摘要： 分析了封闭图形内外裁剪的本质，将它们统一为连通区域的求交集运算。通过以二次B样条曲线为基础的有向环来表示区域，并构造环之间的交点表等给出了一般二次曲线窗口上的裁剪算法。

关键词: B样条曲线, 裁剪, 有向环

Abstract: This paper analyzes the essence of inside and outside clipping of close graphs, which is unified to intersection operation of connected regions. Region can be presented by directed rings based on quadratic B-spline curves. This clipping algorithm is presented through the construction of a list of points of intersection between the rings.

Key words: B-spline curve, Clipping, Directed ring