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66 lines
1.7 KiB
C++
66 lines
1.7 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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// QuickBook Example
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// Copyright (c) 2011 Barend Gehrels, Amsterdam, the Netherlands.
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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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//[correct
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//` Shows how to correct a polygon with respect to its orientation and closure
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#include <iostream>
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#include <boost/geometry.hpp>
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#include <boost/geometry/geometries/adapted/tuple_cartesian.hpp>
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#include <boost/assign.hpp>
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int main()
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{
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using boost::assign::tuple_list_of;
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typedef boost::geometry::model::polygon
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<
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boost::tuple<int, int>
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> clockwise_closed_polygon;
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clockwise_closed_polygon cwcp;
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// Fill it counterclockwise (so wrongly), forgetting the closing point
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boost::geometry::exterior_ring(cwcp) = tuple_list_of(0, 0)(10, 10)(0, 9);
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// Add a counterclockwise closed inner ring (this is correct)
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boost::geometry::interior_rings(cwcp).push_back(tuple_list_of(1, 2)(4, 6)(2, 8)(1, 2));
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// Its area should be negative (because of wrong orientation)
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// and wrong (because of omitted closing point)
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double area_before = boost::geometry::area(cwcp);
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// Correct it!
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boost::geometry::correct(cwcp);
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// Check its new area
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double area_after = boost::geometry::area(cwcp);
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// And output it
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std::cout << boost::geometry::dsv(cwcp) << std::endl;
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std::cout << area_before << " -> " << area_after << std::endl;
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return 0;
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}
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//]
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//[correct_output
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/*`
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Output:
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[pre
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(((0, 0), (0, 9), (10, 10), (0, 0)), ((1, 2), (4, 6), (2, 8), (1, 2)))
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-7 -> 38
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]
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*/
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//]
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