KR101644704B1 - Apparatus and method for image processing for saturation enhancement - Google Patents

Apparatus and method for image processing for saturation enhancement Download PDF

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KR101644704B1
KR101644704B1 KR1020140148372A KR20140148372A KR101644704B1 KR 101644704 B1 KR101644704 B1 KR 101644704B1 KR 1020140148372 A KR1020140148372 A KR 1020140148372A KR 20140148372 A KR20140148372 A KR 20140148372A KR 101644704 B1 KR101644704 B1 KR 101644704B1
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brightness
color space
input
output
color
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KR20160050370A (en
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이병욱
박준희
이지원
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이화여자대학교 산학협력단
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Abstract

An image processing apparatus and method for improving saturation are disclosed.
The image processing method includes the steps of: determining an output brightness of a first color space using an input brightness of a first color space, an input luminance of a second color space, and an output luminance of a second color space in an input image ; And determining an output color coordinate of the second color space using the brightness plane of the first color space according to the output brightness and the input brightness.

Description

[0001] APPARATUS AND METHOD FOR IMAGE PROCESSING FOR SATURATION ENHANCEMENT [0002]

The present invention relates to an image processing apparatus and method for enhancing saturation, and more particularly, to an apparatus and method for increasing the saturation while preserving color in a YCbCr color space.

Conventional 3D color histogram equalization is one of the powerful techniques for improving the contrast of color images. In particular, the luminance contrast can be effectively improved by allowing the histogram to be evenly distributed in the gray scale histogram.

The Naik technique can be utilized so as not to cause a gamut problem when the brightness contrast is improved in the conventional RGB color space. At this time, according to the Naik technique, although the image can be improved without changing the hue, there is a problem that the saturation is lowered.

Therefore, there is a need for a method that can effectively improve the saturation while improving the brightness of the image in the RGB color space.

In the present invention, the output brightness of the RGB color space is determined using the input luminance and output luminance of the color space representing the input brightness and luminance of the RGB color space in the input image, and the output brightness of the RGB color space is used to represent the luminance It is possible to provide an apparatus and method for improving chroma while preserving hue in a color space representing luminance by determining the output color coordinates of the second color space in the color space.

The present invention also relates to a device for improving chroma in a color space such as YCbCr by changing the hue to an RGB space to enhance saturation and then converting it to an original color space without performing a simple operation, Method can be provided.

An image processing method according to an embodiment of the present invention is a method of processing an input image using input brightness of a first color space, input luminance of a second color space, and output luminance of a second color space, Determining an output brightness of the space; And determining an output color coordinate of a second color space using a brightness plane of the first color space according to the output brightness and the input brightness, wherein the first color space is an RGB color space, Wherein the color space is a YCbCr color space in which the RGB color space is converted according to a color space conversion formula, the input brightness and the output brightness are defined as (R + G + B) / 3, the input brightness and the output brightness are YCbCr color Can be defined as Y, which is the luminance component of the space.

The step of determining output brightness of the image processing method according to an embodiment of the present invention may determine the output brightness by applying the input brightness, the input brightness, and the output brightness to Equation (1).

[Equation 1]

Figure 112014104152181-pat00001

The brightness plane of the first color space of the image processing method according to an exemplary embodiment of the present invention may include a first brightness plane and a second brightness plane having a brightness value smaller than that of the first brightness plane.

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The step of increasing the saturation of the image processing method according to an embodiment of the present invention may include increasing the saturation of the input brightness and the output brightness when the input brightness and the output brightness are darker than the brightness of the first brightness plane, The output color coordinates of the second color space may be determined using the output luminance and the input color coordinates of the second color space.

The step of increasing the saturation of the image processing method according to an embodiment of the present invention may include increasing the saturation of the first brightness plane when the input brightness is darker than the brightness of the first brightness plane and the output brightness is brighter than the brightness of the first brightness plane Mapping the input brightness; Determining a mapping color coordinate of the mapped point using a mapping luminance of an input color coordinate, the input luminance, and a point mapped to the input brightness of the second color space; And determining an output color coordinate of the second color space using a straight line connecting the mapped point and white, the mapping luminance, the mapping chromaticity coordinate, and the output luminance of the input image.

The step of increasing the saturation of the image processing method according to an exemplary embodiment of the present invention may be performed when the input brightness is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness is larger than the input brightness , The output color coordinate of the second color space may be determined using a straight line connecting the input color coordinates and white, the output luminance, the input luminance, and the input color coordinates of the second color space.

The step of increasing the saturation of the image processing method according to an exemplary embodiment of the present invention may be performed when the input brightness is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness is smaller than the input brightness , The output color coordinates of the second color space may be determined using a straight line connecting the input color coordinates and black, the output luminance, the input luminance, and the input color coordinates of the second color space.

The step of increasing the saturation of the image processing method according to an exemplary embodiment of the present invention may include increasing the saturation of the second brightness plane when the input brightness is brighter than the brightness of the second brightness plane and the output brightness is darker than the brightness of the second brightness plane Mapping the input brightness; Determining a mapping color coordinate of the mapped point using a mapping luminance of an input color coordinate, the input luminance, and a point mapped to the input brightness of the second color space; And determining an output color coordinate of the second color space using a straight line connecting the mapped point and black, the mapping luminance, the mapping chromaticity coordinate, and the output luminance of the input image.

The step of increasing the saturation of the image processing method according to an embodiment of the present invention may include increasing the saturation of the input brightness and the output brightness when the input brightness and the output brightness are brighter than the brightness of the second brightness plane, The output color coordinates of the second color space may be determined using the output luminance and the input color coordinates of the second color space.

The image processing apparatus according to an embodiment of the present invention determines the output brightness of the first color space using the input brightness of the first color space, the input luminance of the second color space, and the output luminance of the second color space in the input image An output brightness determiner; And an output color coordinate determining unit determining an output color coordinate of the second color space using the brightness plane of the first color space according to the output brightness and the input brightness.

The output brightness determiner of the image processing apparatus according to an embodiment of the present invention can determine the output brightness by applying the input brightness, the input brightness, and the output brightness to Equation (1).

[Equation 1]

Figure 112014104152181-pat00002

The first color space of the image processing apparatus according to an exemplary embodiment of the present invention may be a color space in which brightness of an image is increased when colors of an input image are mixed and a color space may be a color space of brightness of an input image .

The brightness plane of the first color space of the image processing apparatus according to an embodiment of the present invention may include a first brightness plane and a second brightness plane having a smaller brightness value than the first brightness plane.

The output color coordinate determining unit of the image processing apparatus according to an exemplary embodiment of the present invention determines the output color coordinate of the input color coordinate system based on a straight line connecting the input color coordinate system and the black color when the input brightness and the output brightness are darker than the brightness of the first brightness plane, The output color coordinates of the second color space may be determined using the luminance and the input color coordinates of the second color space.

The output color coordinate determining unit of the image processing apparatus according to an exemplary embodiment of the present invention determines the output color coordinate of the input color coordinate of the input image in a first brightness plane when the input brightness is darker than the brightness of the first brightness plane and the output brightness is brighter than the brightness of the first brightness plane. Determines a mapping color coordinate of the mapped point using the mapping brightness of the input color coordinate, the input luminance, and the input brightness of the second color space, and maps the mapped point and white The output color coordinates of the second color space can be determined using the connecting line, the mapping luminance, the mapping chromaticity coordinates, and the output luminance of the input image.

The output color coordinate determining unit of the image processing apparatus according to an exemplary embodiment of the present invention may be configured such that when the input brightness is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness is larger than the input brightness, The output color coordinates of the second color space may be determined using a straight line connecting the color coordinates and white, the output luminance, the input luminance, and the input color coordinates of the second color space.

The output color coordinate determination unit of the image processing apparatus according to an exemplary embodiment of the present invention may be configured such that when the input brightness is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness is smaller than the input brightness, The output color coordinates of the second color space may be determined using a straight line connecting the color coordinates and the black color, the output luminance, the input luminance, and the input color coordinates of the second color space.

The output color coordinate determination unit of the image processing apparatus according to an exemplary embodiment of the present invention determines the output color coordinates of the input color coordinate of the input image in a case where the input brightness is brighter than the brightness of the second brightness plane and the output brightness is darker than the brightness of the second brightness plane, Determines a mapping color coordinate of the mapped point using the mapping brightness of the input color coordinate, the input luminance, and the input brightness of the second color space, The mapping color luminance, the mapping chromaticity coordinates, and the output luminance of the input image to determine the output color coordinate of the second color space.

The output color coordinate determining unit of the image processing apparatus according to an exemplary embodiment of the present invention determines the output color coordinates of the input color coordinate and a straight line connecting the input color coordinate and the white when the input brightness and the output brightness are brighter than the brightness of the second brightness plane, And an output color coordinate of the second color space using the input color coordinates of the second color space.

According to an embodiment of the present invention, the output brightness of the RGB color space is determined using the input luminance and the output luminance of the second color space representing the input brightness and luminance of the first color space such as the RGB color space in the input image , The output chromaticity of the second color space of the color space indicating the luminance is determined using the output brightness of the determined RGB color space to improve the chroma while preserving the hue in the color space showing the luminance.

1 is a block diagram illustrating an image processing apparatus according to an embodiment of the present invention.
2 is an example of a brightness plane of an RGB color space according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a process of compensating colors in a YCbCr color space according to an exemplary embodiment of the present invention. Referring to FIG.
4 is a diagram illustrating an image processing result for a Macbeth chart according to an embodiment of the present invention.
5 is a diagram illustrating an image processing result of an actual image according to an embodiment of the present invention.
6 is a diagram illustrating an image processing method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The image processing method according to an embodiment of the present invention can be performed by an image processing apparatus.

1 is a block diagram illustrating an image processing apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the image processing apparatus 100 according to an embodiment of the present invention may include an output brightness determining unit 110 and an output color coordinate determining unit 120.

The output brightness determining unit 110 determines an output brightness of the first color space using the input brightness of the first color space, the input luminance of the second color space, and the output luminance of the second color space, Can be determined.

In this case, the first color space may be a color space in which colors are represented by an additive mixing method in which the brightness of the image is increased by mixing the colors of the input image, and the second color space may be a color space including the brightness of the input image. For example, the first color space may be an RGB color space whose brightness increases when at least two colors of Red, Green, and Blue are mixed. At this time, the input brightness and the output brightness may be defined as (R + G + B) / 3.
The second color space may be a luminance Y and color difference signal C b, and YC b C r color space constituting the color based on the C r. Here, C b is a chrominance between a color of the input image and a blue color having the same luminance as the color, C r is a color difference between a color of the input image and a red color having the same luminance as the color . At this time, the luminance of the YC b C r color space may be Y.
In addition, the conversion equation between the RGB color space and the YCbCr color space is as follows.
Y = 0.299 R + 0.587 G + 0.114 B,
C b = -0.1687 R-0.311 G + 0.5 B,
C r = 0.5 R-0.419 G-0.0813 B,

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The output brightness determining unit 110 may determine the output brightness of the first color space by applying the input brightness of the first color space, the input brightness of the second color space, and the output brightness of the second color space to Equation (1) have.

Figure 112014104152181-pat00003

The output color coordinate determining unit 120 can determine the output color coordinate of the second color space using the brightness plane of the first color space according to the output brightness of the first color space and the input brightness of the first color space.

In this case, the brightness plane of the first color space may include a first brightness plane and a second brightness plane having a brightness value smaller than that of the first brightness plane. For example, the first brightness plane may be formed at a position where the brightness value is 1/3 in the first color space, and the second brightness plane may be formed at a position where the brightness value is 2/3 in the first color space.

When the input brightness of the first color space and the output brightness of the first color space are darker than the brightness of the first brightness plane, the output color coordinate determining unit 120 determines whether the input color coordinate is black, The output color coordinates of the second color space can be determined using the input luminance of the first color space, the output luminance of the second color space, and the input color coordinates of the second color space.

For example, a first brightness plane is formed at a position where the brightness value of the first color space is 1/3, and the input brightness n i of the first color space and the output intensity of the first color space ) n o can satisfy Equation (2). In addition, n i denotes the brightness of the input color coordinate, and is defined as n i = (r i + g i + b i ) / 3. In this case, r may denote Red, g may denote Green, and B may denote Blue. And r, g, b are

Figure 112016063112396-pat00004
Lt; / RTI >

Figure 112014104152181-pat00005

At this time, the brightness of the output color coordinate of the second color space may become brighter than the brightness of the input color coordinate. Accordingly, the output color coordinate determining unit 120 can determine the output color coordinates of the second color space by linear interpolation between the input color coordinates of the second color space and black (0, 0). For example, the output color coordinate determining unit 120 may determine the output color coordinates C bo and C ro of the second color space using Equation (3).

Figure 112014104152181-pat00006

Where Y i is the input luminance of the second color space and Y o is the output luminance of the second color space. Further, C bi may be a coordinate of an input color coordinate of C b of a color difference of the second color space, and C ri may be a coordinate of an input color coordinate of C r of a color difference of the second color space. And, C bo may be a first and a second output color coordinates of a color space of C b of the color difference color space, C ro is the second output of the color space of the color coordinate of the second color difference of the C r color space.

When the input brightness of the first color space is darker than the brightness of the first brightness plane and the output brightness of the first color space is brighter than the brightness of the first brightness plane, The output color coordinates of the second color space can be determined by mapping the input brightness to the first brightness plane.

Specifically, the output color coordinate determiner 120 may map the input brightness of the first color space to the first brightness plane. Next, the output color coordinate determining unit 120 determines the mapping of the mapped points using the input color coordinates of the second color space, the input luminance of the second color space, and the mapping luminance of the point to which the input brightness of the first color space is mapped The coordinates of the color coordinates can be determined. Finally, the output color coordinate determining unit 120 can determine the output color coordinate of the second color space by using a straight line connecting the mapped point and white, a mapping luminance, a mapping chromaticity coordinate, and an output luminance of the input image.

For example, the first brightness plane is formed at a position where the brightness value of the first color space is 1/3, the input brightness n i of the first color space, and the output brightness n o of the first color space satisfy Equation 4 Can be satisfied.

Figure 112014104152181-pat00007

In this case, the output color coordinate determining unit 120 is the input brightness n i a first luminance plane in the mapping, and outputs the luminance Y o and the first luminance plane the point maps the luminance Y i 'for a second color space using the map to the The output color coordinates C bo and C ro can be determined. In this case, mapping the luminance Y i 'can be the input luminance Y i of the input brightness value n i is mapped into a first luminance plane. For example, the output color coordinate determiner 120 may determine (Y i ', C bi ', C ri ') coordinates of a point mapped to the first brightness plane using Equation (5).

Figure 112014104152181-pat00008

The output color coordinate determining unit 120 linearly interpolates the output color on a straight line connecting the mapped point and white (1 0 0) as shown in Equation (6) to obtain the output color coordinates C bo and C ro of the second color space You can decide.

Figure 112014104152181-pat00009

When the input brightness of the first color space is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness of the second color space is larger than the input brightness of the second color space, Unit 120 determines the output color coordinate of the second color space using a straight line connecting the input color coordinate and white, an output luminance of the second color space, an input luminance of the second color space, and an input color coordinate of the second color space .

For example, a first brightness plane is formed at a position where the brightness value of the first color space is 1/3, a second brightness plane is formed at a position where the brightness value of the first color space is 2/3, The input brightness n i of the color space, the input luminance Y i of the second color space, and the output luminance Y o can satisfy Equation (7).

Figure 112014104152181-pat00010

At this time, the output color coordinate determining unit 120 determines the linear interpolation between the input color coordinate and the output color coordinate of the second color space using the output luminance Y o on a straight line connecting the input color coordinate and white (1 0 0) , It is possible to determine the output color coordinates C bo and C ro of the second color space.

Figure 112014104152181-pat00011

When the input brightness of the first color space is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness of the second color space is smaller than the input brightness of the second color space, Unit 120 determines the output color coordinate of the second color space using a straight line connecting the input color coordinate and black, an output luminance of the second color space, an input luminance of the second color space, and an input color coordinate of the second color space .

For example, a first brightness plane is formed at a position where the brightness value of the first color space is 1/3, a second brightness plane is formed at a position where the brightness value of the first color space is 2/3, The input brightness n i of the color space, the input luminance Y i of the second color space, and the output luminance Y o can satisfy Equation (9).

Figure 112014104152181-pat00012

At this time, the output color coordinate determining unit 120 determines the linear interpolation between the input color coordinate and the output color coordinate of the second color space using the output luminance Y o on a straight line connecting the input color coordinate and the black color (0 0 0) , It is possible to determine the output color coordinates C bo and C ro of the second color space.

Figure 112014104152181-pat00013

When the input brightness of the first color space is brighter than the brightness of the second brightness plane and the output brightness of the first color space is darker than the brightness of the second brightness plane, The output color coordinates of the second color space can be determined by mapping the input brightness to the second brightness plane.

Specifically, the output color coordinate determiner 120 may map the input brightness of the first color space to the second brightness plane. Next, the output color coordinate determining unit 120 determines the mapping of the mapped points using the input color coordinates of the second color space, the input luminance of the second color space, and the mapping luminance of the point to which the input brightness of the first color space is mapped The color coordinates can be determined. Finally, the output color coordinate determiner 120 may determine an output color coordinate of the second color space using a straight line connecting the mapped point and black, a mapping luminance, a mapping chromaticity coordinate, and an output luminance of the input image.

For example, a second brightness plane is formed at a position where the brightness value of the first color space is 2/3, and the input brightness n i of the first color space and the output brightness n o of the first color space satisfy Equation (11) Can be satisfied.

Figure 112014104152181-pat00014

At this time, the output color coordinate determiner 120 maps the input brightness n i to the second brightness plane, and uses the mapping brightness Y i 'of the point mapped to the output brightness Y o and the second brightness plane, The output color coordinates C bo and C ro can be determined. For example, the output color coordinate determining unit 120 may determine the coordinates (Y i ', C bi ', C ri ') of the point mapped to the second brightness plane using Equation (12).

Figure 112014104152181-pat00015

Here, Y i 'may be a mapping brightness determined by linear mapping between input color coordinates and white, and n i ' may be an input brightness mapped to the second brightness plane.

The output color coordinate determining unit 120 linearly interpolates the output luminance Y o on a straight line connecting the mapped point and black (0 0 0) as shown in Equation (13) to obtain the output color coordinate C bo of the second color space C ro can be determined.

Figure 112014104152181-pat00016

In addition, when the input brightness of the first color space and the output brightness of the first color space are brighter than the brightness of the second brightness plane, the output color coordinate determining unit 120 determines a straight line connecting the input color coordinates and white, The output color coordinates of the second color space can be determined using the input luminance, the output luminance of the second color space, and the input color coordinates of the second color space.

For example, the second brightness plane is formed at a position where the brightness value of the first color space is 2/3, and the input brightness n i of the first color space and the output brightness n o of the first color space satisfy Equation (14) Can be satisfied.

Figure 112014104152181-pat00017

In this case, both the input brightness of the first color space and the output brightness of the first color space may be located between the second brightness plane of the first color space and white (1 0 0). Accordingly, the output color coordinate determining unit 120 can determine the output color coordinates of the second color space by linear interpolation between the input color coordinates of the second color space and white (1, 0). For example, the output color coordinate determining unit 120 may determine the output color coordinates C bo and C ro of the second color space using Equation (15).

Figure 112014104152181-pat00018

The image processing apparatus 100 according to an embodiment of the present invention using the input luminance and the output luminance of the input brightness of the RGB color space from the input image and YC b C r color space and determines output brightness of the RGB color space, By determining the output color coordinates of the second color space in the YC b C r color space using the output brightness of the determined RGB color space, it is possible to reduce the color saturation even if the color saturation increases in the YC b C r color space It is possible to improve the saturation.

2 is an example of a brightness plane of an RGB color space according to an embodiment of the present invention.

The image processing apparatus 100 may divide the RGB color space into three through the brightness plane as shown in FIG. For example, as shown in FIG. 2, the image processing apparatus 100 may use a first brightness plane 210 located at a 1/3 point in the RGB color space and a brightness plane 220 located at a 2/3 point in the RGB color space The RGB color space can be divided into three.

In addition, the position of the brightness plane referred to in the present invention is not limited, and may be varied according to the embodiment. For example, the brightness plane may be located at the x / y point (where x and y are different real numbers) in the RGB color space. In other words, the brightness plane may exist at any point in the RGB color space, and the present invention is not limited thereto.

3 is a view illustrating a method of compensating colors in the color space YC b Cr according to one embodiment of the invention.

The image processing apparatus 100 may use an arithmetic average of red, green, and blue, which are the intensities of the RGB color space, as n. In addition, the image processing device 100 may define a Y of YC b C r color space into a luminance.

Then, the image processing unit 100 may define the brightness of the output image output from the brightness of the input image which is input n i, the image processing apparatus 100 to the image processing apparatus 100 to n o. The image processing apparatus 100 may define the luminance of the input image to be input to the image processing apparatus 100 as Y i and define the luminance of the output image output from the image processing apparatus 100 as Y o .

At this time, the image processing apparatus 100 can determine n o by applying Y i , Y o, and n i to Equation (16).

Figure 112014104152181-pat00019

If the output brightness is darker than the input brightness, such as n o <n i , Y o <Y i , the output color coordinate of the output image is the linear interpolation between the input color coordinate of the input image and black (0, 0, 0)

Figure 112016063112396-pat00020
. In addition, when the output brightness becomes brighter than the input brightness, the output color coordinate of the output image is linearly interpolated with the input color coordinate of the input image and white (1, 1, 1)
Figure 112016063112396-pat00021
Wow
Figure 112016063112396-pat00022
.

For example, in Figure 3 the input color coordinate 310 is a straight line that is connected to the black (0, 0, 0) Thus, lightening, As the luminance is bright in the Y i to Y o, the output color coordinates C o '(320 ) Can be changed from n i to n o '. In other words

Figure 112016063112396-pat00023
.

However, the input color coordinate 310 in case that brightness along the line is connected with a white (1,1,1), As the luminance is bright in the Y i to Y o, the brightness of the output color coordinates C o (330) is n i n o . &lt; / RTI &gt;

At this time, if the coordinates of the output color coordinate C o (330) are defined as (r o , g o , b o ) and (Y o , Cb o , Cr o )

Figure 112016063112396-pat00024
The
Figure 112016063112396-pat00025
. According to the YCbCr color space and the RGB color space conversion formula, a = 1, b = 0.476, and c = 0.230 can be calculated. In other words,
Figure 112016063112396-pat00026
.

Then, the image processing apparatus 100 corrects the input color coordinates of the YC b C r color space according to the determined Y i , Y o , n i, and n o to calculate the output color coordinates of the second color space in the YC b C r color space You can decide.

That is, the image processing device 100 may be calculated by the complexity quickly and simply determine the high n o, fast the RGB color space to YC b C r color space conversion using the equation (15).

4 is a diagram illustrating an image processing result for a Macbeth chart according to an embodiment of the present invention.

In FIG. 4, a1 represents a Macbeth chart in an overexposed environment, and a2 represents a Macbeth chart in a low exposure environment. And, b1 and b2 are the results of applying the conventional method to a1 and a2, respectively, and c1 and c2 are the results of applying the present invention to a1 and a2, respectively. Referring to FIG. 4, it can be seen that the saturation of c1 and c2 is relatively higher than that of b1 and b2.

5 is a diagram illustrating an image processing result of an actual image according to an embodiment of the present invention.

In FIG. 5, a1 represents the actual image in the overexposed environment, and a2 represents the actual image in the low exposure environment. And, b1 and b2 are the results of applying the conventional method to a1 and a2, respectively, and c1 and c2 are the results of applying the present invention to a1 and a2, respectively. Referring to FIG. 4, it can be seen that the saturation of c1 and c2 is relatively higher than that of b1 and b2. Also, c1 and c2 are much more natural and livelier than b1 and b2.

6 is a diagram illustrating an image processing method according to an embodiment of the present invention.

In step 610, the output brightness determining unit 110 calculates the output brightness of the first color space using the input brightness of the first color space, the input brightness of the second color space, and the output brightness of the second color space You can decide. For example, the first color space is a RGB color space and second color space may be a YC b C r color space.

In step 620, the output color coordinate determining unit 120 determines the output color coordinates of the second color space using the brightness plane of the first color space according to the output brightness of the first color space and the input brightness of the first color space determined in step 610, Can be determined. For example, the first brightness plane may be formed at a position where the brightness value is 1/3 in the first color space, and the second brightness plane may be formed at a position where the brightness value is 2/3 in the first color space.

In this case, when the input brightness of the first color space and the output brightness of the first color space are darker than the brightness of the first brightness plane, the output color coordinate determining unit 120 determines a straight line connecting the input color coordinate and black, The output color coordinates of the second color space can be determined using the input luminance of the first color space, the output luminance of the second color space, and the input color coordinates of the second color space.

When the input brightness of the first color space is darker than the brightness of the first brightness plane and the output brightness of the first color space is brighter than the brightness of the first brightness plane, The output color coordinates of the second color space can be determined by mapping the input brightness to the first brightness plane. Specifically, the output color coordinate determiner 120 may map the input brightness of the first color space to the first brightness plane. Next, the output color coordinate determining unit 120 determines the mapping of the mapped points using the input color coordinates of the second color space, the input luminance of the second color space, and the mapping luminance of the point to which the input brightness of the first color space is mapped The color coordinates can be determined. Finally, the output color coordinate determining unit 120 can determine the output color coordinate of the second color space by using a straight line connecting the mapped point and white, a mapping luminance, a mapping chromaticity coordinate, and an output luminance of the input image.

When the input brightness of the first color space is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness of the second color space is larger than the input brightness of the second color space, Unit 120 determines the output color coordinate of the second color space using a straight line connecting the input color coordinate and white, an output luminance of the second color space, an input luminance of the second color space, and an input color coordinate of the second color space .

When the input brightness of the first color space is a value between the brightness of the first brightness plane and the brightness of the second brightness plane and the output brightness of the second color space is smaller than the input brightness of the second color space, Unit 120 determines the output color coordinate of the second color space using a straight line connecting the input color coordinate and black, an output luminance of the second color space, an input luminance of the second color space, and an input color coordinate of the second color space .

When the input brightness of the first color space is brighter than the brightness of the second brightness plane and the output brightness of the first color space is darker than the brightness of the second brightness plane, The output color coordinates of the second color space can be determined by mapping the input brightness to the second brightness plane. Specifically, the output color coordinate determiner 120 may map the input brightness of the first color space to the second brightness plane. Next, the output color coordinate determining unit 120 determines the mapping of the mapped points using the input color coordinates of the second color space, the input luminance of the second color space, and the mapping luminance of the point to which the input brightness of the first color space is mapped The color coordinates can be determined. Finally, the output color coordinate determiner 120 may determine an output color coordinate of the second color space using a straight line connecting the mapped point and black, a mapping luminance, a mapping chromaticity coordinate, and an output luminance of the input image.

In addition, when the input brightness of the first color space and the output brightness of the first color space are brighter than the brightness of the second brightness plane, the output color coordinate determining unit 120 determines a straight line connecting the input color coordinates and white, The output color coordinates of the second color space can be determined using the input luminance, the output luminance of the second color space, and the input color coordinates of the second color space.

In the present invention, the output brightness of the RGB color space is determined using the input luminance and output luminance of the color space representing the input brightness and luminance of the RGB color space in the input image, and the output brightness of the RGB color space is used to represent the luminance By determining the output color coordinates of the second color space of the color space, it is possible to improve the chroma while preserving the hue in the color space representing the luminance.

Further, in the present invention, when a luminance component in a color space such as YCbCr is changed, after the luminance conversion for changing the hue to RGB space and improving the saturation is performed, the luminance conversion The saturation can be improved.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

110: output brightness determining unit
120: output color coordinate determining unit

Claims (14)

Determining an output brightness of the first color space using the input brightness of the first color space, the input luminance of the second color space, and the output luminance of the second color space in the input image; And
Determining an output color coordinate of the second color space using the brightness plane of the first color space according to the output brightness and the input brightness,
Lt; / RTI &gt;
Wherein determining the output brightness comprises:
Determining the output brightness by applying the input brightness, the input brightness, and the output brightness to Equation (1)
The first color space is an RGB color space
The second color space is a YCbCr color space in which the RGB color space is converted according to a color space conversion formula,
The input brightness and output brightness are defined as (R + G + B) / 3,
Wherein the input luminance and the output luminance are defined as Y, which is a luminance component of a YCbCr color space.
[Equation 1]
Figure 112016063112396-pat00027
 delete delete The method according to claim 1,
Wherein the brightness plane of the first color space
And a second brightness plane having a smaller brightness value than the first brightness plane and the first brightness plane. 5. The method of claim 4,
Wherein the step of determining an output color coordinate of the second color space comprises:
Wherein when the input brightness and the output brightness are darker than the brightness of the first brightness plane, the input color coordinate and the input color coordinate of the second color space are used as a straight line connecting the input color coordinate and the black color, Wherein an output color coordinate of the color space is determined. 5. The method of claim 4,
Wherein the step of determining an output color coordinate of the second color space comprises:
Mapping the input brightness to a first brightness plane when the input brightness is darker than the brightness of the first brightness plane and the output brightness is brighter than the brightness of the first brightness plane;
Determining a mapping color coordinate of the mapped point using a mapping luminance of an input color coordinate, the input luminance, and a point mapped to the input brightness of the second color space; And
Determining an output chromaticity coordinate of the second color space using a straight line connecting the mapped point and white, the mapping luminance, the mapping chromaticity coordinate, and the output luminance of the input image,
And an image processing method. 5. The method of claim 4,
Wherein the step of determining an output color coordinate of the second color space comprises:
Wherein the input brightness is a value between the brightness of the first brightness plane and the brightness of the second brightness plane, and when the output brightness is larger than the input brightness, a straight line connecting the input color coordinate and white, the output brightness, And the output color coordinate of the second color space is determined using the input color coordinates of the second color space. 5. The method of claim 4,
Wherein the step of determining an output color coordinate of the second color space comprises:
The input brightness is a value between the brightness of the first brightness plane and the brightness of the second brightness plane, and when the output brightness is smaller than the input brightness, a straight line connecting the input color coordinate and black, And an output color coordinate of the second color space is determined using an input color coordinate of the second color space. 5. The method of claim 4,
Wherein the step of determining an output color coordinate of the second color space comprises:
Mapping the input brightness to a second brightness plane when the input brightness is brighter than the brightness of the second brightness plane and the output brightness is darker than the brightness of the second brightness plane;
Determining a mapping color coordinate of the mapped point using a mapping luminance of an input color coordinate, the input luminance, and a point mapped to the input brightness of the second color space; And
Determining an output color coordinate of the second color space using a straight line connecting the mapped point and black, the mapping luminance, the mapping chromaticity coordinates, and the output luminance of the input image,
And an image processing method. 5. The method of claim 4,
Wherein the step of determining an output color coordinate of the second color space comprises:
Wherein when the input brightness and the output brightness are brighter than the brightness of the second brightness plane, the input color coordinate and the input color coordinate of the second color space are used as a straight line connecting the input color coordinate and white, Wherein the output color coordinates of the space are determined. An output brightness determining unit for determining an output brightness of the first color space by using the input brightness of the first color space, the input brightness of the second color space, and the output brightness of the second color space in the input image; And
An output color coordinate determining unit for determining an output color coordinate of the second color space using the brightness plane of the first color space according to the output brightness and the input brightness,
Lt; / RTI &gt;
The output brightness determining unit may determine,
Determining the output brightness by applying the input brightness, the input brightness, and the output brightness to Equation (1)
The first color space is an RGB color space
The second color space is a YCbCr color space in which the RGB color space is converted according to a color space conversion formula,
The input brightness and output brightness are defined as (R + G + B) / 3,
Wherein the input luminance and the output luminance are defined as Y, which is a luminance component of a YCbCr color space.
[Equation 1]
Figure 112016063112396-pat00028
 delete delete 12. The method of claim 11,
Wherein the brightness plane of the first color space
And a second brightness plane having a smaller brightness value than the first brightness plane and the first brightness plane.
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