Sunlight readable enhancement method for mobile phone display screen

Abstract

The invention relates to the technical field of intelligent mobile phone display control and image processing, in particular to a mobile phone display screen sunlight readable enhancement method which is suitable for a TFT LCD display screen or an OLED display screen of an intelligent mobile phone. Extracting average picture brightness and gray level distribution characteristics of the display content; the reflection environment brightness is estimated based on the equivalent reflection parameter kR of factory calibration, the environment contrast including reflection items is calculated, and the white field brightness required for achieving the target environment contrast is obtained through reverse derivation; under the comprehensive constraint of display side energy budget and power temperature rise, brightness closed loop is realized for the LCD through backlight control quantity, and high power consumption content is suppressed for the OLED through global brightness and APL amplitude limiting; and meanwhile, the low-gray recognizable degree is improved by utilizing tone mapping or segmented gamma generated on the basis of a recognizable degree mapping lookup table, and smooth anti-jitter is realized through hysteresis and change rate limitation. Compared with the prior art, reflection estimation and an environment contrast closed loop are taken as a core, power consumption temperature rise hard constraint and recognizable degree driven gamma mapping are superposed, readability in a strong light environment is improved, and endurance and temperature rise are taken into consideration.

Description

Technical Field This invention relates to the field of smartphone display control and image processing technology, and in particular to a method for enhancing the sunlight readability of a mobile phone display screen. Background Technology Smartphone screen readability significantly decreases when exposed to direct sunlight or strong diffused light outdoors. This is mainly because ambient light reflects off the cover glass, polarizer, and laminated surfaces, increasing black level brightness and compressing the effective dynamic range, resulting in a washed-out image and difficulty in discerning low-gray details and text edges.

[0001] Existing technologies typically improve outdoor readability by increasing peak brightness, applying anti-reflective coatings, or performing gamma / contrast enhancement. However, simply increasing brightness significantly increases power consumption and temperature rise, and under reflective conditions, it may still result in "brighter but less clear" images. Image enhancement alone is insufficient to guarantee low grayscale discernibility under strong reflection. Furthermore, most solutions lack a calculable closed loop targeting "ambient contrast including reflectivity" and a control framework that hardens battery life and temperature rise constraints into power limits, making it difficult to simultaneously achieve both strong light readability and battery life. Summary of the Invention I. Purpose of the Invention The purpose of this invention is to provide a method for enhancing the readability of a mobile phone display screen in sunlight. By estimating the brightness of the reflective environment and calculating the environmental contrast including the reflective term, the white field brightness required to achieve the target environmental contrast is derived. Under the constraints of energy budget and temperature rise on the display side, the global brightness and APL of the backlight of the TFT LCD or OLED are controlled. At the same time, tone mapping or segmented gamma is generated based on the discernibility mapping to improve the discernibility of low grayscale. Frequent switching and flicker are suppressed by hysteresis and rate of change limits, thereby significantly improving readability in strong light environments while taking into account battery life and temperature rise.

[0002] II. Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: Step S1, Status Acquisition Obtain ambient light illuminance E and ambient light color temperature Tc, obtain display screen or overall device temperature T, obtain battery state of charge SoC and user expected remaining usage time Th, obtain the display content of the current frame or the most recent N frames and calculate the content feature set F, wherein the content feature set F includes at least average screen brightness APL and grayscale histogram H.

[0003] Step S2, Estimation of ambient brightness of reflected light Based on the ambient illuminance E and the equivalent reflection parameter kR obtained from factory calibration, the reflected ambient luminance Lr is estimated, satisfying: Lr = kR × E.

[0004] Step S3: Environmental contrast calculation and target determination Measure or estimate the white luminance Lw and black luminance Lb under the current display configuration, and calculate the ambient contrast ratio (ACR) using the following formula: ACR = (Lw + Lr) / (Lb + Lr).

[0005] Determine the target ambient contrast ratio (ACRt), with ACRt ranging from 4 to 10, and ACRt not less than 5 in outdoor strong light mode.

[0006] Step S4, Calculation of required white point brightness Calculate the white field luminance Lwreq required to achieve the target ambient contrast based on ACRt, Lb, and Lr: Lwreq = ACRt × (Lb + Lr) Lr, Lwreq is limited to the panel's white point capability limit Lwmax; when Lwreq exceeds Lwmax, a degraded target is allowed to be generated and compensated for by enhancing low grayscale discernibility.

[0007] Step S5: Generation of energy budget and power temperature rise constraint Based on the SoC and Th, the on-side energy budget Eb is calculated, and the allowable average power limit Pav is obtained: Pav = Eb / Th.

[0008] Simultaneously, an instantaneous power upper limit Pth is generated based on temperature T, forming a comprehensive power constraint: Plim = min(Pav, Pth).

[0009] Step S6: Determine the brightness control amount related to the panel type. When the display is a TFT LCD, determine the backlight control amount Ibl so that the white field brightness Lw reaches or approaches Lwreq and the display power Pdisp does not exceed Plim; When the display is OLED, determine the global brightness control value Lo and the APL limiting parameter APLlim so that the white field brightness Lw reaches or approaches Lwreq and the display power Pdisp does not exceed Plim; Pdisp is calculated from the panel power consumption model obtained from the factory calibration.

[0010] Step S7: Tone mapping or segmented gamma generation and application based on identifiable targets. Based on Lr, a low grayscale distinguishability target JNDt is generated, and a tone mapping or segmented gamma parameter G is generated through the factory-preset distinguishability mapping lookup table LUTJ and applied to the image output, so that the minimum distinguishability of the low grayscale segment is not lower than JNDt.

[0011] Step S8, Smoothing and Anti-jitter A hysteresis interval ΔE is introduced for E, and a rate of change limit is set for Ibl or Lo to achieve a smooth transition between mode switching and brightness changes, avoiding frequent switching and flickering.

[0012] Compared with the prior art, the method for enhancing sunlight readability of mobile phone displays of the present invention has the following beneficial effects: 1. Using ambient brightness estimation and ambient contrast ratio (ACR) with reflection as the core of the closed loop, it directly targets the root cause of reflection-induced blackening, and the path to improve readability under strong light is clear and quantifiable.

[0013] 2. By reverse-engineering the required white field brightness Lwreq, and performing brightness control under the constraints of Lwmax, power consumption and temperature rise, a calculable and constrained collaborative optimization of strong light readability and battery life temperature rise is achieved.

[0014] 3. Improve low-grayscale visibility by using tone mapping or segmented gamma generated by LUTJ, and reduce the problems of low-grayscale washout and unclear text edges under strong light conditions.

[0015] 4. Frequent switching is suppressed by hysteresis and rate of change limits, achieving a smooth transition and a better user experience.

[0016] 5. The same control framework is compatible with both TFT LCD and OLED, and can be mapped to backlight control or global brightness and APL limiting control respectively, which facilitates engineering implementation and large-scale application. Attached Figure Description Figure 1 This is a flowchart of the method for enhancing sunlight readability of a mobile phone display screen according to the present invention; Figure 2 This is a system structure block diagram for implementing the mobile phone display sunlight readability enhancement method of the present invention. Detailed Implementation To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0017] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are limited to relative positions on the specified view, rather than absolute positions.

[0018] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0019] Please see Figure 1 and Figure 2 The present invention relates to a method for enhancing the sunlight readability of a mobile phone display screen, specifically a method for improving the sunlight readability of a smartphone display screen under strong ambient light conditions, applicable to TFT LCD displays and OLED displays, comprising the following steps: Step S1, Status Acquisition: Acquire ambient light illuminance E and ambient light color temperature Tc, acquire display screen or whole machine temperature T, acquire battery state of charge SoC and user expected remaining usage time Th, acquire the display content of the current frame or the most recent N frames and calculate the content feature set F, wherein the content feature set F includes at least average screen brightness APL and grayscale histogram H; Step S2, Estimation of reflected ambient brightness: Based on the ambient illuminance E and the equivalent reflection parameter kR obtained from factory calibration, estimate the reflected ambient brightness Lr, wherein Lr satisfies Lr = kR × E; Step S3, Ambient Contrast Calculation and Target Determination: Under the current display configuration, measure or estimate the white field brightness Lw and black field brightness Lb, and calculate the ambient contrast ACR according to ACR = (Lw + Lr) / (Lb + Lr), and determine the target ambient contrast ACRt. The value of ACRt is in the range of 4 to 10, and ACRt is not less than 5 in outdoor strong light mode. Step S4, Calculation of required white point brightness: Calculate the white point brightness Lwreq required to achieve the target ambient contrast based on ACRt, Lb, and Lr, satisfying Lwreq = ACRt × (Lb + Lr). Lr, and limit Lwreq to the panel's white field capability limit Lwmax; Step S5, Energy budget and power temperature rise constraint generation: Based on the SoC and Th, calculate the display-side energy budget Eb and obtain the allowable average power upper limit Pav, where Pav = Eb / Th. At the same time, generate the instantaneous power upper limit Pth based on the temperature T to form the comprehensive power constraint Plim, where Plim = min(Pav, Pth); Step S6, Determination of brightness control amount related to panel type: When the display screen is a TFT LCD, determine the backlight control amount Ibl so that the white-field brightness Lw reaches or approaches Lwreq and the display power Pdisp does not exceed Plim; when the display screen is an OLED, determine the global brightness control amount Lo and the APL limit parameter APLlim so that the white-field brightness Lw reaches or approaches Lwreq and the display power Pdisp does not exceed Plim, where Pdisp is calculated by the panel power consumption model obtained from factory calibration; Step S7, Generation and application of tone mapping or piecewise gamma based on the recognizability target: Generate the low-gray-scale recognizability target JNDt based on Lr, and generate the tone mapping or piecewise gamma parameter G through the pre-factory preset recognizability mapping lookup table LUTJ and apply it to the image output to make the minimum recognizability of the low-gray segment not lower than JNDt; Step S8, Smoothing and anti-jitter: Introduce a hysteresis interval ΔE for E, and set a change rate limit for Ibl or Lo to achieve a smooth transition of mode switching and brightness change.

[0020] The content feature set F further includes the edge density Ed and the text probability Pt, and based on F, the display content is at least divided into text type, graphical interface type, photo type or video type, and different tone mapping intensities and sharpening weights are used for different categories.

[0021] The outdoor strong light mode is triggered by the environmental light intensity threshold Eth, and when E ≥ Eth, let ACRt take values from 5 to 10, and when E < Eth, let ACRt take values from 4 to 6.

[0022] When the calculated Lwreq exceeds Lwmax, generate the degradation target ACRt,deg = (Lwmax + Lr) / (Lb + Lr), and increase the tone mapping weight of the low-gray segment to compensate for readability.

[0023] Eb is calculated as Eb = Er × ηdisp, where Er = SoC × Enom, Enom is the nominal energy of the battery, and ηdisp is the display-side budget coefficient, and ηdisp ranges from 0.15 to 0.35.

[0024] The temperature constraint Pth adopts a piecewise strategy: when T ≤ T1, Pth = Pmax; when T1 < T < T2, Pth decreases linearly; when T ≥ T2, Pth = Pmin, where T1 ranges from 38 to 42 degrees Celsius, T2 ranges from 45 to 48 degrees Celsius, and Pmin is 50 to 70 percent of Pmax.

[0025] When the display screen is a TFT LCD, the backlight control amount Ibl is obtained by back-calculating from Lwreq through a backlight brightness model, and ACR compliance is preferably ensured under the premise of satisfying Plim.

[0026] When the display screen is an OLED, the upper limit of Lo is adaptively adjusted with APLlim, and APLlim is calculated from the content feature set F to suppress the increase in power consumption and temperature rise caused by high APL content.

[0027] The inputs of the LUTJ at least include Lr and Lwmax, and the outputs at least include the segmented gamma parameter G or the tone mapping lookup table LUTG.

[0028] The "reach or approach" is defined as satisfying |ACR ACRt| / ACRt ≤ ε, where ε ranges from 0.05 to 0.10.

[0029] The ambient light color temperature Tc is used to adjust the global color rendering matrix C to reduce color deviation in strong light mode and maintain the stability of skin color and gray scale.

[0030] The equivalent reflection parameter kR is obtained through the following factory calibration: at multiple illuminance points Ei from 500 lux to 100000 lux, make the screen display all black or turn off the display and measure the apparent black field brightness Lb_meas(Ei), establish a fitting relationship with Lb_meas(Ei) = Lb0 + kR × Ei, obtain kR by least squares fitting, and write kR into the panel parameter area.

[0031] The panel power consumption model is a factory-calibrated model: for TFT LCD, Pdisp = P0 + a1×Ibl + a2×Ibl²; for OLED, Pdisp = P0 + b1×Lo×APL + b2×Lo²×APL; and when the display is OLED, APLlim is used to limit the effective value of APL or limit the upper limit of Lo, so that Pdisp does not exceed Plim.

[0032] The generation of LUTJ includes: taking Lr and Lwmax as inputs, constraining the brightness difference between adjacent outputs under strong light conditions according to the minimum distinguishability threshold JNDt of the low gray segment, generating a tone mapping lookup table LUTG or a set of segmented gamma parameters, and writing LUTJ and LUTG into non-volatile memory.

[0033] The segmented gamma parameter G includes the segment point g, the low gray segment gamma g1, and the medium gray segment gamma g2, where g is 24 to 80, g1 is 1.4 to 2.0, and g2 is 2.0 to 2.6. In strong light mode, g1 is reduced to improve the low gray output.

[0034] The hysteresis interval satisfies Ehi = Eth×(1+r) and Elo = Eth×(1+r). r), where r is between 0.10 and 0.20, and a maximum change rate limit is set for Ibl or Lo so that the change does not exceed 5 percentage points every 200 ms, and a gradient blending window of 3 to 10 frames is set for LUTG switching. Detailed Implementation

[0035] I. Definition and Units of Key Quantities The unit of ambient illuminance E is lux.

[0036] The units for ambient reflectance Lr, white field luminance Lw, and black field luminance Lb are cd per square meter.

[0037] Ambient contrast ratio (ACR) = (Lw + Lr) / (Lb + Lr).

[0038] The unit for the user's expected remaining usage time Th is hours.

[0039] The unit of the displayed energy budget Eb is watt-hours.

[0040] The display side power Pdisp and constraint Plim are in watts.

[0041] II. System Structure The terminal includes an ambient light sensor, a temperature sensor, a battery management module, a display control unit, a display driver module, and an image processing module. The ambient light sensor, temperature sensor, and display control unit are each connected to the image processing module, and the display driver module is connected to both the display control unit and the battery management module. The ambient light sensor outputs E and Tc; the temperature sensor outputs T; and the battery management module outputs SoC and battery nominal energy Enom, among other information. The display control unit performs reflection estimation, ACR calculation, target generation, energy budget and power constraint calculation, and issues Ibl or Lo and APLlim based on the panel type, while also issuing tone mapping or segmented gamma parameters.

[0042] III. Factory Calibration 1. Calibration of reflection parameter kR Multiple illuminance points Ei were set up in a standard lighting chamber, covering an area from 500 lux to 100,000 lux. The screen was then set to full black or off, and the apparent black level luminance Lb_meas(Ei) was measured. A fitting relationship was established: Lb_meas(Ei) = Lb0 + kR × Ei.

[0043] Least squares fitting is performed on multiple Ei to obtain kR, and kR is written into the panel parameter region. The typical range of kR is 1×10^-4 to 5×10^-3 cd per square meter per lux.

[0044] 2. White field capability upper limit Lwmax and black field benchmark Lb0 calibration Lb0 was measured in a darkroom; the upper limit of white field capability, Lwmax, was measured under permissible power consumption and temperature rise conditions. Recommended range: Lwmax for LCD is 600 to 1600 cd per square meter; Lwmax for OLED is 800 to 2500 cd per square meter; Lb0 is recommended to be less than 2 cd per square meter.

[0045] 3. Panel power consumption model calibration and OLED APL limiting Fitting a power consumption model for TFT LCD: Pdisp = P0 + a1×Ibl + a2×Ibl^2, Where Ibl is the normalized backlight control value, ranging from 0 to 1.

[0046] Fitting a power consumption model for OLED: Pdisp = P0 + b1×Lo×APL + b2×Lo^2×APL, Where Lo is the normalized global luminance, ranging from 0 to 1, and APL is the average picture luminance, ranging from 0 to 1.

[0047] When the display is an OLED, APLlim is enabled during operation to limit the effective value of APL to min(APL, APLlim) or to limit the upper limit of Lo, so that Pdisp does not exceed Plim.

[0048] 4 LUTJ Generation and Piecewise Gamma Parameter Range With Lr and Lwmax as the LUTJ inputs, the output is the tone mapping lookup table LUTG or the piecewise gamma parameter G. The generation principle is to constrain the adjacent output luminance difference by the minimum distinguishable threshold JNDt in the low gray segment under strong light conditions, so as to improve the distinguishability of the low gray segment. The piecewise gamma parameters include the segmentation point g-point, the low gray segment gamma g1, and the middle gray segment gamma g2: the g-point takes values from 24 to 80, g1 takes values from 1.4 to 2.0, and g2 takes values from 2.0 to 2.6. In the strong light mode, g1 is reduced to raise the low gray output, so as to ensure that the minimum distinguishability of the low gray segment is not lower than JNDt.

[0049] IV. Runtime Control Flow 1 State Acquisition Periodically acquire E, Tc, T, SoC, Th, and extract APL and H from the displayed content; optionally extract Ed and Pt and adjust the tone mapping intensity and sharpening weight according to the content category; optionally use Tc to adjust the global color rendering matrix to reduce color cast.

[0050] 2 Reflection Estimation and ACR Calculation Estimate the reflected ambient luminance according to Lr = kR×E. Measure or estimate Lw and Lb, and calculate the ambient contrast according to ACR = (Lw + Lr) / (Lb + Lr). The outdoor strong light mode is triggered by the threshold Eth. When E ≥ Eth, ACRt takes values from 5 to 10; when E < Eth, ACRt takes values from 4 to 6. Calculate Lwreq = ACRt×(Lb + Lr) Lr calculates Lwreq and limits it to Lwmax. When Lwreq > Lwmax, generate the degraded target ACRt,deg = (Lwmax + Lr) / (Lb + Lr), and increase the tone mapping weight compensation in the low gray segment.

[0051] 3 Energy Budget and Power Temperature Rise Constraint The display-side energy budget is calculated as Eb = Er×ηdisp, where Er = SoC×Enom, and ηdisp ranges from 0.15 to 0.35. The allowable average power upper limit Pav = Eb / Th. The temperature rise constraint Pth adopts a piecewise strategy: when T≤T1, Pth = Pmax; when T1<T<T2, it linearly decreases; when T≥T2, Pth = Pmin, where T1 ranges from 38 to 42 degrees Celsius, T2 ranges from 45 to 48 degrees Celsius, and Pmin is 50 to 70 percent of Pmax. The comprehensive power constraint Plim = min(Pav, Pth). During operation, the power consumption model is used to calculate Pdisp and Pdisp is forced not to exceed Plim.

[0052] 4 Brightness control and clipping When it is a TFT LCD, Ibl is inversely calculated from Lwreq according to the brightness model, and Ibl is adjusted under the power consumption constraint to make Lw reach or approach Lwreq, giving priority to ensuring that the ACR meets the standard.

[0053] When it is an OLED, Lo is determined, and APLlim is linked to limit the power consumption and temperature rise caused by high APL content. The criterion for "reach or approach" can use |ACR ACRt| / ACRt ≤ ε, where ε ranges from 0.05 to 0.10.

[0054] 5 Tone mapping or piecewise gamma driven by recognizability The input Lr and Lwmax are sent to LUTJ, and the output is LUTG or the piecewise gamma parameter G, which is applied to the image output. In the strong light mode, g1 is reduced or a stronger low gray is selected to enhance LUTG to ensure that the minimum recognizability in the low gray segment is not lower than JNDt.

[0055] V. Smoothing and anti-jitter Set the entry threshold Ehi and the exit threshold Elo: Ehi = Eth×(1+r), Elo = Eth×(1 r), where r ranges from 0.10 to 0.20. Set a maximum change rate limit for Ibl or Lo so that the change in every 200 ms does not exceed 5 percentage points. Set a 3-to-10-frame gradual blending window for the LUTG switch to ensure smooth brightness and gamma changes and reduce the sense of flicker and mutation.

[0056] VI. Testing and data templates Test conditions: Panel type LCD and OLED; Illuminance 500, 2000, 10000, 50000, 100000 lux; Content type text, UI, photo, video; Initial temperature 25 degrees Celsius and 40 degrees Celsius; SoC 20%, 50%, 80%; Th 2, 4, 8 hours.

[0057] Record fields: E, kR, Lr, Lw, Lb, ACR, ACRt, whether it meets the standard, Pdisp, Plim, whether it exceeds the limit, Tmax, low gray-scale identifiable pass rate, subjective score.

[0058] Recommended criteria for acceptance: When E≥50000 lux, ACR is not lower than 5 or reaches the maximum achievable ACR after downgrading; Pdisp does not exceed Plim; Tmax does not exceed 48 degrees Celsius; low grayscale recognition pass rate is improved by at least 20% compared to the non-enabled scheme.

[0059] Compared with the prior art, the method for enhancing sunlight readability of mobile phone displays of the present invention has the following beneficial effects: 1. Using ambient brightness estimation and ambient contrast ratio (ACR) with reflection as the core of the closed loop, it directly targets the root cause of reflection-induced blackening, and the path to improve readability under strong light is clear and quantifiable.

[0060] 2. By reverse-engineering the required white field brightness Lwreq, and performing brightness control under the constraints of Lwmax, power consumption and temperature rise, a calculable and constrained collaborative optimization of strong light readability and battery life temperature rise is achieved.

[0061] 3. Improve low-grayscale visibility by using tone mapping or segmented gamma generated by LUTJ, and reduce the problems of low-grayscale washout and unclear text edges under strong light conditions.

[0062] 4. Frequent switching is suppressed by hysteresis and rate of change limits, achieving a smooth transition and a better user experience.

[0063] 5. The same control framework is compatible with both TFT LCD and OLED, and can be mapped to backlight control or global brightness and APL limiting control respectively, which facilitates engineering implementation and large-scale application.

[0064] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for enhancing sunlight readability of a mobile phone display screen, applicable to TFT LCD displays and OLED displays, characterized in that, Includes the following steps: Step S1, Status Acquisition: Acquire ambient light illuminance E and ambient light color temperature Tc, acquire display screen or whole machine temperature T, acquire battery state of charge SoC and user expected remaining usage time Th, acquire the display content of the current frame or the most recent N frames and calculate the content feature set F, wherein the content feature set F includes at least average screen brightness APL and grayscale histogram H; Step S2, Estimation of reflected ambient brightness: Based on the ambient illuminance E and the equivalent reflection parameter kR obtained from factory calibration, estimate the reflected ambient brightness Lr, wherein Lr satisfies Lr = kR × E; Step S3, Ambient Contrast Calculation and Target Determination: Under the current display configuration, measure or estimate the white field brightness Lw and black field brightness Lb, and calculate the ambient contrast ACR according to ACR = (Lw + Lr) / (Lb + Lr), and determine the target ambient contrast ACRt. The value of ACRt is in the range of 4 to 10, and ACRt is not less than 5 in outdoor strong light mode. Step S4, Calculation of required white point brightness: Calculate the white point brightness Lwreq required to achieve the target ambient contrast based on ACRt, Lb, and Lr, satisfying Lwreq = ACRt × (Lb + Lr). Lr, and limit Lwreq to the panel's white field capability limit Lwmax; Step S5, Energy Budget and Power Temperature Rise Constraint Generation: Calculate the display-side energy budget Eb based on SoC and Th and obtain the allowable average power limit Pav, satisfying Pav = Eb / Th. At the same time, generate the instantaneous power limit Pth based on temperature T, forming a comprehensive power constraint Plim, satisfying Plim = min(Pav, Pth). Step S6, determination of brightness control amount related to panel type: When the display screen is a TFT LCD, determine the backlight control amount Ibl so that the white field brightness Lw reaches or approaches Lwreq and the display power Pdisp does not exceed Plim; When the display screen is OLED, the global brightness control quantity Lo and the APL limiting parameter APLlim are determined so that the white field brightness Lw reaches or approaches Lwreq and the display power Pdisp does not exceed Plim, where Pdisp is calculated from the panel power consumption model obtained by factory calibration. Step S7, tone mapping or segmented gamma generation and application based on identifiable target: generate low grayscale identifiable target JNDt based on Lr, and generate tone mapping or segmented gamma parameters G through the factory-preset identifiable mapping lookup table LUTJ and apply them to the image output so that the minimum identifiability of the low grayscale is not lower than JNDt. Step S8, Smoothing and Anti-jitter: Introduce a hysteresis interval ΔE to E, and set a rate of change limit for Ibl or Lo to achieve a smooth transition between mode switching and brightness changes.

2. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, The content feature set F further includes edge density Ed and text probability Pt, and based on F, the displayed content is divided into at least text, graphical interface, photo or video categories, and different tone mapping intensities and sharpening weights are applied to different categories.

3. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, The outdoor strong light mode is triggered by the ambient light illuminance threshold Eth, and when E ≥ Eth, ACRt is set to 5 to 10, and when E < Eth, ACRt is set to 4 to 6.

4. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, When the calculated Lwreq exceeds Lwmax, a downgrade target ACRt,deg = (Lwmax + Lr) / (Lb + Lr) is generated, and the weight of the low gray segment tone mapping is increased to compensate for readability.

5. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, The Eb is calculated as Eb = Er × ηdisp, where Er = SoC × ​​Enom, Enom is the nominal energy of the battery, and ηdisp is the display-side budget coefficient, with ηdisp ranging from 0.15 to 0.

35.

6. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, The temperature constraint Pth adopts a segmented strategy: when T ≤ T1, Pth = Pmax; when T1 < T < T2, Pth decreases linearly; when T ≥ T2, Pth = Pmin, where T1 is 38 to 42 degrees Celsius, T2 is 45 to 48 degrees Celsius, and Pmin is 50 to 70 percent of Pmax.

7. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, When the display screen is a TFT LCD, the backlight control quantity Ibl is obtained by inverse calculation from Lwreq through the backlight brightness model, and ACR is prioritized to meet the requirements under the premise of satisfying Plim.

8. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, When the display is an OLED, the upper limit of Lo is adaptively adjusted according to APLlim, which is calculated from the content feature set F to suppress the increase in power consumption and temperature caused by high APL content.

9. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, The input of the LUTJ includes at least Lr and Lwmax, and the output includes at least the piecewise gamma parameter G or the tone mapping lookup table LUTG.

10. The method for enhancing sunlight readability of a mobile phone display screen as described in claim 1, characterized in that, The term "reaching or approaching" is defined as satisfying |ACR ACRt| / ACRt ≤ ε, where ε ranges from 0.05 to 0.10.

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