KR20110054145A - Apparatus and method for compensating color of image, and the recording media storing the program performing the said method - Google Patents

Abstract

PURPOSE: An apparatus and method for compensating a color of an image, and a recording media storing the program performing the method are provided to prevent the color movement occurring in a color image sequence. CONSTITUTION: An apparatus for compensating a color of an image comprises: a region extraction unit(120) for extracting a colorless region from an input image by comparing an input image with a reference image; a first compensating value estimating unit(130) for estimating a first compensating value for each color channel; a second compensating value estimating unit(140) for estimating a second compensating value for each color channel; and a color compensating unit(150) for compensating a color in an input image based on a gain value.

Description

Apparatus and method for compensating color of image, and the recording media storing the program performing the said method}

The present invention relates to an apparatus for correcting image color, a method thereof, and a recording medium having recorded thereon a program for implementing the method. More particularly, the present invention relates to an image color correction apparatus and method for correcting color imbalance in addition to maintaining color homeostasis, and a recording medium on which a program for implementing the method is recorded.

When an image is acquired using a digital imaging device, not only the internal factors of the device but also the external environment are affected. The biggest influence among the external environment is a light source that determines the type of light, and depending on the color temperature of the light source, even if the same object is obtained with different colors. As such, when the color of the image currently acquired is changed by the color temperature of the external light, color constancy of the object is broken and color imbalance occurs. In general, this phenomenon is defined as a white balance (unbalanced). On the other hand, a color temperature may change with a frame due to internal factors of the acquired video. This phenomenon is defined as color rolling. Color rolling is a phenomenon in which the color temperature of the image is continuously changed even though the image is acquired in the same environment, and occurs when the entire color of the image appears repeatedly with different brightness values such as yellow, blue, and achromatic.

As such, when the color of the image is changed due to an internal or external factor of the image input apparatus, the stability of the video decreases and a problem such as flicker occurs. In addition, there is a difficulty in the application of the image, such as object detection (color detection) as the color continuously changes. Therefore, conventionally, various methods have been proposed to reduce color rolling.

Conventionally, a method using an auto iris lens is commonly used as a method of reducing color rolling. By using an auto iris lens, since a constant light can be received with respect to a shutter speed, an image can be obtained without a color rolling phenomenon. However, there is a problem in that the manufacturing cost of the camera is rapidly increased when the automatic iris adjustment lens is included in the camera configuration because of the high price.

As a method of reducing color rolling, there is also a line lock mode method in which a sampling frequency of an image is matched with a power source frequency of an external light source (eg, a fluorescent lamp). This method compensates the difference between the power source frequency of the external light source and the sampling frequency of the image, which is a fundamental problem of color rolling, so that a constant image can be obtained without changing the color temperature. However, this method requires the additional configuration of hardware, which leads to the problem of increased manufacturing cost and device volume.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an image color correction apparatus and method for simultaneously performing color fluidity suppression and color imbalance correction occurring in a color image sequence, and a recording in which a program for implementing the method is recorded. The purpose is to provide the medium.

The present invention has been made to achieve the above object, an area extraction unit for comparing the input image and the reference image, and extracts an achromatic region from the input image through the comparison; A first compensation value estimator estimating a first compensation value for each color channel to compensate for a difference in color characteristic values of the target channel region selected from the achromatic region in consideration of color characteristic values of the reference channel region selected from the achromatic region; Estimating a second compensation value for each color channel that compensates for a difference in color characteristic values of a second channel region that is the same channel as the first channel and is selected from the achromatic region in consideration of color characteristic values of the first channel region selected from the reference image; A second compensation value estimator; And a color corrector configured to correct a color in the input image using a gain value obtained from the first compensation value and the second compensation value.

Preferably, the first compensation value estimating unit estimates the first compensation value for each color channel by using a ratio value of the color characteristic average value of the reference channel region to the color characteristic average value of the target channel region.

Preferably, the second compensation value estimator estimates the second compensation value for each color channel by using a ratio value of the color characteristic average value of the first channel region to the color characteristic average value of the second channel region.

Preferably, the color corrector uses a multiplication value of the first compensation value and the second compensation value as the gain value.

Preferably, the area extractor includes a reference image selector which selects an image having a maximum brightness value when there is no motion as the reference image.

Preferably, the region extracting unit extracts the target region as an achromatic region when the target region selected from the input image is included in an achromatic region of a predetermined light source based on a color temperature.

Preferably, the area extractor comprises: an image comparator comparing the input image with the reference image; A motion region extractor which extracts a motion region from the input image through the comparison; And an achromatic region extraction unit configured to extract the achromatic region from a non-movement region, which is a region other than the extracted motion region, from the input image. More preferably, the image comparison unit classifies and compares the input image and the reference image in block units, and the motion region extraction unit distributes colors between a target block included in the input image and a target block included in the reference image. If the difference is greater than or equal to a predetermined reference value, the object block is extracted as a motion area.

Preferably, the image color correction apparatus is provided in an apparatus for decoding an input image, and uses an image that is color interpolated as the input image.

In addition, the present invention comprises the steps of (a) comparing the input image and the reference image, and extracting the achromatic region from the input image through the comparison; (b) estimating a first compensation value for each color channel that compensates for the difference in color characteristic values of the target channel region selected from the achromatic region in consideration of the color characteristic values of the reference channel region selected from the achromatic region; (c) second compensation for each color channel considering the color characteristic value of the first channel region selected from the reference image to compensate for the difference in color characteristic values of the second channel region identical to the first channel and selected from the achromatic region; Estimating a value; And (d) correcting a color in the input image using a gain value obtained from the first compensation value and the second compensation value.

Preferably, the step (b) estimates the first compensation value for each color channel by using a ratio value of the color characteristic mean value of the reference channel region to the color characteristic mean value of the target channel region.

Preferably, in the step (c), the second compensation value is estimated for each color channel by using a ratio value of the color characteristic mean value of the first channel region to the color characteristic mean value of the second channel region.

Preferably, step (d) uses a multiplication value of the first compensation value and the second compensation value as the gain value.

Preferably, the step (a) selects an image having a maximum brightness value when there is no motion as the reference image, and if the target region selected from the input image is included in the achromatic region of a predetermined light source based on a color temperature, The target area is extracted as an achromatic area.

Preferably, the step (a) comprises the steps of (aa) comparing the input image and the reference image by dividing each block; (ab) extracting a motion region from the input image through the comparison, and moving the target block when the difference in the color distribution between the target block included in the input image and the target block included in the reference image is greater than or equal to a predetermined reference value. Extracting to an area; and (c) extracting the achromatic region from the input image in the non-motion region, which is a region other than the extracted movement region.

According to the present invention, the following effects can be obtained. First, color rolling may be removed from an image by simultaneously performing color fluidity suppression and color imbalance correction occurring in a color image sequence. In addition, it is possible to obtain a consistent image without changing the brightness and color, and to improve the quality of the image. Second, since the color imbalance is corrected while maintaining the color homeostasis, no flicker occurs and the digital imaging apparatus can be stably driven. Third, the cost of manufacturing a camera can be reduced because it is implemented in software according to the signal processing method without adding hardware.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even if displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the following will describe a preferred embodiment of the present invention, but the technical idea of the present invention is not limited thereto and may be variously modified and modified by those skilled in the art.

1 is a block diagram schematically illustrating an image color correction apparatus according to a preferred embodiment of the present invention. According to FIG. 1, the apparatus 100 for correcting an image color includes an image input unit 110, an area extractor 120, a first compensation value estimator 130, a second compensation value estimator 140, and a color corrector ( 150, an image output unit 160, a power supply unit 170, and a controller 180.

The image color correction apparatus 100 performs color imbalance correction as well as color fluidity suppression (color rolling phenomenon prevention) generated in the color image sequence. In detail, the image color correcting apparatus 100 operates as follows. First, the image color correction apparatus 100 detects a motion inside an image by comparing a preset reference frame with a current frame. Thereafter, the image color correction apparatus 100 compensates for the brightness change of the current frame by using the color characteristics of each channel of the achromatic region included in the still region extracted on the current frame and the reference frame. The image color correction device 100 prevents color fluidity occurring on the time axis of the image sequence and simultaneously solves color imbalance occurring in one image. In addition, while having a certain brightness in the image, the color of the object appears to be most similar to the actual.

The image color correction apparatus 100 contributes to improving color by compensating for the brightness of the image by using the weight. The color rolling phenomenon is caused by a change in the amount of light received in each frame due to a difference between a 60 Hz power supply frequency for supplying fluorescent lamps and a 59.94 Hz sampling frequency for video. In this case, a change in the amount of light received by the light receiving unit of the sensor may be large for a B channel value having a shorter wavelength than R and G, and a color change of each channel may be different depending on the type of ambient light source. In addition, for each time point, the wavelength of light emitted from the fluorescent lamp may vary, which is also one of the causes of color rolling.

The image color correcting apparatus 100 suppresses color fluidity appearing in a series of images from a signal processing point of view. In particular, the image color correction apparatus 100 is applied to an image after a color interpolation process in an ISP (Image Signal Processing) module to prevent color fluidity of a video, and simultaneously performs white balance with color rolling suppression. do.

The image color correction device 100 is provided in an apparatus for decoding an input image. In the present exemplary embodiment, the present invention is not limited thereto, and the image color correcting apparatus 100 may be provided in an apparatus for encoding an input image. The image color correction device 100 may be provided in, for example, a surveillance camera.

The image input unit 110 performs a function of receiving an image.

The region extractor 120 compares the input image frame with the reference image frame, and extracts an achromatic region from the input image frame through the comparison. The region extractor 120 includes a reference image frame selector 121, an image frame comparator 122, a motion region extractor 123, and an achromatic region extractor 124. The following description refers to FIG. 2.

The reference image frame selector 121 selects a reference image frame as a reference for the brightness compensation set for color rolling removal. Preferably, the reference image frame selector 121 selects an image frame having a maximum brightness value as the reference image frame when there is no movement.

The image frame comparator 122 performs a function of comparing the input image frame with the reference image frame. Preferably, the image frame comparison unit 122 compares the input image frame and the reference image frame in block units.

The motion region extractor 123 extracts a motion region from the input image frame by comparing the input image frame with the reference image frame. In this embodiment, the moving area is extracted to obtain the moving area by excluding the moving area from the input image frame.

The motion region extractor 123 extracts the object block as the motion region when the difference in the color distribution between the object block included in the input image frame and the target block included in the reference image frame is equal to or greater than a predetermined reference value. The motion region extractor 123 may include a first color distribution value calculator (not shown), a second color distribution value calculator (not shown), and a color distribution comparison unit (not shown). In the above description, the first color distribution calculator calculates a color distribution value of each block with respect to blocks included in the input image frame. Also, the second color distribution calculator performs a function of calculating a color distribution value of each block with respect to blocks included in the reference image frame. In addition, the color distribution comparison unit performs a function of comparing the color distribution values between the specific block included in the input image frame and the comparison target block included in the reference image frame.

The motion determination method is performed by grasping the degree of change between the reference frame and the input frame. In this embodiment, the algorithm is performed on the assumption that the frame is a reference frame according to an accurate reference. In the present embodiment, a frame having the brightest brightness in a state of no motion is selected as the reference frame. The reason for this is as follows. First, it should be a suitable standard for judging movement. Second, when color fluidity occurs, it is advantageous to reduce color rolling by converging to the brightest part.

Intra-frame motion determination detects local motion based on a comparison of the reference frame and the input frame. At this time, since most hardware configurations have restrictions on the use of frame memory, the present embodiment uses a block motion map based motion determination method of determining a motion after dividing a frame into a plurality of blocks.

First, when a frame is divided into blocks, an average is extracted as color distribution statistics for each block. Then, it is determined that there is a local movement for the large difference between each block average through comparison with the reference frame. On the other hand, there is no local movement for similar parts. In this case, the m-th block average in the input frame may be defined as follows.

In the above, N _m represents the position of a pixel belonging to the m-th block, and A (i, j) represents the A channel component in (i, j) of the input frame.

와 같다. 이 과정으로부터 얻어진 결과값은 블록 단위의 로컬 모션 맵(local motion map)(300)으로, 움직임 영역(310)과 비움직임 영역(320)을 포함한다. 도면부호 330은 입력 영상 프레임을 가리키며, 도면부호 340은 기준 영상 프레임을 가리킨다.Based on this, whether the local motion of the m-th block is determined as shown in Equation 2. Meanwhile, the process of obtaining the block unit motion map in FIG. 3 is shown in Equation 2.

Same as The result obtained from this process is a local motion map 300 in blocks, and includes a motion region 310 and a non-movement region 320. Reference numeral 330 denotes an input image frame, and reference numeral 340 denotes a reference image frame.

In the above, A means any one of the R channel, G channel, B channel. gain is a weight value for correcting the difference in brightness between the reference frame and the current frame, and Thres (·) is a hard decision function for determining whether to move. In general, for real-time implementation, gain uses the brightness correction value from the previous frame. In this case, in order to integrate local motion information distributed for each channel, a block having local motion in one channel is determined as a block having local motion according to Equation 3 below.

If the m-th block is found to have no motion, it is determined whether or not the achromatic region is used for this region.

The non-movement area extractor extracts the non-movement area from the other areas except for the motion area extracted from the input image frame. Excluding the moving area from the input image frame, the moving area can be easily obtained. Therefore, such a moving area extracting portion may not be provided in this embodiment.

The achromatic region extraction unit 124 extracts an achromatic region from the extracted non-movement region. Preferably, the region extractor 120 extracts the target region as the achromatic region when the target region selected from the input image frame is included in the achromatic region of the predetermined light source based on the color temperature.

There are various ways to extract achromatic regions. In this embodiment, an achromatic extraction method based on color temperature is used as an achromatic extraction method. The following description refers to FIG. 4. In FIG. 4, the achromatic region of the general light source is shown as a combination of an x region and a y region. When the pixel components of a given block are converted into x and y values, if the region composed of the pixel components is included in the region 400 shown in FIG. 4, the region may be regarded as an achromatic region. On the other hand, if not included, this area can be regarded as a normal color gamut.

Again, this will be described with reference to FIG. 1.

The first compensation value estimator 130 considers the color characteristic values of the reference channel region selected from the achromatic region to compensate for the difference in the color characteristic values of the target channel region selected from the achromatic region, that is, between channels. It estimates the color compensation value. Preferably, the first compensation value estimator 130 estimates the first compensation value for each color channel by using a ratio value of the color characteristic average value of the reference channel region to the color characteristic average value of the target channel region.

The first compensation value estimator 130 includes a reference channel selector 131. The reference channel selector 131 selects a reference channel from at least two channels included in the achromatic region. Preferably, the reference channel selector 131 selects the G channel as the reference channel. This is because, in general, the G channel represents the brightness information of the video among the three R, G, and B channels.

The first compensation value estimator 130 calculates a ratio of each of the R, G, and B channels with respect to the achromatic region of the input image frame. This function of the first compensation value estimator 130 contributes to improving color homeostasis by eliminating color imbalance through the difference compensation between channels.

The color fluidity and color imbalance that appear in the R, G, and B channels, respectively, are represented as a product of a constant ratio as follows using statistical characteristics of each channel described in Equation (3).

R _out = gain _R R

G _out = gain _G G

B _out = gain _B B

At this time, as a way to solve the color imbalance, based on the method of von kries to adjust the color shift appearing in the R, B channel as a reference to the G channel as follows.

는 입력 프레임에서 R 채널, G 채널, B 채널 각각에서의 색 특성 평균값을 의미한다. 또한, R, G, B는 입력 프레임에서 R 채널, G 채널, B 채널 각각에서의 색상값을 의미한다.In the above description, R _AWB , G _AWB , and B _AWB mean a compensation value in each of the R channel, the G channel, and the B channel. Also,

Denotes an average value of color characteristics in each of the R channel, the G channel, and the B channel in the input frame. In addition, R, G, and B denote color values of the R, G, and B channels in the input frame.

The second compensation value estimator 140 considers the color characteristic values of the first channel region selected from the reference image to compensate for the difference in the color characteristic values of the second channel region identical to the first channel and selected from the achromatic region. A function of estimating a second compensation value, that is, a color compensation value between frames is performed. Preferably, the second compensation value estimator 140 estimates the second compensation value for each color channel by using a ratio value of the color characteristic mean value of the first channel region to the color characteristic mean value of the second channel region.

The second compensation value estimator 140 calculates an R, G, and B ratio in the achromatic region of the reference image frame. The second compensation value estimator 140 compensates the brightness using the R, G, and B ratios obtained from the achromatic region of the input image frame together with the calculated ratio. The second compensation value estimator 140 prevents color fluidity and removes color rolling through the compensation.

The second compensation value estimator 140 adjusts the ratio between the reference frame and the input frame according to Equation 5 below to prevent color fluidity.

In the above description, R _CRS , G _CRS , and B _CRS mean a second compensation value in each of the R channel, the G channel, and the B channel. In addition, R _target , G _target , and B _target mean color characteristic average values of each of the R channel, the G channel, and the B channel in the reference frame.

The color corrector 150 corrects colors in the input image frame by using gain values obtained from the first compensation value and the second compensation value.

The color corrector 150 includes a gain value calculator 151. The gain value calculator 151 calculates a multiplication value of the first compensation value and the second compensation value as a gain value. The gain value calculator 151 may calculate the sum of the first compensation value and the second compensation value as a gain value.

If the brightness between the frames is unified (CRS; Color Rolling Suppression) to solve the color unbalance of the input frame (AWB; Auto White Balance), the influence of the AWB is canceled and one integrated weight can be obtained. This weight is obtained by multiplying the first color correction value by AWB and the second color correction value by CRS, as described in Equation 6.

In the above description, gain _R , gain _G , and gain _B mean weights in the R channel, the G channel, and the B channel, respectively. In addition, G _current means a color value of the G channel which is a reference channel in the input frame.

The weights contain information that is inversely proportional to time, as well as information about interframe movement. Therefore, when the motion is larger than a predetermined reference value, a small weight is given to reflect the similarity with the input frame.

The change amounts of R, G, and B in the achromatic region with respect to the finally obtained image sequence are as shown in FIG. 5. FIG. 5A shows the achromatic average change amount of the input image, and FIG. 5B shows the achromatic average change amount of the output image to which the present embodiment is applied. As can be seen by comparing (a) and (b) of FIG. 5, in this embodiment, a consistent image can be obtained without changing brightness or color, and the quality of the image can be improved.

는 직접 계산하여 입력 프레임에 적용하기엔 어려움이 따르기 때문에 보통 추정을 한다. 이때, 바로 이전 프레임 정보를 이용할 수도 있지만, 잡음의 영향으로 정확성이 떨어진다. 그래서, 본 실시예에서는 입력 프레임 채널 특성을 다음과 같이 추정한다.However, the channel characteristics of the input frame

Is usually estimated because it is difficult to calculate and apply to the input frame. In this case, the previous frame information may be used, but accuracy is lowered due to noise. Thus, in this embodiment, the input frame channel characteristics are estimated as follows.

The input frame channel characteristic estimation method proposed in the present embodiment is as shown in Equation 7, and the estimated time can be reduced by eliminating unnecessary high frequency components using a cumulative average and weighting the input frame closer to the input frame.

은 각 프레임에서의 무채색 영역의 평균값을 나타낸다. A(i, j)는 입력 영상의 (i, j) 화소 위치에서의 A 채널 값이며, N은 해당 프레임의 무채색 영역에 대한 집합이다.In the above,

Represents the average value of the achromatic region in each frame. A (i, j) is an A channel value at the (i, j) pixel position of the input image, and N is a set of achromatic regions of the frame.

The input frame channel characteristic estimation method can compensate for the change amount by using the cumulative average of the change amount, and minimizes the effect of the change caused by noise on the mean value. The input frame channel characteristic estimation method weights more to an input frame closer to the reference frame than the weight calculation method described above.

The image output unit 160 performs a function of outputting an image that has been color corrected.

The power supply unit 170 supplies power to each unit constituting the image color correction device 100.

The controller 180 controls the overall operation of each unit constituting the image color correcting apparatus 100.

The image color correction apparatus 100 described above improves color homeostasis of each frame while maintaining color of the color image sequence by removing color rolling. The features of the image color correction device 100 are summarized as follows.

First, high-quality images having a constant color can be obtained by applying to a case where color fluidity occurs and color imbalance occurs with respect to a color image sequence acquired by a color imaging system.

Second, by combining the compensation value to compensate for the brightness and the balance value for each channel through comparison between the current frame and the reference frame, it is possible to solve both color fluidity and color imbalance in a single process.

Third, in order to solve the color rolling phenomenon, it is necessary to select a frame that is a reference for brightness. In the present exemplary embodiment, a still image having maximum brightness and no motion in the screen is set as the reference image.

Fourth, as the compensation value, the ratio of the value representing the statistical characteristics of the current frame and the reference frame is defined, but only the representative value of the region without motion is used.

Fifth, in order to exclude the area where the motion of the object inside the image is located, the moving area must be extracted first. In the present embodiment, whether the motion is determined by comparing the degree of change between the reference frame and the current frame with respect to the same position.

Sixth, in the method of compensating for the difference in brightness of the current frame, a compensation weight is obtained to equally compensate all pixel positions of the current frame.

Seventh, when using the frame information when extracting the motion region, if the use of frame memory is limited, the image frame is divided into k blocks and replaced with a block representative value.

Next, an image color correction method will be described. 6 is a flowchart illustrating an image color correction method according to an exemplary embodiment of the present invention. The following description refers to FIG. 6.

First, the image input unit 110 receives an image (S600).

Thereafter, the area extractor 120 compares the input image frame with the reference image frame, and extracts an achromatic region from the input image frame through the comparison (S610). The region extractor 120 selects an image frame having a maximum brightness value when there is no motion as the reference image frame. When the object region selected from the input image frame is included in the achromatic region of a predetermined light source based on the color temperature, the region extractor 120 selects the object region. Extract into achromatic regions.

The achromatic region extraction process of the region extraction unit 120 will be described in more detail as follows. In a first step, the image frame comparison unit 122 compares the input image frame and the reference image frame in block units. Then, in the second step, the motion region extractor 123 extracts the motion region from the input image frame through the comparison, but the difference in the color distribution between the target block included in the input image frame and the target block included in the reference image frame If the value is equal to or greater than the predetermined reference value, the object block is extracted as the motion area. Thereafter, in the third step, the achromatic image extracting unit 124 extracts the achromatic region from the remaining regions other than the movement region extracted from the input image frame, that is, the non-moving region.

Subsequently, the first compensation value estimator 130 estimates a first compensation value for each color channel that compensates for the difference in color characteristic values of the target channel region selected from the achromatic region in consideration of the color characteristic values of the reference channel region selected from the achromatic region. (S620). Preferably, the first compensation value estimator 130 estimates the first compensation value for each color channel by using a ratio value of the color characteristic average value of the reference channel region to the color characteristic average value of the target channel region.

Subsequently, the second compensation value estimator 140 compensates the difference in the color characteristic values of the second channel region that is the same channel as the first channel and is selected from the achromatic region in consideration of the color characteristic values of the first channel region selected from the reference image. A second compensation value for each color channel is estimated (S630). Preferably, the second compensation value estimator 140 estimates the second compensation value for each color channel by using a ratio value of the color characteristic mean value of the first channel region to the color characteristic mean value of the second channel region.

Thereafter, the color corrector 150 corrects the color in the input image frame using gains obtained from the first compensation value and the second compensation value (S640). Preferably, the color corrector 150 uses a multiplication value of the first compensation value and the second compensation value as a gain value.

Thereafter, the image output unit 160 outputs the color corrected image (S650).

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium. The computer-readable recording medium may be a magnetic storage medium (for example, a ROM, a floppy disk, a hard disk, a magnetic tape, etc.), an optical reading medium (for example, a CD-ROM, a DVD, an optical data storage device, etc.). And storage media such as carrier waves (eg, transmission over the Internet).

The above description is merely illustrative of the technical idea of the present invention, and various modifications, changes, and substitutions may be made by those skilled in the art without departing from the essential characteristics of the present invention. will be. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Color rolling problems are common with stationary cameras such as surveillance cameras. This is because of the low cost camera used in the nature of the product. Previously, modules such as apertures were additionally configured to eliminate color rolling. However, there is a problem that the manufacturing cost and the volume of the product is increased, the competitiveness of the product is reduced. The present invention can be implemented in the ISP by solving the color rolling problem by signal processing, and at the same time can solve the color problem. When the present invention is applied to various imaging devices such as surveillance cameras and fixed PC cameras, it is possible to further enhance the product competitiveness of camera manufacturers.

1 is a block diagram schematically illustrating an image color correction apparatus according to a preferred embodiment of the present invention.

2 is a block diagram schematically showing a region extraction unit according to a preferred embodiment of the present invention.

3 is a diagram related to a process of obtaining a local motion map in units of blocks.

4 is a graph applied to an achromatic extraction method based on color temperature.

5 is a diagram illustrating an amount of change in R, G, and B in the achromatic region for the finally obtained image sequence.

6 is a flowchart illustrating an image color correction method according to an exemplary embodiment of the present invention.

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

100: image color correction device 110: image input unit

120: region extraction unit 121: reference image frame selection unit

122: image frame comparator 123: motion region extractor

124: achromatic region extraction unit 130: first compensation value estimation unit

131: reference channel selector 140: second compensation value estimator

150: color correction unit 151: gain value calculation unit

160: video output unit

Claims (16)

A region extraction unit which compares an input image with a reference image and extracts an achromatic region from the input image through the comparison; A first compensation value estimator estimating a first compensation value for each color channel to compensate for a difference in color characteristic values of the target channel region selected from the achromatic region in consideration of color characteristic values of the reference channel region selected from the achromatic region; Estimating a second compensation value for each color channel that compensates for a difference in color characteristic values of a second channel region that is the same channel as the first channel and is selected from the achromatic region in consideration of color characteristic values of the first channel region selected from the reference image; A second compensation value estimator; And A color corrector configured to correct a color in the input image by using a gain value obtained from the first compensation value and the second compensation value Image color correction apparatus comprising a. The method of claim 1, And the first compensation value estimator estimates the first compensation value for each color channel by using a ratio value of the average color characteristic of the reference channel region to the average color characteristic of the target channel region. . The method of claim 1, The second compensation value estimator estimates the second compensation value for each color channel by using a ratio value of the average color characteristic of the first channel region to the average color characteristic of the second channel region. Correction device. 4. The method according to any one of claims 1 to 3, And the color corrector uses a multiplication value of the first compensation value and the second compensation value as the gain value. The method of claim 1, And the area extractor comprises a reference image selector which selects an image having a maximum brightness value when there is no motion as the reference image. The method of claim 1, And extracting the target area into the achromatic region when the target region selected from the input image is included in an achromatic region of a predetermined light source based on a color temperature. The method of claim 1, The area extraction unit, An image comparison unit comparing the input image with the reference image; A motion region extractor which extracts a motion region from the input image through the comparison; And An achromatic region extraction unit for extracting the achromatic region from the input image to the non-moving region except for the extracted motion region Image color correction apparatus comprising a. The method of claim 7, wherein The image comparison unit classifies and compares the input image and the reference image in block units, The motion area extractor extracts the object block as a motion area when the difference in the color distribution between the object block included in the input image and the target block included in the reference image is greater than or equal to a predetermined reference value. . The method of claim 1, The image color correction apparatus is provided in a device for decoding an input image, and the image color correction apparatus, characterized in that for using the image interpolated (color interpolated) to the input image. (a) comparing an input image with a reference image and extracting an achromatic region from the input image through the comparison; (b) estimating a first compensation value for each color channel that compensates for the difference in color characteristic values of the target channel region selected from the achromatic region in consideration of the color characteristic values of the reference channel region selected from the achromatic region; (c) second compensation for each color channel considering the color characteristic value of the first channel region selected from the reference image to compensate for the difference in color characteristic values of the second channel region identical to the first channel and selected from the achromatic region; Estimating a value; And (d) correcting a color in the input image using a gain value obtained from the first compensation value and the second compensation value; Image color correction method comprising the. 11. The method of claim 10, And (b) estimating the first compensation value for each color channel by using a ratio value of the average color characteristic of the reference channel region to the average color characteristic of the target channel region. 11. The method of claim 10, In the step (c), the second compensation value is estimated for each color channel by using a ratio value of the average color characteristic of the first channel area to the average color characteristic of the second channel area. Calibration method. 11. The method of claim 10, In the step (d), the multiplication value of the first compensation value and the second compensation value is used as the gain value. 11. The method of claim 10, In the step (a), the image having the maximum brightness value is selected when there is no motion as the reference image, and when the target region selected from the input image is included in the achromatic region of the predetermined light source based on the color temperature, the target region is achromatic. Image color correction method characterized in that the extraction to the area. 11. The method of claim 10, In step (a), (aa) comparing the input image with the reference image by dividing the data in blocks; (ab) extracting a motion region from the input image through the comparison, and moving the target block when the difference in the color distribution between the target block included in the input image and the target block included in the reference image is greater than or equal to a predetermined reference value. Extracting into regions; And (ac) extracting the achromatic region from the input image in the non-moving region except for the extracted movement region Image color correction method comprising the. In a computer-readable recording medium, A recording medium having recorded thereon a program for implementing the method according to any one of claims 10 to 15.

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