the case where the shooting scene is a scene under an indoor fluorescent lamp that is not outdoor, the fluorescent lamp areas B and C are selected as the top two areas, so that the WB correction coefficient corresponding to the indoor fluorescent lamp can be obtained correctly. It becomes possible.

  According to this outdoor weighting factor calculation process, the outdoor weighting factor is calculated based only on the distribution of the WB evaluation value, so that the processing amount can be reduced and the processing time can be shortened as compared with the conventional method. In addition, it is possible to perform stable WB even in outdoor green scenes regardless of brightness information.

Further, the white balance correction coefficient calculating means (2) 210 calculates the calculated G / R, G / B per pixel and the outdoor WB target based on the calculated outdoor weighting rate as shown in Expression 5. To obtain white balance correction coefficients Rgain, Bgain (second white balance correction coefficient) (S108: outdoor weighting process). The outdoor WB target is a white balance coefficient corresponding to a high color temperature light source, and is a coefficient (a value stored in advance) that provides an optimal white balance outdoors in fine weather.

  Finally, the white balance correction unit 214 performs white balance correction by multiplying the R and B pixels of the entire screen by WB correction coefficients Rgain and Bgain (S109: white balance correction coefficient multiplication process). .

  In the present embodiment, it has been described that the WB evaluation value corresponding to green is distributed in the fluorescent lamp area. For example, even if the light source is an LED, the LED having a color temperature in a predetermined range is used. It is also conceivable that the WB evaluation value corresponding to green is distributed in the area corresponding to this LED. Therefore, the area used when calculating the outdoor weighting rate is not limited to the fluorescent lamp area, but corresponds to a white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed. If it is the area of.

  In the present embodiment, the fluorescent lamp area has been described with respect to the two areas of the white fluorescent lamp area B and the daylight white fluorescent lamp area C. However, the number of fluorescent lamp areas is not limited to this, and two or more fluorescent lamp areas are set. Anything is acceptable. Moreover, although the example which selects two upper areas from the green area A and the fluorescent lamp areas B and C was demonstrated, the selection number should just be suitably selected according to the setting number of a fluorescent lamp area.

  In the present embodiment, the calculated outdoor weighting factor is used for white balance correction. However, in the above processing for calculating the outdoor weighting factor, that is, whether the shooting scene of the image is outdoor using the distribution of white balance evaluation values. Because it is processing (outdoor determination) for acquiring outdoor information regarding whether or not, the calculated outdoor weighting rate is not limited to white balance control, but is other than automatic recognition processing or AF processing of shooting scenes that require outdoor determination. Of course, it can be applied to processing.

  According to the above processing for calculating the outdoor weighting rate, a high accuracy and stable outdoor weighting rate is required with a small processing load. Therefore, not only in the white balun correction, but also in other processing that requires information on whether it is outdoor or not. Effectively, outdoor weighting rate can be utilized.

  According to the image processing apparatus according to the present embodiment described above, it is possible to perform scene outdoor determination with low processing load and high accuracy and stability. In addition, it is possible to easily perform good white balance correction.

[Second Embodiment]
Hereinafter, other embodiments of the image processing apparatus according to the present embodiment will be described. Note that the description of the same points as in the first embodiment will be omitted as appropriate.

  In the first embodiment, the top two areas having the largest number of evaluation values determined in the green area A and the fluorescent lamp areas B and C are selected, and the outdoor weighting rate is calculated based on the number of evaluation values in the area. However, the WB correction coefficient corresponding to the indoor fluorescent lamp can be obtained more satisfactorily by performing the process of lowering the weight on the number of evaluation values determined as the fluorescent lamp area in the present embodiment.

  Hereinafter, the processing will be described with reference to a processing flowchart shown in FIG. First, a series of processes from the RGB integrated value acquisition process (S201) to the fluorescent lamp evaluation value determination process (S206) are performed in the same manner as in the first embodiment (S101 to S106).

  In this embodiment, after the fluorescent lamp evaluation value determination process (S206) by the fluorescent lamp evaluation value determination means 207, the weighting means 213 weights the number of evaluation values determined to be a fluorescent light area (S207: fluorescent light). Evaluation value number weighting process).

  The weighting (weighting coefficient) for the fluorescent lamp area can be set to 0.5, for example. In this case, for example, if the number of evaluation values determined as the white fluorescent lamp area B in Formula 3 is 100 and the number of evaluation values determined as the day white fluorescent lamp area C in Formula 4 is 120, after weighting The number of evaluation values is 50 and 60, respectively.

  In this way, by setting the weight for the fluorescent lamp area below 1.0, depending on the subject, even in an indoor fluorescent lamp scene, it is possible to prevent the problem that the outdoor weight ratio increases because the evaluation value spans a plurality of areas including the fluorescent lamp area. Can do. In addition, the weighting with respect to a fluorescent lamp area is not limited to 0.5, It is possible to set suitably in the range of 1.0 or less.

  Hereinafter, the upper area determination, outdoor weighting factor calculation processing (S208) to white balance correction coefficient calculation processing (S210) are performed in the same manner as in the first embodiment (S107 to S109).

  As described above, according to the image processing apparatus according to the second embodiment, by calculating the outdoor weighting rate using the weighted evaluation value number of the fluorescent lamp area, the WB corresponding to the indoor fluorescent lamp is obtained. The correction coefficient can be calculated more satisfactorily, and even in fluorescent lamp scenes where evaluation values are distributed across the fluorescent lamp area and the green area, and in outdoor green scenes, stable outdoor judgment and white balance correction are possible. Become.

  The white balance control by the image processing apparatus described above can also be executed by a program (image processing program). The present invention is also applied to a recording medium in which the image processing program is recorded so as to be executable by a computer.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

1 Sub LCD
2 Release shutter (SW1)
3 Flash unit 4 Mode dial (SW2)
5 Distance measuring unit 6 Remote control light receiving unit 7 Lens unit 8 AFLED
9 Strobe LED
10 LCD Monitor 11 Optical Finder 12 Zoom Button TELE (SW4)
13 Power switch (SW13)
14 Zoom button WIDE (SW3)
15 Self-timer / deletion switch (SW5)
16 Menu switch (SW6)
17 OK switch (SW12)
18 Left / image confirmation switch (SW11)
19 Lower / Macro switch (SW10)
20 Up / Strobe switch (SW7)
21 Right switch (SW8)
22 Display switch (SW9)
23 Memory card throttle 30 ROM
31 Operation unit 32 Motor driver 33 SDRAM
34 Memory Card 110 Signal Processing IC
111 CPU
112 CCD I / F
113 Resize processing unit 115 Memory controller 116 Display output control unit 117 Compression / decompression unit 118 Media I / F
119 YUV converter 120 F / E
121 CCD
122 CDS
123 AGC
124 A / D converter 125 Timing generator 201 Block division means 202 RGB integration means 203 White balance evaluation value acquisition means 204 White extraction means 205 White balance correction coefficient calculation means (1)
206 Green evaluation value determination means 207 Fluorescent lamp evaluation value determination means 208 Upper area determination means 209 Outdoor weight ratio calculation means 210 White balance correction coefficient calculation means (2)
211 Green area setting means 212 Fluorescent lamp area setting means 213 Weighting means 214 White balance correction means c Black body radiation curve A Green area B White fluorescent lamp area C Daylight white fluorescent lamp area

JP 2008-301279 A JP 2006-174281 A JP 2004-274367 A

Claims (8)

First area setting means for presetting a first area including an area outside the white extraction range in which a white balance evaluation value corresponding to an outdoor green subject on a digital image is distributed;
Second area setting means for setting in advance a plurality of second areas corresponding to white extraction ranges in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed;
White balance evaluation value acquisition means for acquiring a white balance evaluation value from a digital image;
It is determined whether the white balance evaluation value acquired by the white balance evaluation value acquisition means is within a white extraction range, and a first white balance correction is performed based on the white balance evaluation value determined to be within the white extraction range First white balance correction coefficient calculating means for calculating a coefficient;
It is determined whether or not the white balance evaluation value acquired by the white balance evaluation value acquisition means is distributed in the first area, and the number of white balance evaluation values distributed in the first area is acquired. Area determination means;
It is determined whether the white balance evaluation value is distributed in any of the plurality of second areas, and the number of white balance evaluation values distributed in each second area of the plurality of second areas is determined respectively. Second area determination means for acquiring;
Of the first area and the plurality of second areas, an upper area for obtaining a plurality of upper areas having a large number of white balance evaluation values acquired by the first area determination means and the second area determination means. Area determination means;
Second white balance correction for calculating a second white balance correction coefficient based on white balance evaluation values distributed in a plurality of upper areas obtained by the upper area determination means and the first white balance correction coefficient Coefficient calculating means ,
Outdoor information on whether or not the digital image corresponds to an outdoor scene is obtained based on the number of white balance evaluation values distributed in each of the plurality of upper areas obtained by the upper area determination means. An image processing apparatus. An outdoor weight ratio calculating means for determining an outdoor weight ratio as the outdoor information;
The second white balance correction coefficient calculating means calculates the second white balance correction coefficient by a weighted average based on the outdoor weight ratio between a white balance coefficient corresponding to a high color temperature light source and the first white balance correction coefficient. The image processing apparatus according to claim 1 , wherein: Weighting means for performing a process of reducing weighting for each of the number of white balance evaluation values acquired by the second area determination means;
The upper area determination unit uses the number of white balance evaluation values acquired by the first area determination unit and the number of white balance evaluation values weighted by the weighting unit to determine the first area and Of the plurality of second areas, a plurality of upper areas having a large number of white balance evaluation values are obtained,
The outdoor weight ratio calculation means uses the number of white balance evaluation values acquired by the first area determination means and the number of white balance evaluation values weighted by the weighting means, to determine the upper area determination means. The image processing apparatus according to claim 2 , wherein the outdoor weighting rate is obtained based on the number of white balance evaluation values distributed in each of a plurality of upper areas obtained by the step. The said 2nd area determination means determines whether the said white balance evaluation value distributes in either a white fluorescent lamp area or a daylight white fluorescent lamp area, The any one of Claim 1 to 3 characterized by the above-mentioned. The image processing apparatus according to item 1. Further comprising imaging means for converting the light incident from the optical system into an electrical signal and outputting it as the digital image,
The image processing apparatus according to any one of 4 claims 1, wherein said image processing apparatus is a digital camera. A first area setting process for presetting a first area including an area outside the white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed;
A second area setting process in which a plurality of second areas corresponding to a white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed are set;
White balance evaluation value acquisition processing for acquiring a white balance evaluation value from a digital image;
It is determined whether the white balance evaluation value acquired by the white balance evaluation value acquisition process is within a white extraction range, and the first white balance correction is performed based on the white balance evaluation value determined to be within the white extraction range A first white balance correction coefficient calculation process for calculating a coefficient;
It is determined whether the white balance evaluation value acquired by the white balance evaluation value acquisition process is distributed in the first area, and the number of white balance evaluation values distributed in the first area is acquired. Area determination processing;
It is determined whether the white balance evaluation value is distributed in any of the plurality of second areas, and the number of white balance evaluation values distributed in each second area of the plurality of second areas is determined respectively. A second area determination process to be acquired;
Of the first area and the plurality of second areas, an upper area for obtaining a plurality of upper areas having a large number of white balance evaluation values acquired by the first area determination process and the second area determination process. Area determination processing;
Based on the number of white balance evaluation values distributed in each area of a plurality of upper areas obtained by the upper area determination process, a process for obtaining outdoor information regarding whether or not the digital image corresponds to an outdoor scene;
Second white balance correction for calculating a second white balance correction coefficient based on white balance evaluation values distributed in a plurality of upper areas obtained by the upper area determination process and the first white balance correction coefficient And a coefficient calculation process . A first area setting process for presetting a first area including an area outside the white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed;
A second area setting process in which a plurality of second areas corresponding to a white extraction range in which white balance evaluation values corresponding to outdoor green subjects on a digital image are distributed are set;
White balance evaluation value acquisition processing for acquiring a white balance evaluation value from a digital image;
It is determined whether the white balance evaluation value acquired by the white balance evaluation value acquisition process is within a white extraction range, and the first white balance correction is performed based on the white balance evaluation value determined to be within the white extraction range A first white balance correction coefficient calculation process for calculating a coefficient;
It is determined whether the white balance evaluation value acquired by the white balance evaluation value acquisition process is distributed in the first area, and the number of white balance evaluation values distributed in the first area is acquired. Area determination processing;
It is determined whether the white balance evaluation value is distributed in any of the plurality of second areas, and the number of white balance evaluation values distributed in each second area of the plurality of second areas is determined respectively. A second area determination process to be acquired;
Of the first area and the plurality of second areas, an upper area for obtaining a plurality of upper areas having a large number of white balance evaluation values acquired by the first area determination process and the second area determination process. Area determination processing;
Based on the number of white balance evaluation values distributed in each area of a plurality of upper areas obtained by the upper area determination process, a process for obtaining outdoor information regarding whether or not the digital image corresponds to an outdoor scene;
Second white balance correction for calculating a second white balance correction coefficient based on white balance evaluation values distributed in a plurality of upper areas obtained by the upper area determination process and the first white balance correction coefficient An image processing program that causes a computer to execute coefficient calculation processing . A recording medium on which the image processing program according to claim 7 is recorded so as to be executable on a computer.

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