In our system , firstly , we pre - process envelope image , introduce basic method of two - value and noise ' s filtering accordingly , and present a way of deskew based on hht algorithm 在系統(tǒng)中,首先對(duì)信封圖象進(jìn)行了預(yù)處理并給出了相應(yīng)的二值化、噪聲濾除方法,提出一種基于hht的傾斜校正的方法。