实现B样条曲线的绘制，包括逼近和插值。逼近是指通过控制节点求得节点向量，再进行曲线拟合。插值是指通过数据节点反求控制节点，并由数据节点求得节点向量，再进行曲线拟合。-The realization of B spline curves, including approximation and interpolation. Approximation is to obtain the node vector through the control node, and then curve fitt