KR101298646B1 - Method of controlling digital image processing apparatus wherein face area is efficiently searched - Google Patents

Abstract

The present invention provides a control method of a digital image processing apparatus for searching for a face region in a preview mode and marking the retrieved face region on a display image, comprising steps (a) and (b). In step (a), if the rate of change of the focus value of the current image or the rate of change of the luminance value with respect to the previous image is larger than the set ratio, the face region is searched using the entire image-data of the current image. In step (b), if there is at least one face area in step (a), the at least one face area is marked on the display image.

Description

Method of controlling digital image processing apparatus wherein face area is efficiently searched}

1 is a perspective view showing the front and top appearance of a digital camera as a digital image processing apparatus to which the control method according to the present invention is applied.

FIG. 2 is a rear view showing a rear outer shape of the digital camera of FIG. 1;

FIG. 3 is a diagram showing the overall configuration of the digital camera of FIG. 1. FIG.

4 is a flow chart showing the main algorithm of the digital camera processor of FIG.

FIG. 5 is a flowchart illustrating an example of a face marking algorithm that is repeatedly performed in units of frames in the preview mode performing step of FIG. 4 when the face marking mode is set in the performing of the setting mode of FIG. 4.

FIG. 6 is a diagram illustrating a pixel structure of a unit frame in order to explain a focus value or a luminance value of an image in steps S51 and S55 of FIG. 5.

FIG. 7 is a diagram illustrating a pixel structure of a set partial area in a unit frame of FIG. 6.

FIG. 8 is a flowchart illustrating another example of a face marking algorithm repeatedly performed in units of frames in the preview mode performing step of FIG. 4 when the face marking mode is set in the performing of the setting mode of FIG. 4.

 <Explanation of symbols for the main parts of the drawings>

1 ... digital camera, 11 ... self-timer lamp,

12 ... flash, 13 ... shutter release button,

15 ... function buttons, 16 ... ASR mode button,

17 ... power button, 19 ... flash-light sensor, 20 ... lens, 22 ... camera-status lamp,

23 ... special-effect button, 24 ... camera strap hook,

25 ... earphone connection, MIC ... microphone,

SP ... speaker, 35 ... display panel,

36 ... + / - button, 39 ... Zoom / 9 split / volume button,

42 ... play / printer button, 43 ... mode button,

OPS ... Optical system, OEC ... Photoelectric conversion unit, M _Z ... Zoom motor, M _F ... Focus motor,

M _A ... aperture motor, 501 ... analog-to-digital converter,

502 ... timing circuit, 503 ... real time clock,

504 ... DRAM, 505 ... EEPROM, 506 ... memory card interface, 507 ... digital camera processor, 508 ... RS232C interface, 509 ... video filter, 21a ... USB connection, 21b ... RS232C connection, 21c ... video output, 510 ... lens driver, 511 ... flash controller, 512 ... microcontroller, INP ... user input, LAMP ... light emitter, 513 ... audio processor, 514 ... LCD driver, 62 ... flash memory, 601 ... unit frame,

602 ... setting subarea, 701 ... unit of measurement of focus value.

The present invention relates to a control method of a digital image processing apparatus, and more particularly, to a method of controlling a digital image processing apparatus for searching for a face region in a preview mode and marking the detected face region on a display image. It is about.

As a typical digital image processing apparatus, for example, a digital camera of U.S. Patent No. 6,097,431 (entitled "Method and system for reviewing and navigating among images on an image capture unit") is exemplified.

In the conventional digital image processing apparatus as described above, when the face marking mode is set, the face area is periodically searched in the preview mode and the detected face area is marked on the display image.

Well-known face recognition algorithms are used as face regions are periodically searched. Face recognition algorithms include algorithms using symmetry of the face, algorithms using hair color and face color, and algorithms using contours of the face.

Since there are relatively many comparison steps in this face recognition algorithm, the execution time is relatively long. Accordingly, when the face marking mode is set, the overall processing speed of the digital image processing apparatus may be slowed down as the face region is periodically searched in the preview mode.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method of a digital image processing apparatus capable of improving the overall processing speed by efficiently reducing the number of face region searches in a preview mode when the face marking mode is set. .

According to an aspect of the present invention, there is provided a control method of a digital image processing apparatus for searching for a face region in a preview mode and marking the detected face region on a display image, the method including steps (a) and (b). .

In the step (a), if the rate of change of the focus value of the current image or the rate of change of the luminance value with respect to the previous image is larger than the set ratio, the face region is searched using all the image-data of the current image.

In step (b), if at least one face area exists in step (a), the at least one face area is marked on the display image.

According to the control method of the digital image processing apparatus of the present invention, in the step (a), the position of the face region (s) in the previous image and the position of the face region (s) in the current image are the same. Since the face area is searched only when the number is small, the number of face area searches can be efficiently reduced in the preview mode. In other words, the overall processing speed can be improved efficiently.

If the rate of change of the focus value of the current image or the rate of change of the luminance value with respect to the previous image is not greater than the set ratio in the step (a), the position and the current image of the face area (s) in the previous image This is because the location of the face area (s) in E is likely to be the same.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Timer lamp 11, flash 12, shutter release button 13, and ASR (Advanced Shake) 13 are provided on the front and the top of the digital camera 1 as a digital image processing apparatus according to the present invention, Reduction button 16, a power button 17, a lens unit 20, a microphone MIC, and a speaker SP.

The self-timer lamp 11 operates during the set time from when the shutter release button 13 is depressed to when it starts capturing an image in the self-timer mode. In addition, the self-timer lamp 11 generates auxiliary light according to the user's selection.

The ASR mode button 16 is used to compensate for camera shake. The ASR mode button 16 is also used as a lock button. For example, when the ASR mode button 16 is pressed for less than one second, the image stabilization function is performed. When the ASR mode button 16 is pressed for more than one second, the lock function in the playback mode is performed.

The shutter release button 13 has a two-stage structure. That is, when the user operates the wide angle-zoom button 39 _W and the tele-zoom button 39 _T and then presses the shutter release button 13 by one step, the SH1 signal from the shutter release button 13 is turned on ), And the SH2 signal from the shutter release button 13 is turned on when the second stage is pressed. In the still image shooting mode and the moving image shooting mode, the image is captured after the SH2 signal is turned on. In the continuous shooting mode, the image is continuously captured while the SH1 signal is turned on.

2, a digital camera 1 according to the present invention includes function buttons 15, a camera-state lamp 22, a special-effect button 23, a camera strap hook 24, There are a connection section 25, a display panel 35, a +/- button 36, a zoom / 9 division / volume button 39, a reproduction / printer button 42 and a mode button 43.

The function buttons 15 are used by the user to perform specific functions of the digital camera 1 and are used as direction-movement buttons of the active cursor in the menu screen of the display panel 35, And is used to switch between the file and the recording medium.

The camera-state lamp 22 is used to show various operational states of the camera. The special-effect button 23 is used to set special effects on the image to be photographed. The +/- button 36 is used to adjust the shutter speed for night view shooting and the like.

The zoom / 9split / volume button 39 is used to perform a zooming operation in shooting or playback mode, to display nine pictures in a single playback mode, or to adjust the volume of audio. Used for

The reproduction / printer button 42 is used for switching between the reproduction mode and the preview mode or for direct output to the printer.

The mode button 43 is used to select a PMP (Portable Media Player) mode or various shooting modes.

Fig. 3 shows the overall configuration of the digital camera 1 of Fig. Referring to Figs. 1 to 3, the overall configuration and operation of the digital camera 1 of Fig. 1 will be described as follows.

An optical system (OPS) including a lens unit and a filter unit optically processes light from a subject. The lens portion of the optical system OPS includes a zoom lens, a focus lens, and a compensation lens. When the user presses the zoom / 9 division / volume button 39 included in the user input unit INP in the preview mode or the moving image shooting mode, a corresponding signal is input to the micro controller 512. Accordingly, as the micro controller 512 controls the lens driving unit 510, the zoom motor M _Z is driven to move the zoom lens.

Meanwhile, in the automatic focusing mode, the main controller built in the digital camera processor 507 controls the driving unit 510 through the micro controller 512 to drive the focus motor M _F. Thus, the focus lens is moved. In this process, the number of drive steps of the focus motor M _F , for example, the position of the focus lens where the high frequency component of the image signal is the largest, is set. Reference symbol M _A denotes a motor for driving an aperture (not shown).

A photoelectric conversion unit OEC of a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) converts light from the optical system OPS into an electrical analog signal. Here, the digital camera processor 507 controls the timing circuit 502 to control the operations of the photoelectric conversion unit (OEC) and the analog-digital conversion unit 501. A CDS-ADC (Correlation Double Sampler and Analog-to-Digital Converter) element 501 as an analog-to-digital conversion section processes an analog signal from the photoelectric conversion section OEC to remove high frequency noise, And then converted into a digital signal.

The real-time clock 503 provides time information to the digital camera processor 507. The digital camera processor 507 processes digital signals from the CDS-ADC device 501 to generate digital image signals classified into luminance and chrominance signals.

The light-emitting section (LAMP) driven by the microcontroller 512 according to the control signals from the digital camera processor 507 incorporating the main controller includes a self-timer lamp 11 and a camera-state lamp 22 .

The user input unit INP includes a shutter release button 13, function buttons 15, an ASR mode button 16, a power button 17, a special-effect button 23, a +/- button 36, Zoom / 9 split / volume buttons 39, playback / printer buttons 42, mode buttons 43, and the like are included.

A digital image signal from the digital camera processor 507 is temporarily stored in a dynamic random access memory (DRAM) 504. An algorithm necessary for the operation of the digital camera processor 507 is stored in an EEPROM (Electrically Erasable and Programmable Read Only Memory) 505. In the memory card interface (MCI) 506, the user's memory card is detached. In the flash memory (FM), setting data necessary for the operation of the digital camera processor 507 is stored. In the memory card interface 506, a plurality of memory cards are detached and removed as user's recording media.

The digital video signal from the digital camera processor 507 is input to the LCD driver 514, whereby an image is displayed on the display panel 35.

The digital video signal from the digital camera processor 507 is transmitted through the USB (Universal Serial Bus) connection unit 21a or the RS232C interface 508 and the connection unit 21b through the serial communication in the interface unit 21 And can be transmitted as a video signal through the video filter 509 and the video output unit 21c.

The audio processor 513 outputs the audio signal from the microphone MIC to the digital camera processor 507 or the speaker SP and outputs the audio signal from the digital camera processor 507 to the speaker SP.

On the other hand, the micro controller 512 controls the operation of the flash controller 511 in accordance with the signal from the flash-light amount sensor 19 to drive the flash 12. [

FIG. 4 shows a main algorithm of the digital camera processor 507 of FIG. A main algorithm of the digital camera processor 507 of FIG. 3 will be described with reference to FIGS. 1 to 4 as follows.

When operation power is applied to the digital camera 1, the digital camera processor 507 executes initialization (step S1). When this initialization step S1 is executed, the digital camera processor 507 performs a preview mode (step S2). In this preview mode, the input image is displayed on the display panel 35.

Next, when the SH1 signal as the first stage signal from the shutter release button 13 is in the On state (step S3), the digital camera processor 507 performs the shooting mode (step S4).

Next, when signals corresponding to the setting mode are input from the input signals from the user input unit INP (step S5), a setting mode for setting the operating conditions according to the input signals from the user input unit INP is performed (Step S6).

On the other hand, if no termination signal is generated (step S7), the digital camera processor 507 determines whether a conversion signal to another arbitrary mode has been generated (step S8).

If no conversion signal to another mode is generated in step S8, the digital camera processor 507 repeats step S2 and the following steps. If a conversion signal to any other mode, for example, a playback mode, is generated in step S8, the digital camera processor 507 repeatedly performs the step S2 and subsequent steps after performing the mode (step S9). do.

FIG. 5 is an example of a face marking algorithm that is repeatedly performed in units of frames in the preview mode performing step S2 of FIG. 4 when the face marking mode is set in the performing setting mode step S6 of FIG. 4. Shows. FIG. 6 illustrates the pixel structure of the unit frame 601 to explain the focus value or the luminance value of the image in steps S51 and S55 of FIG. 5. FIG. 7 illustrates a pixel structure of the setting partial region 602 in the unit frame of FIG. 6. 6 and 7, reference numeral R denotes a red pixel, G denotes a green pixel, and B denotes a blue pixel, respectively.

5 to 7, an example of the face marking algorithm repeatedly performed in units of frames in the preview mode performing step S2 of FIG. 4 will be described.

First, the digital camera processor 507 determines that the rate of change (D _AF ) or the rate of change (D _Y ) of the focus value of the image of the current frame with respect to the image of the previous frame is the set ratio (D _TH1 , D _TH2 ). If larger (steps S51 and S55), the face region is searched using the entire image-data of the image of the current frame (step S52).

In the face area searched (step S52), well-known face recognition algorithms are used. As described above, face recognition algorithms include algorithms using symmetry of the face, algorithms using hair color and face color, and algorithms using contours of the face.

If at least one face area exists in the search step S52 (step S53), the digital camera processor 507 marks the corresponding face area (s) on the display image (step S54).

If in step S51 and S55 the change rate D _AF or the change rate D _Y of the focus value of the image of the current frame with respect to the image of the previous frame is not greater than the set ratios D _TH1 , D _TH2 . The position of the face area (s) in the image of the previous frame and the position of the face area (s) in the image of the current frame are likely to be the same.

Therefore, the face area is searched only for the image of the current frame in which the position of the face area (s) in the image of the previous frame and the position of the face area (s) in the image of the current frame are less likely to be the same. In the preview mode (S2 of FIG. 4), the number of face area searches can be efficiently reduced. In other words, the overall processing speed can be improved efficiently.

Additionally, in steps S51 and S55, the change ratio D _AF and the change ratio D _Y of the focus value of the image of the current frame relative to the image of the previous frame are greater than the set ratios D _TH1 , D _TH2 . Otherwise, the digital camera processor 507 may use the entire image-data recently to search for the facial region, that is, the elapsed time T _PA from the time when step S52 was recently performed to the current time, for example, Measure the number of elapsed frames.

Herein, if the elapsed time T _PA reaches the set time T _SET , for example, the number of set frames (step S56), the digital camera processor 507 uses the entire image-data of the image of the current frame. The face area is searched (step S52).

If at least one face area exists in the search step S52 (step S53), the digital camera processor 507 marks the corresponding face area (s) on the display image (step S54).

As described above, the steps S51 to S56 are repeatedly performed in units of frames.

In the above steps S51 and S55, the change ratio D _AF and the change ratio D _Y of the focus value of the image of the current frame with respect to the image of the previous frame are set in the unit frame 601 of FIG. 6. It is measured only for the partial region (602 of FIG. 6). By such an effective measurement method, the processing speed of the digital camera processor 507 may be further improved.

Referring to FIG. 7, in the setting partial area 602, the first unit measuring area 701 is G ₁₂ , R ₁₃ , G ₁₄ , B ₂₂ , G ₂₃ , B ₂₄ , G ₃₂ , R ₃₃ , and G ₃₄ . When set, the first focus value F ₇₀₁ in the first unit measurement area ₇₀₁ is measured by Equation 1 below.

In Equation 1, D _G23 is a gray value of the pixel G ₂₃ , D _G12 is a gray value of the pixel G ₁₂ , D _G14 is a gray value of the pixel G ₁₄ , D _G32 is a gray value of the pixel G ₃₂ , And D _G34 indicate the gray level values of the pixel G ₃₄ , respectively.

Similarly, when the second unit measurement area is set to G ₁₄ , R ₁₅ , G ₁₆ , B ₂₄ , G ₂₅ , B ₂₆ , G ₃₄ , R ₃₅ , and G ₃₆ , the second focus in the second unit measurement area The value F ₇₀₂ is measured by Equation 2 below.

The sum of the focus values of all the unit measurement areas as described above becomes the focus value in the setting partial area 602, which is regarded as the focus value FV in the corresponding frame 601.

When the focus value in the current frame is FV _i and the focus value in the previous frame is FV _i-1 , the rate of change (D _AF ) of the focus value of the image of the current frame with respect to the image of the previous frame is expressed by the following equation. Obtained by 3.

On the other hand, in obtaining the luminance value in the setting partial region 602, the second grayscale values are obtained by multiplying the grayscale values of each pixel by the weight for each color, and then the sum of all of the second grayscale values is obtained. The luminance value in the setting partial region 602, that is, the luminance value Y _i in the frame 601 is considered. In obtaining the second gray scale values, for example, the gray value of the red pixel R or the blue pixel B is multiplied by 0.2, and the gray value of the green pixel G is multiplied by 0.6.

When the luminance value in the current frame is Y _i and the luminance value in the previous frame is Y _{i -1} , the ratio of change (D _Y ) of the luminance value of the image of the current frame to the image of the previous frame is expressed by the following equation. Obtained by 4.

8 illustrates another example of a face marking algorithm that is repeatedly performed in units of frames in the preview mode performing step S2 of FIG. 4 when the face marking mode is set in the performing setting mode step S6 of FIG. 4. Shows. The algorithm is described with reference to FIG. 8 as follows.

First, the digital camera processor 507 of FIG. 5 determines whether there is at least one face region in the previous frame (step S81).

If at least one face area exists in step S81, the digital camera processor 507 sets the rate of change (D _AF ) or the rate of change (D _Y ) of the focus value of the image of the current frame to the image of the previous frame. It is determined whether it is greater than the ratio D _TH1 , D _TH2 (steps S82 and S86). Here, the change ratio D _AF or the change ratio D _Y of the focus value of the image of the current frame to the image of the previous frame is obtained as described above with reference to FIGS. 6 and 7. That is, the measurement is made only for the set partial area (602 in FIG. 6) in the unit frame (601 in FIG. 6).

In steps S82 and S86, if the change ratio D _AF of the focus value or the change ratio D _Y of the luminance value is larger than the set ratios D _TH1 and D _TH2 , the digital camera processor 507 may display the entire image of the current image. The face area is searched using the data (step S83).

If at least one face area exists in step S83 (step S84), the face area (s) are marked on the display image (step S85).

If at least one face region does not exist in step S81, the elapsed time (T _PA ) from the time point of recently searching for the face region to the current time point using the entire image-data is measured, for example, the number of elapsed frames is measured. . Here, if the elapsed time (T _PA ) has reached the set time (T _SET ), for example, the number of set frames (step S87), the digital camera processor 507 uses the entire image-data of the current image to face it. The area is searched (step S83). If at least one face area exists in step S83 (step S84), the face area (s) are marked on the display image (step S85).

If the elapsed time T _PA has not reached the set time T _SET in step S87, the digital camera processor 507 searches for the face area using the reduced image-data of the image of the current frame (step S88). ). In this case, the reduced image data refers to data whose resolution is lower than that of the entire image data. If at least one face area exists in step S88 (step S84), the digital camera processor 507 marks the face area (s) on the display image (step S85).

Steps S81 to S88 are repeatedly performed in units of frames.

As described above, according to the control method of the digital image processing apparatus according to the present invention, when the position of the face region (s) in the previous image and the position of the face region (s) in the current image are less likely to be the same. Since only the face area is searched, the number of times of face area search can be efficiently reduced in the preview mode. In other words, the overall processing speed can be improved efficiently.

If the rate of change of the focus value of the current image or the rate of change of the luminance value with respect to the previous image is not larger than the set ratio, the position of the face region (s) in the previous image and the face region (s) of the current image This is because the location is likely to be the same.

The present invention is not limited to the above embodiments, but may be modified and improved by those skilled in the art within the spirit and scope of the invention as defined in the claims.

Claims (10)

A control method of a digital image processing apparatus for searching for a face region in a preview mode and marking the detected face region on a display image, (a) searching for a face region using all image-data of the current image when the rate of change of the focus value of the current image or the rate of change of the luminance value of the previous image is larger than a preset ratio; And and (b) marking the at least one face region on a display image if there is at least one face region in the step (a). 2. The method of claim 1, wherein in step (a) A control method of a digital image processing apparatus, wherein a rate of change of a focus value of a current image and a rate of change of a luminance value of a previous image are measured only for a set partial region of an image. 3. The method of claim 2, (c) If the rate of change of the focus value of the current image and the rate of change of the luminance value with respect to the previous image in step (a) are not greater than the set ratio, from the time of recently searching for the face region using the entire image-data; Measuring an elapsed time to a current time; And (d) if the elapsed time reaches a set time in step (c), searching for a face region using all image-data of the current image; And (e) if at least one face region exists in step (d), marking the at least one face region on a display image. The method of claim 3, And controlling the steps (a) to (e) by frame unit. The method of claim 4, wherein in steps (c) and (d), And the elapsed time is the number of elapsed frames and the set time is the number of set frames. A control method of a digital image processing apparatus for searching for a face region in a preview mode and marking the detected face region on a display image, (a) determining whether at least one face area exists in a previous image; (b) if there is at least one face region in step (a), determining whether a change rate of a focus value or a change rate of a luminance value of a current image is greater than a set ratio; (c) if the rate of change of the focus value or the rate of change of the luminance value is larger than a preset rate in step (b), searching for a face region using all image-data of the current image; (d) marking at least one face area on a display image if at least one face area exists in step (c); (e) if at least one face region does not exist in step (a), measuring an elapsed time from a time point of recently searching for a face region using the entire image-data to a current time point; And (f) searching for a face region using all image-data of the current image when the elapsed time reaches a set time in step (e); And and (g) marking the at least one face region on a display image if there is at least one face region in the step (f). The method of claim 6, (h) searching for a face region using the reduced image-data of the current image if the elapsed time does not reach the set time in step (e); And (i) if at least one face region exists in step (h), marking the at least one face region on a display image. The method of claim 7, wherein in step (b), A control method of a digital image processing apparatus, wherein a rate of change of a focus value of a current image and a rate of change of a luminance value of a previous image are measured only for a set partial region of an image. 9. The method of claim 8, And controlling the steps (a) to (i) repeatedly in units of frames. The method of claim 9, wherein in steps (e) and (f): And the elapsed time is the number of elapsed frames and the set time is the number of elapsed frames.

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