GDAL / Programování / Vektorová data
Z FreeGIS portál
< GDAL
Tato stránka obsahuje ukázku zdrojového textu demonstračního programu využívající pro přístup k vektorovým datům knihovnu GDAL.
Vypsání atributů
C++
1 #include <iostream>
2 #include "ogrsf_frmts.h"
3
4 using std::cout;
5 using std::cerr;
6 using std::endl;
7
8 int main(int argc, char **argv)
9 {
10 const char *filename;
11
12 OGRDataSource *poDS;
13 OGRLayer *poLayer;
14 OGRFeatureDefn *poFDefn;
15
16 if (argc != 2) {
17 cerr << "Pouziti: " << argv[0] << " shapefile" << endl;
18 return 1;
19 }
20
21 filename = argv[1];
22
23 // registrovat dostupne OGR ovladace
24 OGRRegisterAll();
25
26 // otevrit ShapeFile pro cteni
27 poDS = OGRSFDriverRegistrar::Open(filename, FALSE);
28 if (poDS == NULL) {
29 cerr << "Otevreni '" << filename << "' selhalo." << endl;
30 return 1;
31 }
32
33 // nacist prvni OGR vrstvu (tj. Shapefile)
34 poLayer = poDS->GetLayer(0);
35 if (poLayer == NULL) {
36 cerr << "Nelze nacist OGR vrstvu." << endl;
37 return 1;
38 }
39
40 // ziskat informace o vrstve
41 poFDefn = poLayer->GetLayerDefn();
42
43 cout << "Detekovana OGR vrstva '" << poFDefn->GetName() << "'.\n\n";
44
45 for(int iField = 0; iField < poFDefn->GetFieldCount(); iField++) {
46 // ziskat informace o atributovem sloupci
47 OGRFieldDefn *poFieldDefn = poFDefn->GetFieldDefn(iField);
48 cout << poFieldDefn->GetNameRef() << endl;
49 }
50
51 return 0;
52 }
Python
1 import sys
2 from osgeo import ogr
3
4 def error(msg):
5 sys.exit(msg)
6
7 def main(filename):
8 # otevrit ShapeFile pro cteni
9 ds = ogr.Open(filename)
10 if ds is None:
11 error("Otevreni '{}' selhalo.".format(filename))
12
13 # nacist prvni OGR vrstvu (tj. Shapefile)
14 lyr = ds.GetLayer(0)
15 if lyr is None:
16 error("Nelze nacist OGR vrstvu.")
17
18 # ziskat informace o vrstve
19 feat_defn = lyr.GetLayerDefn()
20
21 print("OGR vrstva '{}' obsaguje {} geoprvku".format(feat_defn.GetName(), lyr.GetFeatureCount()))
22 print("Seznam atributu:")
23 # ziskat informace o atributovem sloupci
24 for i in range(feat_defn.GetFieldCount()):
25 field_defn = feat_defn.GetFieldDefn(i)
26 print("\t {}".format(field_defn.GetNameRef()))
27
28 return 0
29
30 if __name__ == "__main__":
31 if len(sys.argv) != 2:
32 sys.stderr.write("Pouziti: %s shapefile\n" % sys.argv[0])
33 sys.exit(0)
34
35 sys.exit(main(sys.argv[1]))
Prostorové predikáty
Pro PostGIS je vhodné nastavit
export PGCLIENTENCODING=WIN1250 export PG_USE_COPY=YES
C++
1 #include <iostream>
2 #include <ctime>
3 #include "ogrsf_frmts.h"
4
5 using std::cerr;
6 using std::endl;
7 using std::cout;
8
9 OGRDataSource *open_dsn(const char *dsn)
10 {
11 OGRDataSource *poDs;
12
13 poDs = OGRSFDriverRegistrar::Open(dsn, FALSE);
14 if (!poDs)
15 cerr << "Otevreni " << dsn << " selhalo." << std::endl;
16
17 return poDs;
18 }
19
20 int compute_number(OGRLayer *poLayer1, OGRLayer *poLayer2)
21 {
22 int count, i;
23 int nfeat;
24 bool found;
25
26 OGRFeature *poFeat1, *poFeat2;
27 OGRGeometry *poGeom1, *poGeom2;
28
29 count = 0;
30
31 nfeat = poLayer1->GetFeatureCount();
32
33 /* sekvencne cti prvky z vsrtvy 1 (body) */
34 poLayer1->ResetReading();
35 i = 0;
36 while(true) {
37 cerr << "\r" << i << "/" << nfeat;
38 poFeat1 = poLayer1->GetNextFeature();
39 if (!poFeat1)
40 break;
41 poGeom1 = poFeat1->GetGeometryRef();
42 if (!poGeom1 || poGeom1->getGeometryType() != wkbPoint)
43 continue;
44
45 /* sekvencne cti prvky z vrstvy 2 (polygony) */
46 found = false;
47 poLayer2->ResetReading();
48 poLayer2->SetSpatialFilter(poGeom1);
49 while (!found) {
50 poFeat2 = poLayer2->GetNextFeature();
51 if (!poFeat2)
52 break;
53 poGeom2 = poFeat2->GetGeometryRef();
54 if (!poGeom2 || poGeom2->getGeometryType() != wkbPolygon)
55 continue;
56
57 if (poGeom1->Within(poGeom2)) {
58 found = true;
59 }
60
61 OGRFeature::DestroyFeature(poFeat2);
62 }
63 if (found)
64 count++;
65
66 OGRFeature::DestroyFeature(poFeat1);
67 i++;
68 }
69 cerr << "\r";
70
71 return count;
72 }
73
74 int main(int argc, char **argv)
75 {
76 const char *dsn1, *dsn2, *relation;
77 // const char *pszDriverName = "SQLite";
78 const char *pszDriverName = "PostgreSQL";
79 char **papszLCO;
80 time_t start;
81 OGRSFDriver *poDriver;
82 OGRDataSource *poDs1, *poDs2, *poDsSL;
83 OGRLayer *poLayer1, *poLayer2;
84
85 if (argc != 3) {
86 cerr << "Pouziti: " << argv[0]
87 << " <bodova vrstva> <polygonova vrstva>" << endl;
88 return 1;
89 }
90
91 dsn1 = argv[1];
92 dsn2 = argv[2];
93 relation = argv[3];
94
95 // registrovat dostupne OGR ovladace
96 OGRRegisterAll();
97
98 cout << "Nacitam data..." << endl;
99 // otevrit dsn1, dsn2 pro cteni
100 poDs1 = open_dsn(dsn1);
101 poDs2 = open_dsn(dsn2);
102 if (!poDs1 || !poDs2) {
103 return 1;
104 }
105
106 // nacist prvni OGR vrstvu
107 poLayer1 = poDs1->GetLayer(0);
108 poLayer2 = poDs2->GetLayer(0);
109 if (!poLayer1 || !poLayer2 ) {
110 cerr << "Nelze nacist OGR vrstvu." << endl;
111 return 1;
112 }
113
114 // konverze dat do databaze SpatiaLite
115 cout << "Ukladam data do databaze PostGIS..." << endl;
116 poDriver = OGRSFDriverRegistrar::GetRegistrar()->GetDriverByName(pszDriverName);
117 if (!poDriver) {
118 cerr << "Driver " << pszDriverName << " neni dostupny" << endl;
119 return 1;
120 }
121 // poDsSL = poDriver->Open("tmp.sqlite", TRUE);
122 poDsSL = poDriver->Open("PG:dbname=pgis_test", TRUE);
123 if (!poDsSL) {
124 char **papszDSCO = NULL;
125 // papszDSCO = CSLSetNameValue(papszDSCO, "SPATIALITE", "YES");
126 // poDsSL = poDriver->CreateDataSource("tmp.sqlite", papszDSCO);
127 }
128 papszLCO = NULL;
129 papszLCO = CSLSetNameValue(papszLCO, "OVERWRITE", "YES");
130 poLayer1 = poDsSL->CopyLayer(poLayer1, "points", papszLCO);
131 poLayer2 = poDsSL->CopyLayer(poLayer2, "polygons", papszLCO);
132
133 cout << "Analyzuji data..." << endl;
134 start = time(NULL);
135 cout << "Pocet bodu: " << compute_number(poLayer1, poLayer2)
136 << "/" << poLayer1->GetFeatureCount() << endl;
137 cout << "Cas vypoctu: " << time(NULL) - start << " sec" << endl;
138
139 OGRDataSource::DestroyDataSource(poDsSL);
140 OGRDataSource::DestroyDataSource(poDs1);
141 OGRDataSource::DestroyDataSource(poDs2);
142
143 return 0;
144 }
