CN106454301B - A kind of color gamut matching method based on Lxy linear chromas space - Google Patents

Abstract

The invention discloses a color gamut matching method based on the Lxy linear chromaticity space. Through the chromaticity model, three dimensional indicators of color calibration are redefined in the Lxy space, including relative brightness, chromaticity direction and saturation; According to this definition, the color gamut matching is realized, which greatly improves the calculation speed and execution efficiency, is conducive to the realization of hardware programming, and has lower requirements for decoding hardware parameters such as storage space and maximum main frequency, while maintaining the traditional color gamut The advantage of matching algorithm white balance point does not drift.

Description

A Color Gamut Matching Method Based on Lxy Linear Chromaticity Space

technical field

The invention relates to the field of display design, in particular to a color gamut matching method based on Lxy linear chromaticity space.

Background technique

With the continuous development and breakthrough of display technology, compared with earlier CRT, LCD and other types of displays, the current OLED technology and quantum dot backlight technology have greatly expanded the range of colors that display devices can represent. However, while the display effect is continuously optimized and the picture quality is continuously improved, the difference in the performance of the same image content on displays with different color gamuts is also increasing. In order to be compatible with different basic properties such as primary colors and color gamuts of different display devices, color gamut matching is the most commonly used method. The traditional color gamut matching method is based on the Lab color space. In order to ensure the premise of color gamut matching with constant hue angle in this space, a large number of complex calculations and data storage are required. The color gamut of the display is reconstructed and stored in the Lab space by high-density sampling, and then according to different matching Algorithm for color mapping. The traditional color gamut matching algorithm can maintain the chromaticity fluctuation before and after matching to a large extent, and at the same time, the white balance point will not drift due to matching. However, the complex calculation process puts forward huge requirements for the hardware implementation of real-time decoding, and the design and implementation costs are very high.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a color gamut matching method based on the Lxy linear chromaticity space. Through the chromaticity model, the three dimensional indicators of color calibration are redefined in the Lxy space , the color gamut matching is realized according to the definition, the calculation process is simple, and the deficiency of the prior art is solved.

Technical solution: In order to achieve the above object, the present invention adopts a color gamut matching method based on Lxy linear chromaticity space, which is characterized in that the method comprises the following steps:

1) Define the color dimension in the Lxy linear color gamut space;

2) Map the color coordinate points to achieve color gamut matching.

Further, in step 1), the color dimension includes three dimensional parameters, and the three dimensional parameters include relative brightness, chromaticity direction and saturation;

In the definition of the original color gamut, the maximum brightness of the display is L _omax , and the brightness of the color itself in the original color gamut is L _o , then the relative brightness of the original color gamut

Define the color coordinates of the white balance point displayed in the original color gamut as (x _wo , y _wo ), and the color coordinates as (x _o , y _o ), then the chromaticity direction of the color is the direction from the white balance point to the color point vector direction;

Define the point where the white balance point intersects the color gamut boundary along the chromaticity direction in the original color gamut is a point with 100% saturation, and the color saturation is the ratio of the distance from this point to the white balance point and the intersection point of the color gamut boundary to the white balance point.

Further, the three dimensional parameters are associated with the color gamut of the display where the color is located.

Further, through the three dimensional parameters in step 1), the color in the original color gamut is mapped to the color coordinate point in the target color gamut that has the same characteristic parameters as it, to achieve color gamut matching.

Furthermore, if the saturation of a color point in the original color gamut is 0, the chromaticity direction of the point does not need to be considered, and the saturation of the mapping point of the target color gamut should also be 0, and the relative brightness remains unchanged.

Beneficial effects: the present invention discloses a color gamut matching method based on Lxy linear chromaticity space. The method is based on 1931CIE chromaticity space, and redefines three dimensions of color calibration in Lxy space through a reasonable chromaticity model index. One-to-one mapping of colors is realized according to the new definition in the original color gamut and the target color gamut. Compared with the traditional color gamut mapping in the Lab space, this color gamut matching algorithm greatly improves the calculation speed and execution efficiency, which is conducive to the realizability of hardware programming, and the storage space, the highest main frequency and other decoding hardware parameters. The requirements are also lower, and at the same time, the advantage of the traditional color gamut matching algorithm that the white balance point does not drift is maintained.

Description of drawings

Figure 1 is a schematic diagram of the chromaticity direction

Figure 2 is a schematic diagram of the value of saturation

Figure 3 is a schematic diagram of the relative brightness, chromaticity direction and saturation of the color coordinate point in the original color gamut color point and the target color gamut mapping point in their respective color gamuts

Fig. 4 is the distribution of each color coordinate in the implementation example

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

A color gamut matching method based on Lxy linear chromaticity space, is characterized in that, the method comprises the following steps:

1) Define the color dimension in the Lxy linear color gamut space;

The color dimension includes three dimensional parameters, the three dimensional parameters include relative brightness, chromaticity direction and saturation; the three dimensional parameters defined above are all related to the color gamut of the display where the color is located. Even for points with the same xy coordinates, the three dimensional parameters are not necessarily the same under different color gamuts.

In the definition of the original color gamut, the maximum brightness of the display is L _omax , and the brightness of the color itself in the original color gamut is L _o , then the relative brightness of the original color gamut

Define the color coordinates of the white balance point displayed in the original color gamut as (x _wo , y _wo ), and the color coordinates as (x _o , y _o ), then the chromaticity direction of the color is the direction from the white balance point to the color point vector Direction; Vector as shown in Figure 1.

Define the point where the white balance point intersects the color gamut boundary along the chromaticity direction in the original color gamut is a point with 100% saturation, and the color saturation is the ratio of the distance from this point to the white balance point and the intersection point of the color gamut boundary to the white balance point. Calculate the value of the ratio, as shown in Figure 2.

2) Map the color coordinate points to achieve color gamut matching.

Further, through the three dimensional parameters in step 1), the color in the original color gamut is mapped to the color coordinate point in the target color gamut that has the same characteristic parameters as it, to achieve color gamut matching.

That is, among the color coordinate points mapped to each other, the original color gamut color point (x _o , y _o ) and the target color gamut mapping point (x _t , y _t ) have the same relative brightness, chromaticity direction and saturation in their respective color gamuts degrees, as shown in Figure 3. If the saturation of a color point is 0 in the original color gamut, the chromaticity direction of the point does not need to be considered, and the saturation of the mapping point of the target color gamut should also be 0, and the relative brightness remains unchanged.

Specific examples:

The simulation environment is two monitors with different color coordinates of the three primary colors and the white balance point. The gamma values of the two monitors are both 2.2. The specific color gamut distribution is as follows:

In original color gamut:

Original red primary color (x _ro , y _ro )=(0.64,0.33);

Original green primary color (x _go , y _go )=(0.30,0.60);

Original blue primary color (x _bo , y _bo )=(0.15,0.06);

Original white balance (x _wo , y _wo ) = (0.3127, 0.329);

In target color gamut:

Target red primary color (x _rt , y _rt )=(0.67,0.33);

Target green primary color (x _gt , y _gt )=(0.21,0.71);

Target blue base color (x _bt , y _bt )=(0.14,0.08);

Target white balance (x _wt , y _wt )=(0.31, 0.316).

The grayscale combination of a certain pixel point P is [128,234,65], then the color coordinates of this point are (x _s , y _s )=(0.333,0.5408), and the relative brightness l _o in the original color gamut =0.6422.

The chromaticity direction of this point is the direction pointed by the vector from the white balance point to the color point, specifically, the direction represented by the vector [0.0203,0.2118].

The intersection point of the chromaticity direction and the boundary of the original color gamut is (0.3359, 0.5715). By calculating the ratio of the distance from the color point to the white point and the distance from the boundary intersection point to the point, the saturation of this point can be obtained as 0.8735.

So far, the characterization parameters of the color in all dimensions of the original color gamut have been calculated. In order to achieve one-to-one mapping in the target color gamut, in the same chromaticity direction, the intersection point with the target color gamut boundary is (0.3376, 0.6043), and when the saturation is the same, the color coordinates of the mapping point of the target color gamut are (0.3341, 0.5679) , the reverse conversion grayscale combination is [158,244,62].

The distribution of each color coordinate point involved in the above algorithm is shown in Figure 4.

So far, under the condition that both the original color gamut and the target color gamut are determined, the matching of any grayscale combination is completely realized.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (4)

1. a kind of color gamut matching method based on Lxy linear chromas space, which is characterized in that this approach includes the following steps：

1) in Lxy linear chroma definition space color dimensions；

2) chromaticity coordinates point is mapped, realizes colour gamut matching；

In step 1), the color dimension includes three dimensional parameters, which includes relative luminance, chromaticity direction And saturation degree；

It defines in original color gamut, display maximum brightness is L_omax, color intrinsic brightness is L in original color gamut_o, then original color gamut Relative luminance

It is (x to define the white balance point chromaticity coordinates shown in original color gamut_wo,y_wo), color chromaticity coordinates is (x_o,y_o), then the color Chromaticity direction be the direction be directed toward to color point vector of white balance point；

Defining white balance point in original color gamut, along chromaticity direction and the point that gamut boundary intersection is saturation degree 100%, color is full It is color chromaticity coordinates point to white balance point distance and gamut boundary intersection point to the ratio of white balance point distance with degree.

2. a kind of color gamut matching method based on Lxy linear chromas space as described in claim 1, which is characterized in that described Three dimensional parameters are associated with the display color gamut where color.

3. a kind of color gamut matching method based on Lxy linear chromas space as described in claim 1, which is characterized in that pass through Three dimensional parameters in step 1), the color in original color gamut is mapped in target color gamut with it with identical characterization parameter Chromaticity coordinates point, realize colour gamut matching.

4. a kind of color gamut matching method based on Lxy linear chromas space as claimed in claim 3, which is characterized in that if color Color spot saturation degree in original color gamut is 0, then without considering, the mapping point saturation degree of target color gamut is also answered in the chromaticity direction of the point It is 0, and relative luminance is constant.