二次b样条和三次b样条曲线画法，完全按照定义来做的，支持多个点的绘制。比贝塞尔曲线好画，贝塞尔曲线有三个点和四个点的画法，点再多就需要拟合了-B-spline quadratic and cubic b-spline curve drawing, done in full accordance with the definition of support to draw more points. Good Bibeisaier curve drawing, Bezier curve with t