三次Beizer曲线方程，找到轮廓中的特征点，然后根据两个相邻的特征点拟合成一段三次Beizer曲线，控制点AB是借助周围几个点得到的(In the three Beizer curve equation, the feature points in the contour are found, and then a three Beizer curve is synthesized according to two adjacent feature points. The control po