纯底层实现缓冲区算法

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arcgis

arcgis

首先，画线，如图：

然后，生成缓冲区如图：

具体代码如下，完美纯底层实现arcgis的buffer功能


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

namespace LineBuffer
{
   
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public Point Origin = new Point(0, 0);
        public Point[] points = new Point[4];
        public int Num = 0;
        public Graphics g;
        public Pen pen;
        public double buffer=0;//缓冲区值
      
        public bool m_bColor=false;
       // PointF
        private void Form1_Load(object sender, EventArgs e)
        {
            this.StartPosition = FormStartPosition.CenterScreen;
            this.BackColor = Color.White;         //设置窗体背景颜色
        }
       
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (Num < 4)
            {
                Origin.X = e.X;
                Origin.Y = e.Y;
                points[Num] = Origin;
                if (Num % 2 == 1)
                {
                    g = this.CreateGraphics();          //创建Graphics对象实例
                    Pen p = new Pen(Color.Black, 1);      //设置画笔颜色和宽度
                    g.DrawLine(p, points[Num - 1], points[Num]);  //绘制直线
                }
                
                    Num++;
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            g = this.CreateGraphics(); 
            g.Clear(Color.White);       //清空窗体背景
            Num = 0;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text.Trim() == "" || textBox1.Text == null)
            {
                MessageBox.Show("请输入缓冲变量值!");
            }
            else if (Num == 4)
            {
                buffer = Convert.ToDouble(textBox1.Text);
                DrawBuffer();
                /*//单轨迹缓冲区
                //处理绘制的点
                 StringBuilder strCoords = new StringBuilder();

                 for (int i = 0; i < 2; i++)
                {
                if (strCoords.Length > 0) strCoords.Append(";");
                strCoords.Append(points[i].X.ToString() + "," + points[i].Y.ToString());
                }

                string strpoints=LineBuffer.PolylineBuffer.GetBufferEdgeCoords(strCoords.ToString(), buffer);

                //if (strpoints.Trim().Length < 1) return "";
                string[] strCoords1 = strpoints.Split(new char[] { ';' });


                List<PointF> coords = new List<PointF>();

                foreach (string coord in strCoords1)
                {
                    string[] arcoord = coord.Split(new char[] { ',' });
                    PointF pf = new PointF();
                    pf.X =Convert.ToInt32( Convert.ToDouble(arcoord[0]));
                    pf.Y = Convert.ToInt32(Convert.ToDouble(arcoord[1]));
                    coords.Add(pf);
                }

                

                g = this.CreateGraphics();          //创建Graphics对象实例
                Pen p = new Pen(Color.Red, 1);      //设置画笔颜色和宽度


                for(int i=1;i<coords.Count;i++)
                {
                    g.DrawLine(p, coords[i-1],coords[i]);

                }
                */

               // g.DrawLine(p, points[Num - 1], points[Num]);  //绘制直线







            }
        }

        //获取扫描边界
        public Point GetExtent()
        {
            Point extent=new Point(0,0);

            for (int i = 0; i < points.Length; i++)
            {
                extent.X = Math.Max(points[i].X, extent.X);
                extent.Y = Math.Max(points[i].Y, extent.Y);
            }
            extent.X +=(int)buffer + 1;
            extent.Y += (int)buffer + 1;
            return extent;
        }

        //像素扫描法画缓冲
        public void DrawBuffer()
        {
            Point extent = GetExtent();

            Point cPointTmp=new Point();
            g = this.CreateGraphics();
            double fLength1 =buffer + 0.5;
            double fLength2 =buffer - 0.5;

                double fDistanceToLine1;
                double fDistanceToLine2;
                if (false == m_bColor)
                {
                    for (int x = 0; x <= extent.X; x++)
                    {
                        for (int y = 0; y <= extent.Y; y++)
                        {
                            cPointTmp.X = x;
                            cPointTmp.Y = y;
                            fDistanceToLine1 = DistanceLine(points[0], points[1], cPointTmp);
                            fDistanceToLine2 = DistanceLine(points[2], points[3], cPointTmp);
                            if (fLength1 >= fDistanceToLine1 && fLength2 < fDistanceToLine1)
                            {
                                if (fLength2 < DistanceLine(points[2], points[3], cPointTmp))
                                {
                                    Bitmap bm = new Bitmap(1, 1);     //这里调整点的大小   
                                    bm.SetPixel(0,0, Color.Red);       //设置点的颜色   
                                    g.DrawImageUnscaled(bm, cPointTmp.X, cPointTmp.Y);       //具体坐标
                                }
                                  
                            }
                            else if (fLength1 >= fDistanceToLine2 && fLength2 < fDistanceToLine2)
                            {
                                if (fLength2 < DistanceLine(points[0], points[1], cPointTmp))
                                {
                                    Bitmap bm = new Bitmap(1, 1);     //这里调整点的大小   
                                    bm.SetPixel(0, 0, Color.Red);       //设置点的颜色   
                                    g.DrawImageUnscaled(bm, cPointTmp.X, cPointTmp.Y);       //具体坐标
                                }
                            }
                            else
                            {
                            }
                        }
                    }
                }
                else
                {
                    for (int x = 0; x <= extent.X; x++)
                    {
                        for (int y = 0; y <= extent.Y; y++)
                        {
                            cPointTmp.X = x;
                            cPointTmp.Y = y;
                            fDistanceToLine1 = DistanceLine(points[0], points[1], cPointTmp);
                            fDistanceToLine2 = DistanceLine(points[2], points[3], cPointTmp);
                            if (fLength1 >= fDistanceToLine1 && fLength2 < fDistanceToLine1)
                            {
                                if (fLength2 < DistanceLine(points[2], points[3], cPointTmp))
                                {
                                    Bitmap bm = new Bitmap(1, 1);     //这里调整点的大小   
                                    bm.SetPixel(0, 0, Color.Red);       //设置点的颜色   
                                    g.DrawImageUnscaled(bm, cPointTmp.X, cPointTmp.Y);       //具体坐标
                                }
                                //else if(fLength2 >= DistanceLine(szPoint[2],szPoint[3],cPointTmp))
                                //	SetPixel(dc,cPointTmp.x,cPointTmp.y,RGB(255,0,255));
                            }
                            else if (fLength1 >= fDistanceToLine2 && fLength2 < fDistanceToLine2)
                            {
                                if (fLength2 < DistanceLine(points[0], points[1], cPointTmp))
                                {
                                    Bitmap bm = new Bitmap(1, 1);     //这里调整点的大小   
                                    bm.SetPixel(0, 0, Color.Red);       //设置点的颜色   
                                    g.DrawImageUnscaled(bm, cPointTmp.X, cPointTmp.Y);       //具体坐标
                                }
                                //else if(fLength2 >= DistanceLine(szPoint[0],szPoint[1],cPointTmp))
                                //	SetPixel(dc,cPointTmp.x,cPointTmp.y,RGB(255,0,255));
                            }
                            else
                            {
                            }
                            if (0.5 > fDistanceToLine1 || 0.5 > fDistanceToLine2)
                            {

                                Bitmap bm = new Bitmap(1, 1);     //这里调整点的大小   
                                bm.SetPixel(0, 0, Color.Black);       //设置点的颜色   
                                g.DrawImageUnscaled(bm, cPointTmp.X, cPointTmp.Y);       //具体坐标
                                
                                continue;
                            }
                            if (fLength2 >= fDistanceToLine1 || fLength2 >= fDistanceToLine2)
                            {

                                Bitmap bm = new Bitmap(1, 1);     //这里调整点的大小   
                                bm.SetPixel(0, 0, Color.Yellow);       //设置点的颜色   
                                g.DrawImageUnscaled(bm, cPointTmp.X, cPointTmp.Y);       //具体坐标
                                
                            }
                        }
                    }
                }
        
        
        }


        // 返回两点之间的距离
        public double Distance(Point p1, Point p2)
        {
            double fDistance = Math.Sqrt((p1.X - p2.X) * (p1.X - p2.X) + (p1.Y - p2.Y) * (p1.Y - p2.Y));
            return fDistance;
        }
      

        //返回扫描点到指定线段的距离
        public double  DistanceLine(Point p1, Point p2, Point p)
        {
          
            double f = (p2.X-p1.X) * (p.X-p1.X) + (p2.Y-p1.Y) * (p.Y-p1.Y);

            //p到直线p1p2的投影点不在线段p1p2上，而且离p1点最近
            if (f < 0) return Distance(p1,p);
           
            double d = (p2.X - p1.X) * (p2.X - p1.X) + (p2.Y - p1.Y) * (p2.Y - p1.Y);

            //p到直线p1p2的投影点不在线段p1p2上，而且离p2点最近

            if (f > d) return Distance(p2, p);

            // p在p1p2线段上的投影点在线段p1p2上

            f = f / d;
           
            double fx = p1.X + f * (p2.X- p1.X);
            double fy = p1.Y + f * (p2.Y -p1.Y);
            double fDistance = Math.Sqrt((p.X - fx) * (p.X - fx) + (p.Y - fy) * (p.Y - fy));
            return fDistance;
        }
  
    }
}