KR20150040559A - Apparatus for Improving Image Quality and Computer-Readable Recording Medium with Program Therefor - Google Patents

Abstract

Provided is an apparatus for improving an image quality based on an interesting area and a computer-readable recording medium therefor. The apparatus comprises the steps of: obtaining a recorded image; dividing the image into a plurality of blocks; calculating a degree of movement of a target block by the divided blocks; generating one or more block groups by grouping similar blocks according to the degree of the movement which is calculated by the blocks; and revising a block pixel value for a different block group by using a different method for a quality improvement.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality improvement apparatus based on a region of interest and a computer readable recording medium therefor.

The present embodiment relates to a picture quality improvement apparatus based on a region of interest and a computer-readable recording medium therefor.

It should be noted that the following description merely provides background information related to the present embodiment and does not constitute the prior art.

Camera sensors that acquire images are sensitive to environmental changes such as lighting and weather, and may degrade the image quality to such an extent that it is difficult to identify images in a low-light and bad weather environment. Therefore, in this environment, image quality improvement technology is a very important factor and it is indispensable for a video surveillance camera installed and operated outdoors.

Contrast enhancement, sharpness enhancement, and noise reduction techniques are commonly used to improve images with degraded image quality.

These image enhancement techniques are classified into a global method for improving the image quality of an entire area of the image and a local method for improving the image quality by dividing the image into a plurality of blocks and processing each block independently. .

In the case of the global technique, the algorithm is simplified and the processing speed is fast by improving the image quality by uniformizing the entire image, but the image quality improvement effect is small. On the other hand, in the case of the regional technique, The improvement is more effective than the global technique, but the image processing algorithm is complicated and the processing speed is slowed down.

The embodiment of the present invention has a main purpose of improving the image quality by improving the image quality at the center of the area of interest compared to the existing method by applying different image quality improvement methods to the foreground and background areas in the photographed image and improving the speed by reducing the amount of computation .

According to an embodiment of the present invention, there is provided an image processing apparatus including an image acquiring unit acquiring a photographed image; A block dividing unit dividing the image into a plurality of blocks; A motion calculating unit for calculating the degree of motion of the corresponding block for each of the divided blocks; A block grouping unit for grouping similar blocks according to the degree of motion calculated for each block to generate at least one block group; And an image quality enhancement unit for correcting pixel values of the block by different image quality improvement methods for different block groups.

Here, the image quality improving apparatus may further include a threshold value setting unit that receives an input for setting the threshold value.

The motion calculation unit may calculate a motion vector calculated by estimating motion in the previous frame as the motion degree.

In addition, the block grouping unit may generate the block group among the blocks whose difference in degree of motion between the blocks is equal to or less than a threshold value, and the block group in which the motion degree is larger than the preset size, And a block group whose motion level is equal to or less than a predetermined size is set as a background group.

Wherein the image quality enhancement unit performs at least one of histogram adjustment for improving the contrast ratio and gamma adjustment for improving edge sharpness for each block for the ROI group, And at least one of the boundary of the ROI group and the background group may be subjected to a blending process.

According to another embodiment of the present invention, there is provided a computer-readable storage medium storing a program for causing a computer to execute: Dividing the image into blocks of preset sizes; Calculating a degree of motion of the corresponding block for each of the divided blocks; Generating at least one block group by grouping similar blocks according to the degree of motion calculated for each block; And correcting a pixel value of a block by different image quality improving methods for different block groups. The present invention also provides a computer-readable recording medium having recorded thereon a program for performing a correction of a pixel value of a block.

The embodiment of the present invention can maximize the improvement effect by using the local image quality improvement technique and improve the speed by reducing the unnecessary operation by using the global image quality improvement technique in the background part, It is effective.

In addition, it is possible to simultaneously improve the improvement effect and the speed compared to the conventional method by improving the image quality based on meaningful information based on the viewer of the image.

1 is a block diagram schematically showing an image quality improving apparatus 100 according to an embodiment of the present invention.
2 is a diagram showing the result of grouping blocks of an image.
3 is a flowchart schematically illustrating an image quality improvement method according to an embodiment of the present invention.

Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing an image quality improving apparatus 100 according to an embodiment of the present invention.

1, the image quality improvement apparatus 100 according to an exemplary embodiment of the present invention includes an image acquisition unit 110, an image storage unit 120, a block division unit 130, a motion calculation unit 140, A block grouping unit 150, a threshold setting unit 160, and an image quality improving unit 170. The image quality improving apparatus 100 according to an exemplary embodiment of the present invention includes an image obtaining unit 110, an image storing unit 120, a block dividing unit 130, a motion calculating unit 140, a block grouping unit 150, The threshold value setting unit 160 and the image quality improving unit 170. However, the present invention is not limited thereto, and some of the components may be omitted or may be implemented by including other components.

The image acquiring unit 110 acquires an image taken by the image photographing apparatus from an image photographing apparatus (not shown) interlocked with the image quality improving apparatus 100. That is, the image acquiring unit 110 acquires the photographed image of a predetermined area to be photographed from the image photographing apparatus installed at a specific point. Here, the photographed image may be a single frame or an image including a plurality of frames. On the other hand, the image acquisition unit 110 may receive the image photographed from the image photographing apparatus in real time, but may acquire the stored image in the image photographing apparatus by a predetermined period. In this embodiment, the image acquisition unit 110 specifies that the image acquisition unit 110 acquires an image photographed from the image photographing apparatus. However, the present invention is not limited to this, and the image quality improvement apparatus 100 may include a photographing module for photographing the image, It is possible to directly acquire the photographed image by using the corresponding photographing module.

In addition, in acquiring the photographed image, the image source may be directly received, but the image may be received in a form in which the photographed image is encoded.

The image storage unit 120 stores the image acquired by the image acquisition unit 110 and stores the captured image in the process of improving the image quality. That is, the image storage unit 120 stores the photographed image, and provides the stored image when the motion calculation unit 140 or the like requests the photographed image.

The block dividing unit 130 divides the acquired image into a plurality of blocks. The block dividing unit 130 divides an image into blocks of a predetermined size or various sizes before dividing the region of interest of the input image. On the other hand, the block may be divided into a predetermined size by dividing the block in the image, but a motion vector included in the image information transmitted for each divided block may be used as the degree of motion.

In general, in the H.264 / AVC standard for image coding, the motion of the moving image in the moving image coding process is divided into small blocks such as 4 × 4, 4 × 8, 8 × 4, and 8 × 8, In the case of a simple area with little motion, it is divided into relatively large blocks such as 8 × 8, 8 × 16, 16 × 8, and 16 × 16. The degree of motion between image frames can be measured by using blocks having variable sizes of various types as described above.

The motion calculation unit 140 estimates the motion for each of the divided blocks and calculates the degree of motion of the corresponding block. The motion calculation unit 140 receives a previous frame stored in the image storage unit 120 from the image storage unit 120 and calculates a motion vector for each block in the current frame, A motion estimation (Motion Estimation) for finding the smallest SAD (Sum of Difference) is performed, and a motion vector is calculated according to the result of the motion estimation. Here, the motion vector calculated for each divided block can be used as the degree of motion. Here, the method of calculating a motion vector through motion estimation is a well-known matter, and thus a detailed description thereof will be omitted.

The motion vector may be extracted directly from the image through motion estimation, but may be transmitted with the motion vector included in the transmitted image information when the transmitted image is coded and transmitted. In this case, the motion calculating unit 140 may calculate the degree of motion of each block using the motion vector included in the transmitted image information.

The block grouping unit 150 groups similar blocks according to the degree of motion calculated for each block, for example, a motion vector to generate one or more block groups.

2 is a diagram showing the result of grouping blocks of an image.

FIG. 2 shows a result obtained by dividing an image into blocks of various sizes and then grouping the motion vectors according to the blocks.

As can be seen from the image of FIG. 2, the blocks including the car in the image have similar degrees of motion when compared with the previous frame. That is, the blocks in the area A show similar motion when compared with the previous frame. That is, when a motion vector is used as a measure indicating the degree of motion, the blocks in the area A have similar motion vectors. Therefore, the blocks of the area A can be grouped into one block group as a similar block.

Similarly to the area A, in the case of the area B, the blocks of the area B can be grouped into one block group when the corresponding blocks have the similar size of motion vectors.

The reference of the motion vector size for performing the block grouping may be changed according to the embodiment, and may be adjusted according to the image characteristics.

The threshold value setting unit 160 receives an input from a user using a keyboard or other input device to set a threshold value which is a maximum size difference between motion vectors for grouping motion vectors. In addition, the threshold setting unit 160 may set a minimum motion vector size to group blocks having a motion vector value equal to or greater than a predetermined size.

The reference block group and the background block group may be grouped according to whether the motion vector of the block has a set minimum motion vector size or more.

In this manner, the block grouping unit 150 generates a foreground block group among blocks having a size of a motion vector equal to or larger than a preset size and a size difference between motion vectors of blocks is equal to or less than a threshold value, To generate a background block group.

Therefore, a block group having a relatively large motion vector and a relatively large motion vector is set as a foreground group, that is, a region of interest, and blocks having a motion vector of less than a predetermined size are set as a background group.

The image quality improving unit 170 corrects the pixel values of the blocks by different image quality improving methods for different block groups.

The picture quality improvement unit 170 performs picture quality improvement based on the block characteristics. That is, the global picture quality improvement technique is applied to the entire block group for the block groups classified into the background according to the degree of motion, and the local picture quality improvement technique is applied to each block for the block groups classified into the foreground.

The image quality improvement unit 170 improves the contrast ratio by uniformly distributing the luminance through the light source estimation for all the blocks globally, without distinction of the blocks for the background block group, and enhances the sharpness of the edges . Here, both the light source estimation and the edge analysis for equalizing the distribution of the luminance may be performed, but either one of the two methods may be performed.

Light has a distinctive color called color temperature, in which Kelvin (K) is used. Generally, human vision ability automatically adjusts the sensitivity to color, so even if light of any color temperature is illuminated, human perception of color is very slight. However, since an image pick-up device such as a camera or a camcorder senses the color reflecting the color temperature as it is, when the light source is changed, the images taken by the image pick-up device have different colors.

For example, sunlight on a sunny day has a high color temperature, so images taken by an image pickup device are blue overall, while sunlight at sunset or sunset time has a low color temperature, It becomes red. To solve this problem, white balance is performed after light source estimation. This serves to correct the distortion of the image tones when the photographed image is deflected in at least one of the red (R), green (G), and blue (B) components according to the color temperature.

Here, the method of estimating the light source and the method of balancing the white are known matters, so that detailed description will be omitted.

The edge analysis can be performed by various methods such as detecting the edge components in the image and analyzing the edge components to adjust the sharpness of the horizontal component edge or the vertical component edge. Since the edge sharpness adjustment through the edge analysis is a known matter, a further detailed description will be omitted.

In addition, the picture quality improving unit 170 improves the contrast ratio by adjusting the histogram independently for each block in the foreground block group and improves the sharpness of the edge in the block through gamma adjustment. Here, both the histogram adjustment for improving the contrast ratio and the gamma adjustment for improving the edge sharpness may be performed, but either one of the two methods may be performed.

The histogram adjustment method is a method of re-modeling the histogram so as to maximize the contrast ratio visually by analyzing the histogram of the block.

There are a variety of methods for controlling the contrast ratio through the adjustment of the histogram, and these are known matters and will not be described in detail.

The gamma correction operation is a method for improving the sharpness of the edge by maintaining a linear relationship between the optical signal input to the camera and the optical signal output from the display device. The detailed description will be omitted.

The image quality improving unit 170 performs a blending process on the boundary between the foreground group and the background group to remove the discontinuity between the foreground and the background so that the image can be seen as natural.

When image processing is performed for each block group as described above, the color information may be abruptly changed at the boundary line between two block groups, so unnatural lines can be seen. Therefore, images can be smoothly transferred between the two block groups through color blending . Meanwhile, since the details of the blending method are well known, a detailed description thereof will be omitted.

As the use of digital imaging equipment increases rapidly, image degradation occurs in various environments. Typically, outdoor CCTV cameras may degrade image quality due to bad weather such as fog, sea, smoke, etc., and may degrade the picture quality especially for illumination changes such as low light and backlight.

Since the degradation of the image degrades the image and degrades the sharpness, the correction technique using the image enhancement technique is essential to the user.

3 is a flowchart schematically illustrating an image quality improvement method according to an embodiment of the present invention.

As shown in FIG. 3, the image quality improvement method according to an exemplary embodiment of the present invention includes a process of acquiring a photographed image (S510), a process of dividing an image into a plurality of blocks (S520) A step S540 of grouping similar blocks according to the degree of motion calculated for each block to generate one or more block groups in operation S540, (Step S550).

In the process of acquiring an image (S510), an image photographed by the image photographing device is acquired from a photographing device (not shown). That is, the image acquiring unit 110 acquires the photographed image of a predetermined area to be photographed from the image photographing apparatus installed at a specific point.

In the process of dividing an image into a plurality of blocks (S520), the acquired image is divided into blocks of a preset size, for example. However, the predetermined size does not necessarily mean the same size. As described above, information about the size at which the block is divided into the transmitted image may be transmitted.

In step S530 of calculating the degree of motion of the block, motion is estimated for each of the divided blocks to calculate the degree of motion of the corresponding block. Here, a motion vector included in the image information transmitted for each of the divided blocks may be used as the degree of motion.

In this manner, when a size of a motion vector is equal to or larger than a preset size, a foreground block group is generated among blocks having a size difference of motion vectors between blocks equal to or less than a threshold value, and a background block group is generated when the size of the motion vector is equal to or less than a preset size .

In the process of correcting the pixel value of the block (S550), the pixel value of the block is corrected by different image quality improving methods for different block groups. That is, a global picture quality improvement technique is applied to the block groups classified into the background group according to the degree of motion of the block, and a local picture quality improvement technique is applied to the block groups classified into the foreground group.

For the background block group, uniform distribution of luminance is uniformed through light source estimation globally without distinction of blocks, and contrast ratio is improved and edge sharpness is improved by edge analysis.

Also, for the foreground block group, the contrast ratio is improved by adjusting the histogram independently for each block, and the sharpness of the edge in the block is improved by gamma adjustment.

After the pixel value is corrected, the boundary between the foreground group and the background group is subjected to a blending process to remove the discontinuity between the foreground and the background so that the image can be seen as natural.

3, steps S310 to S350 are sequentially executed. However, the present invention is not limited thereto. That is, FIG. 3 is not limited to the time series order, since it would be applicable to changing or executing the steps described in FIG. 3 or executing one or more steps in parallel.

As described above, the method for performing the image quality improvement described in FIG. 3 can be implemented by a program and recorded on a computer-readable recording medium. A program for implementing the image quality improvement according to the present embodiment is recorded and a computer-readable recording medium includes all kinds of recording devices for storing data that can be read by a computer system. Examples of such computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, etc., and also implemented in the form of a carrier wave (e.g., transmission over the Internet) . The computer readable recording medium may also be distributed over a networked computer system so that computer readable code is stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present embodiment can be easily inferred by programmers in the technical field to which the present embodiment belongs.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: Picture quality improvement device 110:
120: image storage unit 130: block division unit
140: motion calculation unit 150: block grouping unit
160: threshold value setting unit 170: image quality improvement unit

Claims (11)

An image acquiring unit acquiring a photographed image;
A block dividing unit dividing the image into blocks of predetermined sizes;
A motion calculating unit for calculating the degree of motion of the corresponding block for each of the divided blocks;
A block grouping unit for grouping similar blocks according to the degree of motion calculated for each block to generate at least one block group; And
An image quality improvement unit that applies different image quality improvement methods to different block groups,
And an image quality enhancement device for enhancing image quality. The method according to claim 1,
Wherein the motion calculating unit calculates a motion vector calculated by estimating motion in a previous frame as the motion degree. 3. The method of claim 2,
Wherein the block grouping unit generates the block group among the blocks whose difference in degree of motion between the blocks is equal to or less than a threshold value. The image quality improvement apparatus according to claim 3,
Further comprising: a threshold value setting unit configured to set a threshold value for receiving an input for setting the threshold value. The apparatus of claim 1, wherein the block grouping unit comprises:
Wherein the at least one block group is set as a region of interest group in which the motion level is greater than a predetermined size and the block group in which the motion level is less than a preset level is set as a background group. 6. The image processing apparatus according to claim 5,
Wherein at least one of histogram adjustment for improving the contrast ratio and gamma adjustment for improving edge sharpness is performed for each of the blocks in the ROI. 6. The image processing apparatus according to claim 5,
Wherein at least one of light source estimation and edge analysis is performed on the background group to equalize the distribution of brightness globally. 6. The image processing apparatus according to claim 5,
Wherein the boundary region between the ROI group and the ROI group is subjected to a blending process. On the computer,
Acquiring a photographed image;
Dividing the image into blocks of preset sizes;
Calculating a degree of motion of the corresponding block for each of the divided blocks;
Generating at least one block group by grouping similar blocks according to the degree of motion calculated for each block; And
A process of correcting a pixel value of a block by different image quality improving methods for different block groups
Readable recording medium having recorded thereon a program for executing the program. 10. The method of claim 9,
Wherein the generating the at least one block group comprises:
Wherein the block group having the motion level greater than the predefined size is set as the ROI group and the block group having the motion level equal to or less than the predefined size is set as the background group as the at least one block group. Readable recording medium. 11. The method of claim 10,
Performing at least one of histogram adjustment and gamma adjustment on each block for the ROI group,
Wherein at least one of light source estimation for equalizing the luminance distribution and edge analysis for improving the edge sharpness is performed for the background group.

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