What artistic technique does Grass by the Green River use to shape the image of a thinking woman?

This poem skillfully uses the technique of positive and negative contrast to shape a woman's boudoir thinking image. The first half of this poem is a picture of a young woman enjoying spring. The grass by the river is green, the weeping willows in the garden are gloomy, and the "Yingying" image of a young woman, the bright moonlight in Wan Ru, appears on the tall buildings. The second half of the poem points out: "An empty bed is hard to keep." On the one hand, it is a spring scene full of business, as beautiful as the face of spring flowers; On the one hand, there is an empty boudoir, and on the other hand, there are tearful eyes staring at the sky-two diametrically opposite contrasts, which make readers deeply realize that this young woman's lonely life is at the expense of her flower-like youth. Who doesn't appreciate the deep sadness arising from the sharp contrast between bright colors and empty hearts?