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使用GDAL/OGR读取点、线矢量文件


GDAL中对矢量数据的读写操作都是基于OGR库,只要编译了GDAL库就可以使用OGR库,不用另外编译,但须添加相应的头文件#include “ogrsf_frmts.h”。我读取的文件为shp文件,shp文件只有一个图层,相对比较简单。对于点、线矢量文件,这里不只是if (wkbPoint==geotype)和if ( wkbLineString==geotype),还有multiPoint和multiLine类型,具体的读入到下一篇读取polygon时在说明。

 
 ////////////////////////////////获取图层
 int iLayerCount=poSrcDS->GetLayerCount();
 OGRLayer*poLayer=poSrcDS->GetLayer(0);
 if (poLayer==NULL)
 {
  QMessageBox::information(this,tr(“Waring”), tr(“获取图层失败!”)); 
  OGRDataSource::DestroyDataSource(poSrcDS);
  return;
 }
 ////////////////初始化图层
 poLayer->ResetReading();
 ///////////////获取属性表表头信息
 int iFeatureCount=poLayer->GetFeatureCount();   //获得要素个数
 OGRSpatialReference *shp_spf;              
 shp_spf=poLayer->GetSpatialRef();                     //获得矢量数据的投影信息

 int PNum=0;             //记录点的个数
 int flag;           //用于标记数据类型
 vector<double> PointX;                                     //用于存点数据
 vector<double> PointY;
 
 vector<int>LPointNum; //获取线状数据上线条个数
 int LNum=0;                                         //用于记录第几条线

 vector<int>GPointNum;//获取多边形数据上多边形个数
 int GNum=0;                                      //记录第几个多边形

 OGRFeatureDefn*poDefn=poLayer->GetLayerDefn();
 int iFieldCount =poDefn->GetFieldCount();
 for (int iAttr=0;iAttr<iFieldCount;iAttr++)
 {
  OGRFieldDefn*poField=poDefn->GetFieldDefn(iAttr); 
  /* cout<<poField->GetNameRef()<<“:”<<poField->GetFieldTypeName(poField->GetType())<<“(“<<poField->GetWidth()<<“,”<<poField->GetPrecision()<<“)”<<endl;*/
 }
 OGRFeature*poFeature=NULL;
 //////遍历图层中的每个要素
 while ((poFeature=poLayer->GetNextFeature())!=NULL)
 {
  ///获取要素中的几何体
  OGRGeometry*poGeometry=poFeature->GetGeometryRef();
  OGRwkbGeometryType geotype;   
  geotype=poGeometry->getGeometryType();   //获取该文件类型,点状、线状or面状  
     OGRPoint *poPoint=NULL;
  OGRLineString *poLine=NULL;
 

  if (wkbPoint==geotype)                                    //若该要素为点状
  {
   flag=1;
   poPoint=(OGRPoint*)poGeometry;
   PointX.push_back(poPoint->getX());
   PointY.push_back(poPoint->getY());
   poEnvelope=new OGREnvelope;           //获取该要素的四至范围
   poGeometry->getEnvelope(poEnvelope);
   if(0==PNum)
   {
    minX=poEnvelope->MinX;
    minY=poEnvelope->MinY;
    maxX=poEnvelope->MaxX;
    maxY=poEnvelope->MaxY;
    PNum++;
   }
   else
   {
    if((poEnvelope->MinX)<minX) minX=poEnvelope->MinX;
    if((poEnvelope->MinY)<minY) minY=poEnvelope->MinY;
    if((poEnvelope->MaxX)>maxX) maxX=poEnvelope->MaxX;
    if((poEnvelope->MaxY)>maxY) maxY=poEnvelope->MaxY;
    PNum++;
   }
  }
  if ( wkbLineString==geotype)                           //若该要素为线状
  {
   flag=2;
   poLine=(OGRLineString*)poGeometry;
   if (poLine->IsEmpty())
   {
    continue;
   }
   poEnvelope=new OGREnvelope;           //获取该要素的四至范围
   poGeometry->getEnvelope(poEnvelope);
   if(0==LNum)
   {
   minX=poEnvelope->MinX;
   minY=poEnvelope->MinY;
   maxX=poEnvelope->MaxX;
   maxY=poEnvelope->MaxY;
   }
   else
   {
    if((poEnvelope->MinX)<minX) minX=poEnvelope->MinX;
    if((poEnvelope->MinY)<minY) minY=poEnvelope->MinY;
    if((poEnvelope->MaxX)>maxX) maxX=poEnvelope->MaxX;
    if((poEnvelope->MaxY)>maxY) maxY=poEnvelope->MaxY;
   }
   LPointNum.push_back(poLine->getNumPoints());
   OGRRawPoint *Lpoints=new OGRRawPoint[LPointNum.at(LNum)];
   poLine->getPoints(Lpoints,NULL);
   for (int k=0;k<LPointNum.at(LNum);k++)
   {
   PointX.push_back(Lpoints[k].x);
   PointY.push_back(Lpoints[k].y);
   }
   LNum++;
   delete []Lpoints;
  }



转载自:https://blog.csdn.net/guoqiong07/article/details/38295759