CN114880914A - Regional dimming model based on multi-objective optimization - Google Patents

Regional dimming model based on multi-objective optimization Download PDF

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CN114880914A
CN114880914A CN202110993249.7A CN202110993249A CN114880914A CN 114880914 A CN114880914 A CN 114880914A CN 202110993249 A CN202110993249 A CN 202110993249A CN 114880914 A CN114880914 A CN 114880914A
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individual
value
backlight
individuals
image
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张涛
齐望
赵鑫
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Tianjin University
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00Computer-aided design [CAD]
    • G06F30/20Design optimisation, verification or simulation
    • G06F30/27Design optimisation, verification or simulation using machine learning, e.g. artificial intelligence, neural networks, support vector machines [SVM] or training a model
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06NCOMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
    • G06N3/00Computing arrangements based on biological models
    • G06N3/12Computing arrangements based on biological models using genetic models
    • G06N3/126Evolutionary algorithms, e.g. genetic algorithms or genetic programming
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406Control of illumination source
    • G09G3/342Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F2111/00Details relating to CAD techniques
    • G06F2111/06Multi-objective optimisation, e.g. Pareto optimisation using simulated annealing [SA], ant colony algorithms or genetic algorithms [GA]

Abstract

The local dimming technology can improve the display quality of the display system and reduce the power consumption of the system. Setting the optimal backlight brightness matrix by the local dimming method is key to enable the local dimming system to achieve the optimal performance. The regional dimming problem model is established by regarding regional dimming as a multi-objective optimization problem, taking improvement of image distortion, improvement of image contrast and reduction of system power consumption as optimization targets. In order to effectively solve the multi-target optimization problem, the invention improves a multi-target evolutionary algorithm (MOEA/D) based on decomposition, fuses the MOEA/D and the SFLA, and provides an improved multi-target evolutionary calculation method which is named as MOEA/D-SFLA. Experimental results prove that compared with a regional dimming method based on parameters, the MOEA/D-SFLA can simultaneously improve image distortion, improve image contrast and reduce system power consumption. MOEA/D-SFLAs have higher performance than some improved MOEA/D.

Description

Regional dimming model based on multi-objective optimization
One, the technical field
The method is applied to the HDR display system, and based on multi-objective optimization, the regional dimming technology in the display system is improved and optimized. The method aims to find a balance point of image quality, power consumption and contrast of the display system.
Second, background Art
1. Decomposition-based multi-objective optimization problem
The idea of multi-objective decomposition mainly means that a multi-objective optimization problem is decomposed into a certain number of sub-problems, and then each sub-problem is optimized simultaneously. In a classical decomposition-based multi-objective optimization evolutionary algorithm (MOEA/D), the MOEA/D does not treat the MOP as a whole, but decomposes the multi-objective optimization problem into several single-objective sub-problems by weight vectors, optimizes all sub-problems simultaneously by using neighborhood relations between sub-problems determined by euclidean distances between weight vectors, wherein the decomposition is achieved by an aggregation method, and the common decomposition method is: weighted summation, Chebyshev method and boundary crossing method. The mathematical expressions of the three decomposition methods are respectively:
(1) weighted Summation (WS). The single-target optimization problem obtained after the decomposition by the method is as follows:
Figure BSA0000250964000000011
subject x∈Ω
the weighted sum decomposition method carries out accumulation processing on all objective functions and then solves the overall subproblems.
(2) Chebyshev method. The single-target optimization problem obtained after the decomposition by the method is as follows:
Figure BSA0000250964000000012
subject to x∈Ω
wherein
Figure BSA0000250964000000013
As a reference point, for each
Figure BSA0000250964000000014
By changing the weight vector, more different Pareto optimal solutions can be obtained by using MOEA/D of TCH decomposition method.
(3) Penalty based boundary intersection method (PBI). The single-target optimization problem obtained after the decomposition by the method is as follows:
min imize g pbi (x|λ,z * )=d 1 +θd 2
Figure BSA0000250964000000015
subject to x∈Ω
where θ is a penalty factor. When the number of the solving targets is more than 2 MOPs, if the weight vectors with the same distribution are used, the MOEA/D using the PBI decomposition method has better effect than the MOEA/D using the TCH decomposition method, but the cost is required to be paid for the MOEA/D, and therefore an effective penalty factor theta must be set.
2. Local dimming
In an LCD display system, since liquid crystals cannot emit light autonomously, it is necessary to provide brightness by means of backlight LEDs to display video or images. The local dimming means that an input image is partitioned, and the LED of each partition is independently controlled to emit light according to the image characteristics of the partition, so that the image quality can be effectively improved and the power consumption can be reduced by the local dimming technology. The existing LED area dimming technology can be generally divided into two parts of area backlight extraction and liquid crystal pixel compensation. The backlight extraction means that when an image is input into a display system, the image is partitioned, backlight brightness of each partition is obtained according to different algorithms, and finally a backlight matrix of the whole image is obtained. After the backlight extraction is performed on the input image, since the size of the backlight value is determined by the corresponding image content characteristics, in order to ensure that the display brightness of the image in actual display is kept as constant as possible when the backlight is fully bright, the pixel value of the display image needs to be further adjusted according to the backlight information, so that the light transmission amount is effectively controlled according to the size of the backlight value, and the process is called pixel compensation.
The most basic and classical methods in area backlight extraction are the maximum and average methods. The maximum value method takes the maximum value of the pixel gray level in the image area as the partition backlight brightness, although the image brightness can be improved, the energy-saving effect is poor, and the method is very sensitive to noise; the average value method is to take the average value of the pixel gray levels in the image area as the partition backlight brightness, and compared with the maximum value method, the energy-saving effect is greatly improved, but the display brightness of the image highlight area is easily reduced, the display brightness of the image dark area is improved, and the image after dimming is still easily distorted. In addition, the backlight extraction algorithm also includes a table look-up method, a CDF method, a gaussian function method, a dynamic threshold method, and the like. The table look-up method is that on the basis of the average value method, a backlight correction value is added according to the brightness information of the subareas, and the obtained result is the backlight brightness of the area; the CDF method utilizes the gray level histogram of each subarea of the image to obtain the probability density curve of each subarea, the probability density curves of the subareas are accumulated to obtain the CDF curve, a preset threshold value K is mapped to a CDF curve gray level axis, the subarea backlight brightness value is obtained, a backlight correction value is added according to the brightness information of the subarea, and the obtained result is the backlight brightness of the area. The method comprises the steps of extracting backlight by using an average value and a variance of brightness of an input image, obtaining a gray value for separating a foreground from a background by using a maximum inter-class variance method through a dynamic threshold method, carrying out binarization processing on the image to calculate a subarea backlight adjusting coefficient, further determining a subarea backlight dimming gray level and a subarea backlight dimming ratio, and finally obtaining a subarea backlight value by using the subarea backlight dimming ratio in combination with a maximum value and the average value.
Third, the invention
The technical scheme adopted by the invention is as follows: optimizing a local dimming algorithm by utilizing decomposition-based multi-objective optimization, comprising the following steps of:
1. a regional dimming model based on multi-objective optimization is characterized by comprising the following steps:
(1) initialization: and initializing the multi-objective optimization parameters and the image parameters.
(2) Iterative evolution: and generating a filial generation individual by using a genetic operator and evaluating.
(3) Updating: updating the neighborhood by using a Chebyshev aggregation method, comparing the optimal conditions of the filial generation individuals and the neighbor individuals according to the aggregation value, and then updating the neighborhood. Finally, the outer population EP is updated, the non-dominant solution is added to the EP, and the dominant solution is removed from the EP.
2. The regional dimming model based on multi-objective optimization according to 1, is characterized in that the step 1) comprises:
(1) after the image is read in, the image is down-sampled to improve the operation speed.
(2) Setting the maximum iteration times maxgen, the population size N and the neighbor scale size T, generating a group of uniformly distributed weight vectors, calculating Euclidean distances of the weight vectors, and storing the index values of the nearest T neighbors of each weight vector in B.
(3) And carrying out backlight extraction on the sampled image to obtain a backlight matrix, changing the two-dimensional backlight matrix into a one-dimensional individual as an initial individual, setting the optimizing range within plus or minus 20 of the brightness value of the individual, and if the brightness is higher than 255 or lower than 0, setting the backlight value to be 255 or 0.
(4) N individuals are randomly generated by the initial individual, each individual is evaluated, and the evaluation values are normalized to improve the algorithm performance.
(5) Setting the EP of the external population to be empty, and storing the individual in the iterative process
3. The multi-objective optimization-based regional dimming model initialization process according to the method 2, wherein in the step 4), an individual objective function value is obtained from each individual in the initialization population, and the evaluation process comprises the following steps:
(1) and changing the one-dimensional individuals into a two-dimensional backlight matrix, performing backlight smoothing operation on the backlight matrix to obtain the backlight matrix with the same size as the input image, and performing pixel compensation on the matrix.
(2) Calculating the mean square error mse of the compensated image, wherein the formula is as follows:
Figure BSA0000250964000000031
(3) calculating power consumption pc and contrast cr, wherein the formula is as follows:
Figure BSA0000250964000000032
Figure BSA0000250964000000041
4. the multi-objective optimization-based local dimming model according to claim 1, wherein, in step 2), two references are randomly selected from b (i), then a new solution is generated for two parent individuals and xl by using a genetic operator, if a certain dimension of a child individual exceeds a set upper or lower brightness value, the brightness value of the dimension is set as the upper or lower brightness value, and finally the function value of the child individual is evaluated.
5. The regional dimming model based on multi-objective optimization according to 1 is characterized in that in step 3), the neighborhood is updated by using a frog leap thought, and the method comprises the following steps:
(1) comparing the aggregation function value of the filial generation individual with the aggregation function values of the T neighbors, if the filial generation individual is better than a certain neighbor, replacing the neighbor with the filial generation individual, otherwise, performing the second step
(2) And (3) sequencing according to the frog population fitness value to obtain the optimal frog and the worst frog in the neighbors, generating an individual by using the information of the optimal frog, comparing the aggregation function value of the individual with the aggregation function values of the T neighbors, replacing the neighbor by the individual if the individual is better than the neighbor, and otherwise, carrying out the third step.
(3) Two individuals were randomly generated to replace the worst two individuals in the neighborhood.
Description of the drawings
The attached drawing is an improved process for updating a neighborhood solution by multi-objective optimization based on decomposition adopted by the invention.
Fifth, detailed description of the invention
1. Initialization
1.1 setting experiment parameters including maximum iteration times gen, algorithm population scale N, neighbor scale T, cross probability pc and variation probability pm, and determining an upper limit xmax and a lower limit xmin of a decision variable.
1.2 obtaining N evenly distributed weight vectors
1.3 down-sampling the image gray-scale map, obtaining a group of backlight values based on LUT algorithm, and randomly generating a plurality of groups of backlight values by the group of backlight values
1.4 evaluate this set of solutions, get the original objective function values, store the minimum of the target values for each sub-problem into z, which is the best value found so far, and add the non-dominated solution to the outer population EP.
1.5, calculating Euclidean distance between the weight vectors, and searching indexes of T weight vectors nearest to each weight vector.
2. Iterative evolution
2.1 randomly taking two indexes k and l in B, generating a filial generation unit for two parents and using a genetic operator, and if a certain dimension of the filial generation unit exceeds a set upper limit value or lower limit value, setting the dimension as the upper limit value or lower limit value.
2.2 evaluating the offspring individuals to obtain three objective function values.
3 updating
And 3.1 updating the neighbor B (i) according to the selected aggregation method, selecting a Chebyshev method in the text, comparing the individuals in the neighbor according to a formula of the Chebyshev method to update the value of the corresponding subproblem, and generating a new solution to replace the worst individual in the neighbor solution through a frog-leap algorithm if the update does not occur.
3.2 update the outer population EP, update according to calculating the value of each subproblem, add non-dominant solutions to the EP, remove dominant solutions from the EP.

Claims (5)

1. A regional dimming model based on multi-objective optimization is characterized by comprising the following steps:
1) initialization: initializing multi-objective optimization parameters and image parameters;
2) iterative evolution: generating a filial generation individual by using a genetic operator and evaluating;
3) updating: updating the neighborhood by using a Chebyshev aggregation method, comparing the optimal conditions of the filial individuals and the neighbor individuals according to the aggregation value, then updating the neighborhood, finally updating the external population EP, adding the non-dominant solution into the EP, and removing the dominant solution from the EP.
2. The regional dimming model based on multi-objective optimization according to 1, is characterized in that the step 1) comprises:
1) after an image is read in, the image is down-sampled to improve the operation speed;
2) setting the maximum iteration times maxgen, the population size N and the neighbor scale size T, generating a group of uniformly distributed weight vectors, calculating Euclidean distances of the weight vectors, and storing index values of the nearest T neighbors of each weight vector in B;
3) carrying out backlight extraction on the sampled image to obtain a backlight matrix, changing a two-dimensional backlight matrix into a one-dimensional individual as an initial individual, setting the optimizing range within plus or minus 20 of the brightness value of the individual, and if the brightness is higher than 255 or lower than 0, setting the backlight value to be 255 or 0;
4) randomly generating N individuals by the initial individual, evaluating each individual, and carrying out normalization processing on the evaluation value to improve the algorithm performance;
5) and setting the external population EP to be empty, and storing the individuals in the iteration process.
3. The multi-objective optimization-based regional dimming model initialization process according to the method 2, wherein in the step 4), an individual objective function value is obtained from each individual in the initialization population, and the evaluation process comprises the following steps:
1) changing the one-dimensional individuals into a two-dimensional backlight matrix, performing backlight smoothing operation on the backlight matrix to obtain the backlight matrix with the same size as the input image, and performing pixel compensation on the matrix;
2) calculating the mean square error mse of the compensated image;
3) calculating power consumption pc and contrast cr, wherein the formula is as follows:
Figure FSA0000250963990000011
4. the multi-objective optimization-based local dimming model according to claim 1, in step 2), two indexes are randomly selected from b (i), then a genetic operator is used for two parent individuals to generate a new solution, if a certain dimension of a child individual exceeds a set upper limit value or a set lower limit value of brightness, the brightness value of the dimension is set as the upper limit value or the lower limit value, and finally the function value of the child individual is evaluated.
5. The regional dimming model based on multi-objective optimization according to 1 is characterized in that in step 3), the neighborhood is updated by using a frog leap thought, and the method comprises the following steps:
1) comparing the aggregation function value of the filial generation individual with the aggregation function values of the T neighbors, if the filial generation individual is better than a certain neighbor, replacing the neighbor with the filial generation individual, otherwise, performing the second step;
2) sorting according to the frog population fitness value to obtain the optimal frog and the worst frog in the neighbors, generating an individual by using the information of the optimal frog, comparing the aggregation function value of the individual with the aggregation function values of the T neighbors, replacing the neighbor by the individual if the individual is better than the neighbor, and otherwise, performing the third step;
3) two individuals were randomly generated to replace the worst two individuals in the neighborhood.
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