KR101448539B1 - Image processing method and apparatus, and digital photographing apparatus using thereof - Google Patents

Abstract

The present invention relates to an image processing method and an image processing method, and an image processing method according to an embodiment of the present invention uses a gamma correction to smooth the image quality smoothly and softly on a face region and a region having similar luminance, Thereby maximizing the effect of the brightness of the whole image.

Face, gamma correction, image processing

Description

TECHNICAL FIELD The present invention relates to an image processing method and apparatus, and a digital photographing apparatus using the image processing method and apparatus.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image processing, and more particularly, to an image processing method and apparatus capable of smoothly and softly processing an image at the time of image shooting using gamma correction.

Techniques for detecting an object such as a face, for example, from an image captured by a digital camera and performing image processing in accordance with the detection result of the object, for example, adjusting the white balance according to the brightness of the subject Techniques for controlling the flash light emission according to the brightness of the subject are increasing.

Users of digital cameras, on the other hand, have a strong desire to make their pictures look more beautiful and bright. These users have the inconvenience of copying the pictures stored in the digital camera to a PC and editing the pictures by using an image editing program such as Photoshop.

Depending on the needs of these users, recently released digital cameras are equipped with a so-called "color mode" function that allows the photographed portrait to appear in full bloom. If you set up the "Color Mode" and take a picture of a person, you can get a picture of a bright and bright environment overall, especially the skin of your face is soft and soft.

However, such "bright mode" performs face detection in the photographed image, and when there is a face, the entire photographed image is subjected to blur processing. In particular, blurring is performed on the entire face of the person, so that the sharpness of the entire face is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing method and apparatus capable of smoothly and softly processing image quality of an image photographed using gamma correction.

Another object of the present invention is to provide a digital photographing apparatus using the same.

According to an aspect of the present invention, there is provided an image processing method including: detecting a predetermined face region in an input image; Performing auto exposure (AE) around the detected face area; Determining an AE target level that includes a luminance value for the detected face region; And increasing the gamma curve gamma value based on the determined luminance value of the AE target level.
And the contrast of the input image is controlled to be low.
And selecting an image processing mode for the input image.
According to another aspect of the present invention, there is provided an image processing apparatus including a face region detecting unit detecting a face region from an input image; An image signal processing unit for performing auto exposure (AE) around the detected face region and determining an AE target level including a luminance value for the detected face region; And a gamma correction controller for increasing a gamma value of the gamma curve based on the determined luminance value of the AE target level.
And the gamma correction control unit controls the contrast of the input image to be low.
And an image processing mode selection unit for selecting an image processing mode for the input image.
According to another aspect of the present invention, there is provided a recording medium on which a program for executing the method according to another embodiment of the present invention is recorded.

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According to another aspect of the present invention, there is provided a digital photographing apparatus including the image processing apparatus according to another embodiment of the present invention.

The image processing method according to an embodiment of the present invention can maximize the effect of brightness of the whole image by smoothly and softly processing the image quality on the face area and the similar luminance area instead of the entire image.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts may be omitted so as not to disturb the gist of the present invention.

In addition, terms and words used in the following description and claims should not be construed to be limited to ordinary or dictionary meanings, but are to be construed in a manner consistent with the technical idea of the present invention As well as the concept.

1 is a block diagram of a digital camera according to an embodiment of the digital photographing apparatus 100 of the present invention. Fig. 2 is a block diagram for explaining the digital signal processing unit 70 of the digital photographing apparatus.

1, the digital camera 100 includes an optical unit 10, an optical drive unit 11, an image pickup device 15, an image pickup device control unit 16, an operation unit 20, an image processing mode selection unit A program storage unit 30, a buffer storage unit 40, a data storage unit 50, a display control unit 60, a data driving unit 61, a scan driving unit 63, a display unit 65, (DSP) 70, as shown in FIG.

The optical section 10 receives an optical signal from a subject and provides it to the imaging element 13. [ The optical unit 10 may include at least one lens, such as a zoom lens for controlling the angle of view to be narrowed or widened according to the focal length, and a focus lens for focusing the subject. In addition, the optical portion 10 may further include an iris for adjusting the amount of light.

The optical driver 11 controls the position of the lens, opening and closing of the diaphragm, and the like. The focus can be adjusted by moving the position of the lens. In addition, the amount of light can be adjusted by controlling the opening and closing of the diaphragm. The optical driving unit 11 can control the optical unit 10 according to a control signal automatically generated by a video signal input in real time or a control signal manually input by an operation of a user.

The optical signal transmitted through the optical section 10 reaches the light-receiving surface of the image pickup element 15 and forms an image of the object. The image pickup element 15 is a photoelectric conversion element that converts an optical signal into an electric signal. For example, a CCD (Charge Coupled Device) or a CIS (Complementary Metal Oxide Semiconductor Image Sensor) can be used. The sensitivity of the image pickup element 15 can be adjusted by the image pickup element controller 16. The image pickup element control unit 16 can also control the image pickup element 15 in accordance with a control signal automatically generated by the video signal inputted in real time or a control signal manually inputted by the user's operation.

The operation unit 20 is a place where a control signal from the outside of a user or the like can be input. The operation unit 20 includes a shutter-release button for inputting a shutter-release signal for exposing the image pickup device 15 to light for a predetermined period of time, a power button for inputting power, There are various function buttons such as a wide angle-zoom button and a telephoto-zoom button for narrowing or narrowing the angle of view, a mode selection for character input, shooting mode, and playback mode, a white balance setting function selection, and an exposure setting function selection. The operation unit 20 may have various types of buttons as described above, but the present invention is not limited thereto. The operation unit 20 may be implemented in any form such as a keyboard, a touch pad, a touch screen, and a remote controller.

The image processing mode selection unit 21 receives the image processing mode for the image captured by the user. Here, the image processing mode is a mode for expressing a captured image beautifully and beautifully. In addition, the user can select the intensity of the image processing through the image processing mode selection unit 21, for example, strong processing, intermediate processing, and weak processing. Thus, the user can select whether to process the image of the portrait or not and the strength. The abnormal image processing mode selection unit 21 is separated from the operation unit 20. However, the function of the image processing mode selection unit 21 may be performed by the operation unit 20. [

The digital photographing apparatus 100 includes a program storage unit 30 for storing programs such as an operating system and an application system for driving the digital photographing apparatus, a buffer storage unit 40 for temporarily storing data or result data necessary for the operation, And a data storage unit 50 for storing various information necessary for the program, including an image file including a video signal.

The digital camera 100 further includes a display control unit 60 for controlling the display of the operation state of the digital camera 100 or the image information photographed by the digital camera 100, a data driver 61 And a display unit 65 for displaying a predetermined image according to a signal input from the scan driver 63, the data driver 61 and the scan driver 63. The display unit 65 may include a liquid crystal display panel (LCD), an organic light emitting display panel (OLED), and an electrophoretic display panel (EDD).

The digital camera 100 includes a DSP 70 that processes input image signals and controls each of the components according to an external input signal.

DSP 70 will be described with reference to FIG.

2, the digital signal processing unit 70 includes a control unit 71, a video signal processing unit 72, a face region detection unit 73, and a gamma correction control unit 74. Here, the digital signal processing unit and the image processing apparatus used in the claims should be interpreted in the same sense.

The control unit 71 controls the overall operation of the digital signal processing unit 70.

The image signal processing unit 72 converts the image signal input from the image pickup element 15 into a digital signal. In addition, gamma correction is performed to convert a video signal according to human vision. In addition, image signal processing such as color filter array interpolation, color matrix, color correction, and color enhancement is performed.

In addition, the video signal processing unit 72 may perform an auto white balance or an auto exposure algorithm when the function is set. Further, the size of the image data is adjusted using a scaler, and the image data is compressed to form an image file of a predetermined format. Conversely, the image file is decompressed. The video signal processing unit 72 may perform the above-described video signal processing on the video signal input in real-time in the live-view mode before photographing and the video signal input by the shutter-release signal. At this time, different video signal processing may be performed for each of the video signals.

In the preferred embodiment of the present invention, the video signal processing unit 72 converts the video signal input from the imaging device 15 into a digital signal and transmits the digital signal to the face area detection unit 73. When the face area detection unit 73 detects a predetermined face area, the AE calculation is performed on the detected face area. Therefore, the brightness of the entire image is centered on the face region.

Here, the AE calculation and function will be described. The RGB image signals of the detected face area are integrated and provided to the control unit 71, and the control unit 71 calculates the average brightness of the face area, that is, The luminance of the area is detected. Then, the control unit 71 calculates an exposure value, i.e., an EV value, suitable for photographing. Then, the control unit 71 determines the aperture value (F value) and the shutter speed of the CCD based on the EV value in accordance with a predetermined program and performs AE. Although the image signal processing unit 72 performs the AE operation described above, it may be performed in a separate AE operation unit.

The gamma correction means that the difference between the brightness of the input image and the brightness of the output image is corrected, and the gamma correction is performed on the basis of the brightness of the input image and the output brightness By adjusting the gamma curve. In the preferred embodiment of the present invention, the image signal processing unit 72 performs gamma correction by modifying the gamma curve under the control of the gamma correction control unit 74. [

The face area detection unit 73 detects the face area from the image input through the image pickup device 15. [ Specifically, the face area detection unit 72 detects an area having a feature of a face included in the face, for example, an area having flesh color, a part having a pupil, an area having a face shape, and the like as a face area.

The face area detection method or algorithm has many techniques and can be used for face detection according to the preferred embodiment of the present invention. For example, the face region can be detected using a motion vector technique, a feature point detection technique, and an AdaBoost learning technique.

The gamma correction control unit 74 outputs a control signal for causing the video signal processing unit 72 to correct the gamma curve based on the AE calculation result of the video signal processing unit 71. [ Preferably, the gamma correction control section 74 increases the brightness of the AE target portion, i.e., the face region, according to the AE calculation. This can increase the brightness of the face area by setting the gamma of the AE target portion high. If the gamma of the face part is set high, the parts in the luminance similar to the face area in the whole image become the same bright, so that the bright image as a whole can be obtained.

In addition, it is desirable that the low brightness portion maintains the existing gamma curve. This is because, when the gamma of the low brightness portion is increased, a lot of noise occurs. Preferably, the contrast of the input image is controlled to be low, and a blurred image is obtained by lowering the overall contrast, so that a smooth and bright image to be achieved in the preferred embodiment of the present invention can be obtained. Here, the high and low levels can be arbitrarily determined depending on the degree of image processing effect. That is, it is not necessary to specify the degree of high and low.

Referring to FIG. 3, a gamma curve 320 before the control of the gamma correction controller 74 and a gamma curve 310 after the control are shown. Here, the horizontal axis is the luminance value of the input image and the vertical axis is the luminance value of the output image. Reference numeral 340 denotes an AE target level according to the AE operation of the video signal processing unit 72. As shown in the figure, it can be seen that the AE target of the gamma curve 320 before the control and the AE target of the gamma curve 310 after the control are higher. Therefore, the gamma curve at the AE target level, that is, in the vicinity of the luminance value in the detected face area becomes higher, and the brightness of the face area becomes brighter. The brightness of the portion in the same luminance band as the luminance value of the face region also becomes brighter, and the brightness of the entire image is brightened.

4 is a flowchart illustrating an image processing method according to another embodiment of the present invention.

Referring to FIG. 4, in step 400, the image processing mode is selected. Here, the image processing mode refers to a process of rendering the image softer and brighter than the original image. In step 402, it is determined whether a face area is detected in the input image. If the face area is detected, the flow advances to step 404 to perform an AE operation on the detected face area. In step 406, based on the AE calculation result, the gamma curve in the AE target portion is corrected. Preferably, since the AE target portion is the face region, it is preferable to increase the brightness of this portion. In other words, by raising the gamma curve for the face portion, the surrounding regions with similar luminance with the face region are brightened equally. Therefore, it is possible to produce a bright and bright image for the entire image.

Alternatively, optionally, the gamma curve of the low luminance band remains the same as the existing gamma. This is because a lot of noise may occur when the gamma of the low luminance band is raised.

Although the embodiments described above have been described with reference to a digital camera as an example of a digital photographing apparatus to which the present invention can be applied, the present invention is not limited thereto. Those skilled in the art will appreciate that the present invention is also applicable to a camera phone, a personal digital assistant (PDA), and a portable multimedia player (PMP) with a camera function.

Meanwhile, the present invention can be embodied in computer readable code on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored.

Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like in the form of a carrier wave (for example, transmission via the Internet) . In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily deduced by programmers skilled in the art to which the present invention belongs.

The present invention has been described above with reference to preferred embodiments. It will be understood by those skilled in the art that the present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

1 is a schematic block diagram of a digital photographing apparatus 100 according to an embodiment of the present invention.

2 is a block diagram of the digital signal processing unit 70 shown in FIG.

3 is a diagram for explaining gamma curve correction in another embodiment of the present invention.

4 is a flowchart illustrating an image processing method according to another embodiment of the present invention.

Description of the Related Art

21: image processing mode selection unit 70: digital signal processing unit

71: control unit 72: video signal processing unit

73: Face area searching unit 74: Gamma correction control unit

Claims (13)

Detecting a predetermined face area in an input image; Performing auto exposure (AE) around the detected face area; Determining an AE target level that includes a luminance value for the detected face region; And And increasing a gamma value of the gamma curve based on the determined luminance value of the AE target level. delete delete The method according to claim 1, Wherein the contrast of the input image is controlled to be low. The method according to claim 1, Further comprising the step of selecting an image processing mode for the input image. delete 6. A recording medium on which a program for causing a computer to execute the method according to any one of claims 1 to 5 is recorded. A face area detecting unit for detecting a predetermined face area in the input image; An image signal processing unit for performing auto exposure (AE) around the detected face region and determining an AE target level including a luminance value for the detected face region; And And a gamma correction controller for increasing a gamma value of the gamma curve based on the determined luminance value of the AE target level. delete delete 9. The method of claim 8, Wherein the gamma correction control unit includes: And controls the contrast of the input image to be low. 9. The method of claim 8, Further comprising an image processing mode selection unit for selecting an image processing mode for the input image. A digital photographing apparatus comprising the image processing apparatus according to any one of claims 8 to 11.

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