Programování s knihovnou OGR
Tato stránka obsahuje ukázku zdrojového textu demonstračního programu využívající pro přístup k vektorovým datům knihovnu OGR. Program je inspirován skriptem z cvičení GIS2.
Vypsání atributů
C++
#include <iostream>
#include "ogrsf_frmts.h"
using std::cout;
using std::cerr;
using std::endl;
int main(int argc, char **argv)
{
const char *filename;
OGRDataSource *poDS;
OGRLayer *poLayer;
OGRFeatureDefn *poFDefn;
if (argc != 2) {
cerr << "Pouziti: " << argv[0] << " shapefile" << endl;
return 1;
}
filename = argv[1];
// registrovat dostupne OGR ovladace
OGRRegisterAll();
// otevrit ShapeFile pro cteni
poDS = OGRSFDriverRegistrar::Open(filename, FALSE);
if (poDS == NULL) {
cerr << "Otevreni '" << filename << "' selhalo." << endl;
return 1;
}
// nacist prvni OGR vrstvu (tj. Shapefile)
poLayer = poDS->GetLayer(0);
if (poLayer == NULL) {
cerr << "Nelze nacist OGR vrstvu." << endl;
return 1;
}
// ziskat informace o vrstve
poFDefn = poLayer->GetLayerDefn();
cout << "Detekovana OGR vrstva '" << poFDefn->GetName() << "'.\n\n";
for(int iField = 0; iField < poFDefn->GetFieldCount(); iField++) {
// ziskat informace o atributovem sloupci
OGRFieldDefn *poFieldDefn = poFDefn->GetFieldDefn(iField);
cout << poFieldDefn->GetNameRef() << endl;
}
return 0;
}
Python
import sys
import osgeo.ogr as ogr
def main():
if len(sys.argv) != 2:
print >> sys.stderr, "Pouziti: %s shapefile" % sys.argv[0]
return 1
filename = sys.argv[1]
# otevrit ShapeFile pro cteni
ds = ogr.Open(filename)
if ds is None:
print >> sys.stderr, "Otevreni '%s' selhalo." % filename
return 1
# nacist prvni OGR vrstvu (tj. Shapefile)
lyr = ds.GetLayer(0)
if lyr is None:
print >> sys.stderr, "Nelze nacist OGR vrstvu."
# ziskat informace o vrstve
feat_defn = lyr.GetLayerDefn()
print "Detekovana OGR vrstva '%s'.\n" % feat_defn.GetName()
for i in range(feat_defn.GetFieldCount()):
# ziskat informace o atributovem sloupci
field_defn = feat_defn.GetFieldDefn(i)
print field_defn.GetNameRef()
return 0
if __name__ == "__main__":
sys.exit(main())
Prostorové predikáty
C++
#include <iostream>
#include "ogrsf_frmts.h"
#include <geos.h>
using std::cerr;
using std::endl;
using std::cout;
OGRDataSource *open_dsn(const char *dsn)
{
OGRDataSource *poDs;
poDs = OGRSFDriverRegistrar::Open(dsn, FALSE);
if (!poDs)
cerr << "Otevreni " << dsn << " selhalo." << std::endl;
return poDs;
}
int compute_number(OGRLayer *poLayer1, OGRLayer *poLayer2)
{
int count, i;
int nfeat;
bool found;
OGRFeature *poFeat1, *poFeat2;
OGRGeometry *poGeom1, *poGeom2;
count = 0;
nfeat = poLayer2->GetFeatureCount();
/* sekvencne cti prvky z vsrtvy 2 (polygony) */
poLayer2->ResetReading();
i = 0;
while(true) {
cerr << "\r" << i << "/" << nfeat;
poFeat2 = poLayer2->GetNextFeature();
if (!poFeat2)
break;
poGeom2 = poFeat2->GetGeometryRef();
if (!poGeom2 || poGeom2->getGeometryType() != wkbPolygon)
continue;
/* sekvencne cti prvky z vrstvy 1 (body) */
found = false;
poLayer1->ResetReading();
while (found) {
poFeat1 = poLayer1->GetNextFeature();
if (!poFeat1)
break;
poGeom1 = poFeat1->GetGeometryRef();
if (!poGeom1 || poGeom1->getGeometryType() != wkbPoint)
continue;
if (poGeom2->Within(poGeom1)) {
found = true;
}
OGRFeature::DestroyFeature(poFeat1);
}
if (found)
count++;
OGRFeature::DestroyFeature(poFeat2);
i++;
}
return count;
}
int main(int argc, char **argv)
{
const char *dsn1, *dsn2, *relation;
OGRDataSource *poDs1, *poDs2;
OGRLayer *poLayer1, *poLayer2;
if (argc != 3) {
cerr << "Pouziti: " << argv[0]
<< " <bodova vrstva> <polygonova vrstva>" << endl;
return 1;
}
dsn1 = argv[1];
dsn2 = argv[2];
relation = argv[3];
// registrovat dostupne OGR ovladace
OGRRegisterAll();
cout << "Nacitam data..." << endl;
// otevrit dsn1, dsn2 pro cteni
poDs1 = open_dsn(dsn1);
poDs2 = open_dsn(dsn2);
if (!poDs1 || !poDs2) {
return 1;
}
// nacist prvni OGR vrstvu
poLayer1 = poDs1->GetLayer(0);
poLayer2 = poDs2->GetLayer(0);
if (!poLayer1 || !poLayer2 ) {
cerr << "Nelze nacist OGR vrstvu." << endl;
return 1;
}
cout << "Provadim vypocet..." << endl;
cout << "Pocet polygonu: " << compute_number(poLayer1, poLayer2)
<< "/" << poLayer2->GetFeatureCount() << endl;
return 0;
}