The application of foil in ancient poetry is mainly to highlight the main things, use similar things or negative and different things as foils, and play the role of "setting off the clouds and supporting the moon". . foil can be divided into positive foil and contrast foil.
Contrast is to use similar things to set off the things depicted, use tall things to set off higher things, and use good things to set off better things. For example: The water in Peach Blossom Pond is a thousand feet deep, which is not as deep as Wang Lun’s love for me. (Li Bai's "To Wang Lun") The depth of the Peach Blossom Pond highlights the deeper friendship with Wang Lun.
Contrast is a technique that uses certain images to set off the artistic conception from the opposite side and reveal the main idea. "Contrast" in classical poetry often manifests as using movement to contrast stillness (noise to contrast tranquility), music to contrast sadness (music to contrast sadness), virtuality to contrast reality, etc. In terms of contrasting stillness with movement, Wang Wei's "Birds in the Stream" "When people are idle, osmanthus flowers fall, and the night is quiet in the spring sky in the mountains. The moonrise scares the birds, and they sing in the spring stream." The author uses "flowers falling" and "moonrise" , especially the dynamic scenes such as "birdsong", not only reflect the tranquility and charm of the spring stream, but also make the spring stream never dry and show its inherent vitality. Use movement to contrast stillness, and movement and stillness reflect each other.
Another example: "There is a high mark for six dragons to return to the sun above, and there is a rushing wave to return to Sichuan below. The yellow crane cannot fly past, and the ape wants to overcome its sorrow and climb up." (Li Bai's "Shu Road" "Difficult") The poet writes about the difficulty of traveling on the road to Shu. He starts from the front. The mountains standing abruptly above block the movement of the sun god; the winding river below is full of waves. Then, let's make a point and use the yellow crane and the ape to contrast. The yellow crane that soars thousands of miles cannot fly, and the light and agile apes are also worried about climbing. It goes without saying that it is even more difficult for people to walk. The combination of positive and negative , tried his best to describe the difficulties of Shu Road.
Background in ancient poetry