The luminous color and luminous efficiency of LED are related to the materials and processes used to make LEDs, and there are three widely used types: red, green, and blue (R, G, B). Because the LED has a low working voltage (only 1.5-3V), can actively emit light and has a certain brightness, the brightness can be adjusted by voltage (or current), and it is resistant to shock, vibration and long life (100,000 hours), so in large display devices, there is no other display method that is comparable to the LED display mode. The display made of red and green LEDs together as a pixel is called a two-color screen or color screen; The display that puts the red, green, and blue LED tubes together as a pixel is called a three-color screen or a full-color screen. The pixel size of the production of indoor LED display is generally 2-10 mm, often using several LED dies that can produce different primary colors to package into one, the pixel size of outdoor LED display is mostly 12-26 mm, each pixel is composed of a number of various monochrome LEDs, the common finished product is called the pixel tube, the two-color pixel tube is generally composed of 3 red and 2 green, and the three-color pixel tube is composed of 2 red 1 green and 1 blue. Regardless of whether LEDs are used to make a monochrome, two-color or three-color screen, the brightness of each LED that needs to make up the pixels to display the image must be adjustable, and the degree of fineness of the adjustment is the gray level of the display. The higher the gray level, the more delicate and colorful the displayed image is, and the more complex the corresponding display control system is. In general, the color transition is very soft in a 256-level grayscale image, while in a 16-level grayscale color image, the color transition line is very obvious. Therefore, color LED displays are currently required to be made of 256 levels of grayscale.