Environmentally adaptable gamma auto-calibration system and method
Through an environmentally adaptable automatic Gamma calibration system, the Gamma value is calculated in real time and the image signal is converted into a YUV signal. This solves the problems of complex large-screen design and complicated image input signals in traditional display devices, and achieves the balance of image color grayscale and the optimization of human eye comfort.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- STARLIGHT DISPLAY CORP
- Filing Date
- 2023-05-18
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional display devices, especially large screens composed of multiple small panels, face high complexity in driver IC design during Gamma correction. Furthermore, when the image input signal is RGB, the software design is complicated, affecting economic efficiency and failing to achieve optimal image display for human eye comfort.
An environmentally adaptable automatic gamma adjustment system is adopted. Through the signal receiving module, the scene capture module, and the layer perception control module, the gamma value is calculated in real time based on the surrounding environmental parameters, the image signal is converted into a YUV signal, and the gray level is adjusted by using the maximum brightness current value and adaptive offset compensation to optimize the image display quality.
It reduces the software design complexity and hardware specification requirements of ICs in display devices, optimizes image color grayscale, and ensures that images present a consistent grayscale level and optimal eye comfort in different environments.
Smart Images
Figure CN117253433B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a Gamma correction system for a display device, and more particularly to an environmentally adaptable automatic Gamma adjustment system and method thereof. Background Technology
[0002] When digital images are projected onto a display screen, if the image is displayed on the panel without gamma correction, viewers often perceive the image as washed out, overly bright, or too dark. This is due to factors such as the monitor's light-sensing function: the brightness intensity of pixels is not linearly related to the input voltage intensity, and the human eye's way of capturing brightness is disproportionate: in non-extremely dark or non-extremely bright conditions, normal human vision is more sensitive to changes in darker tones. Therefore, in addition to adjusting backlight brightness or panel drive current to adjust image color effects, various display devices on the market are actively improving the accuracy of gamma correction, aiming to achieve overall image visual brightness correction by precisely adjusting the balance of color grayscale in pixel values.
[0003] However, traditional display devices often adjust the Gamma value through the terminal driver IC of the overall device circuitry. This architecture increases the circuit design complexity of the driver IC, especially for display devices that use multiple small and medium-sized panels to form a large screen. The complexity is further amplified because the driver IC on each small and medium-sized panel needs to be set with synchronous or serial signals. Furthermore, if the image input signal received by the display screen is an RGB signal, the complexity of the software design is further increased because the setting value of each RGB signal source needs to be changed, which is detrimental to the economic efficiency of industrial development. Therefore, this invention aims to explore how to use YCbCr conversion technology to convert any image input signal source into a YUV signal while simultaneously calculating or looking up the optimal Gamma value based on real-time device ambient environmental parameters. This would address the shortcomings of existing technologies, optimize the grayscale balance of the image color, and achieve the most comfortable image display effect for human eyes. Summary of the Invention
[0004] The main objective of this invention is to provide a calibration system that can automatically correct the Gamma value according to environmental conditions, so as to optimize the driving current of the display screen and the grayscale value of the image color by optimizing the environmental parameters, thereby improving the overall image quality.
[0005] To achieve the above objectives, the present invention provides an environmentally adaptable automatic gamma adjustment system, which is installed in a display device to automatically correct the gamma value according to the surrounding environment, thereby adjusting the grayscale perception of an image. The system includes a signal receiving module, a context capture module, and a grayscale control module. The signal receiving module selects an image signal source, receives and converts the image signal into a plurality of first YUV signals. The context capture module detects the surrounding environment and captures at least one environmental data point, and calculates a gamma control parameter for the display screen based on the environmental data. The grayscale control module calculates a maximum brightness current value from the environmental data, and simultaneously uses the gamma control parameter to calculate the plurality of first YUV signals into a plurality of second YUV signals, transmitting the maximum brightness current value and the plurality of second YUV signals to the display device so that the display screen can display the image based on the maximum brightness current value and the plurality of second YUV signals.
[0006] The environmental data includes air quality, weather conditions, and ambient brightness. The display device displays the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the grayscale levels exceed 256, the level control module, while calculating the plurality of second YUV signals using the Gamma control parameter, further employs adaptive offset compensation to adjust the brightness values of grayscale levels 0-8, ensuring that there are no consecutive 0 outputs in the brightness values of grayscale levels 0-8. This adaptive offset compensation involves counting the total number of grayscale levels with a brightness value of 0 in grayscale levels 1-8, reading the minimum brightness value in grayscale levels 1-8, listing the missing decimal integer values and their quantities within the non-contiguous value range of grayscale levels 1-8, filling this minimum brightness value into the first grayscale level, and then linearly adjusting at least a portion of the brightness values in grayscale levels 0-8 sequentially using this decimal integer value. The display device displays the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the grayscale level is greater than 256 levels, the level control module will use an adaptive adjustment to adjust the brightness values of the 0th to 8th grayscale levels when calculating the multiple second YUV signals using the Gamma control parameter, so that the brightness values of the 0th to 8th grayscale levels do not have more than 4 consecutive 0 brightness values output.
[0007] Furthermore, the display screen is composed of a plurality of display panels, and the display device uses one of the plurality of display panels as the master display and the others as slave displays. The master display panel receives the plurality of second YUV signals and the maximum brightness current value transmitted by the hierarchy control module, and then drives the other slave display panels to display the image using the same plurality of second YUV signals and the maximum brightness current value. This results in a uniform grayscale level for the image displayed on the screen. The hierarchy control module has a memory storage component, which allows the module to calculate and cache the corresponding plurality of second YUV signals using the Gamma control parameter, or to look up the plurality of second YUV signals stored in the memory storage component using the Gamma control parameter. The memory storage component and the display device's memory each have a first Gamma parameter conversion table and a second Gamma parameter conversion table, respectively, allowing the hierarchy control module to use the first Gamma parameter conversion table in conjunction with the second Gamma parameter conversion table. The multiple second YUV signals are obtained by looking up the table, thereby enabling the memory storage component to provide a multi-selective number of Gamma groups even with low memory storage capacity. The level control module is equipped with a temperature protection component and a maximum brightness conversion component. The temperature protection component is electrically connected to the display screen and receives the real-time operating temperature feedback from the display screen. When it is determined that the real-time operating temperature is not within a safe range, the maximum brightness conversion component is driven to adjust the maximum brightness current value. In addition, the level control module converts the multiple second YUV signals into multiple RGB signals.
[0008] The signal receiving module analyzes the image signal to obtain the corresponding image grayscale distribution data. The layer perception control module analyzes the image grayscale distribution data and outlines the range where the image grayscale is mainly concentrated. Then, it uses the image signal in the range to calculate the Gamma control parameter to obtain the plurality of second YUV signals corresponding to the full grayscale level. This improves the fineness of the grayscale presentation in the range, thereby enriching the presentation of details in the overall dark or bright image and satisfying the visual perception of the human eye.
[0009] In summary, this invention utilizes the layering control module to preprocess the image signal and directly provide the display device with the maximum current parameter after white balance and the plurality of second YUV signals most suitable for human eye comfort. This allows the display screen to directly project the image using the received parameters or data without separately calculating the R, G, and B signals, thereby reducing the software design complexity and hardware specification requirements of the IC in the display device. Furthermore, to provide the plurality of second YUV signals most suitable for human eye comfort, the inventors use the environmental data extracted by the scene capture module to calculate the Gamma control parameter. Based on this, the Gamma value most suitable for human eye perception is selected according to the actual surrounding environment, so that even if the image is a crow flying in the dark, it can still be clearly presented to the viewer without any discrepancies, that is, achieving optimized display quality and improving the comfort of human vision. Attached Figure Description
[0010] Figure 1 This is an architectural diagram of a preferred embodiment of the present invention.
[0011] Figure 2 This is a flowchart of a preferred embodiment of the present invention.
[0012] Figure 3 This is a schematic diagram of another preferred embodiment of the present invention.
[0013] Figure 4 This is a flowchart of another preferred embodiment of the present invention.
[0014] Figure 5 This is an application diagram of another preferred embodiment of the present invention.
[0015] Explanation of reference numerals in the attached figures: 1-Automatic Gamma Adjustment System; 10-Signal Receiving Module; 100-First YUV Signal; 11-Context Capture Module; 110-Environmental Data; 111-Gamma Control Parameter; 12-Layer Sensing Control Module; 1200-Second YUV Signal; 121-Memory Storage Component; 122-Maximum Brightness Conversion Component; 1220-Maximum Brightness Current Value; 123-Temperature Protection Component; 20-Display Screen; S10~S14-Steps; S20~S250-Steps. Detailed Implementation
[0016] To enable those skilled in the art to clearly understand the content of this invention, please refer to the following description and accompanying drawings.
[0017] Please see Figure 1 , Figure 2The figures are an architecture diagram and a flowchart of a preferred embodiment of the present invention. As shown, the environmentally adaptable automatic gamma adjustment system 1 is installed in a display device (not shown) to automatically correct the gamma value according to the surrounding environment, so as to adjust the gray level perception of an image presented to the viewer. It is equipped with a signal receiving module 10, a context capture module 11 and a gray level control module 12, and the automatic adjustment method of the automatic gamma adjustment system 1 may include the following steps.
[0018] In step S10, the signal receiving module 10 selects an image signal source to receive an image signal and convert it into a plurality of first YUV signals 100. In step S11, the scene capture module 11 detects the surrounding scene and captures at least one environmental data 110, and calculates a Gamma control parameter 111 for the display screen 20 of the display device based on the environmental data 110. In step S12, while the leveling control module 12 calculates the environmental data 110 to obtain a maximum brightness current value 1220, in step S13, the leveling control module 12 uses the Gamma control parameter 111 to calculate the plurality of first YUV signals 100 into a plurality of second YUV signals 1200. In step S14, the layering control module 12 transmits the maximum brightness current value 1220 and the plurality of second YUV signals 1200 to the display device so that the display screen 20 can display the image based on the maximum brightness current value 1220 and the plurality of second YUV signals 1200.
[0019] Please see Figures 3-5 The figures show an architecture diagram, flowchart, and schematic diagram of another preferred embodiment of the present invention. As shown, the environmentally adaptable automatic gamma adjustment system 1 is installed in a display device (not shown) and includes a signal receiving module 10, a context capture module 11, and a layering control module 12. This module automatically corrects the gamma value based on the surrounding context to adjust the grayscale level of an image presented to the viewer. The layering control module 12 includes a memory storage component 121, a maximum brightness conversion component 122, and a temperature protection component 123. The temperature protection component 123 is electrically connected to the display screen 20. The automatic adjustment method of the automatic gamma adjustment system 1 may include the following steps.
[0020] In step S20, the signal receiving module 10 selects an image signal source, such as HDMI, eDP / DP, DVI, LVDS, VGA, MHL, V-by-One HS, or MIPI-DSI, and receives an image signal (Sig). Ima.The image signal is converted into a plurality of first YUV signals 100. In step S21, the scene capture module 11 detects the surrounding scene and captures at least one environmental data 110, such as air quality (PM), weather conditions (D) and ambient brightness (A), and calculates a Gamma control parameter (G) 111 of the display screen 20 of the display device based on the environmental data 110. In step S22, while the layering control module 12 calculates the environmental data 110 to obtain a maximum brightness current value 1220, in step S23, the layering control module 12 uses the Gamma control parameter 111 to calculate the plurality of first YUV signals 100 into a plurality of second YUV signals 1200 with the best human eye comfort effect and caches them in the memory storage component 121. Alternatively, the layering control module 12 uses the Gamma control parameter 111 to look up a table (LUT) to obtain the plurality of second YUV signals 1200 stored in the memory storage component 121. The memory storage component 121 and the memory of the display device may each be provided with a first Gamma parameter conversion table and a second Gamma parameter conversion table, so that the layering control module 12 can use the first Gamma parameter conversion table and the second Gamma parameter conversion table to look up the plurality of second YUV signals 1200. Thus, if the memory storage component 121 has a low memory storage capacity and the number of built-in Gamma lookup tables is limited, the second Gamma parameter conversion table in the memory of the display device can be used to further look up and convert the Gamma parameters, so as to provide the layering control module 12 with a variety of Gamma groups, so as to achieve the effect that the displayed color brightness of the image is adapted to the surrounding environment.
[0021] Step S24: The maximum brightness current value 1220 and the plurality of second YUV signals 1200 are transmitted to the driver IC of the display device so that the display screen 20 can display the image based on the maximum brightness current value 1220 which takes into account the surrounding environment parameters and the plurality of second YUV signals 1200 which have the best effect on human eye comfort. In this way, the color error of each gray level is effectively reduced and the detail of the dark gray level color is improved, thereby meeting the expectations of human eye image viewing. Incidentally, the display screen 20 may be composed of a plurality of display panels, and the display device makes one of the plurality of display panels the main display and the others the slave display. After the main display panel receives the plurality of second YUV signals 1200 and the maximum brightness current value 1220 transmitted by the layering control module 12, it drives the other slave display panels to display the image using the plurality of second YUV signals 1200 and the maximum brightness current value 1220. Accordingly, the image displayed on the display screen 20 presents a uniform grayscale sense and exhibits consistent brightness and color.
[0022] Furthermore, the layering control module 12 can convert the plurality of second YUV signals 1200 into a plurality of RGB signals, and then transmit them to the display screen 20 together with the maximum brightness current value 1220. In step S25, the temperature protection component 123 receives the real-time operating temperature (Temp.) fed back by the display screen 20, and determines whether the real-time operating temperature is within a safe range, such as 55℃~80℃. If not, the real-time operating temperature is higher or lower than the safe range value. In step S250, the temperature protection component 123 drives the maximum brightness conversion component 122 to adjust the maximum brightness current value 1220. In this embodiment, when the signal receiving module 10 receives the image signal, it analyzes the image signal to obtain the corresponding image grayscale distribution data. After the layer perception control module 12 analyzes the image grayscale distribution data and outlines the range where the image grayscale is mainly concentrated, it uses the image signal in the range to calculate the Gamma control parameter 111 to obtain the plurality of second YUV signals 1200 corresponding to the full grayscale level. This improves the fineness of the grayscale presentation in the range, so that the overall dark or bright image can be further enriched in terms of the presentation of detailed images to satisfy the visual perception of the human eye.
[0023] Furthermore, the display device can display the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the grayscale level is greater than 256 levels, the level control module 12, after calculating the plurality of second YUV signals 1200 using the Gamma control parameter 111, further uses an adaptive offset compensation to adjust the brightness values of the 0th to 8th grayscale levels in the dark field so that the brightness values of the 0th to 8th grayscale levels do not have consecutive 0 outputs; or, an adaptive adjustment can be used to adjust the brightness values of the 0th to 8th grayscale levels so that the brightness values of the 0th to 8th grayscale levels do not have more than 4 consecutive 0 brightness values output. For example, when displaying a 13-bit image, the Y grayscale values shown in the table below can be obtained by using the multiple second YUV signal 1200 conversion formulas proposed in this invention. In the Gamma 1.8 curve, it is found that there are consecutive brightness values of 0 in the dark field grayscale. At this time, the adaptive offset compensation can count the total number of grayscale levels with brightness values of 0 in the 1st to 8th grayscale levels and read the minimum brightness value in the 1st to 8th grayscale levels. After listing the missing decimal integer values and their quantities in the non-continuous value range in the 1st to 8th grayscale levels, the minimum brightness value is filled into the 1st grayscale level. Then, the brightness values of at least some of the grayscale levels in the 0th to 8th grayscale levels are linearly adjusted sequentially using this decimal integer value. In other words, the layering control module 12 can perform adaptive offset compensation on the grayscale brightness values in the Gamma 1.8 curve. After statistically obtaining the total number of grayscale levels with a brightness value of 0 in the first to eighth grayscale levels: 1, the minimum brightness value in the first to eighth grayscale levels, and the missing decimal integer values in the non-contiguous value range of the first to eighth grayscale levels: 3, 5, 7, 8, 10, 11, 13, 14, and 15, the brightness value 1 is filled into the first grayscale level. Then, the missing decimal integer value 3 is used to linearly adjust the brightness values in the first to eighth grayscale levels. Based on this, the brightness distribution details of the dark grayscale levels are further improved, thereby further improving the image quality.
[0024]
[0025] The modules described in this invention are implemented through hardware or software supplemented by hardware. For example, the definitions of the signal receiving module 10, the scene interception module 11, and the layer sensing control module 12 essentially refer to the integration of various hardware devices such as CPUs, microprocessors, memory, or signal transmitters, and the technical features implemented by software programs. Furthermore, this invention can of course include a GUI interface allowing viewers to adjust the Gamma value or brightness, or switch to a sleep mode with a black screen, etc. The memory storage component 121 can be integrated onto an FPGA circuit board, so that the plurality of second YUV signals 1200 and the maximum brightness current value 1220 output by this invention are integrated and exported to the driver IC of the display screen 20 through the FPGA circuit for operation.
[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention; therefore, any equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.
Claims
1. An environmentally adaptable automatic gamma adjustment system, installed in a display device to automatically correct the gamma value according to the surrounding environment, so as to adjust the grayscale perception of an image, characterized in that: The environmentally adaptable automatic gamma adjustment system includes a signal receiving module, a context capture module, and a layer sensing control module. The signal receiving module selects an image signal source, receives and converts the image signal into a plurality of first YUV signals. The context capture module detects the surrounding environment and captures at least one environmental data point, and calculates a gamma control parameter for the display screen of the display device based on the environmental data. The layer sensing control module calculates the environmental data to obtain a maximum brightness current value, and simultaneously uses the gamma control parameter to calculate the plurality of first YUV signals and converts them into a plurality of second YUV signals. The maximum brightness current value and the plurality of second YUV signals are then transmitted to the display device so that the display screen can display the image based on the maximum brightness current value and the plurality of second YUV signals. The environmental data includes at least one of air quality, weather conditions, and ambient brightness. The display screen is composed of a plurality of display panels, and the display device makes one of the plurality of display panels the master display and the others the slave display. After the master display panel receives the plurality of second YUV signals and the maximum brightness current value transmitted by the layering control module, it drives the other slave display panels to display the image using the plurality of second YUV signals and the maximum brightness current value. Accordingly, the image displayed on the display screen presents a uniform grayscale level.
2. The environmentally adaptable automatic Gamma calibration system as described in claim 1, characterized in that, The layering control module includes a memory storage component, allowing the layering control module to calculate and cache the corresponding plurality of second YUV signals using the Gamma control parameter, or to look up the plurality of second YUV signals stored in the memory storage component using the Gamma control parameter. The memory storage component and the display device's memory each include a first Gamma parameter conversion table and a second Gamma parameter conversion table, respectively, allowing the layering control module to use the first Gamma parameter conversion table in conjunction with the second Gamma parameter conversion table. The multiple second YUV signals are obtained by looking up the table, thereby enabling the memory storage component to provide a multi-selective number of Gamma groups even with low memory storage capacity. The level control module is equipped with a temperature protection component and a maximum brightness conversion component. The temperature protection component is electrically connected to the display screen and receives the real-time operating temperature feedback from the display screen. When it is determined that the real-time operating temperature is not within a safe range, the maximum brightness conversion component is driven to adjust the maximum brightness current value. In addition, the level control module converts the multiple second YUV signals into multiple RGB signals.
3. The environmentally adaptable automatic Gamma calibration system as described in claim 2, characterized in that, The display device displays the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the number of grayscale levels is greater than 256, the level control module, when calculating the multiple second YUV signals using the Gamma control parameter, further uses an adaptive offset compensation to adjust the brightness values of grayscale levels 0 to 8, so that there are no consecutive 0 outputs in the brightness values of grayscale levels 0 to 8. The adaptive offset compensation involves counting the total number of grayscale levels with a brightness value of 0 in grayscale levels 1 to 8 and reading the minimum brightness value in grayscale levels 1 to 8. After listing the missing decimal integer values and their quantities in the non-contiguous value range of grayscale levels 1 to 8, the minimum brightness value is filled into the first grayscale level. Then, the brightness values of at least some of the grayscale levels 0 to 8 are linearly adjusted sequentially using this decimal integer value.
4. The environmentally adaptable automatic Gamma calibration system as described in claim 2, characterized in that, The display device displays the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the grayscale level is greater than 256 levels, the level control module will use an adaptive adjustment to adjust the brightness values of the 0th to 8th grayscale levels when calculating the multiple second YUV signals using the Gamma control parameter, so that the brightness values of the 0th to 8th grayscale levels do not have more than 4 consecutive 0 brightness values output.
5. An environmentally adaptable automatic gamma adjustment system, installed in a display device to automatically correct the gamma value according to the surrounding environment, so as to adjust the grayscale perception of an image, characterized in that: The environmentally adaptable automatic gamma adjustment system includes a signal receiving module, a context capture module, and a layer sensing control module. The signal receiving module selects an image signal source, receives and converts the image signal into a plurality of first YUV signals. The context capture module detects the surrounding environment and captures at least one environmental data point, and calculates a gamma control parameter for the display screen of the display device based on the environmental data. The layer sensing control module calculates the environmental data to obtain a maximum brightness current value, and simultaneously uses the gamma control parameter to calculate the plurality of first YUV signals and converts them into a plurality of second YUV signals. The maximum brightness current value and the plurality of second YUV signals are then transmitted to the display device so that the display screen can display the image based on the maximum brightness current value and the plurality of second YUV signals. The environmental data includes at least one of air quality, weather conditions, and ambient brightness; the signal receiving module analyzes the image signal to obtain corresponding image grayscale distribution data; the layering control module analyzes the image grayscale distribution data to outline the range where the image grayscale is mainly concentrated, and then uses the image signal in the range to calculate the Gamma control parameter to obtain the plurality of second YUV signals corresponding to the full grayscale levels.
6. The environmentally adaptable automatic Gamma calibration system as described in claim 5, characterized in that, The layering control module includes a memory storage component, allowing the layering control module to calculate and cache the corresponding plurality of second YUV signals using the Gamma control parameter, or to look up the plurality of second YUV signals stored in the memory storage component using the Gamma control parameter. The memory storage component and the display device's memory each include a first Gamma parameter conversion table and a second Gamma parameter conversion table, respectively, allowing the layering control module to use the first Gamma parameter conversion table in conjunction with the second Gamma parameter conversion table. The multiple second YUV signals are obtained by looking up the table, thereby enabling the memory storage component to provide a multi-selective number of Gamma groups even with low memory storage capacity. The level control module is equipped with a temperature protection component and a maximum brightness conversion component. The temperature protection component is electrically connected to the display screen and receives the real-time operating temperature feedback from the display screen. When it is determined that the real-time operating temperature is not within a safe range, the maximum brightness conversion component is driven to adjust the maximum brightness current value. In addition, the level control module converts the multiple second YUV signals into multiple RGB signals.
7. The environmentally adaptable automatic Gamma calibration system as described in claim 6, characterized in that, The display device displays the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the number of grayscale levels is greater than 256, the level control module, when calculating the multiple second YUV signals using the Gamma control parameter, further uses an adaptive offset compensation to adjust the brightness values of grayscale levels 0 to 8, so that there are no consecutive 0 outputs in the brightness values of grayscale levels 0 to 8. The adaptive offset compensation involves counting the total number of grayscale levels with a brightness value of 0 in grayscale levels 1 to 8 and reading the minimum brightness value in grayscale levels 1 to 8. After listing the missing decimal integer values and their quantities in the non-contiguous value range of grayscale levels 1 to 8, the minimum brightness value is filled into the first grayscale level. Then, the brightness values of at least some of the grayscale levels 0 to 8 are linearly adjusted sequentially using this decimal integer value.
8. The environmentally adaptable automatic Gamma calibration system as described in claim 6, characterized in that, The display device displays the image using 8-bit, 13-bit, 16-bit, or 24-bit grayscale images. When the grayscale level is greater than 256 levels, the level control module will use an adaptive adjustment to adjust the brightness values of the 0th to 8th grayscale levels when calculating the multiple second YUV signals using the Gamma control parameter, so that the brightness values of the 0th to 8th grayscale levels do not have more than 4 consecutive 0 brightness values output.