JP2014135589A - Image processing device, control method therefor, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always accurately extract a subject by high-pass filter processing while reducing influence of noise.SOLUTION: A system control circuit 50 and an image processing circuit 20, when performing extraction processing of a subject in an image obtained as a result of photographing the subject, reduce the image in accordance with photographing sensitivity in the photographing or noise level in the image to generate a reduced image, detect an edge of the subject in the reduced image, and output an edge detection result.

Description

  The present invention relates to an image processing apparatus used in an imaging apparatus using a solid-state imaging device, a control method thereof, and a control program.

  In general, in an imaging apparatus such as a digital camera, a main subject is recognized and the main subject is tracked for autofocus. Further, the imaging apparatus may perform image processing for extracting the main subject from the image and optimizing the main subject, and may perform special effect processing such as blurring the background of the image.

  In particular, when the subject and the background are separated from each other in the image, it is required to improve the accuracy of subject extraction.

  Here, as one of methods for extracting a subject in an image, there is a method for extracting edge information by performing high-pass filter processing on the image.

  However, with this method, it is difficult to distinguish between random noise superimposed on an image and an edge due to high-pass filter processing. In particular, it may be difficult to extract an edge during high-sensitivity imaging with a high noise level.

  For this reason, an image pickup apparatus that separately obtains a noise level to be superimposed on an image obtained as a result of photographing and uniformly subtracts the noise level from an edge signal obtained from a high-pass filter processing result to eliminate the influence of noise. Yes (see Patent Document 1).

JP 2010-171614 A

  However, as in Patent Document 1, if the noise level is uniformly subtracted from the edge signal obtained as a result of the high-pass filter process, an edge component having a level lower than the noise level cannot be detected. As a result, the subject may not be accurately extracted from the image.

  Accordingly, an object of the present invention is to provide an image processing apparatus, a control method thereof, and a control program that can always accurately extract a subject by high-pass filter processing.

  In order to achieve the above object, an image processing device according to the present invention is an image processing device that extracts a subject from an image obtained as a result of photographing the subject, and is used for photographing sensitivity at the time of photographing or in the image. A reduction processing unit that reduces the image to a reduced image according to a noise level; and a first edge detection unit that detects an edge of the subject in the reduced image and outputs an edge detection result. It is characterized by.

  A control method according to the present invention is a control method of an image processing apparatus that performs extraction processing on the subject in an image obtained as a result of photographing the subject, depending on the photographing sensitivity at the time of photographing or the noise level in the image. The image processing apparatus includes a reduction processing step for reducing the image to obtain a reduced image, and an edge detection step for detecting an edge of the subject in the reduced image and outputting an edge detection result.

  The control program according to the present invention is a control program used in an image processing apparatus that extracts a subject in an image obtained as a result of photographing the subject, and the computer included in the image processing device performs photographing at the time of photographing. In accordance with sensitivity or a noise level in the image, a reduction processing step for reducing the image to obtain a reduced image, and an edge detection step for detecting an edge of the subject in the reduced image and outputting an edge detection result. It is made to perform.

  According to the present invention, it is possible to reduce the influence of noise and always extract a subject with high accuracy by high-pass filter processing.

1 is a block diagram illustrating a configuration of an example of an imaging apparatus including an image processing apparatus according to a first embodiment of the present invention. 2A and 2B are diagrams for explaining edge extraction processing performed by the camera illustrated in FIG. 1, in which FIG. 1A is a diagram illustrating an original image, FIG. 2B is a diagram illustrating an image obtained by performing high-pass filter processing on the original image; ) Is a diagram showing an edge region of the original image, (d) is a diagram showing an image obtained by reducing the original image and subjected to high-pass filter processing, (e) is a diagram showing an edge region of the image shown in (d), (f) is a diagram showing the result of combining the edge region shown in (c) and the edge region shown in (e). It is a block diagram for demonstrating the edge extraction process performed with the camera shown in FIG. It is a figure which shows an example of the table of the synthesis | combination ratio used when synthesize | combining the edge determination result shown in FIG. 2A and 2B are diagrams for explaining a high-pass filter and a low-pass filter used in edge determination processing performed by the camera shown in FIG. 1, in which FIG. 1A is a diagram illustrating an example of a high-pass filter, and FIG. FIG.

  Hereinafter, an imaging device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an example of an imaging apparatus including an image processing apparatus according to the first embodiment of the present invention.

  The illustrated imaging apparatus 100 is, for example, a digital camera (hereinafter simply referred to as a camera) and includes a photographing lens unit (hereinafter simply referred to as a photographing lens) 10. A shutter 12 having a diaphragm function is disposed at the rear stage of the photographing lens 10. An imaging element 14 such as a CCD or CMOS element that converts an optical image into an electrical signal is disposed behind the shutter 12. An analog signal that is an output of the image sensor 14 is converted into a digital signal (image data) by the A / D converter 16.

  Although not shown, a barrier is disposed on the front side of the photographic lens 10, and this barrier covers the photographic lens 10, the shutter 12, and the image sensor 14 to prevent the dirt and damage thereof. Is.

  The timing generation circuit 18 supplies a clock signal or a control signal to the image sensor 14, the A / D converter 16, and the D / A converter 26. The timing generation circuit 18 is controlled by the memory control circuit 22 and the system control circuit 50.

  Note that if the accumulation time of the image sensor 18 is controlled by an electronic shutter by controlling the reset timing of the image sensor 18, moving image shooting or the like can be performed by the electronic shutter.

  The image processing circuit 20 receives the image data that is the output of the A / D converter 16 or the image data from the memory control circuit 22 and performs a resizing process such as predetermined pixel interpolation and reduction and a color conversion process.

  In addition, the image processing circuit 20 performs electronic zoom by performing a cut-out process and a scaling process for cutting out a partial area of the image data as an image.

  The image processing circuit 20 performs predetermined arithmetic processing using image data obtained as a result of imaging. The system control circuit 50 controls the exposure control unit 40 and the distance measurement control unit 42 based on the calculation result to perform exposure control and distance measurement control. As a result, TTL (through the lens) AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash pre-emission) processing are performed.

  Further, the image processing circuit 20 performs predetermined calculation processing using image data obtained as a result of imaging, and performs TTL AWB (auto white balance) processing based on the calculation result.

  The memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32. Image data that is output from the A / D converter 16 is written into the memory 30 via the image processing circuit 20 and the memory control circuit 22 or directly via the memory control circuit 22.

  The display image data written in the memory 30 is sent to the image display unit 28 via the memory control circuit 22. As a result, an image corresponding to the image data is displayed on the image display unit 28.

  Note that an electronic finder function can be realized by sequentially displaying images obtained by imaging on the image display unit 28 (for example, LCD).

  The display of the image display unit 28 can be turned on / off under the control of the system control circuit 50. When the display is turned off, the power consumption of the imaging apparatus 100 can be greatly reduced.

  The memory 30 stores still images or moving images obtained as a result of shooting. The memory 30 has a sufficient storage capacity for storing a predetermined number of still images or a moving image for a predetermined time.

  By using this memory 30, a large number of images can be stored at high speed even in continuous shooting or panoramic shooting in which a plurality of still images are continuously shot. The memory 30 is also used as a work area for the system control circuit 50.

  The compression / decompression circuit 32 compresses or decompresses image data by adaptive discrete cosine transform (ADCT) or the like. For example, the compression / decompression circuit 32 reads the image data stored in the memory 30 using the operation of the shutter 12 as a trigger, performs compression processing, and writes the compressed image data in the memory 30.

  The compression / decompression circuit 32 reads the compressed image data read from the recording medium 200 into the memory 30, performs the decompression process, and writes the decompressed image data into the memory 30. The image data written to the memory 30 by the compression / decompression circuit 32 is filed by the system control circuit 50 and recorded on the recording medium 200 via the interface 90.

  The exposure control unit 40 controls the shutter 12 under the control of the system control circuit 50. Further, the exposure control unit 40 performs flash light control in cooperation with the flash 48. The distance measurement control unit 42 controls the focusing of the photographing lens 10 under the control of the system control circuit 50.

  As described above, the system control circuit 50 controls the exposure control unit 40 and the distance measurement control unit 42 based on the calculation result of the image processing circuit 20 to perform TTL exposure control and distance measurement control.

  The zoom control unit 44 controls zooming of the photographing lens 10 under the control of the system control circuit 50. The flash 48 is controlled by the system control circuit 50, and performs the flash light control while projecting AF auxiliary light for focusing.

  A system control circuit 50 controls the entire imaging apparatus 100. The nonvolatile memory 31 is, for example, a flash ROM, and constants, variables, programs, and the like for operation of the system control circuit 50 are stored in the nonvolatile memory memory 31.

  The non-volatile memory 31 defines an area for storing information related to the camera and an area for storing user setting information, and the system control circuit 50 reads and restores the information and settings at the time of activation.

  The mode dial switch 60 is used when the power source 86 is turned on or off. Further, the mode dial switch 60 is configured such that, for example, the operation mode of the system control circuit 50 is an automatic exposure mode such as a program AE mode, a fully automatic mode, a manual exposure mode, a sleeping face shooting mode, a panoramic shooting mode, a playback mode, a multi-screen playback / It is used when switching to the erase mode or PC connection mode.

  When the shutter button 62 is being operated (half-pressed), the first shutter switch SW1 is turned on, and the first shutter switch signal SW1 is given to the system control circuit 50.

  Thus, the system control circuit 50 starts shooting preparation operations such as AF (autofocus) processing, AE (automatic exposure) processing, AWB (auto white balance) processing, and EF (flash pre-flash) processing.

  When the operation of the shutter button 62 is completed (fully pressed), the second shutter switch SW2 is turned on, and the second shutter switch signal SW2 is given to the system control circuit 50.

  As a result, the system control circuit 50 performs exposure processing for writing image data to the memory 30 after reading the signal from the image sensor 14, development processing using computations by the image processing circuit 20 and the memory control circuit 22, and image data from the memory 30. A series of imaging processes such as a recording process in which image data is written to the recording medium 200 after being read and compressed by the compression / decompression circuit 32 is started.

  In response to the operation of the display changeover switch 66, the system control circuit 50 performs display switching in the image display unit 28. As a result, when photographing is performed using the optical viewfinder 104, power supply to the image display unit 28 is cut off, thereby saving power.

  The operation unit 70 has various buttons, a touch panel, a rotary dial, and the like. Various buttons include, for example, a menu button, a set button, a macro button, an image display on / off button, a multi-screen playback page break button, a flash setting button, a single shooting / continuous shooting / self-timer switching button, menu movement + (plus) There are a button, a menu shift- (minus) button, a playback image shift + (plus) button, a playback image- (minus) button, a shooting image quality selection button, an exposure correction button, and a date / time setting button.

  When the menu button is operated, the system control circuit 50 displays a menu screen for performing various settings on the image display unit 28. The user can intuitively make various settings by operating various buttons by looking at the menu screen displayed on the image display unit 28.

  The zoom switch 72 is used when the user issues an image magnification change instruction. The zoom switch 72 includes a tele switch that changes the imaging field angle to the telephoto side and a wide switch that changes the wide angle side.

  By operating the zoom switch 72, the system control circuit 50 instructs the zoom control unit 44 to change the imaging field angle of the photographic lens 10 and performs an optical zoom operation.

  It should be noted that by operating the zoom switch 72, an electronic zooming change of the imaging angle of view is performed by an image cut-out process and a pixel interpolation process by the image processing circuit 20.

  The power source 86 includes a primary battery such as an alkaline battery or a lithium battery, or a secondary battery such as a NiCd battery, a NiMH battery, or a Li battery, and an AC adapter.

  An interface (I / F) 90 is an interface with the recording medium 200. The interface 90 is connected to a connector 206 provided on the recording medium 200 by a connector 92. The recording medium 200 includes an interface 204 and a recording unit 202, and a semiconductor memory or a magnetic disk is used as the recording unit 202.

  The communication unit 110 performs various communication processes related to USB, IEEE 1394, LAN, or wireless communication. A connector (an antenna in the case of wireless communication) 112 connects the communication unit 110 to an external device such as a printer.

  When a printer is connected to the connector 112, for example, an image file (image data) recorded on the recording medium 200 is transferred to the printer, and an image can be directly printed by the printer without using a PC or the like.

  If the optical viewfinder 104 is used, it is possible to take an image without using the electronic viewfinder function of the image display unit 28.

  The optical viewfinder 104 includes a part of display contents displayed on a part of the display unit 54, for example, an in-focus display, a camera shake warning display, a flash charge display, a shutter speed display, an aperture value display, and an exposure correction display. Is displayed.

  The system control circuit 50 performs various photographing preparation operations when the power supply 86 is turned on by the mode dial switch 60 in the photographing capable mode. When the photographing preparation operation is completed, the system control circuit 50 controls the memory control circuit 22 to display a through image on the image display unit 28.

  Here, the through image refers to an image captured by the image sensor 14 in order to execute a finder function before and after capturing a still image.

  In the through image display state, the image data sequentially written to the image display memory 24 via the image sensor 14, A / D converter 16, image processing circuit 20, and memory control circuit 22 is stored in the memory control circuit 22 and D. It is sequentially sent to the image display unit 28 via the / A converter 26. Thereby, an electronic viewfinder (EVF) function is performed.

  FIG. 2 is a diagram for explaining edge extraction processing performed by the camera shown in FIG. FIG. 2A is a diagram illustrating an original image, and FIG. 2B is a diagram illustrating an image obtained by performing high-pass filter processing on the original image. FIG. 2C is a diagram illustrating an edge region of the original image, and FIG. 2D is a diagram illustrating an image obtained by reducing the original image and performing high-pass filter processing. Further, FIG. 2 (e) is a diagram showing the edge region of the image shown in FIG. 2 (d), and FIG. 2 (f) is the edge region shown in FIG. 2 (c) and the edge region shown in FIG. 2 (e). It is a figure which shows the result of having synthesize | combined.

  The image shown in FIG. 2A is an original image showing an image obtained as a result of photographing, and the original image is a YUV image generated in the image processing circuit 20. A main subject 201 and a background 202 exist in the illustrated original image.

  When the image processing circuit 20 performs high-pass filter processing (HPF) on the original image shown in FIG. 2A, an image shown in FIG. 2B is obtained. In the illustrated image, the main subject region 203 has an edge signal and a noise signal. Here, for convenience of explanation, it is assumed that a noise signal exists only in the main subject region 203.

  Then, the image processing circuit 20 divides the image shown in FIG. 2B into a plurality of blocks 204 under the control of the system control circuit 50. In the example shown, the image is divided into 8 × 8 blocks 204.

  The system control circuit 50 controls the image processing circuit 20 to detect the edge of each block 204 and obtain an edge region 205 shown in FIG. Here, the edge signal and the noise signal included in the main subject area are determined as the edge area as indicated by the black background area.

  Here, a method for performing edge extraction by reducing the original image will be described.

  First, the image processing circuit 20 reduces the original image shown in FIG. 2A to a reduced image under the control of the system control circuit 50. Then, the image processing circuit 20 performs high-pass filter processing on the reduced image to obtain the image shown in FIG. In the image shown in FIG. 2D, since the high-pass filter processing is performed after the original image is reduced, the noise level relatively decreases. As a result, in the image shown in FIG. 2D, the main subject region 206 may be regarded as including only an edge signal.

  Then, the image processing circuit 20 divides the image shown in FIG. 2D into a plurality of blocks 207 under the control of the system control circuit 50. In the illustrated example, the image is divided into 4 × 4 blocks 207.

  The system control circuit 50 controls the image processing circuit 20 to detect the edge of each block 207 and obtain an edge region 208 shown in FIG. Here, as shown by the black background area, the edge signal included in the main subject area is determined as the edge area.

  Subsequently, the system control circuit 50 controls the image processing circuit 20 to synthesize the edge region 205 shown in FIG. 2C and the edge region 208 shown in FIG. 2E, as shown in FIG. Get edge region.

  In other words, the influence of noise was reduced, as shown by the black background area, by combining the edge area related to the 1X image including the noise signal and the edge area of the reduced image that does not include the noise signal, although the positional accuracy is coarse. An edge region 209 can be obtained.

  FIG. 3 is a block diagram for explaining edge extraction processing performed by the camera shown in FIG. The edge extraction process shown in FIG. 3 is performed under the control of the system control circuit 50.

  First, image data (RGB signal here) is given to the image processing circuit 50, and the RGB signal is developed to obtain the YUV signal which is the original image (S306).

  In the first system (S301), edge determination is performed on the same-size image. The image processing circuit 50 performs high-pass filter processing on the original image (S307) and then divides the block as described above.

  Then, the image processing circuit 50 integrates the image after the high-pass filter processing for each block (that is, integrates the pixels for each block: S308), and selects the block whose integration result is equal to or greater than a predetermined threshold as an edge region. (S309), the first edge determination result (first edge region) is obtained. The edge determination result is also referred to as an edge detection result.

  In the second system (S302), edge determination is performed on the first reduced image obtained as a result of reduction at the first reduction rate. The image processing circuit 20 reduces the original image at the first reduction ratio to obtain a first reduced image (S311), and then performs high-pass filter processing on the first reduced image (S312).

  The image processing circuit 20 divides the image after the high-pass filter processing into a plurality of blocks, and integrates the image after the high-pass filter processing for each block (S313). Then, the image processing circuit 20 determines a block whose integration result is equal to or greater than a predetermined threshold as an edge region (S314), and obtains an edge determination result.

  Subsequently, the image processing circuit 50 enlarges the edge determination result at a first magnification that is the same as the first reduction ratio and returns the result to the second edge determination result (second edge region) ( S315).

  In the third system (S303), edge determination is performed on the second reduced image obtained as a result of reduction at the second reduction rate that is larger than the first reduction rate. The image processing circuit 20 reduces the original image at the second reduction ratio to obtain a second reduced image (S317), and then performs high-pass filter processing on the second reduced image (S318).

  The image processing circuit 20 divides the image after the high-pass filter processing into a plurality of blocks, and integrates the image after the high-pass filter processing for each block (S319). Then, the image processing circuit 20 determines a block whose integration result is equal to or greater than a predetermined threshold as an edge region (S320), and obtains an edge determination result.

  Subsequently, the image processing circuit 50 enlarges the edge determination result at a second magnification that is the same as the second reduction ratio, and returns the result to the third edge determination result (third edge region) ( S321).

  In the fourth system (S304), edge determination is performed using the luminance signal. First, the image processing circuit 20 divides the original image into a plurality of blocks (S323). Then, the image processing circuit 20 integrates a luminance signal (that is, a luminance value for each pixel) for each block to obtain a luminance integrated value.

  Subsequently, the image processing circuit 20 groups the blocks whose luminance integration values are in a preset range to obtain a luminance group region (S324). Then, the image processing circuit 20 determines that the boundary of the luminance group area is an edge, and obtains a fourth edge determination result (fourth edge area) (S325).

  In the fifth system (S305), edge determination is performed using the color difference signal. First, the image processing circuit 20 divides the original image into a plurality of blocks (S327). Then, the image processing circuit 20 integrates the color difference signal for each block to obtain a color difference integrated value.

  Subsequently, the image processing circuit 20 groups the blocks in which the color difference integral value is in a preset range to obtain a color difference group region (S328). Then, the image processing circuit 20 determines that the boundary of the color difference group area is an edge, and obtains a fifth edge determination result (fifth edge area) (S329).

  As described above, after the system control circuit 50 obtains the first to fifth edge determination results by the image processing circuit 20, the system control circuit 50 determines the fourth edge determination by the predetermined fourth synthesis ratio k4. The result and the fifth edge determination result are combined to obtain a fourth combined edge determination result (S326). Here, the fourth edge determination result is multiplied by k4, and the fifth edge determination result is multiplied by (1-k4).

  Subsequently, the system control circuit 50 combines the third edge determination result and the fourth combined edge determination result with the predetermined third combining ratio k3 to obtain the third combined edge determination result (S322). . Here, the third edge determination result is multiplied by k3, and the fourth combined edge determination result is multiplied by (1-k3).

  Next, the system control circuit 50 combines the second edge determination result and the third combined edge determination result with the predetermined second combining ratio k2 to obtain the second combined edge determination result (S316). . Here, the second edge determination result is multiplied by k2, and the third combined edge determination result is multiplied by (1-k2).

  Further, the system control circuit 50 combines the first edge determination result and the second combined edge determination result with the predetermined first combining ratio k1 to obtain the first combined edge determination result (S310). Here, the first edge determination result is multiplied by k1, and the second combined edge determination result is multiplied by (1-k1). Then, the system control circuit 50 sets the first composite edge determination result as the edge area of the main subject.

  In the above example, the noise level is relatively reduced by reducing the original image. However, the noise level may be reduced by performing low-pass filter processing without reducing the original image. .

  That is, instead of reducing the original image, low-pass filter processing is performed on the original image to generate a low-pass filtered image. Then, the low-pass filtered image is used instead of the reduced image, and the coefficient related to the low-pass filter processing is changed according to the photographing sensitivity or the noise level.

  FIG. 4 is a diagram illustrating an example of a table of combination ratios k1 to k4 used when combining the edge determination results illustrated in FIG.

  When setting the combination ratios k1 to k4, one of the first setting to the fifth setting according to the sensitivity condition (shooting sensitivity) set by the photographer, the sensitivity condition set automatically by the camera, or the noise level. Is selected. Here, first, the imaging sensitivity will be described as an example. The table shown in FIG. 4 is stored in, for example, the nonvolatile memory 31 shown in FIG.

  The system control circuit 50 selects the first setting when the photographing sensitivity (for example, ISO) is equal to or lower than a predetermined first sensitivity. When the shooting sensitivity is equal to or lower than the first sensitivity, the edge region can be determined with high accuracy without being affected by noise. Therefore, here, the first synthesis ratio k1 = 1 is set to the first sensitivity. The edge region is determined using only the system (S301).

  As a result, the system control circuit 50 outputs the first edge determination result as the first combined edge determination result.

  When the photographing sensitivity is equal to or lower than the first sensitivity, the second synthesis ratio k2 to the fourth synthesis ratio k4 are not used.

  When the photographing sensitivity exceeds the first sensitivity and is equal to or lower than the second sensitivity higher than the first sensitivity, the system control circuit 50 selects the second setting. Here, the edge region is determined using the first system (S301) and the second system (S302) with the first composition ratio k1 = 0.5 and the second composition ratio k2 = 1.

  As a result, the system control circuit 50 sets the second edge determination result as the second combined edge determination result, and combines the second combined edge determination result and the first edge determination result by 0.5 times. Then, the first composite edge determination result is output.

  Note that if the photographing sensitivity exceeds the first sensitivity and is equal to or lower than the second sensitivity, the third synthesis ratio k3 and the fourth synthesis ratio k4 are not used.

  When the photographing sensitivity exceeds the second sensitivity and is equal to or lower than the third sensitivity higher than the second sensitivity, the system control circuit 50 selects the third setting. Here, the first synthesis ratio k1 = 0, the second synthesis ratio k2 = 0.5, and the third synthesis ratio k3 = 1, the first system (S301) to the third system (S303). The edge region is determined using.

  As a result, since k3 = 1, the system control circuit 50 sets the third edge determination result as the third combined edge determination result, and since K2 = 0.5, the third combined edge determination result and the second Are combined by multiplying each of the edge determination results by 0.5, and a second combined edge determination result is output.

  Then, since k1 = 0, the system control circuit 50 outputs the second combined edge determination result as the first combined determination result.

  Note that if the photographing sensitivity exceeds the second sensitivity and is equal to or lower than the third sensitivity, the fourth combination ratio k4 is not used.

  When the photographing sensitivity exceeds the third sensitivity and is equal to or lower than the fourth sensitivity higher than the third sensitivity, the system control circuit 50 selects the fourth setting. When the photographing sensitivity exceeds the third sensitivity and is equal to or lower than the fourth sensitivity, the accuracy of the edge region determination by the high-pass filter processing decreases due to the increase of the noise level, so the determination of the edge level is used for the luminance level of the luminance signal.

  Here, it is assumed that the first synthesis ratio k1 = 0, the second synthesis ratio k2 = 0, the third synthesis ratio k3 = 0.5, and the fourth synthesis ratio k4 = 1, the first system (S301 The edge region is determined using the fourth system (S304).

  As a result, since k4 = 1, the system control circuit 50 sets the fourth edge determination result as the fourth combined edge determination result, and since K3 = 0.5, the fourth combined edge determination result and the third Are combined by multiplying each of the edge determination results by 0.5, and a third combined edge determination result is output.

  Since k2 = K1 = 0, the system control circuit 50 outputs the third combined edge determination result as the second combined determination result, and outputs the second combined determination result as the first combined determination result. Will do.

  When the photographing sensitivity exceeds the fourth sensitivity, the system control circuit 50 selects the fifth setting. If the photographing sensitivity exceeds the fourth sensitivity, the accuracy of the edge region determination by the high-pass filter processing is further reduced due to the increase of the noise level. Therefore, the determination of the edge region is performed using the luminance level of the luminance signal and the color difference signal.

  Here, it is assumed that the first synthesis ratio k1 = 0, the second synthesis ratio k2 = 0, the third synthesis ratio k3 = 0.33, and the fourth synthesis ratio k4 = 0.5. The edge region is determined using (S301) to the fourth system (S304).

  As a result, since k4 = 0.5, the system control circuit 50 synthesizes the fifth edge determination result and the fourth edge determination result by multiplying each by 0.5, and the fourth combined edge determination result is obtained. Output.

  Furthermore, since K3 = 0.33, the system control circuit 50 multiplies the fourth combined edge determination result by 0.67, multiplies the third edge determination result by 0.33, and combines the result. The edge judgment result is output.

  Since k2 = K1 = 0, the system control circuit 50 outputs the third combined edge determination result as the second combined determination result, and outputs the second combined determination result as the first combined determination result. Will do.

  In the above description, the shooting sensitivity has been described as an example, but any one of the first setting to the fourth setting may be selected depending on the noise level in the image.

  That is, the system control circuit 50 selects the first setting when the noise level is equal to or lower than the first threshold level (less than the first threshold), and the noise level exceeds the first threshold level and the first threshold value is selected. The second setting is selected to be equal to or lower than a second threshold level higher than the level.

  Similarly, the system control circuit 50 selects the third setting when the noise level exceeds the second threshold level and is equal to or lower than the third threshold level higher than the second threshold level.

  Further, the system control circuit 50 selects the fourth setting when the noise level exceeds the third threshold level and is equal to or lower than the fourth threshold level higher than the third threshold level. Then, the system control circuit 50 selects the fifth setting when the noise level exceeds the fourth threshold level.

  FIG. 5 is a diagram for explaining a high-pass filter and a low-pass filter used in the edge determination process performed by the camera shown in FIG. FIG. 5A is a diagram illustrating an example of a high-pass filter, and FIG. 5B is a diagram illustrating an example of a low-pass filter.

  The camera shown in FIG. 1 generates a calculation result between the filter matrix and the original image while moving the high-pass filter or the low-pass filter pixel by pixel on the original image from left to right and from top to bottom.

  As described above, in the embodiment of the present invention, the original image is subjected to high-pass filter processing to perform edge determination to obtain an edge determination result, and the original image is reduced according to photographing sensitivity or noise level to perform edge determination. Since the edge determination results are obtained and these edge determination results are combined at a predetermined combining ratio to obtain the final edge determination result, the subject can always be extracted with high accuracy.

  Further, when the photographing sensitivity or the noise level is high, edge determination is performed using at least one of the luminance signal and the color difference signal, and the edge determination result and the edge determination result obtained according to the original image are set to a predetermined value. Since the composition is performed at the composition ratio, the subject can be accurately extracted even when the photographing sensitivity or the noise level is high.

  As is apparent from the above description, in the example shown in FIG. 1, at least the image processing circuit 20 and the system control circuit 50 constitute an image processing apparatus. The image processing circuit 20 and the system control circuit 50 function as a reduction processing unit, a first edge detection unit, a second edge detection unit, a synthesis unit, and a third edge detection unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the image processing apparatus. In addition, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the image processing apparatus. The control program is recorded on a computer-readable recording medium, for example.

  Each of the above control method and control program has at least a reduction processing step and an edge detection step.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and the computer (or CPU, MPU, etc.) of the system or apparatus reads the program. To be executed.

14 Image sensor 20 Image processing circuit 22 Memory control circuit 28 Image display unit 40 Exposure control unit 42 Distance control unit 44 Zoom control unit 50 System control circuit 60 Mode dial switch 62 Shutter button

Claims (13)

An image processing apparatus that extracts a subject in an image obtained as a result of photographing the subject,
A reduction processing means that reduces the image to a reduced image according to the shooting sensitivity at the time of shooting or the noise level in the image;
First edge detection means for detecting an edge of the subject in the reduced image and outputting an edge detection result;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the reduction processing unit changes a reduction ratio for reducing the image according to the photographing sensitivity or the noise level.   The image processing apparatus according to claim 2, wherein the reduction processing unit increases a reduction ratio for reducing the image as the photographing sensitivity increases or the noise level increases. Second edge detection means for detecting an edge of the subject in the original image using the image as an original image;
And combining means for combining the edge detection result output from the first edge detection means and the edge detection result output from the second edge detection means into a final edge detection result. The image processing apparatus according to claim 1.   The synthesizing unit synthesizes the edge detection result that is the output of the first edge detection unit and the edge detection result that is the output of the second edge detection unit according to the photographing sensitivity or the noise level. The image processing apparatus according to claim 4, wherein the ratio is changed.   When the photographing sensitivity exceeds a predetermined first sensitivity or the noise level exceeds a predetermined first threshold, the combining means and the edge detection result as the output of the first edge detecting means and the first 6. The image processing apparatus according to claim 4, wherein an edge detection result which is an output of the second edge detection means is synthesized.   The synthesizing unit may detect the first edge when the imaging sensitivity exceeds a second sensitivity higher than the first sensitivity or when the noise level exceeds a second threshold higher than the first threshold. The image processing apparatus according to claim 6, wherein an edge detection result that is an output of a detection unit is output as the final edge detection result.   The synthesizing unit outputs an edge detection result that is an output of the second edge detecting unit when the photographing sensitivity is equal to or lower than the first sensitivity or the noise level is equal to or lower than the first threshold. The image processing apparatus according to claim 6, wherein the image processing apparatus outputs the result as a typical edge detection result. A third edge detecting means for detecting an edge of a subject in the image according to at least one of a luminance signal and a color difference signal in the image;
The synthesizing means may detect the first edge when the photographing sensitivity exceeds a third sensitivity higher than the second sensitivity or when the noise level exceeds a fourth threshold higher than the second threshold. The image processing apparatus according to claim 7, wherein an edge detection result output from the detection unit and an edge detection result output from the third edge detection unit are combined to obtain the final edge detection result.   The image processing apparatus according to claim 4, wherein each of the first edge detection unit and the second edge detection unit detects an edge of the subject by high-pass filter processing. In place of the reduction processing means, low-pass filter processing means for performing low-pass filter processing on the image to generate a low-pass filtered image,
2. The low-pass filter processed image is used instead of the reduced image, and the low-pass filter processing unit changes a coefficient related to the low-pass filter processing according to the photographing sensitivity or the noise level. The image processing apparatus according to any one of 10 to 10. A control method of an image processing apparatus for extracting a subject in an image obtained as a result of photographing the subject,
A reduction processing step to reduce the image to a reduced image according to the shooting sensitivity at the time of shooting or the noise level in the image;
An edge detection step of detecting an edge of the subject in the reduced image and outputting an edge detection result;
A control method characterized by comprising: A control program used in an image processing apparatus for extracting the subject in an image obtained as a result of photographing the subject,
A computer included in the image processing apparatus,
A reduction processing step to reduce the image to a reduced image according to the shooting sensitivity at the time of shooting or the noise level in the image;
An edge detection step of detecting an edge of the subject in the reduced image and outputting an edge detection result;
A control program characterized by causing

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