85 lines
3.3 KiB
C++
85 lines
3.3 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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//
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// Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
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//
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// Use, modification and distribution is subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Boost.Geometry (aka GGL, Generic Geometry Library)
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// SOCI example
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// d: using WKB to retrieve geometries
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// SOCI is a generic C++ template interface to access relational databases
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// To build and run this example, see comments in example a
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// Alternatively compile composing and executing compiler command directoy in examples directory,
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// for example using GCC compiler:
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// g++ -I../../../boost -I/home/mloskot/usr/include/soci \
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// -I /home/mloskot/usr/include/soci/postgresql -I/usr/include/postgresql \
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// -L/home/mloskot/usr/lib -lsoci_core-gcc-3_0 -lsoci_postgresql-gcc-3_0 x03_c_soci_example.cpp
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#include <soci.h>
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#include <soci-postgresql.h>
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#include <exception>
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#include <iostream>
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#include <iterator>
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#include <string>
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#include <vector>
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#include <boost/geometry.hpp>
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#include <boost/geometry/geometries/geometries.hpp>
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#include <boost/geometry/geometries/point_xy.hpp>
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#include <boost/geometry/extensions/gis/io/wkb/read_wkb.hpp>
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#include <boost/geometry/extensions/gis/io/wkb/utility.hpp>
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int main()
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{
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try
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{
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// establish database connection
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soci::session sql(soci::postgresql, "dbname=ggl user=ggl password=ggl");
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// construct schema of table for trees (point geometries)
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sql << "DELETE FROM geometry_columns WHERE f_table_name = 'parcels'";
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sql << "DROP TABLE IF EXISTS parcels CASCADE";
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sql << "CREATE TABLE parcels (id INTEGER)";
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sql << "SELECT AddGeometryColumn('parcels', 'geom', -1, 'GEOMETRY', 2)";
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// insert sample data using plain WKT input
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sql << "INSERT INTO parcels VALUES(1, ST_GeomFromText('POLYGON ((10 10, 10 20, 20 20, 20 15, 10 10))', -1))";
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sql << "INSERT INTO parcels VALUES(2, ST_GeomFromText('POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))', -1))";
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sql << "INSERT INTO parcels VALUES(3, ST_GeomFromText('POLYGON((1 1,2 1,2 2,1 2,1 1))', -1))";
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// query data in WKB form and read to geometry object
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soci::rowset<std::string> rows = (sql.prepare << "SELECT encode(ST_AsBinary(geom), 'hex') AS wkb FROM parcels");
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// calculate area of each parcel
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for (soci::rowset<std::string>::iterator it = rows.begin(); it != rows.end(); ++it)
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{
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// parse WKB and construct geometry object
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std::string const& hex = *it;
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std::vector<unsigned char> wkb;
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if (!boost::geometry::hex2wkb(*it, std::back_inserter(wkb)))
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throw std::runtime_error("hex2wkb translation failed");
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boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > parcel;
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if (!boost::geometry::read_wkb(wkb.begin(), wkb.end(), parcel))
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throw std::runtime_error("read_wkb failed");
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double a = boost::geometry::area(parcel);
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std::cout << "Parcel geometry: " << boost::geometry::wkt(parcel) << std::endl
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<< "\thas area is " << a << " in coordinate units" << std::endl;
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}
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}
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catch (std::exception const &e)
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{
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std::cerr << "Error: " << e.what() << '\n';
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}
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return 0;
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}
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