图形及椭圆形窗口的裁剪算法一则

Clipping Algorithm of Circular Window and Elliptical Window

提出一种图形及椭圆形窗口的裁剪算法．（１）图形窗口：利用圆心到线段的距离来判断该线段与圆是否有交点（２）椭圆形窗口：利用线段的端点到椭圆两焦点的距离之和及椭圆心到该线段的距离来判断该线段与椭圆是否有交点．

The author give a new method of clipping algorithm of circular window and elliptical window.(1) Circular window:It's judge whether there have points of intersection of line and circle or not by distance from circle centre to line.(2)Elliptical window:It's judge whether there have points of intersection of line and ellipse or not by sum of distance from end points of line to two focal points of ellipse.