CN112292851A

CN112292851A - Color gamut correction method and device

Info

Publication number: CN112292851A
Application number: CN201880094881.4A
Authority: CN
Inventors: 刘洋; 许景翔; 裴朝科
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-06-30
Filing date: 2018-06-30
Publication date: 2021-01-29
Anticipated expiration: 2038-06-30
Also published as: CN112292851B; WO2020000477A1

Abstract

A color gamut correction method and device, the method includes: calculating a brightness value corresponding to the first color value; the first color value is a color value of a color on a display gamut of the image source; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of the display screen, and the brightness value corresponding to the first color value includes a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B(ii) a Obtaining voltage drop correspondence according to the brightness value corresponding to the first color value and the first matrixThe color value increment of (a), the color value increment being an increment of a color value of the color caused by a voltage drop across a display gamut of the display screen; the color value increment comprises a red increment value delta R, a green increment value delta G and a blue increment value delta B; the first matrix represents the effect of voltage drop on the color values of the colors over the display gamut of the display screen; and compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment. By implementing the embodiment of the application, the accuracy of displaying colors on the display screen can be improved.

Description

Color gamut correction method and device

Technical Field

The present application relates to the field of display technologies, and in particular, to a color gamut correction method and apparatus.

Background

In the field of display technology, an active-matrix organic light emitting diode (AMOLED) type display has characteristics of being light and thin, low in power consumption, foldable, and wide in color gamut. It is considered as a next generation display technology following a Liquid Crystal Display (LCD). Currently, the AMOLED is gradually applied to terminal devices such as televisions, flat panels, and mobile phones.

When the AMOLED display screen is used for displaying, the brightness is in direct proportion to the current flowing through the AMOLED display screen. And the current will generate a voltage drop when flowing through the traces in the display screen. In particular, the narrower the metal interconnection line, the resistance value increases, which causes a significant voltage drop, and thus causes a display screen to have non-uniform display brightness, which is called IR drop (IR drop). In addition, voltage drop may occur due to influence of threshold voltage and mobility of the driving transistor, threshold voltage shift of the LED, and the like in different display regions. Due to the influence of voltage drop, the brightness value and the chromaticity coordinate corresponding to each color value component of the display screen can generate deviation, so that the color value displayed by the display screen can generate deviation, and the accuracy of the color value displayed by the display screen is reduced.

Disclosure of Invention

The embodiment of the application discloses a color gamut correction method and a color gamut correction device, which can improve the accuracy of a color value displayed by a display screen.

In a first aspect, an embodiment of the present application provides a color gamut correction method, including: calculating a brightness value corresponding to the first color value; the first color value is a color value of a color on a display gamut of an image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of a display screen, and the brightness value corresponding to the first color value comprises a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B(ii) a Obtaining a color value increment corresponding to voltage drop according to the brightness value corresponding to the first color value and the first matrix, wherein the color value increment is the increment of the color value of the color on the display color gamut of the display screen caused by the voltage drop; the color value increments include a red increment value Δ R, a green increment value Δ G, and a blue increment value Δ B; the first matrix represents the effect of the voltage drop on the color value of the color over the display gamut of the display screen; and compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment.

By the color gamut correction method, the brightness value of the first color value is calculated, and then the brightness value corresponding to the first color value and the first matrix are used for obtaining the deviation of the display color value of the display screen caused by voltage drop and compensating the deviation, so that the deviation of the display color of the display screen caused by voltage drop can be reduced, and the accuracy of color display in the equipment is improved.

Optionally, the process of incrementally compensating the voltage drop according to the color value may specifically be: the gamut correction device may first determine a second color value corresponding to the first color value; the second color value is a color value corresponding to the first color value over a display gamut of the display screen, the second color value comprising a red component value R2, a green component value G2, and a blue component value B2; then, overlapping the second color value and the color value increment to obtain a third color value; then compensating the deviation of the color value of the display screen caused by the voltage drop by using the third color value; wherein the third color value includes a red component value R3, a green component value G3, and a blue component value B3.

The first color value is a linear color value, and if the color value received by the gamut correction device is non-linear, for example, the received color value of the first color is: the red component value R0, the green component value G0, and the blue component value B0 are all non-linear. The gamut correction device may first convert the nonlinear color values: the red component value R0, the green component value G0, and the blue component value B0 are converted to linear first color values, including a red component value R1, a green component value G1, and a blue component value B1.

The process of converting the non-linear color value into the linear first color value can be realized by the second lookup table. Specifically, gamma may be 2.2, and the second lookup table may include a mapping relationship between a non-linear color value and a linear first color value; the mapping between the non-linear color value and the linear first color value may be determined by the following formula:

optionally, the second lookup table may have a non-linear color value range corresponding to a linear color value. For example, non-linear color values in the range of (R0- Δ R, R0+ Δ R) each correspond to R1 in the second lookup table. It may also be a non-linear color value corresponding to a linear color value: the linear color value corresponding to the non-linear color value not stored in the second lookup table may be determined by interpolation of the linear first color value corresponding to the non-linear color value stored in the lookup table.

In one embodiment, the determination is madeThe second color value corresponding to the first color value comprises: determining the second color value according to the brightness value corresponding to the first color value and a brightness color conversion formula; the brightness color conversion formula is

Wherein, b_iIs an index parameter corresponding to the color component i, a_iThe coefficients corresponding to the color component i are represented by values of red, green and blue.

In one embodiment, the determining the second color value corresponding to the first color value includes: determining the second color value through a first lookup table, wherein the first lookup table comprises a mapping relation between a brightness value corresponding to the first color value and the second color value, and the mapping relation between the brightness value corresponding to the first color value and the second color value is determined by a brightness color

Determining a conversion formula; the brightness color conversion formula is

Optionally, the brightness may be a brightness value or a brightness range. Specifically, in the first lookup table, one luminance range may correspond to one color value. For example (L)_R0-ΔL，L _R0Brightness values in the range of + Δ L) each correspond to R0 in the first lookup table. In addition, in the first lookup table, one luminance value may correspond to one color value. The color value corresponding to the luminance value not stored in the first lookup table may be determined by interpolation. The first look-up table may be two-dimensional, i.e. the look-up table is a correspondence of luminance to a second color value. The embodiment of the application is realized by using a matrix product and a two-dimensional lookup table, and occupied software and hardware resources are reduced.

In one embodiment, before the determining the second color value corresponding to the first color value, the method further comprises: b is obtained according to the fitting of a plurality of color values of the color component i and the brightness value corresponding to each color value in the plurality of color values_iAnd a_i。

Wherein the fitting yields b_iAnd a_iThe specific process of (2) may be: for the red color component value R, different red color values and the corresponding brightness values of the red color values can be measured and fitted to obtain a_R、b _R. For the green color component value G, different green color values and the corresponding brightness values of the green color values can be measured and fitted to obtain a_G、b _G. For the blue color component value R, different blue color values and the corresponding brightness values of the blue color values can be measured to obtain a_B、b _B。

Illustratively, the specific method of fitting may be implemented using residual sum convergence, gradient descent algorithm, and newton's method convergence.

In the method for determining the coefficients in the brightness conversion formula by the fitting mode, the difference of gamma values during the conversion between linear nonlinearity of the display screens with different process levels is considered, so that the method is more accurate during the color gamut conversion, and the accuracy of the colors displayed by the display screens can be improved.

The above-mentioned brightness value L for calculating the second color value_R、L _GAnd L_BThe color value can be calculated according to the real chromaticity coordinate, so that the influence of the chromaticity coordinate change on the accuracy of the color value is reduced, and the accuracy of the color displayed by the display screen can be improved.

In one embodiment, the calculating the luminance value corresponding to the first color value includes: calculating to obtain the brightness value corresponding to the first color value according to a conversion matrix between the first color space and the second color space and a chromaticity coordinate corresponding to a color component i of the first color value; the first color space is a color space corresponding to a color gamut of the display screen, and the second color space is a color space containing a conversion relationship of converting a color value into a luminance value and converting the color value into a chromaticity coordinate.

In particular, i.e.

Wherein, (xR, yR), (xG, yG), (xB, yB) are chromaticity coordinates and matrix of the display screen R, G and B respectively

Is a color space conversion matrix between a first color space and a second color space.

Alternatively, the first color space may be an sRGB color space and the second color space may be a CIE1931 color space.

In one embodiment, the first matrix comprises a plurality of element values, the plurality of element values are fitted according to a plurality of parameter values of color j and a luminance value corresponding to each parameter value of the plurality of parameter values, and the plurality of parameter values comprises one or more of the following: color values and chromaticity coordinates; the color j is red R, green G, blue B and mixed color; the secondary colors are secondary colors of any two or three of the red, R, green, G, and blue, B.

Specifically, the first matrix is

Wherein, C_RR、C _GGAnd C_BBB can be obtained in the fitting_iAnd a_iWhile obtaining, C_BRIs obtained by measuring multiple chromaticity coordinates (x) of Magenta_M，y _M) And fitting the luminance values corresponding to the chromaticity coordinates. By measuring MagentaMultiple chromaticity coordinates (x)_M，y _M) Fitting the brightness value corresponding to each chromaticity coordinate to obtain C_RB. Measuring chromaticity coordinate and brightness value of Yellow (composed of Red and Green) and Cyan (composed of Green and Blue) respectively to obtain C_RGAnd C_BGC is obtained by measuring the chromaticity coordinates and brightness values of Magenta (consisting of Red and Blue) and Cyan (consisting of Green and Blue)_RBAnd C_GBAnd thus the values of the elements in the first matrix are obtained.

In addition, when the production line is operated, only 4-8 parameter values and brightness values corresponding to different colors need to be measured, wherein the parameter values can be color values or chromaticity coordinates, and the compensation of the color values caused by voltage drop can be realized, so that the measurement time can be saved, and the production line efficiency is improved.

In a second aspect, an embodiment of the present application provides a color gamut correction device, including a processor and a memory, where the memory is used to store program instructions, and the processor is used to call the program instructions to execute: calculating a brightness value corresponding to the first color value; the first color value is a color value of a color on a display gamut of an image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of a display screen, and the brightness value comprises a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B(ii) a Obtaining a color value increment corresponding to voltage drop according to the brightness value corresponding to the first color value and the first matrix, wherein the color value increment is the increment of the color value of the color on the display color gamut of the display screen caused by the voltage drop; the color value increments include a red increment value Δ R, a green increment value Δ G, and a blue increment value Δ B; the first matrix represents the effect of the voltage drop on the color value of the color over the display gamut of the display screen; and compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment.

In the color gamut correcting apparatus, the luminance value of the first color value is calculated, and then the luminance value corresponding to the first color value and the first matrix are used to obtain the deviation of the display color value of the display screen caused by the voltage drop, and compensate the deviation, so that the deviation of the display color of the display screen caused by the voltage drop can be reduced, and the accuracy of color display in the device can be improved.

In one embodiment, the processor is further configured to: determining a second color value corresponding to the first color value; the second color value is a color value corresponding to the first color value over a display gamut of the display screen, the second color value comprising a red component value R2, a green component value G2, and a blue component value B2; the processor is specifically configured to invoke the program instructions to perform: superimposing the second color value and the color value increment to obtain a third color value; compensating for a deviation in color values of the display screen caused by the voltage drop using the third color value; wherein the third color value includes a red component value R3, a green component value G3, and a blue component value B3.

In one embodiment, the processor is specifically configured to: determining the second color value according to the brightness value corresponding to the first color value and a brightness color conversion formula; the brightness color conversion formula is

In one embodiment, the processor is specifically configured to: determining the second color value through a first lookup table, wherein the first lookup table comprises a mapping relation between a brightness value corresponding to the first color value and the second color value, and the mapping relation between the brightness value corresponding to the first color value and the second color value is determined by a brightness-color conversion formula; the brightness color conversion formula is

In one embodiment, the processor is further configured to: b is obtained according to the fitting of a plurality of color values of the color component i and the brightness value corresponding to each color value in the plurality of color values_iAnd a_i。

In one embodiment, the processor is specifically configured to invoke the program instructions to perform: calculating to obtain a brightness value corresponding to the first color value according to a conversion matrix between the first color space and the second color space and a chromaticity coordinate corresponding to a color component i of the first color value; the first color space is a color space corresponding to a color gamut of the display screen, and the second color space is a color space containing a conversion relationship of converting a color value into a luminance value and converting the color value into a chromaticity coordinate.

In a third aspect, an embodiment of the present application provides a color gamut correction device, including a calculation unit, configured to calculate a luminance value corresponding to a first color value; the first color value is a color value of a color on a display gamut of an image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of a display screen, and the brightness value corresponding to the first color value comprises a red brightness value L_RGreen luminance value L_GAnd blueColor brightness value L_B(ii) a An obtaining unit, configured to obtain, according to a luminance value corresponding to the first color value and a first matrix, a color value increment corresponding to a voltage drop, where the color value increment is an increment of a color value of the color on a display color gamut of the display screen due to the voltage drop; the color value increments include a red increment value Δ R, a green increment value Δ G, and a blue increment value Δ B; the first matrix represents the effect of the voltage drop on the color value of the color over the display gamut of the display screen; and the compensation unit is used for compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment.

In one embodiment, the apparatus further comprises: the determining unit is used for determining a second color value corresponding to the first color value; the second color value is a color value corresponding to the first color value over a display gamut of the display screen, the second color value comprising a red component value R2, a green component value G2, and a blue component value B2; the compensation unit is specifically configured to superimpose the second color value and the color value increment to obtain a third color value; compensating for a deviation in color values of the display screen caused by the voltage drop using the third color value; wherein the third color value includes a red component value R3, a green component value G3, and a blue component value B3.

In an embodiment, the determining unit is specifically configured to determine the second color value according to the luminance value and a luminance color conversion formula corresponding to the first color value; the brightness color conversion formula is

In an embodiment, the determining unit is specifically configured to determine the second color value through a first lookup table, where the first lookup table includes a luminance value corresponding to the first color value and the luminance valueThe mapping relation of the second color value, the mapping relation of the brightness value corresponding to the first color value and the second color value is determined by a brightness color conversion formula; the brightness color conversion formula is

In an embodiment, the calculating unit is further configured to fit a plurality of color values of the color component i to a corresponding brightness value of each of the plurality of color values to obtain b_iAnd a_i。

In an embodiment, the calculating unit is specifically configured to calculate, according to a transformation matrix between the first color space and the second color space and a chromaticity coordinate corresponding to a color component i of the first color value, a luminance value corresponding to the first color value; the first color space is a color space corresponding to a color gamut of the display screen, and the second color space is a color space containing a conversion relationship of converting a color value into a brightness value and a chromatic value.

In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, in which program instructions are stored, and when the program instructions are executed by a processor, the method described in the first aspect or any possible implementation manner of the first aspect is implemented.

In a fifth aspect, an embodiment of the present invention provides a computer program product for implementing the method described in the first aspect or any possible implementation manner of the first aspect when the computer program product is run on a processor.

Drawings

The drawings to which embodiments of the present application relate are described below.

Fig. 1 is a scene schematic diagram of color gamut correction provided by an embodiment of the present application;

fig. 2 is an example of an application scenario of color gamut correction provided in an embodiment of the present application;

fig. 3 is a schematic flowchart of a color gamut correction method provided in an embodiment of the present application;

fig. 4 is a schematic structural diagram of a color gamut correction device provided in an embodiment of the present application;

fig. 5 is a schematic structural diagram of another color gamut correction device provided in an embodiment of the present application;

fig. 6 is a schematic structural diagram of an apparatus according to an embodiment of the present disclosure.

Detailed Description

The embodiments of the present application will be described below with reference to the drawings. The terminology used in the description of the embodiments herein is for the purpose of describing particular embodiments herein only and is not intended to be limiting of the application.

First, some concepts or terms referred to by the embodiments of the present application are explained in order to facilitate understanding of the embodiments of the present application.

(1) Gamma correction

Gamma correction is a method for performing nonlinear tone editing on an image, and can detect a dark color part and a light color part in an image signal and increase the proportion of the dark color part and the light color part, thereby improving the contrast effect of the image. The photoelectric conversion characteristics of current display screens, photographic film, and many electronic cameras can all be non-linear. The relationship between the output and the input of these non-linear components can be expressed as a power function, namely: output ═ (input)^γ。

The non-linear conversion of the color values output by the device is due to the fact that the human visual system is not linear, and human senses visual stimuli through comparison. The outside strengthens the stimulus in a certain proportion, and the stimulus is uniformly increased for people. Therefore, the physical quantity increasing in an equal ratio series is uniform to human perception. In order to display the input color according to the human visual law, the linear color value needs to be converted into the nonlinear color value through the nonlinear conversion in the form of the above power function. The value γ of gamma can be determined according to the photoelectric conversion curve of the color space.

(2) Color space

The color may be a different perception of the eye by different frequencies of light, or may represent the presence of different frequencies of light objectively. A color space is a range of colors defined by a coordinate system that one establishes to represent colors. Together with the color model, the color gamut defines a color space. Wherein the color model is an abstract mathematical model representing colors with a set of color components. The color model may include, for example, a Red Green Blue (RGB) mode, a print four Color (CMYK) mode. Color gamut refers to the aggregate of colors that a system is capable of producing. Illustratively, Adobe RGB and sRGB are two different color spaces based on the RGB model.

Each device, such as a display or printer, has its own color space and can only generate colors within its gamut. When moving an image from one device to another, the colors of the image may change on different devices as each device converts and displays RGB or CMYK according to its own color space.

Several commonly used color spaces are described below.

Phi 1931 color space

The CIE1931 color space (also known as CIE1931 XYZ color space) is one of the first mathematically defined color spaces. The CIE XYZ color space is directly measured based on human color vision and can serve as a basis for the definition of other color spaces. The Y parameter used by the CIE XYZ color space is the lightness or brightness of a color. The chromaticity of the color is determined using parameters x and y, the relationship between chromaticity x, y and tristimulus values X, Y and Z being:

the parameters x, Y can be used to determine a color, and for a display screen, the chromaticity coordinates x, Y and the luminance value Y can be measured using a color analyzer. Wherein, X and Z in the tri-stimulus value can be calculated from chromaticity coordinates X and Y and luminance Y:

sRGB color space

sRGB (Standard Red Green blue) color space is a standard RGB color space developed by Hewlett packard and Microsoft in 1996 for displays, printers, and the Internet. It provides a standard method to define colors, allowing various computer peripherals and applications, such as display, print and scan, to have a common language for colors. The color space of sRGB is based on independent color coordinates, and it is possible to make colors correspond to the same color coordinate system in different device usage transmissions without being affected by different color coordinates that these devices have individually. However, the gamut space of sRGB is relatively small. sRGB defines the colors of the three primary colors of red, green, and blue, in which the color value of one of the three primary colors takes the maximum value, and the corresponding color when the color values of the other two colors are both zero represents the one color. For example, in the three primary colors of red, green and blue, the values of the color values R, G and B are all 0-255, and when the value of R, G is zero, the corresponding color represents blue when the value of B is 255.

Conversion between different color spaces is possible, and conversion of the color spaces is described below by taking the CIE1931 color space and the sRGB color space as examples.

The calculation of the three primary colors in sRGB from the CIE XYZ coordinate system first requires its transformation to the CIE XYZ ternary mode. That is, the determination X, Z using equation (3) and equation (4) yields three values X, Y and Z in the CIE1931 color space. Linear R, G and B values are then calculated using the transformation matrix:

sRGB is a color value that reflects a typical display with a real world gamma of 2.2, so the linear value is converted to sRGB using the following transformation formula:

(3) voltage drop

In the field of display technologies, specifically, in the LED display technology, due to the influence of factors such as the drift of the threshold voltage of the driving transistor at different positions, the drift of the threshold voltage of the LED display unit at different positions, and the IR drop (IR drop) of the power line, these factors are converted into the voltage drop generated by the LED display device at different positions, which further causes the current difference and the brightness difference to be perceived by human eyes. The problem of uneven display of the display screen caused by voltage drop needs to be solved through compensation. The threshold voltage shift of the drive transistor, the threshold voltage shift of the LED display unit and the IR drop are described below, respectively.

(ii) threshold voltage drift of drive transistor

The driving transistor may employ a low temperature polysilicon thin film transistor (LTPS TFT) and an Oxide thin film transistor (Oxide TFT). Due to limitations of crystallization processes, transistors fabricated on large-area glass substrates, transistors at different locations often have non-uniformities in electrical parameters such as threshold voltage, mobility, etc., which can translate into current and brightness differences in LED display devices.

Specifically, the current flowing through the LED is I_DataThe brightness of the corresponding display unit is L ═ α I_DataThe threshold voltage of the driving transistor is V_thThe source voltage of the driving transistor is Vs. The brightness of the LED light is:

L＝αI _Data＝αK(V _Data-Vs-V _th) ² (7)

the non-uniformity of the threshold voltage Vth causes non-uniformity of the luminance of the LED light emission, among others. The mobility affects the coefficient K, thereby causing non-uniformity in the brightness of the display screen.

② threshold voltage drift of LED display unit

The LED itself is also aged with an increase in lighting time, and thus the brightness gradually decreases. Specifically, as the LED display unit increases with time, the threshold voltage changes, thereby causing a change in display brightness.

③IR drop

IR drop is a phenomenon that indicates a voltage drop or rise between a voltage and a ground network that occurs in an integrated circuit. The voltage is equal to the product of the current, which may be denoted as "I", and the resistance, which may be denoted as "R", and hence the voltage drop referred to herein as IR drop. With the evolution of semiconductor technology, the width of the metal interconnection line is narrower and narrower, which causes the resistance value of the metal interconnection line to increase, so that a certain IR drop exists in the whole chip range.

On the LED display panel, the drain voltage Vs of the display units at different positions is different due to the IR drop, so that the brightness Lv of the display units at different positions is different, and the brightness of the display screen is uneven.

In the formula (7), V_dataThe relation with the color value displayed by the display screen is V_Dataβ Code, where Code is the color value of the display screen, may take the value of R, G or B. Vs and Vth may be compensated by a compensation circuit or otherwise to cancel the effects of Vs and Vth on luminance. Thus, according to equation (7), the brightness may be related only to the color value Code of the panel, i.e.

L＝sCode ^k (8)

Where s is a coefficient and k is typically 2, different values may be used depending on the device characteristics of the particular drive transistor.

The display screen brightness and chromaticity coordinate deviation caused by the voltage drop directly influences the accuracy of the display color of the display screen.

(3) Color value of display screen

The color value of the display screen refers to values of the three color components R, G and B output to the display screen, the values of R, G and B being non-linear, and the display screen being displayed according to the numerical values. Specifically, after determining a target color value to be displayed, since color gamuts of different display screens are different, the target color value needs to be converted into a color value of the display screen, and if the target color value is determined to be Xt, Yt, and Zt, the color value of the display screen is obtained by conversion according to the following formula:

wherein the content of the first and second substances,

is the value of the color of the display screen,

in, X_R、Y _RAnd Z_RTaking the maximum value of the red color value R of the display screen and the corresponding tristimulus value X_G、Y _GAnd Z_GTaking the maximum value of the green color value G of the display screen and the corresponding tristimulus value X_B、Y _BAnd Z_BAnd taking the corresponding tristimulus value when the display screen blue color value B takes the maximum value. Illustratively, the color values R, G and B of the display screen both take values from 0 to 255, then X_R、Y _RAnd Z_RTaking the corresponding tristimulus value X of 255 as the red color value R of the display screen_G、Y _GAnd Z_GTaking the corresponding tristimulus value X of 255 for the green color value G of the display screen_B、Y _BAnd Z_BAnd taking the corresponding tristimulus value of 255 for the display screen blue color value B.

The display screen related in the embodiment of the present application may be an LED display screen, and may specifically include various organic light-emitting diode (OLED) display screens, such as an AMOLED display screen, a passive matrix organic light-emitting diode (PM-OLED) display screen, and may also include other types of LEDs, and may also include a future emerging type of display, which is not limited in this embodiment of the present application.

Referring to fig. 1, fig. 1 is a scene schematic diagram of color gamut correction according to an embodiment of the present disclosure. As shown in fig. 1, in the color gamut correction scenario, a color gamut of a device needs to be converted from a color gamut of an image source to a display color gamut of a display screen, a color space corresponding to the color gamut of the image source is a first color space, and a second color space may be a color space containing a conversion relationship between a color value and a luminance value, and a chromaticity coordinate, and may be, for example, a CIE1931 color space. In the embodiment of the present application, in the color gamut correction scene, the first color space is an sRGB color space, and the second color space is a CIE1931 color space, which are described as an example, and it can be understood that the color gamut correction scene is not limited to the above example, and the first color space and the second color space may also be other color spaces. Specifically, the color gamut correction scenario may include the following steps:

step one, carrying out linear transformation on the color values of the received colors.

The color value of a color is a color value within the gamut of the image source, since the color value of a color: the red component value R0, the green component value G0, and the blue component value B0 are all non-linear, requiring conversion of the non-linear color values to linear color values prior to color space conversion. A second look-up table 10 may be stored, by means of which second look-up table 10 conversion of non-linear color values into linear color values is achieved. Specifically, the gamma may be 2.2, and the mapping relationship of the second lookup table 10 may be that the input red component value R0, green component value G0 and blue component value B0 are mapped to the red component value R1, green component value G1 and blue component value B1 in sequence. Wherein:

in the second lookup table 10, a non-linear color value range may correspond to a linear color value. For example, non-linear color values in the range of (R0- Δ R, R0+ Δ R) each correspond to R1 in the second lookup table 10. For example, please refer to table 1, where table 1 is an example of a second lookup table provided in an embodiment of the present application.

TABLE 1 example of a second lookup table

R0/G0/B0	0-31	32-63	64-95	……	992-1023
R1/G1/B1	15 ^2.2	47 ^2.2	79 ^2.2	……	1007 ^2.2

As shown in Table 1, the color values R0, G0 and B0 all can take the values of 0-2¹⁰. Taking R0 as an example, for R0 whose values fall within the range of 0-31, the corresponding R1 values in the second lookup table are all 15^2.2For R0 whose values fall within the ranges of 32-63, 64-95 … … 992-1023 in turn, the corresponding values of R1 in the second lookup table are 47 in turn^2.2，79 ^2.2……1007 ^2.2。

In addition, in the second lookup table 10, a non-linear color value may correspond to a linear color value. The linear color values corresponding to the non-linear color values not stored in the second lookup table 10 may be determined by interpolation of the linear color values corresponding to the non-linear color values stored in the lookup table. For example, please refer to table 2, where table 2 is an example of another second lookup table provided in the embodiments of the present application.

Table 2 another example of a second lookup table

R0/G0/B0	0	32	64	……	1023
R1/G1/B1	0	32 ^2.2	64 ^2.2	……	1023 ^2.2

As shown in Table 2, the color values R0, G0 and B0 all can take the values of 0-2¹⁰Taking R0 as an example, the values of R0 are 0, 32, 64 … … 1023, and the corresponding values of R1 in the second lookup table are 0 and 47 in sequence^2.2、79 ^2.2……1007 ^2.2. When the value of R0 is a value other than 0, 32, and 64 … … 1023, the corresponding value of R1 is determined by interpolating the known values of R1 in the second lookup table, for example, when the value of R0 is 25, the value of R1 corresponding to the value of R0 of 25 can be determined by interpolating according to the values of R1 corresponding to the values of R0 of 0, 32, and 64 … … 1023 in turn. In the embodiment of the present application, a specific algorithm used in the interpolation method is not limited, and may be a linear interpolation method, a lagrange interpolation method, or the like, or may use other interpolation methods.

It is to be understood that the above example of the second lookup table is only used for explaining the embodiment of the present application, and should not be construed as limiting. In the embodiment of the present application, the example of gamma being 2.2 is used to describe conversion between a nonlinear color value and a linear color value, the example should not be limited, a specific gamma value may also be determined according to a photoelectric conversion curve of a color space, and the embodiment of the present application does not limit the specific gamma value.

And step two, performing color gamut conversion to obtain the color value of the display screen.

After linear color values of the red component value R1, the green component value G1, and the blue component value B1 are obtained through the second lookup table, color gamut conversion may be performed. The color space conversion involved in the gamut conversion may use equation (5) to obtain the target tristimulus value in CIE1931 color space: xt, Yt and Zt.

Generally, after obtaining the target tristimulus values of the colors in the CIE1931 color space, the target tristimulus values also need to be converted into color values on the display color gamut of the display screen due to the difference of the color gamuts of different display screens. The color space conversion and the color gamut correction of the display screen can be realized simultaneously, and the specific principle is as follows:

in formula (11)

Is the color value within the display gamut of the display screen.

The conversion matrix from the sRGB color space to the 1931 color space may be, specifically, the inverse matrix of the conversion matrix of 3 × 3 in the formula (5). Transforming equation (11) yields:

in formula (11), let

Thus obtaining:

can store

The conversion of the linear color values R1, G1 and B1 output by the second lookup table 10 into linear color values R on the display gamut of the display screen is realized with the 3 × 3 conversion matrix 20_pannel、G _pannelAnd B_pannel。

In addition, a fourth lookup table may also be directly stored, and the fourth lookup table may map linear color values R1, G1 and B1 to color values R on the display gamut of the display screen_pannel、G _pannelAnd B_pannel. The mapping relationship of the fourth lookup table may be obtained by measurement, and a three-dimensional fourth lookup table is established by using a known linear color value and a color value on the display color gamut of the display screen measured by the color analyzer. The three dimensions are respectively R1, G1 and B1, and in the fourth lookup table, the same group of values of the linear color values R1, G1 and B1 can uniquely correspond to the color value R of a group of display screens according to the three dimensions_pannel、G _pannel、B _pannelThe value of (a). When the fourth lookup table searches for the values of R1, G1 and B1 which are not stored, the positions of the linear color values input in the three dimensions of the fourth lookup table are searched, the color values of the display screen are determined through an interpolation method, and the description of the interpolation method can refer to the stepsThe detailed description in the first paragraph is not repeated herein. However, the linear color value stored in the fourth lookup table and the color value of the display screen are limited, so that the accuracy is not high. If the accuracy needs to be improved, a large amount of test time needs to be consumed, and the storage space occupied by the fourth lookup table is huge, so that the hardware cost is increased.

And step three, carrying out nonlinear conversion on the linear color value.

R obtained by the above formula (11)_pannel、G _pannel、B _pannelIs a linear color value over the display gamut of the display screen. In order to ensure that the colors are displayed according to the human visual law, the colors need to be subjected to nonlinear conversion. The non-linear transformation may be implemented by a look-up table similar to the linear transformation in step one. Specifically, the third lookup table 30 may be stored, and the conversion of the linear color value on the display color gamut of the display screen into the non-linear color value may be realized through the third lookup table 30. Specifically, the gamma may be 2.2, and the mapping relationship of the third lookup table 30 may be the red component value R to be input_pannelGreen component value G_pannelAnd blue component value B_pannelMapped sequentially to a red component value R2, a green component value G2, and a blue component value B2. Wherein:

in the third lookup table 30, a linear color value range may correspond to a non-linear color value. For example (R)_pannel-ΔR1，R _pannel+ Δ R1) corresponds to R2 in the second lookup table 10. In addition, in the third lookup table 30, a linear color value may correspond to a non-linear color value. The non-linear color value values corresponding to the linear color value values that are not stored in the third lookup table 30 may be determined by interpolation. The description of the interpolation method may refer to the specific description in step one, and is not repeated here.

Step four, the display screen displays the nonlinear color values on the display color gamut according to the following steps: a red component value R2, a green component value G2, and a blue component value B2.

Based on the color gamut correction scenario described in fig. 1, please refer to fig. 2, and fig. 2 is an example of an application scenario of color gamut correction provided in an embodiment of the present application. As shown in fig. 2, the image source 201 may be an image that the gamut correction device needs to display. The image source 201 may be acquired by a camera, may be locally stored by a color gamut correction device, or may be received from a communication interface, and the source of the image source 201 is not limited in the embodiment of the present application.

The gamut correction device may comprise a display screen 202. As shown in fig. 2, the color gamut correction device is also used to perform color gamut conversion on the color values of the image source 201 to obtain color values on the display color gamut of the display screen. The color value on the display color gamut of the display screen may be used for the display screen 202 to display, and the image after the color gamut conversion corresponding to the color gamut value on the display color gamut of the display screen is the image displayed by the display screen 202, which is the image after the color gamut conversion. Since the color gamut of different devices is different, the accuracy of the color rendering of the display screen 202 can be improved by the above-described color gamut correction.

In the color gamut correction scene example, the voltage drop may cause deviation of the luminance value and the chromaticity coordinate corresponding to each color value component of the display screen, and further, deviation of the color displayed by the display screen occurs, thereby reducing the accuracy of displaying the color by the display screen.

Based on the color gamut correction scenario described in fig. 1 and the color gamut correction scenario example described in fig. 2, embodiments of the present application provide a color gamut correction method and device, which can improve the accuracy of displaying colors on a display screen.

The main inventive principles to which this application relates may include: the voltage drop can cause inaccurate color displayed by the display screen, so that the color value of the color on the color gamut of the image source can be converted into the brightness value on the display color gamut of the display screen, and the increment of the color value of the color corresponding to the voltage drop on the display color gamut of the display screen is obtained according to the brightness value. The deviations of the color values of the colors on the display gamut of the display screen caused by the voltage drop are compensated by the color value increments. Specifically, the corresponding brightness value of the color on the display color gamut of the display screen can be calculated according to the color value of the color on the color gamut of the image source. And then calculating the color value increment on the display color gamut of the display screen corresponding to the voltage drop according to the brightness value corresponding to the first color value and the first matrix. The first matrix therein represents the effect of the voltage drop on the color values over the display gamut of the display screen. By the color gamut correction method, the deviation of the displayed color of the display screen caused by voltage drop can be reduced, and the accuracy of color display in the equipment is improved.

Based on the inventive principles described above, several embodiments provided herein are described below.

Referring to fig. 3, fig. 3 is a schematic flow chart of a color gamut correction method according to an embodiment of the present application. As shown in fig. 3, the color gamut correction method includes, but is not limited to, steps S101 to S103.

S101, the color gamut correction device calculates a brightness value corresponding to the first color value.

Wherein the first color value is a color value of a color on a display gamut of the image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1. The brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of the display screen, and the brightness value corresponding to the first color value includes a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B。

And S102, the color gamut correction device obtains the color value increment corresponding to the voltage drop according to the brightness value corresponding to the first color value and the first matrix.

Wherein the color value increment is an increment of a color value of the color in a display gamut of the display screen caused by the voltage drop; the color value increments include a red increment value Δ R, a green increment value Δ G, and a blue increment value Δ B.

And S103, compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment by the color gamut correction device.

First, the relationship between color, color value, and luminance value will be described. Color is the objective presence of light of different frequencies or the eye's perception of light of different frequencies. The color value is a coordinate value for characterizing a color in a color space, and may be, for example, a coordinate value representing a color in an sRGB color space, and may include a red component value R, a green component value G, and a blue component value B. The luminance value represents the degree of brightness of a color, and may also be referred to as color brightness. The luminance values may be used along with the chromaticity coordinates to characterize the color.

Specifically, the process of incrementally compensating the voltage drop according to the color value may specifically be: the gamut correction device may first determine a second color value corresponding to the first color value; then, overlapping the second color value and the color value increment to obtain a third color value; and finally, compensating the deviation of the color value of the display screen caused by the voltage drop by using the third color value. The third color value may be derived from the incremental superposition of the second color value and the color value. The second color value is the color value of the first color value corresponding over the display gamut of said display screen, the second color value comprising a red component value R2, a green component value G2 and a blue component value B2.

Wherein the third color value is a color value compensated for voltage drop across the display gamut of the display screen. The third color value takes into account the influence of the display characteristics of the display screen on the color value, which includes, for example, the display color gamut of the display screen, the photoelectric conversion characteristics of the display screen, and the like. The third color value includes a red component value R3, a green component value G3, and a blue component value B3.

The respective steps will be described below.

In step S101, the first color value is a linear color value, and if the color value received by the gamut correction device is non-linear, for example, the received color value of the first color: the red component value R0, the green component value G0, and the blue component value B0 are all non-linear. The gamut correction device may first convert the nonlinear color values: the red component value R0, the green component value G0, and the blue component value B0 are converted to linear first color values, including a red component value R1, a green component value G1, and a blue component value B1. For a specific process of converting the non-linear color value into the linear color value, reference may be made to the specific description of step one in the scene described in fig. 1, which is not described herein again.

The display gamut refers to the sum of colors that the display screen can display, i.e., the color rendering range of the display screen. In the world observed by the human eye, the colors of the visible spectrum in nature constitute the largest gamut that encompasses all the colors visible to the human eye. In a coordinate system established according to chromaticity coordinates (x, y), a display color gamut which can be represented by the display screen can be represented by a triangular area formed by connecting three points of RGB. The RGB three points are respectively a chromaticity coordinate point corresponding to red, a chromaticity coordinate point corresponding to green and a chromaticity coordinate point corresponding to blue. The larger the area of the triangle, the larger the display gamut of the display screen.

The chromaticity coordinate refers to a parameter designed in the CIE1931 color space to represent chromaticity of a color. The chromaticity coordinates and the luminance values together may characterize a color. Specifically, the chromaticity of white and gray are the same and are both 0, and the lightness of white and gray are different. Chromaticity may describe the purity of a color, the highest chromaticity being achieved by a single wavelength of intense light (e.g., laser light).

In a possible embodiment, step S101 may be implemented by multiplying by a 3 × 3 matrix, specifically derived as follows:

the target tristimulus values may first be obtained from a transformation matrix between the first color space and the second color space. The first color space is a color space corresponding to a color gamut of the image source, and the second color space is a color space including a conversion relationship between a color value and a luminance value, and a chromaticity coordinate, and may be a CIE1931 color space.

Specifically, the target tristimulus may be obtained from the first color value and the color space conversion matrix:

wherein the target tristimulus stimuli are Xt, Yt, and Zt. If the second color space is CIE1931 color space and the first color space is sRGB color space, the color space conversion matrix in equation (15)

May be the inverse of the conversion matrix in equation (5), which is known to be related only to the first color space and the second color space.

The target tristimulus values can be obtained from the relationship of color values X, Y with Z and chromaticity coordinates in CIE1931 color space, i.e., equations (1), (2), (3), and (4):

wherein (x)_R，y _R)、(x _G，y _G)、(x _B，y _B) Chromaticity coordinates 1 at display screen R, G and B, respectively.

When the second color space is CIE1931 color space, the Y parameter in the target tristimulus values is the brightness value (or lightness value) of the color, that is, Y_R＝L _R，Y _G＝L _G，Y _B＝L _BTherefore, from equation (16), one can obtain:

from equation (15) and equation (17), we can obtain:

in equation (17), let coefficient matrix:

then

The gamut correcting device may store the 3 × 3 coefficient matrix in the formula (20), and multiply the 3 × 3 coefficient matrix before the first color value to obtain the luminance value corresponding to the first color value.

In step S102, the voltage drop causes the accuracy of the color value displayed on the display screen to be reduced. The first matrix represents the effect of voltage drop on the second color value, namely:

wherein the first matrix is

Specifically, the derivation regarding equation (21) is as follows:

due to V_Dataβ Code, i.e. Code proportional to the voltage drop, in combination with equation (8) the effect of the voltage drop on the brightness can be expressed as

Wherein, R3, G3 and B3 are the color values of the colors on the display gamut of the display screen after compensating the voltage drop influence. Specifically, it is desirableIn this case, the color displayed on the display screen is the correct color (i.e., the color corresponding to the first color value). The third color values R3, G3, and B3 are color values compensated for the voltage drop effect and are used as the actual input color values of the display screen, so that the display screen displays a luminance value with a desired luminance value. The ideal brightness value is the brightness value that the display screen accurately outputs when the color value input to the display screen by the image source is the first color value, i.e. the brightness value corresponding to the first color value. The process can improve the accuracy of displaying the color and the brightness of the display screen. In the formula (22), for red R, a_RAs the luminance-color conversion coefficient of the color component R, b_RIs the luminance color conversion index parameter of the color component R. C_RR*L _RThe amount of change, C, in the display screen red color component value R caused by the voltage drop of the red color component_GR*L _GThe change of the display screen red color component value R caused by the voltage drop of the green component, C_BR*L _BIs the amount of change in the display screen red color component value R caused by the voltage drop of the blue component. For green G, a_GIs the luminance color conversion coefficient of the color component G, b_GIs the luminance color conversion index parameter of the color component G. C_GG*L _GThe variation of the green color component value G of the display screen caused by the voltage drop of the green component, C_RG*L _RThe change of the green color component value G of the display screen caused by the voltage drop of the red component, C_BG*L _BIs the amount of change in the green color component value G caused by the voltage drop of the blue component. For blue B, a_BIs the luminance color conversion coefficient of the color component B, B_BIs the luminance color conversion index parameter of the color component B. C_BB*L _BThe amount of change, C, in the display screen blue color component value B caused by the voltage drop of the blue component_GB*L _GThe amount of change, C, in the display screen blue color component value B caused by the voltage drop of the green component_RB*L _RVoltage drop for red componentThe resulting amount of change in the display screen blue color component value B.

Deforming equation (22) yields:

wherein the content of the first and second substances,

before voltage drop compensation is carried out, the color value of the color on the display color gamut of the display screen, namely the second color value, namely:

then

In a possible embodiment, the coefficients (a) of the relationship between the color values and luminance values of the elements of the first matrix, and of the RGB values, are_R、b _R、a _G、b _G、a _B、b _B) The values may be obtained by fitting. The fitting process is specifically described below.

(1) First matrix element C_RR、C _GGAnd C_BBAnd coefficient value a of color value_R、b _R、a _G、b _G、a _B、b _BSolution process of

For a red color component value R, different color values and corresponding luminance values of the respective color values can be measured, which can be obtained from equation (22):

a specific algorithm example of fitting is given below, and it should be understood that the example is only used for explaining the embodiment of the present application and should not be limited, and the process of obtaining the coefficient by fitting may also use other algorithms, which is not limited in the embodiment of the present application.

The formula (25) is formulated as follows

Wherein yi corresponds to different color values, xi corresponds to the brightness measured under yi, i can be an integer with the value of 1-n, and n can also be any integer satisfying 4-n 8.

For equation (26), the residual square sum is found:

wherein

When the sum of the residual error is minimum, the corresponding values of a, b and c can be obtained.

To minimize δ, let the gradient be

Namely, it is

Convergence by the multivariate Newton method is possible, requiring F (a, b, c) to (F)₁，f ₂，f ₃) The Jacobi matrix of (1), wherein:

will be given in equation (27)

As F (a, b, c) in (a)₀，b ₀，c ₀) Nearby, the taylor expansion of the vector value function is:

F(a，b，c)＝F(a ₀，b ₀，c ₀)+DF(a ₀，b ₀，c ₀)·([a，b，c]-[a ₀，b ₀，c ₀])+O([a，b，c]-[a ₀，b ₀，c ₀]) ²

(30)

neglecting O (h)²) And performing linear approximation, then:

F(a，b，c)≈F(a ₀，b ₀，c ₀)+DF(a ₀，b ₀，c ₀)·([a，b，c]-[a ₀，b ₀，c ₀])＝0 (31)

or-DF (a)₀，b ₀，c ₀) ^-1F(a ₀，b ₀，c ₀)≈([a，b，c]-[a ₀，b ₀，c ₀]) (32)

Obtaining fitted a, b and c through successive approximation, and further obtaining a in the formula (24)_R、b _RAnd C_RRThe value of (c).

In respect of a_G、b _G、a _B、b _B、C _GGAnd C_BBCan be analogized to a_R、b _RAnd C_RRThe values of (c) are not described in detail here.

(2) C in the first matrix_BR、C _GR、C _RG、C _BG、C _RBAnd C_GBSolving process of value

Formula for red R

By measuring the chromaticity coordinates and luminance value L of a plurality of color values of Magenta (consisting of Red and Blue)_MCan obtain

Then obtaining a plurality of chromaticity coordinates (x) according to the measurement_M，y _M) Fitting the brightness value corresponding to each chromaticity coordinate to obtain C_BR. Specifically, in fitting, only C in the formula_BRIs an unknown quantity.

Similarly, by measuring the chromaticity coordinate (x) of Yellow (consisting of Red and Green)_Y，y _Y) And a luminance value L_YCan obtain

Then obtaining a plurality of chromaticity coordinates (x) according to the measurement_Y，y _Y) Fitting the brightness value corresponding to each chromaticity coordinate to obtain C_GR. Specifically, in fitting, only C in the formula_GRIs an unknown quantity.

Similarly, for green G and blue B the corresponding formula:

and

likewise, the chromaticity coordinates and brightness values of Yellow (consisting of Red and Green) and Cyan (consisting of Green and Blue) can be measured separately to obtain C_RGAnd C_BGC is obtained by measuring the chromaticity coordinates and brightness values of Magenta (consisting of Red and Blue) and Cyan (consisting of Green and Blue)_RBAnd C_GBAnd thus the values of the elements in the first matrix are obtained.

In step S102, the color gamut correction device may save the calculated first matrix and then calculate the color value increment of the color corresponding to the voltage drop on the display color gamut of the display screen according to equation (21). The color value increment is used for compensating errors caused by voltage drop of the second color value, and the color gamut correction method can reduce the deviation of the color value on the display color gamut of the display screen caused by the voltage drop and improve the accuracy of the color displayed by the device. In addition, when the production line is operated, only 4-8 parameter values and brightness values corresponding to different colors need to be measured, wherein the parameter values can be color values or chromaticity coordinates, and the compensation of the color values caused by voltage drop can be realized, so that the measurement time can be saved, and the production line efficiency is improved.

Step S103 is to add the second color value in the formula (23) and the color value increment to obtain third color values R3, G3, and B3, where the third color value is a color value of the color corrected for voltage drop on the display color gamut of the display screen. The third color value is non-linear and can be used for color display of a display screen.

Alternatively, in step S103, the gamut correction device may hold the coefficient value a_R、b _R、a _G、b _G、a _B、b _B. Then according toEquation (24) calculates a second color value. In addition, the color gamut correction device may store a first lookup table through which the second color value is determined, the first lookup table including a plurality of luminances and the second color value corresponding to each of the plurality of luminances; the second color value for each luminance is determined by the luminance color conversion equation (24). The brightness may be a brightness value or a brightness range. Specifically, in the first lookup table, one luminance range may correspond to one color value. For example (L)_R0-ΔL，L _R0Brightness values in the range of + Δ L) each correspond to R0 in the first lookup table. In addition, in the first lookup table, one luminance value may correspond to one color value. The color value corresponding to the luminance value not stored in the first lookup table may be determined by interpolation. For a detailed description of the interpolation, reference may be made to the detailed description of table 2, which is not repeated here.

The first look-up table may be two-dimensional, i.e. the look-up table is a correspondence of luminance to a second color value. The embodiment of the application is realized by using a matrix product and a two-dimensional lookup table, and occupied software and hardware resources are reduced.

For the display screen, the chromaticity coordinates x and y of the color corresponding to the color value of the display screen change with the change of the driving voltage (and the brightness), and particularly, the chromaticity changes more obviously under the condition of lower brightness, and the matrix formed by the three stimulus values corresponding to the maximum color value which can be displayed by the display screen is used for fitting in the second step of the scene depicted in fig. 1, and the change of the chromaticity coordinates caused by the brightness change is not considered, so that the accuracy of the color value is reduced. As can be seen from the formula (18), the luminance value L used for calculating the second color value in step S103 in the embodiment of the present application_R、L _GAnd L_BThe color value can be calculated according to the real chromaticity coordinate, so that the influence of the chromaticity coordinate change on the accuracy of the color value is reduced, and the accuracy of the color displayed by the display screen can be improved.

In step S103, optionally, the second color values R2, G2, and B2 are not limited to the solution methods of equations (18), (24). The second color value may also be color values R2, G2, and B2 of the color obtained in step three in the scene depicted in fig. 1 on the display color gamut of the display screen, which is not limited in this application.

In addition, for the display screens with different process levels, the gamma values used when the conversion between the linearity and the nonlinearity is carried out are different, and the gamma values used when the conversion between the nonlinearity and the linearity is carried out in the first step and the third step in the scene shown in fig. 1 do not take the difference of the display screens with different process levels into account, so that the accuracy of the color displayed by the display screens is reduced. In the embodiment of the present application, the second color values R2, G2, and B2 may use the solution method of the formulas (18), (24). As can be seen from equations (18) and (24), the conversion between linear and nonlinear color values in step S103 is performed by the coefficient a_R、b _R、a _G、b _G、a _B、b _BThe coefficients are obtained by fitting a plurality of measured color values and corresponding brightness values of the color values of the display screen, so that the conversion between the linearity and the nonlinearity of the color values is more accurate, and the accuracy of the colors displayed by the display screen can be improved.

The method of the present application is described above in detail, and an embodiment of the apparatus provided herein is provided below.

Referring to fig. 4, fig. 4 is a schematic structural diagram of a color gamut correction device according to an embodiment of the present application. As shown in fig. 4, the color gamut correction device may include:

a calculating unit 401, configured to calculate a luminance value corresponding to the first color value; the first color value is a color value of a color on a display gamut of the image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of the display screen, and the brightness value corresponding to the first color value includes a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B；

An obtaining unit 402, configured to obtain, according to a luminance value corresponding to a first color value and a first matrix, a color value increment corresponding to a voltage drop, where the color value increment is an increment of a color value of a color on a display color gamut of a display screen due to the voltage drop; the color value increment comprises a red increment value delta R, a green increment value delta G and a blue increment value delta B; the first matrix represents the effect of voltage drop on the color values of the colors over the display gamut of the display screen;

a compensation unit 403 for compensating for a deviation of the color value of the display screen caused by the voltage drop according to the color value increment.

As a possible implementation, the apparatus further comprises: a determining unit 404, configured to determine a second color value corresponding to the first color value; the second color value is a color value corresponding to the first color value on the display color gamut of the display screen, and the second color value comprises a red component value R2, a green component value G2, and a blue component value B2;

a compensation unit 403, configured to superimpose the second color value and the color value increment to obtain a third color value; compensating for a deviation of a color value of the display screen caused by the voltage drop by using the third color value; wherein the third color value includes a red component value R3, a green component value G3, and a blue component value B3.

As a possible implementation manner, the determining unit 404 is specifically configured to determine the second color value according to the luminance value corresponding to the first color value and a luminance color conversion formula;

the brightness and color conversion formula is

As a possible implementation manner, the determining unit 404 is specifically configured to determine the second color value through a first lookup table, where the first lookup table includes a mapping relationship between a luminance value corresponding to the first color value and the second color value, and the mapping relationship between the luminance value corresponding to the first color value and the second color value is determined by a luminance-color conversion formula;

the brightness and color conversion formula is

As a possible implementation manner, the calculating unit 401 is further configured to fit the multiple color values of the color component i and the corresponding brightness value of each of the multiple color values to obtain b_iAnd a_i。

As a possible implementation manner, the calculating unit 401 is specifically configured to calculate, according to a transformation matrix between the first color space and the second color space and the chromaticity coordinate corresponding to the color component i of the first color value, a luminance value corresponding to the first color value;

the first color space is a color space corresponding to a color gamut of the display screen, and the second color space is a color space containing a conversion relation of converting a color value into a brightness value and converting a color coordinate into a chromaticity coordinate.

As a possible implementation, the first matrix includes a plurality of element values, the plurality of element values are obtained by fitting a plurality of parameter values of the color j and a luminance value corresponding to each of the plurality of parameter values, and the plurality of parameter values includes one or more of the following: color values and chromaticity coordinates; color j is red R, green G, blue B and mixed color; the mixed color is the mixed color of any two or three of red, R, green, G, blue and B.

It should be noted that the implementation of each unit in the color gamut correction device described in fig. 4 may also correspond to the corresponding description of the method embodiment shown in fig. 3, and is not described again here.

Referring to fig. 5, fig. 5 is a schematic structural diagram of another color gamut correction device according to an embodiment of the present application. As shown in fig. 5, the color gamut correction device may include: the system comprises one or more processors 501, a communication interface 502, a memory 503 and a user interface 505, wherein the processors 501, the communication interface 502, the memory 503 and the display screen 505 can be connected through a bus or in other ways, and the embodiment of the application is exemplified by being connected through the bus 504. Wherein:

the processor 501 may be constituted by one or more general-purpose processors, such as a CPU.

The communication interface 502 may be a wired interface (e.g., an ethernet interface) or a wireless interface (e.g., a cellular network interface or using a wireless local area network interface) for communicating with other nodes. In the embodiment of the present application, the communication interface 502 is specifically configured to receive the first color value from the image source.

The memory 503 may include volatile memory (RAM); the memory may also include a non-volatile memory (non-volatile memory), such as a ROM, a flash memory (flash memory), a HDD, or a Solid State Disk (SSD); the memory 503 may also comprise a combination of the above kinds of memories. The memory 503 may be used to store a set of program codes, so that the processor 501 may call the program codes stored in the memory 503 to implement the color gamut correction method of the embodiment of the present application, and in particular, implement the color gamut correction method described in fig. 3.

The display screen 505 may be specifically a touch panel, including a display screen, a touch screen and a touch screen, and may also be a display panel. The display screen may be an LED display screen, and may specifically include various OLED display screens, such as an AMOLED display screen and a PM-OLED display screen, and may also include other types of LEDs, and may also include future emerging types of displays. The display screen 505 is used for displaying according to the third color value.

It should be noted that the color gamut correction device shown in fig. 5 is only one implementation manner of the embodiment of the present application, and in practical applications, the color gamut correction device may further include more or less components, which is not limited herein.

The color gamut correcting device in the embodiment of the present application may include, but is not limited to, a mobile phone, a mobile computer, a tablet computer, a Personal Digital Assistant (PDA), a media player, a smart television, a smart watch, smart glasses, a smart band, and other terminals or devices that include a display screen.

Referring to fig. 6, fig. 6 is a schematic structural diagram of an apparatus according to an embodiment of the present disclosure. As shown in fig. 6, the apparatus may include: a processor 601, and a memory 602 coupled to the processor 601. Wherein:

the processor 601 may be used to read and execute computer readable instructions (program code) stored in the memory 602 to implement some or all of the steps of the methods in the aforementioned method embodiments. In particular implementations, the processor 601 may mainly include a controller, an operator, and a register. The controller is mainly responsible for instruction decoding and sending out control signals for operations corresponding to the instructions. The arithmetic unit is mainly responsible for executing fixed-point or floating-point arithmetic operation, shift operation, logic operation and the like, and can also execute address operation and conversion. The register is mainly responsible for storing register operands, intermediate operation results and the like temporarily stored in the instruction execution process. In particular implementations, the hardware architecture of processor 601 may be an application specific ASIC architecture or the like. The processors 601 may be single core or multi-core.

Herein, the processor 601 may be configured to call an implementation program of the color gamut correction method provided in one or more embodiments of the present application from the memory 602, and execute instructions contained in the program. The result of the execution by the processor 601 may also be output to the display screen, i.e. the processor 601 may send the third color value to the display screen. With regard to the color gamut correction method provided in one or more embodiments of the present application, reference may be made to the foregoing embodiments, and details of implementing the color gamut correction method described in fig. 3 are not repeated here.

It should be noted that the functions corresponding to the processor 601 and the memory 602 may be implemented by hardware design, software design, or a combination of hardware and software, which is not limited herein.

The apparatus depicted in fig. 6 may be embodied as a chip.

The steps of a method or algorithm described in connection with the disclosure of the embodiments of the application may be embodied in hardware or in software program instructions executed by a processor. The software program instructions may consist of corresponding software modules that may be stored in RAM, flash memory, ROM, Erasable Programmable read-only memory (EPROM), Electrically Erasable Programmable read-only memory (EEPROM), registers, a hard disk, a removable hard disk, a compact disc read-only memory (CD-ROM), or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may reside in an ASIC. In addition, the ASIC may be located in a transceiver or a relay device.

Embodiments of the present application also provide a computer-readable storage medium having stored therein instructions, which when executed on a computer or processor, cause the computer or processor to perform one or more steps of any one of the methods described above. The respective constituent modules of the signal processing apparatus may be stored in the computer-readable storage medium if they are implemented in the form of software functional units and sold or used as independent products.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. The technical solution of the present application may be substantially or partially embodied in the form of a software product, or may be a part or all of the technical solution that contributes to the prior art. The computer program product includes one or more computer instructions. The procedures or functions described in accordance with the embodiments of the application are all or partially generated when the computer program instructions are loaded and executed on a computer or processor. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in or transmitted over a computer-readable storage medium. The computer instructions may be transmitted from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

A method of color gamut correction, comprising:

calculating a brightness value corresponding to the first color value; the first color value is a color value of a color on a display gamut of an image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of a display screen, and the brightness value comprises a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B；

Obtaining a color value increment corresponding to voltage drop according to the brightness value corresponding to the first color value and the first matrix, wherein the color value increment is the increment of the color value of the color on the display color gamut of the display screen caused by the voltage drop; the color value increments include a red increment value Δ R, a green increment value Δ G, and a blue increment value Δ B; the first matrix represents the effect of the voltage drop on the color value of the color over the display gamut of the display screen;

and compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment.
The method of claim 1, wherein prior to said incrementally compensating for said voltage drop based on said color value for a deviation in color value of said display screen, said method further comprises:

determining a second color value corresponding to the first color value; the second color value is a color value corresponding to the first color value over a display gamut of the display screen, the second color value comprising a red component value R2, a green component value G2, and a blue component value B2;

the compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment comprises:

superimposing the second color value and the color value increment to obtain a third color value;

compensating for a deviation in color values of the display screen caused by the voltage drop using the third color value; wherein the third color value includes a red component value R3, a green component value G3, and a blue component value B3.
The method of claim 2, wherein determining the second color value corresponding to the first color value comprises:

determining the second color value according to the brightness value corresponding to the first color value and a brightness color conversion formula;

the brightness color conversion formula is

Wherein, b_iIs an index parameter corresponding to the color component i, a_iThe coefficients corresponding to the color component i are represented by values of red, green and blue.
The method of claim 2, wherein determining the second color value corresponding to the first color value comprises:

determining the second color value through a first lookup table, wherein the first lookup table comprises a mapping relation between a brightness value corresponding to the first color value and the second color value, and the mapping relation between the brightness value corresponding to the first color value and the second color value is determined by a brightness-color conversion formula;

the brightness color conversion formula is
Wherein bi is an index parameter corresponding to the color component i,

a _ithe coefficients corresponding to the color component i are represented by values of red, green and blue.
The method of claim 3 or 4, wherein prior to determining the second color value corresponding to the first color value, the method further comprises:

b is obtained according to the fitting of a plurality of color values of the color component i and the brightness value corresponding to each color value in the plurality of color values_iAnd a_i。
The method according to any one of claims 3 to 5, wherein said calculating a luminance value corresponding to the first color value comprises:

calculating to obtain a brightness value corresponding to the first color value according to a conversion matrix between the first color space and the second color space and a chromaticity coordinate corresponding to a color component i of the first color value;

the first color space is a color space corresponding to a color gamut of the display screen, and the second color space is a color space containing a conversion relationship of converting a color value into a luminance value and converting the color value into a chromaticity coordinate.
The method of any one of claims 1 to 6, wherein the first matrix comprises a plurality of element values, the plurality of element values being fitted from a plurality of parameter values for color j and a luminance value corresponding to each of the plurality of parameter values, the plurality of parameter values including one or more of: color values and chromaticity coordinates; the color j is red R, green G, blue B and mixed color; the secondary colors are secondary colors of any two or three of the red, R, green, G, and blue, B.
A color gamut correction apparatus characterized by comprising:

the calculating unit is used for calculating a brightness value corresponding to the first color value; the first color value is a color value of a color on a display gamut of an image source, the first color value including a red component value R1, a green component value G1, and a blue component value B1; the brightness value corresponding to the first color value is a brightness value of the first color value on a display color gamut of a display screen, and the brightness value corresponding to the first color value comprises a red brightness value L_RGreen luminance value L_GAnd a blue luminance value L_B；

An obtaining unit, configured to obtain, according to a luminance value corresponding to the first color value and a first matrix, a color value increment corresponding to a voltage drop, where the color value increment is an increment of a color value of the color on a display color gamut of the display screen due to the voltage drop; the color value increments include a red increment value Δ R, a green increment value Δ G, and a blue increment value Δ B; the first matrix represents the effect of the voltage drop on the color value of the color over the display gamut of the display screen;

and the compensation unit is used for compensating the deviation of the color value of the display screen caused by the voltage drop according to the color value increment.
The apparatus of claim 8, further comprising:

the determining unit is used for determining a second color value corresponding to the first color value; the second color value is a color value corresponding to the first color value over a display gamut of the display screen, the second color value comprising a red component value R2, a green component value G2, and a blue component value B2;

the compensation unit is specifically configured to superimpose the second color value and the color value increment to obtain a third color value; compensating for a deviation in color values of the display screen caused by the voltage drop using the third color value; wherein the third color value includes a red component value R3, a green component value G3, and a blue component value B3.
The apparatus according to claim 9, wherein the determining unit is specifically configured to determine the second color value according to a luminance value corresponding to the first color value and a luminance color conversion formula;

the brightness color conversion formula is

Wherein, b_iIs an index parameter corresponding to the color component i, a_iThe coefficients corresponding to the color component i are represented by values of red, green and blue.
The apparatus according to claim 9, wherein the determining unit is specifically configured to determine the second color value through a first lookup table, the first lookup table including a mapping relationship between a luminance value corresponding to the first color value and the second color value, the mapping relationship between the luminance value corresponding to the first color value and the second color value being determined by a luminance-color conversion formula;

the brightness color conversion formula is
Where bi is an index parameter corresponding to the color component i, a_iThe coefficients corresponding to the color component i are represented by values of red, green and blue.
According to claimThe apparatus of claim 10 or 11, wherein the computing unit is further configured to fit a plurality of color values of the color component i to a corresponding brightness value of each of the plurality of color values to obtain b_iAnd a_i。
The apparatus according to any one of claims 10 to 12, wherein the computing unit is specifically configured to compute a luminance value corresponding to the first color value according to a transformation matrix between the first color space and the second color space and a chromaticity coordinate corresponding to a color component i of the first color value;

the first color space is a color space corresponding to a color gamut of the display screen, and the second color space is a color space containing a conversion relationship of converting a color value into a brightness value and a chromatic value.
The apparatus of any of claims 8 to 13, wherein the first matrix comprises a plurality of element values, the plurality of element values being fitted from a plurality of parameter values for color j and a luminance value corresponding to each of the plurality of parameter values, the plurality of parameter values comprising one or more of: color values and chromaticity coordinates; the color j is red R, green G, blue B and mixed color; the secondary colors are secondary colors of any two or three of the red, R, green, G, and blue, B.
An apparatus, comprising a processor and a memory;

the processor invoking software instructions in the memory to perform the method of any of claims 1-7.
A computer-readable storage medium having stored therein instructions, which when run on a computer or processor, cause the computer or processor to perform the method of any one of claims 1-7.
A computer program product comprising instructions which, when run on a computer or processor, cause the computer or processor to perform the method of any one of claims 1-7.