点到线段的距离模板

 1 public static double PointToSegDist(double x, double y, double x1, double y1, double x2, double y2)
 2 {
 3 double cross = (x2 - x1) * (x - x1) + (y2 - y1) * (y - y1);
 4 if (cross <= 0) return Math.Sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
 5
 6 double d2 = (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
 7 if (cross >= d2) return Math.Sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
 8
 9 double r = cross / d2;
10 double px = x1 + (x2 - x1) * r;
11 double py = y1 + (y2 - y1) * r;
12 return Math.Sqrt((x - px) * (x - px) + (py - y1) * (py - y1));
13 }  

来自：http://blog.csdn.net/angelazy/article/details/38489293/