GMAP.NET控件画圆

关于GMAP.NET地图控件在地图上操作的例子很多，但是关于画圆形的描述很少，我找到了GMAP官方的例子并在此基础上进行了部分的改动，实现了对GMAP地图控件的画圆操作。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using System.Runtime.Serialization;
using GMap.NET;
using GMap.NET.WindowsForms;

namespace tgmap
{
#if !PocketPC
    [Serializable]
    public class GMapMarkerCircle : GMapMarker, ISerializable
#else
   public class GMapMarkerCircle : GMapMarker
#endif
    {
        /// <summary>
        /// In Meters 用米数确定圆
        /// </summary>
        public int Radius;

        /// <summary>
        /// 用两个点确定圆
        /// </summary>
        public PointLatLng P2;

        /// <summary>
        /// 是否用米数确定圆
        /// </summary>
        public bool IsMeter = true;


        /// <summary>
        /// specifies how the outline is painted
        /// </summary>
        [NonSerialized]
#if !PocketPC
        public Pen Stroke = new Pen(Color.FromArgb(155, Color.MidnightBlue));
#else
      public Pen Stroke = new Pen(Color.MidnightBlue);
#endif

        /// <summary>
        /// background color
        /// </summary>
        [NonSerialized]
#if !PocketPC
        public Brush Fill = new SolidBrush(Color.FromArgb(155, Color.AliceBlue));
#else
      public Brush Fill = new System.Drawing.SolidBrush(Color.AliceBlue);
#endif

        /// <summary>
        /// is filled
        /// </summary>
        public bool IsFilled = true;

        public GMapMarkerCircle(PointLatLng p)
           : base(p)
        {
            Radius = 0; // 0m
            P2 = p;
            IsHitTestVisible = false;
        }

        public override void OnRender(Graphics g)
        {
            if (!IsMeter)
                Radius = (int)Overlay.Control.MapProvider.Projection.GetDistance(Position, P2) * 1000;

            int R = (int)((Radius) / Overlay.Control.MapProvider.Projection.GetGroundResolution((int)Overlay.Control.Zoom, Position.Lat)) * 2;

            if (IsFilled)
            {
                g.FillEllipse(Fill, new System.Drawing.Rectangle(LocalPosition.X - R / 2, LocalPosition.Y - R / 2, R, R));
            }
            g.DrawEllipse(Stroke, new System.Drawing.Rectangle(LocalPosition.X - R / 2, LocalPosition.Y - R / 2, R, R));
        }

        public override void Dispose()
        {
            if (Stroke != null)
            {
                Stroke.Dispose();
                Stroke = null;
            }

            if (Fill != null)
            {
                Fill.Dispose();
                Fill = null;
            }

            base.Dispose();
        }

        public bool IsInside(PointLatLng p)
        {
            return (int)Overlay.Control.MapProvider.Projection.GetDistance(Position, p) * 1000 < Radius;
        }

#if !PocketPC

        #region ISerializable Members

        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
        {
            base.GetObjectData(info, context);

            // TODO: Radius, IsFilled
        }

        protected GMapMarkerCircle(SerializationInfo info, StreamingContext context)
           : base(info, context)
        {
            // TODO: Radius, IsFilled
        }

        #endregion

#endif
    }
}

里面描述了两种画圆的方法，一种是根据半径（米）和Marker的Position来画圆，一种是根据Marker的Position和另外一个PointLatLng点来画圆。添加了IsInside方法来确认另一个点是否在圆内。第二种方法是为了实现鼠标点击拖动画圆，鼠标事件代码如下

private GMapOverlay circles = new GMapOverlay("circle"); //放置circle的图层
        private GMapMarkerCircle drawingCircle = null; //正在画的circle
        private bool IsDrawingCircle = false;

        private void MapControl_MouseDown(object sender, MouseEventArgs e)
        {
            circles.Markers.Clear();
            IsDrawingCircle = true;
            drawingCircle = new GMapMarkerCircle(mapControl.FromLocalToLatLng(e.X, e.Y));
            drawingCircle.IsMeter = false;
            circles.Markers.Add(drawingCircle);

            //polygons.Polygons.Clear();
            //IsDrawingPolygon = true;
            //startX = e.X;
            //startY = e.Y;
            //drawingPolygon = new GMapPolygon(new List<PointLatLng>() { mapControl.FromLocalToLatLng(e.X,e.Y)}, "polygon");
            //polygons.Polygons.Add(drawingPolygon);
        }

        private void MapControl_MouseUp(object sender, MouseEventArgs e)
        {
            IsDrawingCircle = false;
            int count = 0;
            markersOverlay.Markers.ToList().ForEach(ma=> {
                if (drawingCircle.IsInside(ma.Position))
                {
                    count++;
                }
            });
            MessageBox.Show("区域内一共有" + count + "个marker(s)");

            //IsDrawingPolygon = false;
            //int count = 0;
            //markersOverlay.Markers.ToList().ForEach(ma => {
            //    if (drawingPolygon.IsInside(ma.Position))
            //    {
            //        count++;
            //    }
            //});
            //MessageBox.Show("区域内一共有" + count  +"个marker(s)");
        }

        private void MapControl_MouseMove(object sender, MouseEventArgs e)
        {
            if (IsDrawingCircle)
            {
                drawingCircle.P2 = mapControl.FromLocalToLatLng(e.X,e.Y);
                mapControl.UpdateMarkerLocalPosition(drawingCircle);
                mapControl.Refresh();
            }

            //if (IsDrawingPolygon)
            //{
            //    drawingPolygon.Points.Clear();
            //    drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(startX,startY));
            //    drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(startX, e.Y));
            //    drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(e.X, e.Y));
            //    drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(e.X, startY));
            //    mapControl.UpdatePolygonLocalPosition(drawingPolygon);
            //    mapControl.Refresh();
            //}
        }

注释的代码是我当初写拖动画矩形的部分，最终实现了鼠标放开后自动数出所画区域内Marker的数量，其实以后也可以对所有区域内的Marker进行进一步操作。

测试结果如下：