Pound is at the subway station. Why does the human face look like a ghost?

This question is more difficult. This poem is a masterpiece of imagist poetry in Europe and America. And the so-called image, how meaningful and difficult to express. In fact, readers can use their imagination to explore the connotation of poetry, which is the characteristic that modern poetry is different from previous poetry. It is said that when Pound wrote this poem, he was deeply influenced by Tang poetry. Then a close reading of Tang poetry may solve this puzzle? I understand that this is the impression left by the poet's quick glance at the subway station. Perhaps, in the subway, due to the special space and the poet's mood at that time, the people waiting for the bus are like ghosts in the eyes of the poet, with "petals blossoming on the wet black branches" behind them, which more directly shows the borrowing of China's ancient poems. There is no transition between the two sentences, which seems abrupt, but it is natural.