KR20070115103A - Method and device for suppressing false color - Google Patents

Abstract

An apparatus and a method for restricting false color are provided to restrict the false color efficiently which is generated around an edge and restrict the false color without performing pretreatment on RGB data by using an edge parameter as it is. A method for restricting false color comprises the following steps of: converting RGB(Red, Green, Blue) data into YCbCr data(800); calculating a brightness parameter by using brightness components of the YCbCr data(802); calculating a color difference average value by using color difference components of the YCbCr data(804); and calculating color difference data, of which the false color is restricted, on the basis of an edge parameter, the calculated brightness parameter and color difference average value(806~816).

Description

False color suppression device and method {Method and Device for Suppressing False Color}

1 is a diagram illustrating a resolution chart of an image reconstructed by a conventional image processing method.

FIG. 2 is a diagram illustrating the overall configuration of an image processing apparatus to which a false color conversion method according to an exemplary embodiment of the present invention is applied.

FIG. 3 is an example of a 5x5 Bayer pattern image for performing color interpolation by the color interpolator of FIG. 2, illustrating an example in which an R component R3 in a RG line is a center pixel. FIG.

4 is a diagram illustrating an example of a 5x5 Bayer pattern image for performing color interpolation by the color interpolation unit, in which G5, a G component in a GB line, is a center pixel;

Figure 5 is a block diagram showing the configuration of a false color suppression unit according to an embodiment of the present invention.

6 is a diagram showing the structure of Yin data according to an embodiment of the present invention.

7 illustrates the form of Cin data according to an embodiment of the present invention.

8 is a flow chart showing the overall flow of the false color suppression method according to an embodiment of the present invention.

9 is a graph showing the relationship between luminance parameters, edge parameters, and color difference correction parameters;

10 is a view showing an image resolution chart in which false colors are suppressed according to the false color suppression method according to the present invention.

The present invention relates to a method and apparatus for suppressing false colors, and more particularly, to a method and apparatus for suppressing false colors generated during image processing restored from an image sensor.

An image sensor is a device that reproduces images by using semiconductor's reaction to light. It detects the brightness and wavelength of different light from each subject and reads the electric value. It functions to make it as level as possible.

The image sensor has only one color filter in one pixel, so that an image to be taken is obtained from a mosaic pattern or a Bayer pattern.

The digital part of the sensor interpolates each of the elements of the pattern, ie, red, green, and blue, to a near real image. Restore

However, the interpolation of a high resolution image uses a limited pattern of information, so colors different from the actual ones are generated. This color is called a false color, where high-frequency components higher than the resolution the sensor can represent (i.e., components above the Nyquist limit) clump up and make the image look clear, but at some higher frequency components, especially edges Many of these false colors appear around

When evaluating the characteristics of an actual sensor, a resolution chart is used to measure the resolution of the sensor, where false colors stand out in these resolution charts, degrading sensor characteristics during evaluation.

FIG. 1 is a diagram illustrating a resolution chart of an image reconstructed by a conventional image processing method. As illustrated in FIG. 1, it can be seen that a false color appears remarkably in a high frequency portion.

In order to solve the problems of the prior art as described above, the present invention is to propose a method and apparatus that can effectively suppress the false color occurring around the edge.

Another object of the present invention is to propose a method and apparatus capable of suppressing false colors without performing preprocessing on R, G, and B data while using edge parameters as they are.

According to an aspect of the present invention to achieve the above object, the step of converting the R, G, B data into YCbCr data (a); Calculating (b) a luminance parameter using the luminance component of the YCbCr data; (C) calculating a color difference average value using the color difference component of the YCbCr data; And (d) calculating color difference data in which the false color is suppressed based on the edge parameter and the luminance parameter and the color difference average value calculated in the step (b) and the step (c). .

The step (b) of calculating the luminance parameter subtracts the minimum luminance value from the maximum luminance value based on the luminance component data in the form of 3x3.

The step (c) of calculating the color difference average value calculates an average value of color difference data of a 1 × 2 form consisting of Cb or Cr components.

The edge parameter may be any one or combination thereof selected from the group consisting of an edge coring parameter, an edge gain parameter and an edge limit parameter.

The step (d) may include calculating a color difference correction parameter by comparing the luminance parameter with an edge coring parameter; Determining whether the chrominance correction parameter exceeds the edge limit parameter; And calculating color difference data in which the false color is suppressed according to a determination result of whether the color difference correction parameter exceeds the edge limit parameter.

When the luminance parameter is smaller than the edge coring parameter, the chrominance correction parameter is set to 0, and when the luminance parameter is larger than the edge coring parameter, the chrominance correction parameter is obtained by multiplying the luminance parameter by the edge gain parameter. Calculate by value

When the color difference correction parameter α is smaller than the edge limit parameter, the value of the color difference correction parameter α is kept as it is, and when the color difference correction parameter α is larger than the edge limit, the value of the color difference correction parameter is The color difference data C_out of which the false color is suppressed is set to be equal to the edge limit parameter, and the following equation is obtained using the color difference correction parameter α and the color difference average value C_ave.

Calculate by

According to another aspect of the invention, the RGB, YCbCr conversion unit for converting the R, G, B data into YCbCr data; A luminance parameter calculator which calculates a luminance parameter using the luminance component of the YCbCr data; A C filter for calculating a color difference average value using the color difference component of the YCbCr data; A false color suppression apparatus is provided that includes a false color suppression unit that performs calculation for false color suppression based on the luminance parameter, color difference average value, and edge parameter.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the false color suppression method and apparatus according to the present invention.

FIG. 2 is a diagram illustrating the overall configuration of an image processing apparatus to which a false color conversion method according to an exemplary embodiment of the present invention is applied.

Referring to FIG. 2, an image processing apparatus to which a false color conversion method according to the present invention is applied may include a color interpolator 200, an camera signal processing intermediate processor 202, and a false color suppressor 204.

The color interpolator 200 is responsible for performing color interpolation on the input Bayer pattern image. This will be described with reference to the drawings.

The color interpolator 200 performs color interpolation on a 5 × 5 Bayer pattern image. E_R, E_G, and E_B, which are output values of R, G, and B values, are output through color interpolation.

The color interpolation method for the 5 × 5 Bayer pattern image is described in detail as follows. The most common color interpolation method, effective interpolation method, will be described.

FIG. 3 is an example of a 5 × 5 Bayer pattern image for performing color interpolation in the color interpolation unit of FIG. 2, and illustrates a case where R3, which is an R component in an RG line, is a center pixel. However, a case in which the R component is the center pixel will be described with reference to FIG. 3. However, considering that the positions of the R and B components are interchanged in the Bayer pattern image, the same applies to the case where the center pixel is the B component in the GB line. Will do.

Rn, Rw, Rs, Re and Kr1, Kr2, Kr3, Kr4 will be defined by the following equations (1) and (2), respectively, for color interpolation when R3, which is an R component in the RG line, is a center pixel.

Then, the output E_G of the G component is expressed by the following equation.

Since the interpolation method of the interpolation unit 420 is conventionally known (for example, Soo-Chang Pei, Fellow, IEEE, Io-Kuong Tam, "Effective Color Interpolation in CCD Color Filter Arrays Using Signal Correlation", IEEE transaction). on circuits and systems for video technology, Vol. 13 (6), June 2003).

Meanwhile, in order to obtain outputs E_B and E_R of interpolated B and R components, Gwn, Gws, Ges, Gen, and Kb1, Kb2, Kb3, and Kb4 are defined as Equations 4 and 5, respectively.

The outputs E_B and E_R of the interpolated B and R components are thus determined as in Equations 6 and 7 below.

Such interpolation may be applied to a 5 × 5 matrix to output E_R, E_G, and E_B.

4 illustrates an example of a 5 × 5 Bayer pattern image for performing color interpolation by the color interpolator, and illustrates a case in which the G component G5 in the GB line is the center pixel. Although the case where the G component is the center pixel in the GB line will be described with reference to FIG. 4, considering that the positions of the R and B components are interchanged in the Bayer pattern image, the center pixel is the G component in the RB line. Will also be the same.

In order to perform color interpolation in the Bayer pattern image of FIG. 4, Gn, Gw, Gs, Ge, and Kr1, Kr2, Kb1, and Kb2 will be defined as Equations 8 and 9, respectively.

Accordingly, in the case of FIG. 4, the outputs E_G, E_R, and E_B of the interpolator 420 are as shown in Equations 10 to 12 below.

In this way, the output is determined in the case where the central pixel is the G component and the R or B component, respectively. Such interpolation can be applied to a 5x5 matrix to output output data E_R, E_G, and E_B.

As described above, when the interpolated R, G, and B data are output from the color interpolation unit, a general intermediate processing operation is performed by the camera signal processing intermediate processing unit 202, and R, G, B Data is input to a false color suppressor 204. Since the operation of the camera signal processing intermediate processor 202 is already known, a detailed description thereof will be omitted.

In Fig. 2, as a processing step before false color suppression, an intermediate process for color interpolation and camera signal processing is shown, but this is only an embodiment to which the present invention is applied, and in addition to these two steps, For example, various processing steps may be preceded, such as processing to improve edge performance. In addition, it will be apparent to those skilled in the art that various color interpolation methods other than the effective color interpolation method described above may also be applied to the color interpolation method.

The false color suppressor 204 functions to suppress a false color generated due to the high frequency component of the image.

Detailed configuration and operation of the false color suppressor 204 will be described with reference to FIG. 5.

5 is a block diagram illustrating a configuration of a false color suppressing unit according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the false color suppressor according to an embodiment of the present invention includes an RGB / YCbCr converter 500, a luminance parameter calculator 502, a C filter 504, a false color suppressor 506, and a plurality of false color suppressors. Line memory 508, 510, 512.

The RGB / YCbCr converter 500 converts the input R, G, and B data into YCbCr data. R, G, and B data are data output after color interpolation and intermediate processing, and color interpolation and intermediate processing may be performed in various ways.

YCbCr data is data mainly used for image compression (for example, MPEG), and includes luminance data Y and color difference data Cb and Cr.

R, G, and B data may be converted into YCbCr data by the following conversion equation.

The equation for converting RGB data into YCbCr data is well known as in Equation 15 above, but is not limited to the above equation, and the ratio may vary depending on the type of image processing system. something to do.

The luminance component Y of the data output from the RGB / YCbCr converter 500 is input to the luminance parameter calculator 502 as Yin.

Also, among the data output from the RGB / YCbCr converter 500, the color difference components Cb and Cr are input to the C filter as Cin.

According to a preferred embodiment of the present invention, two line memories 508 and 510 are included to input Yin data to the luminance parameter calculator 502, and the Yin data may be 3x3 matrix data. In order to suppress the false color, the information of the neighboring pixels is input through the line memory as well as the center pixel.

6 is a diagram illustrating the structure of Yin data according to an embodiment of the present invention.

As illustrated in FIG. 6, the Yin data may be in the form of a 3 × 3 matrix using two line memories, and the luminance parameter calculator calculates the luminance parameter using the Yin data.

According to a preferred embodiment of the present invention, one line memory 512 is included to input Cin data into the C_ filter, and the Cin data may be 1 × 2 matrix data for the Cb component or the Cr component.

7 is a diagram illustrating the form of Cin data according to an embodiment of the present invention.

The RGB / YCbCr converter 500 outputs Y, Cb, and Cr components at a ratio of 4: 2: 2. That is, the RGB / YCbCr converter 500 outputs one component of the Cb component or the Cr component at one clock time, and outputs one Cb component and one Cr component at the time of outputting the two Y components.

Unlike the conventional false color suppression, the present invention calculates a new parameter called luminance parameter Diff_out and is calculated by the luminance parameter calculator 502.

The luminance parameter is calculated using 3 × 3 Yin data provided from the RGB / YCbCR converter 500.

According to a preferred embodiment of the present invention, the luminance parameter calculator 502 may calculate the luminance parameter by the following equation (16).

The C filter 504 functions to calculate the average value C_ave of the Cin data using 1 × 2 Cin data provided from the RGB / YCbCr converter 500.

The average value C_ave of the Cin data is calculated by the following equation (17).

The false color suppressor 506 functions to output color difference data Cout whose false colors are suppressed by using the average parameter and the edge parameter of the luminance parameter input from the luminance parameter calculator and the Cin data input from the C filter.

Here, the edge parameter is a parameter used for edge calculation, and may include edge coring, edge gain, and edge limit. Of course, if necessary, the edge coring, edge gain, and edge limit values may be set to different values from the edge parameters used in the edge operation.

As illustrated in FIG. 5, the false color suppressor may include a color difference correction parameter calculator 520 and a Cout output unit 530.

The color difference correction parameter α is a parameter used for the calculation of Cout, which is color difference data whose false color is suppressed, and the color difference correction parameter α is calculated according to a result of comparing the edge coring parameter among the luminance parameter and the edge parameter.

According to a preferred embodiment of the present invention, the chrominance correction parameter calculator 520 determines whether the luminance parameter is smaller than the edge coring parameter, and if the luminance parameter is smaller than the edge coring parameter, the chrominance correction parameter α is determined. Set to zero.

In addition, when the luminance parameter is larger than the edge coring parameter, the false color suppressor 506 sets the color difference correction parameter α to the value obtained by multiplying the luminance parameter by the edge gain.

When the color difference correction parameter α is calculated by the color difference correction parameter calculator 520, the Cout calculator 530 outputs color difference data in which the false color is suppressed using the color difference correction parameter α.

According to a preferred embodiment of the present invention, the Cout calculator 530 calculates the output value Cout after determining whether the color difference correction parameter α exceeds the edge limit which is an edge parameter.

If the color difference correction parameter α does not exceed the edge limit, the Cout calculation unit 530 uses the color difference correction parameter value as it is for the Cout operation. However, if the color difference correction parameter value exceeds the edge limit, the Cout calculation unit 530 uses the color difference correction parameter value. Reset to the edge limit value.

After resetting the color difference correction parameter in comparison with the edge limit, the Cout calculator calculates Cout by the following equation (18).

In Equation 18, α is a color difference correction parameter, and C_ave is an output value of the C filter.

8 is a flow chart showing the overall flow of the false color suppression method according to an embodiment of the present invention.

Referring to FIG. 8, first, YCbCR conversion is performed on R, G, and B data output through color interpolation and camera signal intermediate processing (step 800).

The luminance parameter is calculated using the Y component output by the YCbCr transform (step 802). The luminance parameter is calculated using 3 × 3 type Yin data input through two line memories. As described above, the luminance parameter may be calculated by subtracting the largest value from the Yin data to the smallest value.

Further, the C_ave value is calculated using the Cb and Cr components output by the YCbCr transform (step 804). Specifically, the C_ave value is calculated using 1 × 2 Cin data consisting of a Cb component or a Cr component.

9 is a graph showing the relationship between the luminance parameter, the edge parameter and the chrominance correction parameter.

In FIG. 9, the x-axis is a luminance parameter and the y-axis is a chrominance correction parameter, and the chrominance correction parameter depends on edge parameter values such as edge coring and edge gain.

9, the false color suppression method of FIG. 8 will be described.

After the luminance parameter and the C_ave value have been calculated, it is determined whether the luminance parameter exceeds edge coring, one of the edge parameters (step 804).

As shown in Fig. 9, when the luminance parameter is smaller than edge coring, the value of the color difference correction parameter is set to 0 (step 808).

If the luminance parameter is larger than edge coring, the value of the luminance parameter is set to a value obtained by multiplying the luminance parameter by the edge gain as shown in FIG. 9 (step 810).

When the color difference correction parameter is calculated according to the luminance parameter value, it is determined whether the color difference correction parameter exceeds the edge limit (step 812).

If the chrominance correction parameter does not exceed the edge limit, the chrominance correction parameter value remains the same, and if the chrominance correction parameter exceeds the edge limit, the chrominance correction parameter is reset to the edge limit value (step 814).

After the color difference correction parameter is reset according to the edge limit value, Cout, which is color difference data whose false color is suppressed by Equation 18, is calculated (step 816).

10 is a diagram illustrating an image resolution chart in which false colors are suppressed according to the false color suppression method according to the present invention.

As shown in FIG. 10, compared to FIG. 1, it can be seen that the false color is removed by suppressing the color difference component around the edge.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

As described above, according to a preferred embodiment of the false color suppression method and apparatus of the present invention, it is possible to efficiently suppress the false color occurring around the edges, while using the edge parameters as it is, R, G, B data There is an advantage that can suppress the false color without performing the preprocessing. .

Claims (15)

Converting the R, G, B data into YCbCr data (a); Calculating (b) a luminance parameter using the luminance component of the YCbCr data; (C) calculating a color difference average value using the color difference component of the YCbCr data; And And (d) calculating color difference data in which the false color is suppressed based on the edge parameter and the luminance parameter calculated in the step (b) and the step (c). . The method of claim 1, And (b) calculating the luminance parameter by subtracting the minimum luminance value from the maximum luminance value based on the 3 × 3 luminance component data. The method of claim 2, The calculating of the color difference average value (c) comprises calculating a mean value of color difference data of a 1 × 2 form consisting of Cb or Cr components. The method of claim 1, And wherein the edge parameter is any one selected from the group consisting of an edge coring parameter, an edge gain parameter, and an edge limit parameter, or a combination thereof. The method of claim 4, wherein Step (d) is, Calculating a color difference correction parameter by comparing the luminance parameter with an edge coring parameter; Determining whether the chrominance correction parameter exceeds the edge limit parameter; And And calculating color difference data in which the false color is suppressed according to a determination result of whether the color difference correction parameter exceeds the edge limit parameter. The method of claim 5, When the luminance parameter is smaller than the edge coring parameter, the chrominance correction parameter is set to 0, and when the luminance parameter is smaller than the edge coring parameter, the chrominance correction parameter is obtained by multiplying the luminance parameter by the edge gain parameter. False color suppression method characterized in that the operation by the value. The method of claim 5, When the color difference correction parameter α is smaller than the edge limit parameter, the value of the color difference correction parameter α is kept as it is, and when the color difference correction parameter α is larger than the edge limit, the value of the color difference correction parameter is Set it to be the same value as the edge limit parameter, The color difference data C_out in which the false color is suppressed is expressed by the following equation using a color difference correction parameter α and a color difference average value C_ave.

False color suppression method characterized by the above-mentioned. An RGB / YCbCr converter for converting R, G, and B data into YCbCr data; A luminance parameter calculator which calculates a luminance parameter using the luminance component of the YCbCr data; A C filter for calculating a color difference average value using the color difference component of the YCbCr data; And a false color suppression unit that performs a calculation for false color suppression based on the luminance parameter, the color difference average value, and the edge parameter. The method of claim 8, And the luminance parameter calculating unit calculates a luminance parameter by subtracting the minimum luminance value from the maximum luminance value based on the luminance component data in the form of 3x3. The method of claim 9, The C filter is a false color suppression device, characterized in that for calculating the average value of the color difference data of the 1 × 2 form consisting of Cb or Cr components. The method of claim 8, And the edge parameter is any one or a combination thereof selected from the group consisting of an edge coring parameter, an edge gain parameter and an edge limit parameter. The method of claim 8, And the false color suppressor calculates color difference data of which false color is suppressed based on the luminance parameter, color difference average value, and edge parameter. The method of claim 12, The false color suppressor, Compute the color difference correction parameter by comparing the luminance parameter with an edge coring parameter, determine whether the color difference correction parameter exceeds the edge limit parameter, and determine whether the color difference correction parameter exceeds the edge limit parameter. And calculating color difference data in which the false color is suppressed according to the determination result. The method of claim 13, The color difference correction parameter is set to 0 when the brightness parameter is smaller than the edge coring parameter, and the color difference correction parameter is equal to the brightness parameter when the brightness parameter is smaller than the edge coring parameter. False color suppression device characterized in that the operation by multiplying the edge gain parameters. The method of claim 14, The false color suppressor, When the color difference correction parameter α is smaller than the edge limit parameter, the value of the color difference correction parameter α is kept as it is, and when the color difference correction parameter α is larger than the edge limit, the value of the color difference correction parameter is Set it to be the same value as the edge limit parameter, The color difference data C_out in which the false color is suppressed is expressed by the following equation using a color difference correction parameter α and a color difference average value C_ave.

False color suppression apparatus characterized by the above-mentioned.

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