[gdal-dev] Create a shape file with polygons

[Jorge Martin]

Hello,

I've tried to develope the program that create a shape file with polygons.
But the GIS open the shp but there is nothing inside only the attributes,
not the polygons. I have the code from Python but I do not know the problem.

Here I paste the code:

int write_shapefilePolygon() {


const char *pszDriverName = "ESRI Shapefile";
OGRSFDriver *poDriver;

OGRRegisterAll();

poDriver =
OGRSFDriverRegistrar::GetRegistrar()->GetDriverByName(pszDriverName);

if( poDriver == NULL )
{
 printf( "%s driver not available.\n", pszDriverName );
exit( 1 );
 }

OGRDataSource *poDS;

poDS = poDriver->CreateDataSource( "Polygon.shp", NULL );

       if( poDS == NULL )
{
 printf( "Creation of output file failed.\n" );
exit( 1 );
 }

OGRLayer *poLayer;

 poLayer = poDS->CreateLayer( "countries", NULL, wkbPolygon, NULL );

          if( poLayer == NULL )
 {
printf( "Layer creation failed.\n" );
exit( 1 );
}

OGRFieldDefn oField( "Name", OFTString );

oField.SetWidth(32);

 if( poLayer->CreateField( &oField ) != OGRERR_NONE )
        {
printf( "Creating Name field failed.\n" );
 exit( 1 );
}

double x, y;
string szName;


 char Line[4000];
char *tmp;


 ifstream infile ("/home/jjmf/Desktop/Shape
files/polygon/ospy_data2/ut_counties.txt", ifstream::in);

while(infile.getline(Line,4000))
 {

 OGRPolygon myPoligon;

tmp = strtok (Line, ":");

szName = string (tmp);


       while (tmp != NULL)
           {


       OGRLinearRing MyRing;// = (OGRLinearRing*)
OGRGeometryFactory::createGeometry(wkbLinearRing);

        tmp = strtok (NULL, ",");

        if(tmp)
        {

               string Coords = string(tmp);

              size_t pos = Coords.find(" ");

              string CoordX = Coords.substr(0,pos);
              string CoordY = Coords.substr(pos);

              x = atof(CoordX.c_str());
               y = atof(CoordY.c_str());

MyRing.addPoint(x,y);


        }

        myPoligon.addRing(&MyRing);

    }

    OGRFeature *poFeature;



      poFeature = OGRFeature::CreateFeature( poLayer->GetLayerDefn() );


       poFeature->SetField( "Name", szName.c_str() );


      poFeature->SetGeometry(&myPoligon);


       if( poLayer->CreateFeature( poFeature ) != OGRERR_NONE )
       {
     printf( "Failed to create feature in shapefile.\n" );
     exit( 1 );
        }

        OGRFeature::DestroyFeature( poFeature );
  }

OGRDataSource::DestroyDataSource( poDS );



 infile.close();

 exit( 0 );



}




Thanks,

Jorge
2011/1/17 Jorge <jormarfe at gmail.com>

> Hi,
>
> Thank you very much in advance. I am developing with C++, but I will try to
> understand the code. I think it will easy.
>
> Thank you.
>
> Jorge
>
> El 17/01/2011, a las 18:18, Paolo Corti <pcorti at gmail.com> escribió:
>
> >> I`m new developing software with GDAL and OGR libraries. I has used the
> code
> >> from the OGR web that read and write a shapefile (points). What I really
> >> want is to read and write shapefiles with polygons.
> >
> > Hi Jorge
> > if you are using Python this [0] is the best resource out there.
> > Look at the sample in week 2 of the tutorial for effectively writing
> > (and reading) a Polygon shapefile.
> > If you are not using Python you should not have too much problems for
> > converting the Python code to the language you are using.
> > Another very good resource is to look at the source code: again,
> > supposing that you are using Python, this sample [1] should work for
> > you
> >
> > ciao
> > P
> >
> > [0] http://www.gis.usu.edu/~chrisg/python/2009/
> > [1]
> http://trac.osgeo.org/gdal/browser/trunk/gdal/swig/python/samples/assemblepoly.py
> >
> > --
> > Paolo Corti
> > GIS specialist and web developer
> > web: http://www.paolocorti.net
> > twitter: @paolo_corti
>
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