Even a scanner or photographic plate with ultra-high accuracy (optical resolution above 5000DPI) cannot reproduce the line shape of a pattern. After scanning the thick line, it becomes a dot matrix image, not a vector figure, so the slight change in the thickness of the line will have a loss. In addition, the line is a spot color line, and the output must be separated. After color separation, it becomes a dot pattern. Overprinter is not allowed to have a great loss, so that after scanning after the thick and fine spot color line output and the original product is very different, with the naked eye can be easily identified, so can prevent duplication, thus achieving the purpose of anti-counterfeiting.