TWI382395B - A backlight modulation and image processing method - Google Patents

Description

Method for backlight adjustment and image processing

The invention relates to a method for backlight modulation and image processing, particularly for appropriately adjusting the brightness of the backlight for different image materials, and reprocessing the original image data to match the brightness of the backlight after the modulation, and maintaining the original Image quality.

In order to save power consumption, an electronic device with an LCD screen will design a simple function of changing the backlight brightness on the backlight module. The user can set the backlight brightness to the bright mode according to the operating state of different electronic devices (bright) Mode) or normal mode. In bright mode, the brightness is about 400 cd/m ² ; if it is in the normal mode, the brightness is about 250 cd/m ² to achieve a simple power saving function. However, there are two problems worthy of improvement in the way of modulating the brightness of the backlight. First, it is necessary to change the backlight mode according to the user's operating state, which is a step for the user; second, for For different input image information, the over-bright or over-bright backlight will affect the image quality of the output, which will cause discomfort when viewing the human eye.

For example, in the case of U.S. Patent No. 5,598,565, the electronic device is configured to adjust the power consumption by setting a power management system for the purpose of saving power loss. The power management system performs power supply control and power saving control for three sub-devices, such as a hard drive disk, a floppy drive disk, and a flat panel display driver. In the power adjustment control part of the two sub-devices of the hard disk device and the floppy disk device, when the portable computer is idle for more than the software setting time, the system will issue a command to turn off the speed operation of the hard disk device and the floppy disk device to save the operation. The purpose of power consumption. In the flat display device adjustment control portion, the user saves the power saving mode switch to perform power saving control. When the power saving mode is enabled, it can be divided into static and dynamic pictures. If it is working in a static picture, determine the position of the cursor, reduce the brightness of pixels in other areas and maintain the brightness of the pixels in this area. In order to achieve power saving effect; if it is working in dynamic picture, the power management system of the flat display device will analyze the image data before and after, because the adjacent dynamic image content generally has little difference, so the foreground and the background are utilized. The method is based on the modulation reference. The foreground data generally belongs to the object that will move. As for the background, it belongs to the stationary background. Therefore, the background is fixed for the stationary background, and only the moving object is maintained. . However, there are still three problems in this method that need to be improved. First, in the adjustment control part of the flat display device, if the user works in the normal operation mode, the power saving mode will not be activated, and the power saving effect will not be achieved. Secondly, when the user works in the power saving mode, since only part of the pixel area will maintain the original brightness, the brightness of other areas will be reduced, and the visual effect of the entire display screen to the user will change. It is dark or visually uncomfortable. Thirdly, for a backlit liquid crystal display, the image quality of the output may be deteriorated due to a decrease in the refresh rate.

In addition, Japanese Patent Publication No. 08-201812 discloses a liquid crystal display device which can dynamically modulate a backlight to improve a conventional control mode. The liquid crystal display device mainly includes an average brightness detecting circuit and a backlight control portion. For example, when the average brightness detection circuit detects that the average brightness level of a picture is high, the backlight control circuit is used to reduce the brightness of the backlight. The case can effectively reduce the phenomenon that the liquid crystal display device is too bright or too dark, so that the user can easily and comfortably use the liquid crystal display device, and the user can directly view and feel the dynamic display effect of the image; in other words, That is to improve the contrast characteristics of the dark screen and the bright screen. However, when the average brightness order is low, the brightness of the liquid crystal display device is improved and the image quality is improved. At the same time, when the black image is displayed, the liquid crystal display device (LCD portion) may have some light rays. The backlight portion leaks out, and this phenomenon of light leakage is called loss of true black, which causes the display image to appear whitish and the display effect is deteriorated. Therefore, although the backlight brightness is increased, the disadvantage of pure black loss is also increased.

Further, Japanese Patent No. 2001-27890 discloses an image display device and an image display mode which dynamically adjust the contrast of an image signal and the brightness of a backlight in a specific relationship. The patented technology increases the dynamic range of the image signal according to a compensation value; the compensation value is based on the average brightness and the degree of image signal displacement. Thereby, the contrast of the image is improved on the display screen, and at the same time, the brightness of the backlight is controlled by adjusting to blur the difference between the brightness of the image and the backlight. Therefore, the contrast of the image can be improved by the above processing. However, if an incomplete (crash) image is included, the dynamic range of the image signal is immediately expanded, thus highlighting the defective portion of the image, which is considered by the user to be a defect. If the dynamic range of the image signal is mixed with a noise signal component, and then expanded, the noise signal component will be emphasized and will be identified as a defect by the user.

Furthermore, Japanese Patent No. 06-102484 discloses a dynamic degree of modulation by the correlation of an image signal with a backlight control signal. That is, when a signal is a dark level and a dark level is greater than a threshold value, the backlight brightness is lowered and the dynamic range of the image signal is expanded at the same time. Conversely, if the dark level is not greater than the boundary value, no adjustment will be made to the backlight brightness and image signal. In the case where the image area of the bright level is not affected, the above-described modulation can reduce the unevenness of the brightness of the dark image area. However, the adjustment of the image signal and the brightness of the backlight is mainly based on the analysis of the dark information of the image signal without referring to other information, such as the average brightness of the image signal, etc., therefore, when the image has no dark order When the image signal is not adjusted, the image quality of the image is not improved.

A method of dynamically modulating an image signal and a backlight control signal is also disclosed in the U.S. Patent No. 7,053,881, which is to improve the disadvantages of the aforementioned Japanese Patent Publication No. 08-201812. The main flow of the method is: inputting an image signal, and simultaneously transmitting to a display control portion, an average brightness detecting portion, and a peak detecting portion for processing; The display control unit converts the input image signal into a data mode that the display device can display; the average brightness detection unit performs average brightness calculation on the image signal of the entire image, and the processed average brightness signal value (ave_signal) is transmitted to the backlight control unit as a reference value for backlight modulation; and the peak detection unit performs peak value calculation for the content of different image signals, and the result may be high state (1) And low state (0), and also provide a peak signal value (pek_signal) to the backlight control as a reference for backlight modulation. Therefore, in the backlight control unit, the backlight is modulated by referring to the average luminance signal value and the peak signal value at the same time. Although this method improves the contrast of the displayed image by the addition of the peak detecting portion, it is affected by the brightness change, but the image quality is lowered, and the display effect of the original image cannot be maintained.

Therefore, the present invention provides a method for backlight modulation and image processing in response to the above problems and disadvantages, so that the backlight is modulated without blurring and affects the visual perception of the user while maintaining image quality.

The invention provides a method for backlight modulation and image processing, which obtains an average image level value by analyzing image information of each image, and calculates an image according to an average image level value. The backlight brightness is reduced, thereby achieving the purpose of backlight modulation, and at the same time, the image information is converted and reset by the color model, thereby obtaining an image output value, so that the flicker phenomenon does not occur when the backlight is modulated. It affects the user's visual perception, while maintaining the color of the image and enhancing contrast.

To achieve the above objective, the present invention provides a backlight modulation and image processing method, which includes the following steps: obtaining an average picture level (APL) and then obtaining a backlight modulation rate, wherein the average image is obtained. The image level value is obtained by analyzing an image information; and the first brightness factor of the image information is obtained, and the first brightness factor is reset to a second brightness factor according to a brightness factor reset model. a scale factor, and then calculating the scale factor and one of the image information input values to obtain an image output value; thereby, according to the backlight modulation rate, the backlight brightness is modulated and the image is processed according to the image output value, To maintain image quality.

With the implementation of the present invention, at least the following advancements can be achieved: 1. By adjusting the brightness of the backlight to achieve power saving effect.

Second, reduce the occurrence of flicker in the process of modulating the backlight.

Third, improve the image contrast to maintain the same image quality as the original image.

In the backlight module, the edge-emitting type LED structure of the present invention is used to effectively reduce the thickness of the backlight module.

The detailed features and advantages of the present invention are described in detail in the embodiments of the present invention, which are to be understood by those of ordinary skill in the art. The objects and advantages associated with the present invention can be readily understood by those skilled in the art.

In order to further understand the objects, structures, features and functions of the present invention, the embodiments are described in detail below. The above description of the present invention and the following description of the embodiments of the invention are intended to illustrate and explain the principles of the invention.

Please refer to FIG. 1 , which is a block diagram of a preferred embodiment of the present invention. The backlight modulation and image processing method of the embodiment includes: step S200: backlight modulation step; and step S300: image processing step .

The step S200 includes: step S210: obtaining an average image level value; and step S220: obtaining a backlight modulation rate.

Please refer to FIG. 2a, which is a block diagram of a method for obtaining an average image level value according to the present invention. The method of step S210 includes: step S211: preset a pixel percentage value; and step S212: analyzing image information, which is Analyze the grayscale value of each pixel in the image, and count the number of pixels of each grayscale value, thereby establishing an analysis statistical information, which can be an analysis statistical graph, and calculate one of the total pixels of the image. The quantity, in which the gray scale value of each pixel in the analysis chart is obtained according to the sub-pixel data of each pixel data, such as max(R, G, B), 1/3*(R+G+B) or 0.299×R+0. 587×G+0.114×B; wherein R, G, and B are image information in the RGB color model, but are not limited to the above method; Step S213: accumulating each gray from the high gray level value to the low gray level value The number of pixels of the order value is obtained to obtain a cumulative number of pixels, thereby analyzing the brightness ratio of the image; step S214: determining whether the number of accumulated pixels is equal to the product of the total number of pixels and the pixel percentage value or greater than the total The minimum integer quantity of the number of pixels and the percentage of the pixel percentage; and step S215: The result of the step S214 is that if the number of accumulated pixels is equal to the product of the total pixel number and the pixel percentage value or the minimum integer quantity of the product of the total pixel quantity and the pixel percentage value, the gray scale value is taken as the average image. Like the level value.

Please refer to FIG. 2b, which is a block diagram of another method for obtaining an average image level value according to the present invention. Step S210′ is another method for obtaining an average image level value, which includes: Step S211: Preset a pixel percentage value; step S216: obtaining a pixel percentage difference, which is obtained by subtracting the pixel percentage value from the value 1 to obtain a pixel percentage difference; and step S212: analyzing image information, which is an analysis image The grayscale value of each pixel, and the number of pixels of each grayscale value is calculated, thereby establishing an analysis statistical information, which can be an analysis statistical graph, and calculating the total number of pixels of the image; S217: accumulating the number of pixels of each grayscale value from the low grayscale value to the high grayscale value to obtain a cumulative number of pixels, thereby analyzing the brightness ratio of the image; and step S218: determining the number of accumulated pixels Whether it is equal to the product of the total pixel quantity and the pixel percentage difference or the minimum integer quantity of the product of the total pixel quantity and the pixel percentage difference; and step S219: when the step 218 determines that the accumulated pixel quantity is equal to the total picture Number of primes and percentage of pixels When the product of the difference value is greater than the minimum integer quantity of the product of the total pixel quantity and the pixel percentage difference, the gray level value at this time is taken as the average image level value.

Please refer to FIG. 2c again, which is a graph for capturing image information according to the present invention, which uses Histogram Analysis to obtain an average image level (APL) value; and the extraction step is to analyze an image. Like the grayscale value of each pixel of the information, the number of pixels of each grayscale value is counted, so that the brightness ratio of the image can be known, and the total number of pixels of the image information can be known. In order to make appropriate light and dark change judgments on the brightness ratio of the image, the number of pixels of each gray scale value is accumulated from the high gray scale value in the analysis chart to the low gray scale value to obtain a cumulative number of pixels. And determining whether the number of accumulated pixels is equal to the product of the total pixel and the pixel percentage value or the minimum integer quantity of the product of the total pixel quantity and the pixel percentage value; when the judgment result is the number of accumulated pixels is equal to the total number of pixels When the product of the pixel percentage value or the minimum integer quantity of the total pixel quantity and the pixel percentage value is multiplied, the grayscale value at this time is taken as the average image level value.

For example, if the preset pixel percentage value is 25%, after analyzing the image information, the brightness and darkness ratio of the image can be known as the total number of pixels of the image information, such as from the high grayscale value. The low grayscale value accumulates the number of pixels of each grayscale value to obtain a cumulative number of pixels. When the number of accumulated pixels is equal to 25% of the total number of pixels, the grayscale value at this time is taken as an average graph. Like the level value. If the number of pixels of each grayscale value is accumulated from the low grayscale value to the high grayscale value to obtain a cumulative number of pixels, the first pixel percentage value is first subtracted from the value 1 to obtain a picture. The percentage difference of the prime percentage is 75%, and when the number of accumulated pixels is equal to 75% of the total number of pixels, the grayscale value at this time is taken as the average image level value.

Please refer to FIG. 3a and FIG. 3b, wherein FIG. 3a is a block diagram of the image processing step of the present invention, and FIG. 3b is a linear relationship diagram of the average image level value and the backlight adjustment rate of the present invention; the method of step S220 includes: Step S221: setting a variable value (var); step S222: obtaining a maximum average image level value (APL _max ); step S223: obtaining a reference value (m); and step S224: obtaining a backlight modulation rate.

The maximum average image level value (APL _max ) is calculated by reading the number of image data bits n of the image information. If the number of image bits is 8, the average image level value is the largest. The value is 2 ⁸ -1, and the reference value (m) is equal to the maximum average image level value (APL _max ) divided by the integer value of the difference between the 1 and the variable value (1-var), or greater than the maximum average image. The level value (APL _max ) is divided by the smallest integer value of the difference (1-var) between 1 and the variable value, that is, m=APL _max /(1-var), where m is an integer, or m>APL _max /(1-var), where m is the smallest integer; backlight modulation rate (BackDim) is obtained by dividing the average image level (APL) by the reference value (m) and adding the variable value (var). That is to say, the backlight modulation rate can be written as the following equation BackDim=(APL/m)+var.

For example, if the variable value is set to 0.5 and the number of image bits is 8, the maximum average image level value (APL _max ) is 255, so the reference value (m) can be further calculated as the value 510. Therefore, the backlight modulation equation can be written as BackDim=(APL/510)+0.5, so after obtaining the average image level value, the average image level value (APL) can be substituted into the backlight modulation equation. Get the backlight modulation rate. Since the average image level value is linear with the backlight modulation rate, the brightness change of the image can be more adaptively modulated during the backlight adjustment process, so that the image is static or dynamic. There will be no flickering during the display, and depending on the image, the backlight modulation will have different modulation results.

Referring to FIG. 1 again, step S300 includes: step S310: obtaining a first brightness factor; step S320: establishing a brightness factor reset model; step S330: resetting the first brightness factor to a brightness factor reset model according to a second brightness factor; step S340: obtaining a scale factor; and step S350: obtaining an image output value.

The method of step S310 is obtained by converting image data from an RGB color model to a YUV color model and then taking a luminance factor in the YUV color model. Because Y is the brightness factor, U and V are the color factors in the YUV color model, and since the embodiment only modulates the backlight, only the brightness factor in the YUV color model is taken as the first brightness factor. The conversion of the RGB color model to the YUV color model may use, for example, the following conversion equation: Y = max (R, G, B); Y = 1/3 * (R + G + B); or Y = 0.299 × R + 0.587 × G + 0 .114×B; wherein R, G, and B are image information in the RGB color model, but are not limited to the above conversion equation. The following description takes the equation of Y=0.299×R+0.587×G+0.114×B as an example.

Please refer to FIG. 4 , which is an image information analysis statistical graph of three different images of the present invention, which is an analysis statistical information of three different images, and if the pixel percentage value is set to 25%, and is high The gray scale value accumulates the number of pixels of each gray scale value to the low gray scale value until the sum of the number of pixels is greater than 25% of the total number of pixels, and the APL ₁ and the APL can be extracted from the three analytical statistical curves respectively. ₂ , APL ₃ three grayscale values as the average image level value, and APL ₁ , APL ₂ , APL ₃ are between 0 and 255 respectively.

Please refer to FIG. 5a, FIG. 5b and FIG. 5c at the same time, which are respectively the resetting factor 1, the reset model 2 and the reset model 3 of the brightness factor of the invention, wherein the average image level value is low (as shown in FIG. 4 ). APL ₁ ), that is to say, the image is dark after being interpreted, then the corresponding turning point of the reset curve is Y=α, and the transition interval of the bright part in the brightness factor reset model is larger. And the brightness of the backlight will be reduced more; or when the average image level is moderate (such as APL _{2 in} Figure 4), that is, the image is bright and dark after the interpretation, the reset curve The turning point is Y=β, and the transition interval of the bright part of the brightness factor reset model will be located close to half, at which time the backlight brightness is reduced by about half; or when the average image level is higher (such as In Fig. 4, APL ₃ ), that is, the image is brightened after being interpreted, the turning point of the reset curve is Y=γ, and the transition interval of the bright portion in the brightness factor reset model is narrower. At this time, the backlight brightness is reduced to a lesser degree; wherein the β system is between α and γ.

That is, the preferred embodiment of step S320 (not limited thereto) is when the first brightness factor is greater than the turning point of the reset curve, and then the first brightness factor is reset after the reset curve is formed. The brightness factor is greater than the first brightness factor; and if the first brightness factor is less than the turning point of the reset curve, the first brightness factor is reset by the reset curve, and the formed second brightness factor is less than or equal to the first Luminance factor; and when the first brightness factor is equal to the turning point of the reset curve, then the second brightness factor is equal to the first brightness factor.

In step S330, the first brightness factor is reset to the second brightness factor according to the brightness factor reset model.

In step S340, the method of obtaining the scale factor is obtained by dividing the second brightness factor (Y') by the first brightness factor (Y), and can also be written as Scale=Y'/Y. The ratio of brightness to be adjusted.

In step S350, the method of obtaining the image output value is to multiply the scale factor (Scale) and one of the image information input values (Ri, Gi, Bi) to obtain an output image output value (Ro). , Go, Bo). That is to say, Ro = Scale × Ri; Go = Scale × Gi; Bo = Scale × Bi.

Thereby, the backlight modulation step S200 and the image processing step S300 are integrated to achieve the power saving effect of modulating the brightness of the backlight, and effectively maintaining the displayed image quality, in addition to improving the image contrast effect, the image quality is also improved. No distortion.

For example, referring to FIG. 6a, it is a color image of an input image in another embodiment of the present invention, which is an image to be subjected to backlight adjustment and image processing, and the image input value is (Ri, Gi, Bi). = (50, 100, 150), according to the method of the present invention, the image input value is first converted from the RGB color model to the YUV color model, according to the conversion equation Y = 0.299 × R + 0.587 × G + 0.114 × B =0.299×50+0.587×100+0.114×150=90.75

It can be known that the first brightness factor (Y) is 90.75, please refer to FIG. 6b at the same time, which is a graph of the brightness factor reset model of the implementation force, and the reset curve is reset according to the brightness factor shown in FIG. 6b. The turning point is Y=66 to reset the first brightness factor (Y) to the second brightness factor (Y'); since the first brightness factor (Y) is known to be 90.75, the second brightness factor can be known ( Y') is 105; then calculate the scale factor (Scale), Scale=Y'/Y=105/90.75=1.167; after calculating the scale factor is 1.167, then the scale factor and the image input value (Ri, Gi , Bi) After the product processing, it can be known that the image output values (Ro, Go, Bo) are Ro = scale × Ri = 1.167 × 50 = 58.35; Go = scale × Gi = 1.167 × 100 = 116.7; Bo = scale ×Bi=1.167×150=175.05; please refer to FIG. 6c again, which is an image color diagram of FIG. 6a after being processed by the image processing step.

From the above results, it can be deduced that Ri:Gi:Bi=50:100:150=1:2:3=Ro:Go:Bo=58.35:116.7:175.05; therefore, the image after image processing can also be known. It can effectively maintain its Hue.

In addition, after the max (Ri, Gi, Bi) analysis of the histogram and the average image level value interpretation, the average image level value is obtained, and the backlight modulation rate BackDim is calculated by the backlight modulation equation. 0.79, BackDim=(150/510)+0.5=0.79.

Please also refer to FIG. 6d, which is an image color image processed by the backlight modulation step in FIG. 6c, that is, the brightness of the backlight should be reduced by 21% so that the brightness of the backlight becomes 79% of the original and the image is processed. The latter image is adjusted to reduce the backlight brightness by 21%, so that the output image quality as shown in FIG. 6d is similar to the input image quality shown in FIG. 6a, and the power saving effect is achieved.

Although the present invention has been disclosed above in the foregoing embodiments, it is not intended to limit the invention. It is within the scope of the invention to be modified and modified without departing from the spirit and scope of the invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

S200. . . Backlight modulation step

S210, S210’. . . Obtain average image level value

S211. . . Preset pixel percentage value

S212. . . Analyze image information

S213. . . Accumulating the number of pixels of each grayscale value from a high grayscale value to a low grayscale value to obtain the number of accumulated pixels

S214. . . Determines whether the number of accumulated pixels is equal to the product of the total number of pixels and the percentage of pixels, or the minimum number of products greater than the total number of pixels and the percentage of pixels.

S215. . . Average image level value

S216. . . Get the percentage difference in pixels

S217. . . Accumulating the number of pixels of each grayscale value from a low grayscale value to a high grayscale value to obtain the number of accumulated pixels

S218. . . Determines whether the number of accumulated pixels is equal to the product of the total pixel quantity and the pixel percentage difference or the minimum integer quantity of the product of the total pixel quantity and the pixel percentage difference.

S219. . . Average image level value

S220. . . Get the backlight modulation rate

S221. . . Set variable value

S222. . . Get the maximum average image level

S223. . . Get reference value

S224. . . Get the backlight modulation rate

S300. . . Image processing steps

S310. . . Get the first brightness factor

S320. . . Establish a brightness factor reset model

S330. . . Reset the first brightness factor to a second brightness factor according to the brightness factor reset model

S340. . . Scale factor

S350. . . Get image output value

1 is a block diagram of a flow of a preferred embodiment of the present invention.

2a is a block diagram of a method for obtaining an average image level value according to the present invention.

2b is a block diagram of another method for obtaining an average image level value according to the present invention.

Figure 2c is a graph of image information captured by the present invention.

Figure 3a is a block diagram of the flow of the image processing steps of the present invention.

Figure 3b is a graph showing the linear relationship between the average image level value and the backlight adjustment rate of the present invention.

FIG. 4 is an image information analysis statistical graph of three different images of the present invention.

Figure 5a is a brightness factor reset model one applied to Figure 4.

Figure 5b is a brightness factor reset model 2 applied to Figure 4.

Figure 5c is a luminance factor reset model three applied to Figure 4.

Figure 6a is a color diagram illustrating an input image in another embodiment of the present invention.

Figure 6b is a graph of the brightness factor reset model of the present embodiment.

Figure 6c is an image color diagram of Figure 6a after being processed by an image processing step.

Figure 6d is an image color diagram of Figure 6c after being processed by a backlight modulation step.

S200. . . Backlight modulation step

S210. . . Obtain average image level value

S220. . . Get the backlight modulation rate

S300. . . Image processing steps

S310. . . Get the first brightness factor

S320. . . Establish a brightness factor reset model

S330. . . Reset the first brightness factor to a second brightness factor according to the brightness factor reset model

S340. . . Scale factor

S350. . . Get image output value

Claims (11)

A backlight modulation and image processing method, comprising the steps of: analyzing an image information to obtain an average image level value, and then obtaining a backlight modulation rate by calculating the average image level value; and analyzing The image information obtains a first brightness factor, and after the first brightness factor is reset to a second brightness factor according to a brightness factor reset model, a scale factor is obtained, and the scale factor is the second brightness factor and the a ratio of the first brightness factor, and then calculating the scale factor and the image input value of the image information to obtain an image output value; thereby, according to the backlight modulation rate, the backlight brightness is modulated according to the The image output value processes the image. The method of claim 1, wherein the method for obtaining the average image level value comprises the steps of: preset a pixel percentage value; analyzing the image information, obtaining an analysis statistical information, and a total The number of pixels; accumulating the number of pixels of each grayscale value from the high grayscale value to the low grayscale value to obtain a cumulative number of pixels; determining whether the number of accumulated pixels is equal to the total number of pixels and the painting The product of the prime percentage value or the minimum integer quantity of the product of the total number of pixels and the percentage of the pixel percentage; and when the number of accumulated pixels is equal to the product of the total number of pixels and the percentage of the pixel, or greater than the total number of pixels When the minimum integer quantity of the product of the pixel percentage value is used, the gray scale value is extracted as the average image level value. The method of claim 1, wherein the method for obtaining the average image level value comprises the steps of: presetting a pixel percentage value; obtaining a pixel percentage difference, which is subtracted by 1 The pixel percentage value is obtained; analyzing the image information to obtain an analysis statistical information and a total number of pixels; and accumulating the number of pixels of each gray level value from the low gray level value to the high gray level value to obtain a cumulative number of pixels; determining whether the number of accumulated pixels is equal to a product of the total pixel quantity and the pixel percentage difference or a minimum integer quantity greater than a product of a total pixel quantity and a pixel percentage difference; and when When the number of accumulated pixels is equal to the product of the total pixel quantity and the pixel percentage difference or the minimum integer quantity of the product of the total pixel quantity and the pixel percentage difference, the gray level value is taken as the average figure. Like the level value. The method of claim 1, wherein the method for obtaining the backlight modulation rate comprises the steps of: setting a variable value; and obtaining a maximum average image level value by reading the image. The information is obtained by calculating the number of bits of the image data n; obtaining a reference value that is greater than the maximum average image level value divided by the value of the difference between the variable value and the reference value, and the reference value is An integer, or a minimum integer value greater than a maximum average image level value divided by a difference between 1 and a variable value; and obtaining the backlight modulation rate, which is the average image level value divided by the reference value In addition, the variable value is used to obtain the backlight modulation rate. The method of claim 1, wherein the first brightness factor is obtained by converting the image information from an RGB color model to a YUV color model, wherein the first brightness factor is The brightness factor in the YUV color model. The method of claim 1, wherein the brightness factor reset model is a reset curve having a turning point. The method of claim 6, wherein the brightness factor reset model is that when the first brightness factor is greater than the turning point, the second brightness factor is greater than the first brightness factor. The method of claim 6, wherein the brightness factor reset model is that when the first brightness factor is less than the turning point, the second brightness factor is less than or equal to the first brightness factor. The method of claim 6, wherein the brightness factor reset model is that when the first brightness factor is equal to the turning point, the second brightness factor is equal to the first brightness factor. The method of claim 1, wherein the scaling factor is calculated by dividing the second luminance factor by the first luminance factor. The method of claim 1, wherein the image output value is obtained by multiplying the image input value by the scale factor.