AE + GDAL实现影像按标准图幅分割（下）

　　在上篇实现了遥感影像的切割，本篇讲切割前的准备。主要分为以下几步：

　　（1）将影像的投影坐标转换为地理坐标，以便于之后的图幅划分。AE坐标转换函数如下

 private bool Proj2Geo(ISpatialReference pspr, double xProj, double yProj, ref double xGeo, ref double yGeo)
         {
             if (pspr is IGeographicCoordinateSystem)
                 return false;
             IProjectedCoordinateSystem pcs = pspr as IProjectedCoordinateSystem;
             ISpatialReference gspr = pcs.GeographicCoordinateSystem;

             IPoint pt = new PointClass();
             pt.PutCoords(xProj, yProj);
             pt.SpatialReference = pspr;
             pt.Project(gspr);
             xGeo = pt.X;
             yGeo = pt.Y;

             return true;
         }

         private bool Geo2Proj(ISpatialReference pspr, double xGeo, double yGeo, ref double xProj, ref double yProj)
         {
             if (pspr is IGeographicCoordinateSystem)
                 return false;
             IProjectedCoordinateSystem pcs = pspr as IProjectedCoordinateSystem;
             ISpatialReference gspr = pcs.GeographicCoordinateSystem;

             IPoint pt = new PointClass();
             pt.PutCoords(xGeo, yGeo);
             pt.SpatialReference = gspr;
             pt.Project(pspr);
             xProj = pt.X;
             yProj = pt.Y;

             return true;
         }

　　（2）计算包含影像的标准图幅的四至，首先我定义了一个格网类

 public class GridInfo
     {
         public double XMin;
         public double XMax;
         public double YMin;
         public double YMax;
         public int rows;
         public int cols;

         public void setGridInfo(double xMax, double xMin, double yMax, double yMin, int rowCount, int colCount)
         {
             XMax = xMax;
             XMin = xMin;
             YMax = yMax;
             YMin = yMin;
             rows = rowCount;
             cols = colCount;
         }
     }

根据比例尺计算格网的大小

 private GridInfo setGridInfoByScale(int scale)
         {
             GridInfo gridInfo = new GridInfo();
             double dxInSnd, dyInSnd;
             switch (scale)
             {
                 case :
                     dxInSnd = Degree.Degree2Second(0.03125);
                     dyInSnd = Degree.Minute2Second(1.25);
                     break;
                 case :
                     dxInSnd = Degree.Degree2Second(0.0625);
                     dyInSnd = Degree.Minute2Second(2.5);
                     break;
                 case :
                     dxInSnd = Degree.Minute2Second(7.5);
                     dyInSnd = Degree.Minute2Second();
                     break;
                 case :
                     dxInSnd = Degree.Minute2Second();
                     dyInSnd = Degree.Minute2Second();
                     break;
                 case :
                     dxInSnd = Degree.Minute2Second();
                     dyInSnd = Degree.Minute2Second();
                     break;
                 case :
                     dxInSnd = Degree.Degree2Second(1.5);
                     dyInSnd = Degree.Degree2Second();
                     break;
                 case :
                     dxInSnd = Degree.Degree2Second();
                     dyInSnd = Degree.Degree2Second();
                     break;
                 case :
                     dxInSnd = Degree.Degree2Second();
                     dyInSnd = Degree.Degree2Second();
                     break;
                 default:
                     dxInSnd = ;
                     dyInSnd = ;
                     break;
             }

             if (dxInSnd == dyInSnd && dxInSnd == 0.0)
                 return null;

             double pXMin = 0.0, pXMax = 0.0, pYMin = 0.0, pYMax = 0.0;
             double gXMin = 0.0, gXMax = 0.0, gYMin = 0.0, gYMax = 0.0;
             if (envelope.SpatialReference is IProjectedCoordinateSystem)
             {
                 Proj2Geo(envelope.SpatialReference, envelope.XMax, envelope.YMax, ref gXMax, ref gYMax);
                 Proj2Geo(envelope.SpatialReference, envelope.XMin, envelope.YMin, ref gXMin, ref gYMin);
             }
             else
             {
                 gXMax = envelope.XMax; gXMin = envelope.XMin;
                 gYMax = envelope.YMax; gYMin = envelope.YMin;
             }
             int cols =Convert.ToInt32(Math.Round(Degree.Degree2Second( - gXMin) / dxInSnd)) + ;
             gridInfo.XMin =  - Degree.Second2Degree(cols * dxInSnd);
             cols = Convert.ToInt32(Math.Round(Degree.Degree2Second( - gXMax) / dxInSnd));
             gridInfo.XMax =  - Degree.Second2Degree(cols * dxInSnd);

             int rows = Convert.ToInt32(Math.Round(Degree.Degree2Second(gYMin) / dyInSnd));
             gridInfo.YMin =Degree.Second2Degree(rows * dyInSnd);
             rows = Convert.ToInt32(Math.Round(Degree.Degree2Second(gYMax) / dyInSnd)) + ;
             gridInfo.YMax =Degree.Second2Degree( rows * dyInSnd);

             gridInfo.rows = Convert.ToInt32(Math.Round(Degree.Degree2Second(gridInfo.YMax - gridInfo.YMin) / dyInSnd));
             gridInfo.cols = Convert.ToInt32(Math.Round(Degree.Degree2Second(gridInfo.XMax - gridInfo.XMin) / dxInSnd));

             if (envelope.SpatialReference is IProjectedCoordinateSystem)
             {
                 Geo2Proj(envelope.SpatialReference, gridInfo.XMax, gridInfo.YMax, ref pXMax, ref pYMax);
                 Geo2Proj(envelope.SpatialReference, gridInfo.XMin, gridInfo.YMin, ref pXMin, ref pYMin);
                 gridInfo.XMax = pXMax; gridInfo.XMin = pXMin;
                 gridInfo.YMax = pYMax; gridInfo.YMin = pYMin;
             }

             return gridInfo;
         }

　　（3）图幅命名类

 public class FrameName
     {
         private int scale;
         /// <summary>
         ///
         /// </summary>
         /// <param name="Scale">分数比例尺的分母(比例尺为1:50000则参数为50000)</param>
         public FrameName(int Scale)
         {
             scale = Scale;
         }

         public String getFrameName(double longtitude, double latitude)
         {
             int baseRowCount=(int)(latitude / );
             char baseChar = Convert.ToChar('A' + baseRowCount);
             int baseNum = (int)(longtitude / ) + ;

             if (scale == )
                 return String.Format("{0}{1}", baseChar, baseNum);

             char scaleChar = 'E'; //1:50000比例尺的代码为E，其他以后补充
             switch (scale)
             {
                 case :
                     scaleChar='B';break;
                 case :
                     scaleChar = 'C';break;
                 case :
                     scaleChar = 'D';break;
                 case :
                     scaleChar='E';break;
                 case :
                     scaleChar = 'F';break;
                 case :
                     scaleChar = 'G';break;
                 case :
                     scaleChar = 'H';break;
             }

             double dxInSnd, dyInSnd;
             switch (scale)
             {
                 case :
                     dxInSnd = 0.03125;
                     dyInSnd = 0.0208333333;
                     break;
                 case :
                     dxInSnd = 0.0625;
                     dyInSnd = 0.0416666667;
                     break;
                 case :
                     dxInSnd = 0.125;
                     dyInSnd = 0.0833333333;
                     break;
                 case :
                     dxInSnd = 0.25;
                     dyInSnd = 0.1666666667;
                     break;
                 case :
                     dxInSnd = 0.5;
                     dyInSnd = 0.3333333333;
                     break;
                 case :
                     dxInSnd = 1.5;
                     dyInSnd = ;
                     break;
                 case :
                     dxInSnd = ;
                     dyInSnd = ;
                     break;
                 default:
                     dxInSnd = ;
                     dyInSnd = ;
                     break;
             }

             if (dxInSnd == dyInSnd && dxInSnd == 0.0)
                 return null;

             int row = (int)(((baseRowCount + ) *  - latitude)/dyInSnd) + ;
             //int row = 24-((int)(latitude / dyInSnd)) % 24;
             int col = (int)((longtitude % ) /dxInSnd) + ;

             return String.Format("{0}{1}{2}{3}{4}", baseChar, baseNum, scaleChar, row.ToString().PadLeft(, ''), col.ToString().PadLeft(, ''));
         }

     }

　　（4）调用函数进行分割

 private void CreateFrame(GridInfo gridInfo, String outDir, int scale)
         {
             double xLength = (gridInfo.XMax - gridInfo.XMin) / gridInfo.cols;
             double yLength = (gridInfo.YMax - gridInfo.YMin) / gridInfo.rows;
             FrameName frameName = new FrameName(scale);

             for (int i = ; i < gridInfo.rows; i++)
             {
                 double yMin = gridInfo.YMin + i * yLength;
                 double yMax = gridInfo.YMin + (i + ) * yLength;
                 for (int j = ; j < gridInfo.cols; j++)
                 {
                     double xMin = gridInfo.XMin + j * xLength;
                     double xMax = gridInfo.XMin + (j + ) * xLength;
                     String pszOutFile;

                     if (envelope.SpatialReference is IProjectedCoordinateSystem)
                     {
                         double prjX = 0.0, prjY = 0.0;
                         Proj2Geo(envelope.SpatialReference, (xMax + xMin) / , (yMax + yMin) / , ref prjX, ref prjY);
                         pszOutFile = frameName.getFrameName(prjX,prjY);
                     }
                     else
                         pszOutFile = frameName.getFrameName((xMax + xMin) / , (yMax + yMin) / );
                     pszOutFile = outDir + "\\" + pszOutFile + ".tif";
                     CutUpdateImageByAOIGDAL(rasterLyr.FilePath, pszOutFile, xMin, xMax, yMin, yMax, "GTiff");
                 }
             }
         }

　　通过这4步，一个简易的图幅分割工具就做好了。