【C#】点和线段/直线的距离/位置关系

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我是靠谱客的博主无辜铃铛，最近开发中收集的这篇文章主要介绍【C#】点和线段/直线的距离/位置关系，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

Vector2类见前文

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace dian_zhixian
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        Point m_p1;
        Point m_p2;
        Point m_p;

        int index=0;

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (index == 0)
            {
                m_p1 = e.Location;
                index++;
                return;
            }

            if (index == 1)
            {
                m_p2 = e.Location;

                Graphics g = this.CreateGraphics();
                g.DrawLine(Pens.Red, m_p1, m_p2);

                index++;
                return;
            }

            if (index == 2)
            {
                m_p = e.Location;

                Graphics g = this.CreateGraphics();
                Pen pen = new Pen(Color.Blue, 2);
                Brush brush = new SolidBrush(Color.Blue);
                g.DrawEllipse(pen, e.X, e.Y, 2, 2);
                g.FillEllipse(brush, e.X, e.Y, 2, 2);

                index = 0;


                Vector2 vPA = new Vector2(m_p, m_p1);
                Vector2 vAP = new Vector2(m_p1, m_p);
                Vector2 vPB = new Vector2(m_p, m_p2);
                Vector2 vBP = new Vector2(m_p2, m_p);
                Vector2 vAB = new Vector2(m_p1, m_p2);
                Vector2 vBA = new Vector2(m_p2, m_p1);

                //{
                //    //点到直线距离
                //    float PAccPB = System.Math.Abs(vPA.cross_multi_value(vPB));
                //    float ABmo = vAB.mo();
                //    float h = PAccPB / ABmo;
                //    MessageBox.Show("点到直线距离为：" + h);
                //}


                //{
                //    //点到线段距离
                //    float APdcAB = vAP.dot_multi(vAB);
                //    float BPdcBA = vBP.dot_multi(vBA);

                //    if (APdcAB < 0)
                //    {
                //        float APmo = vAP.mo();
                //        MessageBox.Show("点到线段距离为：" + APmo);
                //    }

                //    else if (BPdcBA < 0)
                //    {
                //        float BPmo = vBP.mo();
                //        MessageBox.Show("点到线段距离为：" + BPmo);
                //    }

                //    else
                //    {
                //        float PAccPB = System.Math.Abs(vPA.cross_multi_value(vPB));
                //        float ABmo = vAB.mo();
                //        float h = PAccPB / ABmo;
                //        MessageBox.Show("点到线段距离为：" + h);
                //    }
                //}


                {
                    //点和线段关系

                    float ABccAP = vAB.cross_multi_value(vAP);
                    float APdcAB = vAP.dot_multi(vAB);

                    if (ABccAP < 0)
                        MessageBox.Show("点在线段（向量）AB的左侧");
                    else if (ABccAP > 0)
                        MessageBox.Show("点在线段（向量）AB的右侧");
                    else
                    {
                        if (APdcAB > 0)
                        {
                            if (m_p.X > m_p2.X)
                                MessageBox.Show("点在线段AB的延长线上");
                            else if (m_p.X == m_p2.X)
                                MessageBox.Show("点和线段AB的端点B重合");
                            else
                                MessageBox.Show("点在线段AB上");
                        }
                        else if (APdcAB < 0)
                            MessageBox.Show("点在线段AB的反向延长线上");
                        else
                            MessageBox.Show("点和线段AB的端点A重合");
                    }
                }

            }
        }
    }
}