What do you mean, light and shadow fall on the white wall unintentionally, and the white wall deliberately paints?

Light and shadow inadvertently fell on the white wall. The white wall is intended to be a painter, which means that the shadow of light falls on the wall unintentionally. The white wall intends to draw a picture, that is, the white wall intends to draw a picture. Dan and cyan are two colors commonly used in China's ancient paintings, which are referred to as painting for short. Light and shadow inadvertently fall on the white wall, and the white wall intentionally paints Dan and cyan. These two sentences are from Wu Chuan. In the book, we can know that light and shadow fell on the white wall unintentionally, and the white wall deliberately painted painters, which means that the white wall deliberately painted a picture, giving people a vivid picture.