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;

}