101 lines
3.2 KiB
C++
101 lines
3.2 KiB
C++
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/*****************************************************************************
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*
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* This file is part of Mapnik (c++ mapping toolkit)
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*
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* Copyright (C) 2010 Hermann Kraus
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*****************************************************************************/
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// Mapnik
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#include <mapnik/metawriter.hpp>
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#include <mapnik/metawriter_json.hpp>
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#include <mapnik/expression_evaluator.hpp>
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// STL
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#include <iomanip>
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namespace mapnik {
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metawriter_json::metawriter_json(std::string fn, expression_ptr dflt_expr) : dflt_expr_(dflt_expr), count(0)
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{
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f.open(fn.c_str(), std::fstream::out | std::fstream::trunc);
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if (f.fail()) perror((std::string("Failed to open file ") + fn).c_str());
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f << "{ \"type\": \"FeatureCollection\", \"features\": [\n";
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}
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metawriter_json::~metawriter_json()
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{
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if (f.is_open()) {
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f << " ] }\n";
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f.close();
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}
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std::clog << "Destroying metawriter\n";
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}
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void metawriter_json::add_box(box2d<double> box, Feature const &feature, proj_transform const& prj_trans, CoordTransform const &t, expression_ptr expression)
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{
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expression_ptr e;
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if (expression) {
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e = expression;
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} else {
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e = dflt_expr_;
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}
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if (!e) {
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std::clog << "WARNING: No expression available for JSON metawriter.\n";
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return;
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}
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value_type result = boost::apply_visitor(evaluate<Feature,value_type>(feature),*e);
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UnicodeString text = result.to_unicode();
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/* Coordinate transform in renderer:
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input: layer srs
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prj_trans.backwards() [prj_trans: map -> layer]
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intermediate: map srs
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t_.forward()
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output: pixels
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Our transform:
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input: pixels
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t_.backward()
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intermediate: map srs (available via prj_trans.source())
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trans.forward()
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output: WGS84
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*/
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proj_transform trans(prj_trans.source(), projection("+proj=latlong +datum=WGS84"));
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//t_ coord transform has transform for box2d combined with prj_trans
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box = t.backward(box, trans);
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double minx = box.minx();
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double miny = box.miny();
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double maxx = box.maxx();
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double maxy = box.maxy();
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if (count++) {
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f << ",\n";
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}
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f << std::fixed << std::setprecision(8) << "{ \"type\": \"Feature\",\n \"geometry\": { \"type\": \"Polygon\",\n \"coordinates\": [ [ [" <<
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minx << ", " << miny << "], [" <<
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maxx << ", " << miny << "], [" <<
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maxx << ", " << maxy << "], [" <<
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minx << ", " << maxy << "] ] ] }," <<
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"\n \"properties\": {" << text << "} }";
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}
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};
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