2018-01-04 点和直线的位置关系

语言：c#
需求：已知直线上的两点，判断第三个点与该直线的位置关系。

/// 判断点和直线的位置关系
/// <param name="LineA">直线上的一点</param>
/// <param name="LineB">直线上的另一点</param>
/// <param name="PntM">需要判断的点</param>
/// <returns></returns>
private int JudgePointToLine(Point LineA, Point LineB, Point PntM)
{
    int nResult = 0;
    double ax = LineB.X - LineA.X;
    double ay = LineB.Y - LineA.Y;
    double bx = PntM.X - LineA.X;
    double by = PntM.Y - LineA.Y;
    double judge = ax * by - ay * bx;
    if (judge > 0) {
        nResult = 1;
    }else if (judge < 0){
        nResult = -1;
    }else {
        nResult = 0;
    }
    return nResult;
}