C# 判斷兩條直線是否相交

直接上代碼,過程不復雜

/// <summary>/// 判斷兩條線是否相交/// </summary>/// <param name="a">線段1起點坐標</param>/// <param name="b">線段1終點坐標</param>/// <param name="c">線段2起點坐標</param>/// <param name="d">線段2終點坐標</param>/// <param name="intersection">相交點坐標</param>/// <returns>是否相交 0:兩線平行  -1:不平行且未相交  1:兩線相交</returns>PRivate int GetIntersection(Point a, Point b, Point c, Point d ,ref Point intersection){    //判斷異常    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是同一個點！");         }        else        {            Debug.Print("AB是一個點，CD是一個點，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是一個點，且在CD線段上！");        }        else        {             Debug.Print ("A、B是一個點，且不在CD線段上！");        }        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是一個點，且在AB線段上！");        }        else        {            Debug.Print ("C、D是一個點，且不在AB線段上！");        }    }    if ((b.Y - a.Y) * (c.X - d.X) - (b.X - a.X) * (c.Y - d.Y) == 0)    {        Debug.Print ("線段平行，無交點！");        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 ("線段相交于點(" + intersection.X + "," + intersection.Y + ")！");        return 1; //'相交    }    else    {        Debug.Print ("線段相交于虛交點(" + intersection.X + "," + intersection.Y + ")！");        return -1; //'相交但不在線段上    }}