Generally, pixel values are represented by a byte (8b) after quantization. If the gray value with continuous black-gray-white changes is quantized into 256 gray levels, the gray value ranges from 0 to 255, indicating that the brightness is from dark to light, and the color in the corresponding image is from black to white. Black and white photos contain all shades of gray between black and white, with each pixel value being one of 256 shades of gray between black and white.

The two matrices are superimposed to form a classic graph. No color is filled, and the white circle at the bottom can be clearly seen.
Shake the screen and the visual effect will be noticeable.

That's the beauty of 0-255.