55 lines
1.9 KiB
C++
55 lines
1.9 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) 2006 Artem Pavlenko
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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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//$Id$
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#include <cmath>
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#include <mapnik/map.hpp>
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#include <mapnik/projection.hpp>
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#include <mapnik/distance.hpp>
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#include <mapnik/scale_denominator.hpp>
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namespace mapnik {
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static const double dpi = 90.0; // display resolution
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double scale_denominator(Map const& map,projection const& prj)
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{
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double map_width = map.getWidth();
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double map_height = map.getHeight();
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Envelope<double> const& extent = map.getCurrentExtent();
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double x0 = extent.minx();
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double y0 = extent.miny();
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double x1 = extent.maxx();
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double y1 = extent.maxy();
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if (!prj.is_geographic())
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{
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prj.inverse(x0,y0);
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prj.inverse(x1,y1);
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}
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great_circle_distance distance;
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double d1 = distance(coord2d(x0,y0),coord2d(x1, y1));
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double d0 = sqrt(map_width * map_width + map_height * map_height) / dpi * 0.0254;
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return d1 / d0;
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}
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}
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