Grayscale can also be considered as brightness, which is simply the depth of color. In fact, in our daily life, through the combination of the shades of the three primary colors, a variety of different colors can be formed. The greater the number of gray scales that a product can display, it means that the product has richer color expression and can achieve stronger color levels.

For example, with three primary colors and 16-level grayscale, the color that can be displayed is 16×16×16=4096 colors. However, the 256-level gray scale of current products is very common. The so-called color or gray level refers to the difference between the brightness and darkness of the displayed pixels in a black and white display. In a color display, it is expressed as a difference in color. The more gray levels, the clearer and more vivid the image level. The gray level depends on the number of bits of the refresh memory cell corresponding to each pixel and the performance of the display itself. If the color of each pixel is represented by a 16-bit binary number, we call it a 16-bit image, which can express 2 to the 16th power, that is, 65536 colors.

If each pixel is represented by a 24-bit binary number, we call it a 24-bit image, which can express 2 to the 24th power, that is, 16,777,216 colors. The gray scale is no color, and the RGB color components are all equal. If it is a binary grayscale image, its pixel value can only be 0 or 1, we say its gray level is 2. Let’s use an example to illustrate: A 256-level grayscale image, RGB(100,100,100) represents the grayscale as 100, RGB(50,50,50) represents the grayscale as 50, and the grayscale refers to black and white. The color depth of the point in the image generally ranges from 0 to 255, white is 255, and black is 0. 

Therefore, black and white pictures are also called gray-scale images. They are widely used in the fields of medicine and image recognition. The pixel value after conversion into black and white image (it is a generalized term), the conversion method depends on the application field, generally according to the weighted method, the ratio of R, G, B is generally 3:6:1.