3D LUT color space correction method and system, terminal and storage medium

Abstract

The invention relates to a 3D LUT color space correction method and system, a terminal and a storage medium. The method comprises the following steps: realizing EOTF correction and white point correction of a display based on a post-stage 1D LUT; checking whether the 1DLUT takes effect or not, if so, entering the next step, and otherwise, prompting; color correction of the display is realized based on the 3D LUT of the preceding stage; by adopting the mode and method provided by the invention, the advantages of the 1D LUT and the 3DLUT are integrated, the 3D LUT is adopted for accurate color correction in the preceding stage, and the 1D LUT is adopted for processing the EOTF curve in the later stage, so that the accuracy of color correction is ensured, the smooth EOTF curve can be obtained, and the problems encountered in the current industry are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of color processing and display, and more specifically, to a 3D LUT color space correction method, system, terminal and storage medium. Background Art

[0002] Color space is an abstract mathematical model that defines the range of colors. Usually, color space describes colors in a three-dimensional coordinate system, and common ones include RGB, Yxy, LAB, etc. The following is a schematic diagram of the RGB color space (see the attached manual). Figure 1 ); There are two key factors in color space, one is the white reference value (abbreviated as white point or White Point) and the maximum value of the primary color (RGB Max Value); the other is the electro-optical transfer function (EOTF). Together, they describe the scope of the color space;

[0003] In the process of color space standardization, associations, alliances, and companies in related industries have launched their own color spaces. Among them, the more famous ones are: AdobeRGB, sRGB, DCI-P3, BT2020, etc. (see the attached manual Figure 2 ). Image output devices (monitors, printers, plotters...) that follow the same color space can maintain a high degree of color reproduction consistency.

[0004] Usually, the default color parameters of the panel (LCD, OLED, or other materials) used in the display do not necessarily fully conform to the above color space. Therefore, the manufacturer needs to calibrate the display according to the standard color space parameters.

[0005] At present, there are usually two modes of color space correction. One is to use a one-dimensional lookup table with matrix operation (1D LUT+Matrix); the other is to use a three-dimensional lookup table (3D LUT) (see the appendix of the manual for one-dimensional lookup table and three-dimensional lookup table). Figure 3 );

[0006] The advantages and disadvantages of using 1D LUT color correction are: the processing of RGB primary colors and EOTF is smoother, but because there is only one set of matrices for color transformation, the color correction accuracy of RGB mixed colors is relatively low (see the attached manual). Figure 4 ); The advantages and disadvantages of using 3D LUT color correction are: in the form of three-dimensional coordinates, each group of RGB indexes is a node, and the related 8 nodes form a small color space, and several small color spaces are stacked into a complete color space; among them, the color correction of each small color space is relatively independent, so the color correction accuracy is higher (see the attached manual Figure 4 ).

[0007] On the other hand, due to hardware cost considerations, the index setting of a single color is relatively small (usually 17 or 33) in the 3D LUT mode, so the smoothness of EOTF processing is not ideal; a 3D LUT color space correction method that can combine the advantages of the above two color correction methods is needed. Summary of the invention

[0008] The technical problem to be solved by the present invention is that, in view of the above-mentioned defects of the prior art, a 3D LUT color space correction method with EOTF compensation is provided, and a 3D LUT color space correction system, a 3D LUT color space correction terminal and a computer-readable storage medium are also provided.

[0009] The technical solution adopted by the present invention to solve its technical problem is:

[0010] A 3D LUT color space correction method is constructed, wherein the method comprises the steps of:

[0011] Realize EOTF correction and white point correction of the display based on the 1D LUT of the post-stage;

[0012] Verify whether 1D LUT is effective. If it is effective, proceed to the next step. Otherwise, prompt;

[0013] Color correction of the display is achieved based on the 3D LUT of the previous stage.

[0014] The 3D LUT color space correction method of the present invention, wherein the EOTF correction and white point correction of the display based on the subsequent 1D LUT includes:

[0015] Send a command to the display to turn off all image processing functions of the display;

[0016] Send a sequence of four-color test images of white, red, green and blue with different brightness and measure the color value of each image;

[0017] According to the measured Yxy data sequence, analyze, calculate and generate the final 1D LUT data;

[0018] Write 1D LUT data to the display.

[0019] In the 3D LUT color space correction method of the present invention, the step of sending a sequence of four-color test pictures of white, red, green and blue with different brightness and measuring the color value of each picture comprises:

[0020] The color calibration software sends white, red, green and blue color charts of different brightness to the display end in a certain order, and measures the Yxy value of each chart through a color analyzer.

[0021] The 3D LUT color space correction method of the present invention, wherein the step of analyzing, calculating and generating the final 1D LUT data according to the measured Yxy data sequence comprises:

[0022] Normalize the Y component of the measured Yxy value and then convert it to XYZ tristimulus value according to the following formula;

[0023]

[0024] Y = Y;

[0025]

[0026] In the formula, X, Y, and Z represent the three stimulus values ​​of red, green, and blue, which is an idealized three-dimensional coordinate system established based on the stimulus response of the human eye to the three primary colors; Y, x, and y are the objective data measured by the color analyzer;

[0027] Keep the XYZ values ​​of red, green and blue for each brightness to get several 3*3 matrices; perform row-column transformation on the obtained matrices, and then invert them to get new matrices. These new matrices are the XYZ to RGB characteristic matrices of the display at different three primary color values, recorded as {XYZ to RGB} Original ;

[0028] Using the EOTF and white point coordinates of the target color space as parameters, a set of Yxy data sequences is generated, where the Y component increases from small to large, indicating that the brightness gradually increases; xy remains unchanged, indicating a stable reference white point;

[0029] Convert this set of Yxy data sequence to XYZ values ​​and substitute them into {XYZ to RGB} with different brightness. Original Matrix operation is performed to obtain the corresponding RGB value sequence, which is the data of 1D LUT.

[0030] In the 3D LUT color space correction method of the present invention, the step of verifying whether the 1D LUT is effective comprises:

[0031] Write the 1D LUT data into the display and make it effective, and determine whether the EOTF and white point coordinate values ​​of the display meet the target color space.

[0032] The 3D LUT color space correction method of the present invention, wherein the color correction of the display based on the previous 3D LUT comprises:

[0033] Using the base color node of the 3D LUT as the index, send out the white, red, green, and blue test picture sequences respectively, and then measure the color value of each picture;

[0034] According to the measured Yxy data sequence, color space conversion, color data analysis, calculation and generation of the final 3D LUT data are performed;

[0035] Write the 3D LUT data to the display.

[0036] The 3D LUT color space correction method of the present invention, wherein the color space conversion, color data analysis, calculation and generation of final 3D LUT data according to the measured Yxy data sequence comprises:

[0037] From the measured Yxy data, derive the XYZ to RGB characteristic matrix with 1D LUT in effect, denoted as {XYZ toRGB} 1D LUT ;

[0038] Operate the RGB value of each node of the 3D LUT with the RGB to XYZ matrix of the target color space to obtain a set of standard XYZ tristimulus values ​​based on the target color space;

[0039] Compare this XYZ value with {XYZ to RGB} 1D LUT Matrix operations are performed to obtain 3D LUT data.

[0040] A 3D LUT color space correction system, wherein the system comprises a PC host, a color analyzer and a display to be corrected;

[0041] The color analyzer is used to collect the color value of the display screen and send it to the PC host;

[0042] The PC host is used to perform color correction on the display using the 3D LUT color space correction method described above based on the color values ​​collected by the color analyzer.

[0043] A 3D LUT color space correction terminal comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0044] A computer-readable storage medium stores a computer program, wherein the computer program implements the steps of the above method when executed by a processor.

[0045] The beneficial effects of the present invention are as follows: the present invention realizes EOTF correction and white point correction of a display based on a 1D LUT of a rear stage; verifies whether the 1D LUT is effective, and if so, proceeds to the next step, otherwise a prompt is given; realizes color correction of the display based on a 3D LUT of a front stage; combines the advantages of the above-mentioned two color calibration methods of 1D LUT and 3D LUT, the front stage uses 3D LUT for precise color correction, and the rear stage uses 1D LUT to process the EOTF curve, which not only ensures the accuracy of color calibration, but also obtains a smooth EOTF curve, thereby solving the problems encountered in the current industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work:

[0047] Figure 1 It is a schematic diagram of RGB color space;

[0048] Figure 2 It is a schematic diagram of the various custom color spaces that exist;

[0049] Figure 3 It is a one-dimensional lookup table and a three-dimensional lookup representation;

[0050] Figure 4 This is a schematic diagram of the existing 1D LUT color space correction;

[0051] Figure 5 This is a schematic diagram of the existing 3D LUT color space correction;

[0052] Figure 6 is a flow chart of a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0053] Figure 7 3D LUT color space correction method principle schematic diagram of a preferred embodiment of the present invention;

[0054] Figure 8 It is a schematic diagram of the principle of implementing EOTF and white point correction using 1D LUT in a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0055] Fig. 9 3D LUT color space correction method of a preferred embodiment of the present invention is a schematic diagram of the principle of implementing color correction with 3D LUT;

[0056] Fig.10This is a schematic diagram of measuring the native color value of a display screen using a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0057] Fig.11 This is a schematic diagram of a result of a set of WRGB conversion in a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0058] Fig.12 It is a schematic diagram of deriving XYZ to RGB characteristics from XYZ values ​​by a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0059] Fig.13 It is a schematic diagram of generating 1D LUT data by a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0060] Fig.14 It is a schematic diagram of an XYZ to RGB characteristic matrix derived from a 3D LUT color space correction method in a preferred embodiment of the present invention when a 1D LUT is effective;

[0061] Fig.15 This is a schematic diagram of generating 3D LUT data using a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0062] Fig.16 This is a schematic diagram of color space correction completed by a 3D LUT color space correction method according to a preferred embodiment of the present invention;

[0063] Fig.17 3D LUT color space correction system according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will be described clearly and completely in combination with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are partial embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0065] The 3D LUT color space correction method of the preferred embodiment of the present invention is as follows: Figure 6 See also Figure 7-Figure 16 , the method comprises the steps of:

[0066] S01: Implement EOTF correction and white point correction of the display based on the 1D LUT of the post-stage;

[0067] S02: Check whether 1D LUT is effective. If it is effective, go to the next step, otherwise, prompt;

[0068] S03: Implement color correction of the display based on the 3D LUT of the previous stage;

[0069] The method of the present application combines the advantages of the above-mentioned 1D LUT and 3D LUT color calibration methods. The front stage uses 3D LUT for precise color correction, and the back stage uses 1D LUT to process the EOTF curve. This not only ensures the accuracy of color calibration, but also obtains a smooth EOTF curve, solving the current problems encountered in the industry.

[0070] The specific instructions are as follows:

[0071] like Figure 8 As shown, the EOTF correction and white point correction of the display are first implemented based on the 1D LUT of the later stage, specifically including:

[0072] 1. The color calibration software sends instructions to the monitor through the signal line (DDCCI) to turn off all image processing functions (the purpose is to measure the original color value of the display under the test picture).

[0073] 2. The color calibration software sends a sequence of white, red, green and blue test images of different brightness and measures the color value of each image (usually in Yxy format, where Y represents brightness and x and y represent chromaticity coordinates).

[0074] 3. Based on the measured Yxy data sequence, analyze, calculate and generate the final 1D LUT data on the PC.

[0075] 4. Write the 1D LUT data to the display through the signal line.

[0076] like Fig. 9 As shown, when the 1D LUT is in effect, the color correction of the display is implemented based on the 3D LUT of the previous stage, including:

[0077] 1. The color calibration software issues a command to make the 1D LUT effective. At this time, consider the 1D LUT+Panel as a whole, and its EOTF and white point are consistent with the target color space parameters.

[0078] 2. The color calibration software uses the base color node of the 3D LUT as an index, sends out a sequence of white, red, green, and blue test images, and then measures the color value of each image.

[0079] 3. Based on the measured Yxy data sequence, perform color space conversion, color data analysis, calculation and generate the final 3D LUT data on the PC.

[0080] 4. Write 3D LUT data to the display;

[0081] Furthermore, a sequence of four-color test images of white, red, green, and blue with different brightness is sent, and the color value of each image is measured, including:

[0082] The color calibration software sends white, red, green and blue color charts of different brightness to the display end in a certain order, and measures the Yxy value of each chart through the color analyzer (see Fig.10 ).

[0083] Normalize the Y component of the measured Yxy value and then convert it to XYZ tristimulus value according to the following formula (one set of WRGB conversion results can be found in Fig.11 );

[0084]

[0085] Y = Y;

[0086]

[0087] In the formula, X, Y, and Z represent the three stimulus values ​​of red, green, and blue, which is an idealized three-dimensional coordinate system established based on the stimulus response of the human eye to the three primary colors; Y, x, and y are the objective data measured by the color analyzer;

[0088] Keep the XYZ values ​​of red, green and blue for each brightness to get several 3*3 matrices; perform row-column transformation on the obtained matrices, and then invert them to get new matrices. These new matrices are the XYZ to RGB characteristic matrices of the display at different three primary color values, recorded as {XYZ to RGB} Original (See Fig.12 );

[0089] Using the EOTF and white point coordinates of the target color space as parameters, a set of Yxy data sequences is generated, where the Y component increases from small to large, indicating that the brightness gradually increases; xy remains unchanged, indicating a stable reference white point;

[0090] Convert this set of Yxy data sequence to XYZ values ​​and substitute them into {XYZ to RGB} with different brightness. Original Matrix operation to obtain the corresponding RGB value sequence, which is the data of 1D LUT (see Fig.13 ).

[0091] Write the 1D LUT data into the display and make it effective, and determine whether the EOTF and white point coordinate values ​​of the display meet the target color space.

[0092] When the 1D LUT is in effect, the color calibration software sends white, red, green and blue test pictures again. The R, G and B values ​​of each test picture correspond to the primary color nodes of the 3D LUT, and the Yxy values ​​of each picture are measured with a color analyzer.

[0093] For example, when the display uses a 17*17*17 3D LUT, this step requires measuring 17 sets of Yxy values ​​for white, red, green, and blue. Assuming the data range is 8 bits, the values ​​of the RGB output sequence are: 0, 16, 32, 64...255.

[0094] From the measured Yxy data, the XYZ to RGB characteristic matrix with 1D LUT in effect is derived and recorded as {XYZ toRGB}1D LUT (see Fig.14 );

[0095] By calculating the RGB value of each node of the 3D LUT and the RGB to XYZ matrix of the target color space, a set of standard XYZ tristimulus values ​​based on the target color space can be obtained. By calculating this XYZ value and the {XYZ to RGB}1D LUT matrix, the 3D LUT data can be obtained (see Fig.15 );

[0096] Write 3D LUT data to the display. When 3D LUT and 1D LUT are effective at the same time, the input linear RGB data will be output in accordance with the target color space after two table lookups (see Fig.16 ), complete the color space correction;

[0097] It should be noted that the above-mentioned execution of 1D LUT and 3D LUT allows for some different changes in parameters or steps, and the solutions obtained by slight changes or equivalent replacements made based on existing technical means also fall within the protection scope of this application.

[0098] A 3D LUT color space correction system, such as Fig.17 As shown, the system includes a PC host 100, a color analyzer 101 and a display 102 to be calibrated;

[0099] A color analyzer 101 is used to collect the color values ​​of the display screen and send them to the PC host;

[0100] The PC host 100 is used to perform color correction on the display using the 3D LUT color space correction method described above based on the color values ​​collected by the color analyzer;

[0101] The method of the present application combines the advantages of the above-mentioned 1D LUT and 3D LUT color calibration methods. The front stage uses 3D LUT for accurate color correction, and the back stage uses 1D LUT to process the EOTF curve, which not only ensures the accuracy of color calibration, but also obtains a smooth EOTF curve, solving the problems encountered in the current industry.

[0102] The equipment and environment required for color correction can be:

[0103] Hardware environment: PC host, color analyzer, and display to be calibrated.

[0104] Software environment: Windows 10 / 11 / 7 / XPOS, color correction software.

[0105] Among them, the color correction software can send various instructions to control the display through the DDC bus in the signal cable (Signal Cable), and can also write the final result into the display in the form of LUT.

[0106] A 3D LUT color space correction terminal comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0107] A computer-readable storage medium stores a computer program, wherein the computer program implements the steps of the above method when executed by a processor.

[0108] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A 3D LUT color space correction method, characterized in that: The method comprises the steps of: Realize EOTF correction and white point correction of the display based on the 1D LUT of the post-stage; Verify whether 1D LUT is effective. If it is effective, proceed to the next step. Otherwise, prompt; Color correction of the display is achieved based on the 3D LUT of the previous stage.

2. The 3D LUT color space correction method according to claim 1, characterized in that: The EOTF correction and white point correction of the display based on the post-stage 1DLUT include: Send a command to the display to turn off all image processing functions of the display; Send a sequence of four-color test images of white, red, green and blue with different brightness and measure the color value of each image; According to the measured Yxy data sequence, analyze, calculate and generate the final 1D LUT data; Write 1D LUT data to the display.

3. The 3D LUT color space correction method according to claim 2, characterized in that: The sending of a sequence of four-color test images of white, red, green and blue with different brightness and measuring the color value of each image includes: The color calibration software sends white, red, green and blue color charts of different brightness to the display end in a certain order, and measures the Yxy value of each chart through a color analyzer.

4. The 3D LUT color space correction method according to claim 2 or 3, characterized in that: The analyzing, calculating and generating the final 1D LUT data according to the measured Yxy data sequence includes: Normalize the Y component of the measured Yxy value and then convert it to XYZ tristimulus value according to the following formula; Y = Y; In the formula, X, Y, and Z are the stimulus values ​​of red, green, and blue respectively; x, y, and z are the measured values ​​of red, green, and blue respectively; Keep the XYZ values ​​of red, green and blue for each brightness to get several 3*3 matrices; perform row-column transformation on the obtained matrices, and then invert them to get new matrices. These new matrices are the XYZ to RGB characteristic matrices of the display at different three primary color values, recorded as {XYZ to RGB} Original ; Using the EOTF and white point coordinates of the target color space as parameters, a set of Yxy data sequences is generated, where the Y component increases from small to large, indicating that the brightness gradually increases; xy remains unchanged, indicating a stable reference white point; Convert this set of Yxy data sequence to XYZ values ​​and substitute them into {XYZ to RGB} with different brightness. Original Matrix operation is performed to obtain the corresponding RGB value sequence, which is the data of 1D LUT.

5. The 3D LUT color space correction method according to claim 4, characterized in that: The verification of whether the 1D LUT is effective includes: Write the 1D LUT data into the display and make it effective, and determine whether the EOTF and white point coordinate values ​​of the display meet the target color space.

6. The 3D LUT color space correction method according to claim 1, characterized in that: The color correction of the display based on the 3DLUT of the previous stage includes: Using the base color node of the 3D LUT as the index, send out the white, red, green, and blue test picture sequences respectively, and then measure the color value of each picture; According to the measured Yxy data sequence, color space conversion, color data analysis, calculation and generation of the final 3DLUT data are performed; Write the 3D LUT data to the display.

7. The 3D LUT color space correction method according to claim 6, characterized in that: The color space conversion, color data analysis, calculation and generation of final 3D LUT data according to the measured Yxy data sequence include: From the measured Yxy data, the XYZ to RGB characteristic matrix with 1D LUT in effect is derived, denoted as {XYZ to RGB} 1D LUT ; Operate the RGB value of each node of the 3D LUT with the RGB to XYZ matrix of the target color space to obtain a set of standard XYZ tristimulus values ​​based on the target color space; Compare this XYZ value with {XYZ to RGB} 1D LUT Matrix operations are performed to obtain 3D LUT data.

8. A 3D LUT color space correction system, characterized in that: The system includes a PC host, a color analyzer and a display to be calibrated; The color analyzer is used to collect the color value of the display screen and send it to the PC host; The PC host is used to perform color correction on the display using the 3D LUT color space correction method according to any one of claims 1 to 7 based on the color values ​​collected by the color analyzer.

9. A 3D LUT color space correction terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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