深入理解最強桌面地圖控件GMAP.NET --- 原理篇

如何在你的程序中使用GMAP.NET 搜狗地圖

要使用以下代碼，建議看看初用篇，具體代碼如下所示。

this.MainMap.Position = new PointLatLng(double.Parse(ConfigurationManager.AppSettings["defaultLat"]),double.Parse(ConfigurationManager.AppSettings["defaultLng"]));

this.MainMap.MapProvider.Area = new RectLatLng(30.981178, 105.351914, 2.765142, 4.120995);
this.MainMap.BoundsOfMap = new RectLatLng(30.981178, 105.351914,  2.765142, 4.120995);
this.MainMap.Manager.Mode = AccessMode.CacheOnly;
this.MainMap.MapProvider = GMapProviders.SogouMapProvider;
this.MainMap.DragButton = MouseButton.Left;
this.MainMap.Zoom = 13;
this.MainMap.MinZoom = 8;
this.MainMap.MaxZoom = 24;

 

GMAP.NET 搜狗地圖的效果

普通地圖

衛星地圖

搜狗地圖加載原理

要理解如何加載搜狗地圖，也要理解下加載原理，我們用Chrome打開 http://map.sogou.com/,隨便定位一個地址，打開開發者工具：

可以看到Tile的地址如下：http://p2.go2map.com/seamless1/0/174/717/3/1/744_212.png

分析下Url鏈接參數：

http://p2.go2map.com/seamless1/0/174是固定的

717=729-縮放級別(Zoom)

3=網格橫坐標/200最接近的整數值=Math.Floor(x/200)。

1=網格縱坐標/200最接近的整數值=Math.Floor(y/200)。

744是網格橫坐標。

212是網格縱坐標。

反正上面這些參數我也是東拼西湊了很多資料來的，確實搜狗的很詭異。

 

下面我們看看如何在GMAP.NET中實現搜狗地圖吧。

SogouMapProvider

1)添加abstract class SougouMapProviderBase

由於搜狗地圖也有普通地圖和衛星地圖，因此提供了一個有公共方法的抽象類，可以復用。

public abstract class SogouMapProviderBase : GMapProvider
    {
        public SogouMapProviderBase()
        {
            MaxZoom = null;
            RefererUrl = "http://map.sougou.com";
            Copyright = string.Format("©{0} Sogou Corporation, ©{0} NAVTEQ, ©{0} Image courtesy of NASA", DateTime.Today.Year);    
        }

        public override PureProjection Projection
        {
            get { return MercatorProjection.Instance; }
        }

        GMapProvider[] overlays;
        public override GMapProvider[] Overlays
        {
            get
            {
                if (overlays == null)
                {
                    overlays = new GMapProvider[] { this };
                }
                return overlays;
            }
        }

        protected override bool CheckTileImageHttpResponse(System.Net.HttpWebResponse response)
        {
            var pass =  base.CheckTileImageHttpResponse(response);
            if (!pass)
            {
                 return response.ResponseUri.AbsoluteUri.EndsWith(".png") || response.ResponseUri.AbsoluteUri.EndsWith(".JPG");
            }

            return true;
        }
    }

 

2)添加SougouMapProvider

public class SogouMapProvider: SogouMapProviderBase
    {
        public static readonly SogouMapProvider Instance;
        
        readonly Guid id = new Guid("7E2A0100-7A75-4c49-A2C9-EE1C73947E10");
        public override Guid Id
        {
            get { return id; }
        }

        readonly string name = "SohuMap";
        public override string Name
        {
            get
            {
                return name;
            }
        }

        static SogouMapProvider()
        {
            Instance = new SogouMapProvider();
        }

        public override PureImage GetTileImage(GPoint pos, int zoom)
        {
            string url = MakeTileImageUrl(pos, zoom, LanguageStr);

            return GetTileImageUsingHttp(url);
        }

        string MakeTileImageUrl(GPoint pos, int zoom, string language)
        {
            zoom = zoom - 1;
            var offsetX = Math.Pow(2, zoom);
            var offsetY = offsetX - 1;

            var numX = pos.X - offsetX;
            var numY = -pos.Y + offsetY;

            zoom = zoom + 1;
            
            var zoomLevel = 729 - zoom;
            if (zoomLevel == 710)
            {
                zoomLevel = 792;
            }

            var blo = Math.Floor(numX/200);
            var bla = Math.Floor(numY/200);
            string blos, blas;
            if (blo < 0)
            {
                blos = "M" + (-blo);
            }
            else
            {
                blos = blo.ToString();
            }

            if (bla < 0)
            {
                blas = "M" + (-bla);
            }
            else
            {
                blas = bla.ToString();
            }

            var x = numX.ToString().Replace("-","M"); 
            var y = numY.ToString().Replace("-","M");


            //http://p1.go2map.com/seamless1/0/174/720/0/0/95_25.png
            string url = string.Format(UrlFormat, "1",  zoomLevel, blos, blas, x, y);
            Console.WriteLine("url:" + url);
            return url;
        }

        static readonly string UrlFormat = "http://p{0}.go2map.com/seamless1/0/174/{1}/{2}/{3}/{4}_{5}.png";
    }