In the traditional offset printing method, the graphic information after prepress processing must be printed on the printing machine after being output to film.

Books and periodicals printing usually includes three stages: ① prepress stage; ② printing stage; ③ Post-press processing stage. Among them, the main work of prepress production stage is to design, input, process and output graphic information before printing, and make a printed version (or corresponding electronic file) according to the original manuscript of books and periodicals that has been designed as a whole. Therefore, in the traditional offset printing method, the process after film output and before printing is to make printing plates.