IS.NET客户端聚合GoogleMap浅析（三）处理页面的制作

　　下面我们就来探讨一下处理页面的写法，熟悉Tilelayer的同志都知道，在处理页面需要获取到JS中传递的参数，比如比例尺，索引，范围等，以便在后台调用TcpMap来出图。但是我们这次是调用GoogleMap的缓存图片，完全脱离TcpMap的处理机制，所以请求参数也简化了，只要传递当前图幅的TileBounds即可。我们就可以根据这个Bounds来获取相应的GoogleMap缓存。

     我们获取对应GoogleMap的缓存过程基本分为如下几个步骤：

     获取当前请求图幅的Bounds(viewBounds)->根据GoogelMap的切图规则算得viewBounds四个角点分别位于哪个GoogleMap缓存图幅->将包含请求图幅范围的GoogleMap缓存图幅下载并组合成一幅比较大的图片，并计算范围（nowViewBounds）->根据实际需要的Bounds在图片上进行裁剪->返回结果图片并保存到本地以便下次使用

蓝色范围为GoogleMap的缓存，黄色的问题实际添加到地图上的图片，具体代码相见下面代码。 

<%@ WebHandler Language="C#" Class="GoogleMap" %>

using System;
using System.Web;
using SuperMap.IS.Web;
using SuperMap.IS.Utility;
using System.IO;
using System.Net;
using System.Globalization;
using System.Drawing;
using System.Text;
using System.Collections.Generic;


public class GoogleMap : IHttpHandler
{
    private Dictionary<string, string> Uris = new Dictionary<string, string>();
    private const string MapTileUri = "http://mt{0}.google.cn/vt/lyrs=m@127&hl=zh-CN&gl=cn&src=api&x={1}&y={2}&z={3}&s=Gal";
    private const string SatelliteTileUri = "http://mt{0}.google.cn/vt/lyrs=s@63&gl=cn&x={1}&s=&y={2}&z={3}&s=Gal";
    private string OutPutPath = @"C:\Program Files\SuperMap\SuperMap IS .NET 6\output";   
    private double tileBaseWidth = 400750166.6855785;
    private double tileBaseHeight = 39858478.2258614;
    private string mapType = "Satellite";
    public void ProcessRequest(HttpContext context)
    {
        Uris.Add("Map", MapTileUri);
        Uris.Add("Satellite", SatelliteTileUri);
        //索引
        string tx = context.Request["tx"];
        string ty = context.Request["ty"];
        string msstr = context.Request["ms"];
        string _mapType = context.Request["type"];
        //string offsetX = context.Request["offsetX"];
        //string offsetY = context.Request["offsetY"];
        if (_mapType != null) { mapType = _mapType; }
        int ms = (int)(1 / Double.Parse(msstr));
        //当前请求图幅范围
        MapRect viewBounds = new MapRect(Convert.ToDouble(context.Request["lbx"]), Convert.ToDouble(context.Request["lby"]), Convert.ToDouble(context.Request["rtx"]), Convert.ToDouble(context.Request["rty"]));
        //当前请求图幅比例尺       
        int z = GetZoomLevel(viewBounds.Width, viewBounds.Height);
        //缓存图片名称
        string imgName = "gm_" + tx + "_" + ty + "_" + ms.ToString() + ".png";
        //GoogleMap缓存目录
        string fPath = OutPutPath + @"\GoogleMapCache";
        //地图类别目录
        string fyPath = fPath + @"\" + mapType;
        //GoogleMap分级目录
        string zfPath = fyPath + @"\" + ms.ToString();
        //GoogleMap缓存全路径
        string fullPath = zfPath + @"\" + imgName;
        Bitmap returnBitMap = null;
        if (!Directory.Exists(fPath)) { Directory.CreateDirectory(fPath); }
        if (!Directory.Exists(fyPath)) { Directory.CreateDirectory(fyPath); }
        if (!Directory.Exists(zfPath)) { Directory.CreateDirectory(zfPath); }

        if (File.Exists(fullPath))
        {
            //returnBitMap = new Bitmap(fullPath);
            context.Response.Redirect("http://localhost/IS/Output/GoogleMapCache/"+mapType+"/"+ms.ToString()+"/"+imgName);
        }
        else
        {
            //leftTop是根据经纬度[-180,85]计算得来的 
            //GoogleMap起始坐标
            MapCoord leftTop = new MapCoord(-2.0037508342789244E7, 1.9929239112930678E7);
            //leftTop.X += Double.Parse(offsetX);//1300
            //leftTop.Y += Double.Parse(offsetY); //-6500
            leftTop.X += 1300;
            leftTop.Y += -6500;
            double tileWidth = (-leftTop.X) / Math.Pow(2.0, z - 1);
            double tileHeight = leftTop.Y / Math.Pow(2.0, z - 1);
            //角点所在的图幅
            int x1 = (int)((viewBounds.LeftBottom.X - leftTop.X) / tileWidth);
            int y1 = (int)((leftTop.Y - viewBounds.LeftBottom.Y) / tileHeight);
            int x2 = (int)((viewBounds.RightTop.X - leftTop.X) / tileWidth);
            int y2 = (int)((leftTop.Y - viewBounds.RightTop.Y) / tileHeight);
            //拼接图幅的范围
            MapRect nowViewBounds = new MapRect();
            nowViewBounds.LeftBottom = new MapCoord();
            nowViewBounds.RightTop = new MapCoord();
            nowViewBounds.LeftBottom.X = leftTop.X + x1 * tileWidth;
            nowViewBounds.RightTop.X = leftTop.X + (x2 + 1) * tileWidth;
            nowViewBounds.RightTop.Y = leftTop.Y - y2 * tileHeight;
            nowViewBounds.LeftBottom.Y = leftTop.Y - (y1 + 1) * tileHeight;
            Bitmap bitMap = null;
            bitMap = GetImg(x1, x2, y1, y2, z);
            // bitMap.Save(zfPath + @"\f" + imgName);
            //切图起点  
            int imgWidth = 256 * (x2 - x1 + 1);
            int imgHeight = 256 * (y1 - y2 + 1);
            int xt = (int)(((viewBounds.LeftBottom.X - nowViewBounds.LeftBottom.X) / nowViewBounds.Width) * imgWidth);
            int yt = (int)(((nowViewBounds.RightTop.Y - viewBounds.RightTop.Y) / nowViewBounds.Height) * imgHeight);
            int width = (int)((viewBounds.Width / nowViewBounds.Width) * imgWidth); ;
            int height = (int)((viewBounds.Height / nowViewBounds.Height) * imgHeight);
            returnBitMap = cutMap(bitMap, xt, yt, width, height);
            if ((width != 256 && width != 257) || (height != 256 && height != 257))
            {
                returnBitMap = resizeImg(returnBitMap);
            }
            if (!File.Exists(fullPath))
            {
                returnBitMap.Save(fullPath);
            }
            bitMap.Dispose();
            MemoryStream mss = new MemoryStream();
            returnBitMap.Save(mss, System.Drawing.Imaging.ImageFormat.Png);
            byte[] ImgBytes = mss.ToArray();
            context.Response.BinaryWrite(ImgBytes);
            context.Response.End();
        }       
     }
    //重置大小
    private Bitmap resizeImg(Bitmap bitMap)
    {
        Bitmap newBitMap = new Bitmap(bitMap, 256, 256);      
        return newBitMap;
    }
    //获取地图比例尺
    private int GetZoomLevel(double width, double height)
    {
        double h = tileBaseHeight / height;
        double w = tileBaseWidth / width;
        if (h < 1)
        {
            return 0;
        }
        else
        {
            int hi = (int)(Math.Log(h, 2)) + 1;
            int wi = (int)(Math.Log(w, 2)) + 1;
            int returnI = (hi < wi) ? hi : wi;
            if (returnI > 16)
            {
                if (mapType == "Satellite")
                {
                    returnI = 16;
                }
                else
                {
                    returnI = 17;
                }
            }
            return returnI;
        }
    }
    //切图
    public Bitmap cutMap(Bitmap b, int StartX, int StartY, int iWidth, int iHeight)
    {
        if (b == null) { return null; }
        int w = b.Width;
        int h = b.Height;
        if (StartX >= w || StartY >= h) { return null; }
        if (StartX + iWidth > w) { iWidth = w - StartX; }
        if (StartY + iHeight > h) { iHeight = h - StartY; }
        try
        {
            Bitmap bmpOut = new Bitmap(iWidth, iHeight);           
            Graphics g = Graphics.FromImage(bmpOut);
            g.DrawImage(b, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(StartX, StartY, iWidth, iHeight), GraphicsUnit.Pixel);
            g.Dispose();
            return bmpOut;
        }
        catch
        {
            return null;
        }
    }
    //获取图片
    private Bitmap GetImg(int x1, int x2, int y1, int y2, int z)
    {
        int xCount = x2 - x1 + 1; 
        int yCount = y1 - y2 + 1;
        Bitmap[] bitmaps = new Bitmap[xCount * yCount];
        int index = 0;
        for (int i = 0; i < yCount; i++)
        {
            for (int j = 0; j < xCount; j++)
            {
                bitmaps[index] = new Bitmap(getStream(j + x1, i + y2, z));
                index++;
            }
        }
        Bitmap newBitmap = MergerImg(bitmaps, xCount, yCount);
        return newBitmap;
    }
    //合并图片
    private Bitmap MergerImg(Bitmap[] maps, int xCount, int yCount)
    {
        Bitmap backgroudImg = new Bitmap(xCount * 256, yCount * 256);
        Graphics g = Graphics.FromImage(backgroudImg);
        g.Clear(System.Drawing.Color.White);
        int index = 0;
        for (int j = 0; j < yCount; j++)
        {
            for (int k = 0; k < xCount; k++)
            {
                g.DrawImage(maps[index], k * 256, j * 256, 256, 256);
                index++;
            }
        }
        g.Dispose();
        return backgroudImg;
    }
    //获取图片Stream
    public Stream getStream(int x, int y, int z)
    {
        Stream stream = null;
        if (x < 0 || y < 0)
        {
            stream = WriteImg();
        }
        else
        {           
            string imageUrl = GetTileUrl(x, y, z);
            HttpWebRequest myHttpWebRequest = null;
            HttpWebResponse myHttpWebResponse = null;
            Uri imageUri = new Uri(imageUrl, UriKind.RelativeOrAbsolute);
            try
            {
                myHttpWebRequest = (HttpWebRequest)WebRequest.Create(imageUri);
                myHttpWebRequest.AllowAutoRedirect = true;
                myHttpWebRequest.AllowWriteStreamBuffering = true;
                myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();
                stream = myHttpWebResponse.GetResponseStream();
            }
            catch (System.Net.WebException we)
            {
                stream = WriteImg();
            }
            catch (Exception)
            {
                stream = WriteImg();
            }
        }
        return stream;
    }
    //获取白图填充
    private Stream WriteImg()
    {
        Stream stream = null;
        Bitmap writeImgB = null;
        string writeImg = OutPutPath + @"\writeImg.png";
        MemoryStream ms = new MemoryStream();
        if (File.Exists(writeImg))
        {
            writeImgB = new Bitmap(writeImg);
        }
        else
        {
            //绘制白图            
            writeImgB = new Bitmap(256, 256);
            Graphics g = Graphics.FromImage(writeImgB);
            Pen penColor = new Pen(Color.White, 256);
            g.DrawRectangle(penColor, new Rectangle(0, 0, 256, 256));
            penColor.Dispose();
            g.Dispose();
            writeImgB.MakeTransparent(Color.White);
            if (!File.Exists(writeImg))
            {
                writeImgB.Save(writeImg);
            }
        }
        writeImgB.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
        stream = ms as Stream;
        return stream;
    }
    //获取图片的Url
    private string GetTileUrl(int indexX, int indexY, int level)
    {
        Random r = new Random();
        int i = r.Next(0,3);
        return string.Format(Uris[mapType], i, indexX, indexY, level);
    }
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}