A method for calculating gamma correction of display system

Abstract

The present invention discloses a method for calculating gamma correction of a display system, which uses a curve and linear mixed interpolation method to perform gamma correction calculation on the display system. Specifically, curve interpolation is used between two data binding points that meet the conditions, and linear interpolation is used between two data binding points that do not meet the conditions. The method includes the following steps: first, it is necessary to determine a curve interpolation algorithm and a judgment method for judging whether curve interpolation is applicable between two binding points. Then, two adjacent data binding points are processed in turn. If the curve interpolation conditions are met between the two points, the curve interpolation algorithm is used for interpolation, and if not, the linear interpolation algorithm is used.

Description

Technical Field

[0001] The invention belongs to the technical field of image display and relates to a gamma correction calculation method for a display system. Background Art

[0002] The image display chip has large deviations in some intervals due to its storage space limitation and the actual mapping relationship using function fitting, so it is often replaced by circuit table lookup interpolation. When the hardware limits the number of nodes to be too large, direct use of linear interpolation will encounter large deviations when the distance is far from the node, and the nodes will also have some discontinuities or even jumps due to the large changes in the slopes of the two linear interpolations. A common scenario is that when the gamma binding point is used to adjust the brightness of the display system, using simple linear interpolation will cause the display brightness to be noticeably uneven when adjusted.

[0003] The present invention proposes a display system gamma correction calculation method, aiming to use a small amount of additional overhead to improve the above-mentioned technical problems as much as possible, on the one hand to improve the deviation far away from the node, on the other hand to improve the discontinuity at the node, and in some inapplicable cases, still retain the use of linear interpolation, using a hybrid interpolation method of curve and linear.

[0004] Based on the above problems, the present invention proposes a display system gamma correction calculation method. Summary of the invention

[0005] The present invention proposes a display system gamma correction calculation method, comprising the following steps:

[0006] Step 1, obtain the gamma correction table LUTG;

[0007] Step 2: Find the position of the interpolation point in the correction table;

[0008] Step 3: determine whether the curve interpolation condition is met. If so, proceed to step 4. If not, perform linear interpolation and then output the brightness according to the gamma value obtained by mixed interpolation.

[0009] Step 4, solving the interpolation curve of the four adjacent points;

[0010] Step 5: Calculate whether the interpolation curve has an inflection point within the interval. If yes, perform linear interpolation, and then output the brightness according to the gamma value obtained by mixed interpolation; if no, proceed to step 6;

[0011] Step six, derive an interpolation curve between the two middle points that can be quickly calculated, and output the brightness according to the gamma value obtained by mixed interpolation.

[0012] Furthermore, step 2 includes:

[0013] LUTG: Y = [y0, y1, y2…y n ]=[f(x0,x1,x2…x n )]

[0014] where X = [x0, x1, x2…x n ] is the binding point value, Y=[y0,y1,y2…y n ] is the corresponding output value; the sequenced binding point information is obtained from the gamma correction table, and four adjacent data points are obtained in sequence: (x0, y0), (x1, y1), (x2, y2), (x3, y3), and the interpolation function between the two points (x1, y1) and (x2, y2) is finally obtained.

[0015] Furthermore, step three includes

[0016] Determine whether (y1-y0) / (x1-x0), (y2-y1) / (x2-x1), (y3-y2) / (x3-x2) are increasing or decreasing. If they are increasing or decreasing, they meet the curve interpolation conditions; otherwise, they do not meet the curve interpolation conditions and linear interpolation is performed;

[0017]

[0018] Furthermore, step four includes:

[0019] When the judgment result meets the curve interpolation condition, solve the cubic function that passes through the four points at the same time. If there is no solution, use linear interpolation. Suppose the cubic function is f(x)=ax 3 +bx 2 +cx+d, directly use linear algebra to solve the coefficients

[0020]

[0021] Furthermore, step five includes:

[0022] After obtaining the coefficients, it is necessary to determine whether there is an inflection point of the function in the value interval. If there is an inflection point, linear interpolation is used;

[0023] The process of judging whether there is an inflection point is as follows: First, when a=0, it is necessary to judge Is it in the interval (x0, x3)? If so, perform linear interpolation. When a=0 and b=0, it is a linear function. When a is not 0, judge that f′(x)=3ax 2 Does +2bx+c have a solution in the interval (x0, x3)? If so, it is considered to have an inflection point, and linear interpolation is performed;

[0024] Determine f′(x)=3ax 2 Does +2bx+c have a solution process?

[0025] (5.1) When When it is outside the interval (x0, x3), if f′(x0)*f′(x3)<0, there is a solution, and linear interpolation is performed;

[0026] (5.2) When In the interval (x0, x3), if If any of these holds, there is a solution, and linear interpolation is performed.

[0027] Furthermore, step six includes

[0028] If the curve interpolation conditions are met, use Substitute the value x into the cubic function to obtain a new point (x4, y4), solve the quadratic function that passes through the three points (x1, y1), (x2, y2), and (x4, y4) at the same time, and use the quadratic function as a curve to interpolate (x1, y1) and (x2, y2);

[0029] Suppose the quadratic function is g(x)=ex 2 +fx+g

[0030]

[0031] Substituting the coefficients into the resulting g(x) is the curve interpolation function.

[0032] Since the first two points and the last two points do not meet the calculation conditions, any of the following processing methods is used:

[0033] (6.1) Use linear interpolation directly;

[0034] (6.2) Use two-point interpolation to obtain a new data point to satisfy the condition and then calculate;

[0035] (6.3) Directly use the starting three points or the ending three points to solve the quadratic function;

[0036] (6.4) Use the derivatives of the adjacent interpolation curves and the two points as conditions to find the quadratic function. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Shown is a flow chart of the correction calculation method of the present invention;

[0038] Figure 2 Shown is a hybrid interpolation effect diagram of the present invention;

[0039] Figure 3Shown is a linear interpolation effect diagram of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] See also Figure 1-3 , the present invention provides a display system gamma correction calculation method.

[0042] First, obtain the gamma correction table LUTG.

[0043] LUTG: Y = [y0, y1, y2…y n ]=[f(x0,x1,x2…x n )]

[0044] where X = [x0, x1, x2…x n ] is the binding point value, Y=[y0,y1,y2…y n ] is the corresponding output value; the sequenced binding point information is obtained from the gamma correction table, and four adjacent data points are obtained in sequence: (x0, y0), (x1, y1), (x2, y2), (x3, y3), and the interpolation function between the two points (x1, y1) and (x2, y2) is finally obtained.

[0045] First, determine whether the conditions for curve interpolation are met. The method used in this embodiment is to use (y1-y0) / (x1-x0), (y2-y1) / (x2-x1), (y3-y2) / (x3-x2) to measure whether they are increasing or decreasing. If they are increasing or decreasing, it means that the change of the derivative within the four point interval is likely to be monotonic, which meets the curve interpolation conditions; conversely, if they are not increasing or decreasing, the use of curve interpolation is more likely to result in a larger deviation than linear interpolation. If no new measurement points are added in this interval as data binding points, it is recommended to use linear interpolation.

[0046]

[0047] When the judgment result meets the requirements of curve interpolation, solve the cubic function that passes through these four points at the same time. If there is no solution, use linear interpolation.

[0048] Let the cubic function be f(x)=ax 3 +bx 2+cx+d, directly use linear algebra to solve the coefficients.

[0049]

[0050] After obtaining the coefficients, it is necessary to determine whether there is an inflection point of the function in the value range. If there is an inflection point and the function shape is unstable, linear interpolation is used.

[0051] The judgment process is as follows. First, when a=0, it is necessary to judge Is it in the interval (x0, x3)? If so, use linear interpolation. When a=0 and b=0, it is a linear function. When a is not 0, judge f'(x)=3ax 2 Does +2bx+c have a solution in the interval (x0, x3)? If so, it is considered to have an inflection point and linear interpolation is used.

[0052] Determine f′(x)=3ax 2 Does +2bx+c have a solution process?

[0053] when When outside the interval (x0, x3), if f′(x0)*f′(x3)<0, there is a solution and linear interpolation is required;

[0054] when In the interval (x0, x3), if If any of these holds, there is a solution, and linear interpolation is required.

[0055] If the curve interpolation conditions are met, use Substitute the cubic function in 2 as the x value to obtain a new point (x4, y4), solve the quadratic function that passes through (x1, y1), (x2, y2), and (x4, y4) at the same time, and use this quadratic function as the curve to interpolate (x1, y1) and (x2, y2).

[0056] Suppose the quadratic function is g(x)=ex 2 +fx+g

[0057]

[0058] Substituting the coefficients into the resulting g(x) is the curve interpolation function.

[0059] If the two starting points and the two ending points do not meet the above calculation conditions, there are different ways to handle them, including but not limited to:

[0060] Use linear interpolation directly;

[0061] Use two-point interpolation to get a new data point to satisfy the above conditions and then calculate;

[0062] Directly use the starting three points or the last three points to solve the quadratic function;

[0063] Finds a quadratic function using the derivatives of adjacent interpolation curves and two points as conditions.

[0064] In order to balance the simplicity and stability of calculation, direct linear interpolation is generally used at the beginning and the end.

[0065] So far, the mixed interpolation of data has been completed. Figure 2 and Figure 3 When there are 11 binding points, the mixed interpolation results and the linear interpolation results are shown. It can be observed that the mixed interpolation result is much smoother than the linear interpolation result. In this way, the brightness transition after gamma correction will be smoother and the display system effect will be better.

[0066] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0067] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is limited by the appended claims and their equivalents.

Claims

1. A display system gamma correction calculation method, characterized in that: The following steps are involved: Step 1, obtain the gamma correction table LUTG; Step 2: Find the position of the interpolation point in the correction table; Step 3: determine whether the curve interpolation condition is met. If so, proceed to step 4. If not, perform linear interpolation and then output the brightness according to the gamma value obtained by mixed interpolation. Step 4, solving the interpolation curve of the four adjacent points; Step 5: Calculate whether the interpolation curve has an inflection point within the interval. If yes, perform linear interpolation, and then output the brightness according to the gamma value obtained by mixed interpolation; if no, proceed to step 6; Step 6: derive the interpolation curve between the two middle points, and output the brightness according to the gamma value obtained by mixed interpolation; The second step comprises: LUTG:Y=[y0,y1,y2…y n ]=[f(x0,x1,x2…x n )] where X = [x0, x1, x2…x n ] is the binding point value, Y=[y0,y1,y2…y n ] is the corresponding output value; the arranged binding point information is obtained from the gamma correction table, and four adjacent data points are obtained in sequence: (x0, y0), (x1, y1), (x2, y2), (x3, y3), and the interpolation function between the two points (x1, y1) and (x2, y2) is finally obtained; The step three includes Determine whether (y1-y0) / (x1-x0), (y2-y1) / (x2-x1), (y3-y2) / (x3-x2) are increasing or decreasing. If they are increasing or decreasing, they meet the curve interpolation conditions; otherwise, they do not meet the curve interpolation conditions and linear interpolation is performed; The fourth step comprises: When the judgment result meets the curve interpolation condition, solve the cubic function that passes through the four points at the same time. If there is no solution, use linear interpolation. Suppose the cubic function is f(x)=ax 3 +bx 2 +cx+d, directly use linear algebra to solve the coefficients The step five includes After obtaining the coefficients, it is necessary to determine whether there is an inflection point of the function in the value interval. If there is an inflection point, linear interpolation is used; The process of judging whether there is an inflection point is as follows: First, when a=0, it is necessary to judge Is it in the interval (x0, x3)? If so, perform linear interpolation. When a=0 and b=0, it is a linear function. When a is not 0, judge that f′(x)=3ax 2 Does +2bx+c have a solution in the interval (x0,x3)? If so, it is considered to have an inflection point, and linear interpolation is performed; Determine f′(x)=3ax 2 Does +2bx+c have a solution process? (5.1) When When it is outside the interval (x0,x3), if f′(x0)*f′(x3)<0, there is a solution, and linear interpolation is performed; (5.2) When In the interval (x0,x3), if or If any of them holds true, there is a solution, and linear interpolation is performed; The step six includes If the curve interpolation conditions are met, use Substitute the value x into the cubic function to obtain a new point (x4, y4), solve the quadratic function that passes through the three points (x1, y1), (x2, y2), and (x4, y4) at the same time, and use the quadratic function as the curve for interpolating (x1, y1) and (x2, y2); Suppose the quadratic function is g(x)=ex 2 +fx+g Substituting the coefficients into the resulting g(x) is the curve interpolation function.

2. The method for calculating gamma correction of a display system according to claim 1, characterized in that: The first two points and the last two points do not meet the calculation conditions, so any of the following processing methods are used: (6.1) Use linear interpolation directly; (6.2) Use two-point interpolation to obtain a new data point to satisfy the condition and then calculate; (6.3) Directly use the starting three points or the ending three points to solve the quadratic function; (6.4) Use the derivatives of the adjacent interpolation curves and the two points as conditions to find the quadratic function.

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