PGIS下载离线地图 SQLite+WPF

项目是超高分辨率屏幕墙，实时在线加载PGIS地图速度会比较慢，造成屏幕大量留白。于是使用地图缓存，事先把这个区块的地图全部down下来，使用Sqlite数据库保存。留存。

//Task taskDown = new Task(DownTiles);
//taskDown.Start();
 
private void DownTiles()
        {
            double maxX = 138.796586;
            double maxY = 24.371022;
            double minX = 138.447725;
            double minY = 24.086215;
            double X0 = -;
            double Y0 = ;
            string tempUrl = "";
            HttpWebRequest req = null;
            Stream stream = null;
 
            int bufferLen =  * ;
            int actual;
            byte[] buffer = new byte[bufferLen];
 
            for (int i = ; i < ; i++)//Level
            {
                int cmin = Math.Abs(Convert.ToInt32(Math.Floor((X0 - minX) / ( * MapMethods.GetResoulution(i)))));
                int cmax = Math.Abs(Convert.ToInt32(Math.Floor((X0 - maxX) / ( * MapMethods.GetResoulution(i)))));
                int rmin = Math.Abs(Convert.ToInt32(Math.Floor((Y0 - maxY) / ( * MapMethods.GetResoulution(i)))));
                int rmax = Math.Abs(Convert.ToInt32(Math.Floor((Y0 - minY) / ( * MapMethods.GetResoulution(i)))));
                for (int r = rmin; r < rmax; r++)//循环行
                {
                    for (int c = cmin; c < cmax; c++)//循环列
                    {
                        //Thread.Sleep(100);
                        tempUrl = GetTileUrl(i, r, c);
                        req = (HttpWebRequest)WebRequest.Create(tempUrl);
                        stream = req.GetResponse().GetResponseStream();
 
                        MemoryStream memoryStream = new MemoryStream();
 
                        while ((actual = stream.Read(buffer, , bufferLen)) > )
                        {
                            memoryStream.Write(buffer, , actual);
                        }
                        memoryStream.Position = ;
 
                        SaveTile(i, r, c, StreamToBytes2(memoryStream));
 
                    }
                }
            }
        }
 
        private byte[] StreamToBytes2(MemoryStream input)
        {
            byte[] bytes = new byte[input.Length];
            input.Read(bytes, , bytes.Length);
            return bytes;
        }