What does black and white mean in line drawing?

The color levels in line drawing are summarized as black, white and gray. For example, if the paper is white and the dots, lines and surfaces are black, the uncolored paper is white, the lines are arranged in gray, and the colored blocks are black. Drawing white lines on black paper is just the opposite.

Black, white and gray refer to different levels of light and shade in the picture, with bright blocks being white, dark blocks being black and middle colors being gray. From this point of view, things drawn in white on black paper should be white, leaving a black background or black, and the places represented by lines are gray. I emphasize: without mechanical understanding, black, white and gray refer to different levels of light and shade in the picture, with bright blocks being white, dark blocks being black and the middle color being gray.