C#判断直线是否相交
一般用不上此代码/// <summary>
/// 判断两条线是否相交
/// </summary>
/// <param name="a">线段1起点坐标</param>
/// <param name="b">线段1终点坐标</param>
/// <param name="c">线段2起点坐标</param>
/// <param name="d">线段2终点坐标</param>
/// <param name="intersection">相交点坐标</param>
/// <returns>是否相交 0:两线平行-1:不平行且未相交1:两线相交</returns>
private int GetIntersection(Point a, Point b, Point c, Point d ,ref Point intersection)
{
//判断异常
if (Math.Abs(b.X - a.Y) + Math.Abs(b.X - a.X) + Math.Abs(d.Y - c.Y) + Math.Abs(d.X - c.X) == 0)
{
if (c.X - a.X == 0)
{
Debug.Print("ABCD是同一个点！");
}
else
{
Debug.Print("AB是一个点，CD是一个点，且AC不同！");
}
return 0;
}
if (Math.Abs(b.Y - a.Y) + Math.Abs(b.X - a.X) == 0)
{
if ((a.X - d.X) * (c.Y - d.Y) - (a.Y - d.Y) * (c.X - d.X) == 0)
{
Debug.Print ("A、B是一个点，且在CD线段上！");
}
else
{
Debug.Print ("A、B是一个点，且不在CD线段上！");
}
return 0;
}
if (Math.Abs(d.Y - c.Y) + Math.Abs(d.X - c.X) == 0)
{
if ((d.X - b.X) * (a.Y - b.Y) - (d.Y - b.Y) * (a.X - b.X) == 0)
{
Debug.Print ("C、D是一个点，且在AB线段上！");
}
else
{
Debug.Print ("C、D是一个点，且不在AB线段上！");
}
}
if ((b.Y - a.Y) * (c.X - d.X) - (b.X - a.X) * (c.Y - d.Y) == 0)
{
Debug.Print ("线段平行，无交点！");
return 0;
}
intersection.X = ((b.X - a.X) * (c.X - d.X) * (c.Y - a.Y) - c.X * (b.X - a.X) * (c.Y - d.Y) + a.X * (b.Y - a.Y) * (c.X - d.X)) / ((b.Y - a.Y) * (c.X - d.X) - (b.X - a.X) * (c.Y - d.Y));
intersection.Y = ((b.Y - a.Y) * (c.Y - d.Y) * (c.X - a.X) - c.Y * (b.Y - a.Y) * (c.X - d.X) + a.Y * (b.X - a.X) * (c.Y - d.Y)) / ((b.X - a.X) * (c.Y - d.Y) - (b.Y - a.Y) * (c.X - d.X));
if ((intersection.X - a.X) * (intersection.X - b.X) <= 0 && (intersection.X - c.X) * (intersection.X - d.X) <= 0 && (intersection.Y - a.Y) * (intersection.Y - b.Y) <= 0 && (intersection.Y - c.Y) * (intersection.Y - d.Y) <= 0)
{
Debug.Print ("线段相交于点(" + intersection.X + "," + intersection.Y + ")！");
return 1; //'相交
}
else
{
Debug.Print ("线段相交于虚交点(" + intersection.X + "," + intersection.Y + ")！");
return -1; //'相交但不在线段上
}
}
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