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111 lines
3.7 KiB
C++
111 lines
3.7 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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//
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// Copyright Barend Gehrels 2007-2009, Geodan, Amsterdam, the Netherlands
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// Copyright Bruno Lalande 2008, 2009
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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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//
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// GD example
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// GD is a well-known and often used graphic library to write GIF (and other formats)
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// To build and run this example:
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// 1) This example uses also shapelib, see 08_shapelib_example for necessary proceudre
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// 2) download GD from http://www.libgd.org
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// 3) add 11 files mentioned below to the project or makefile
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// 4) for windows, add define NONDLL to indicate GD is not used as a DLL
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// GD FILES necessary: gd.c, gd_gd.c, gd_gif_out.c, gd_io*.c, gd_security.c, gd_topal.c, gdhelpers.c, gdtables.c
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// Alternativelly, install GD using OSGeo4W installer from http://trac.osgeo.org/osgeo4w/
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// that provides Windows binary packages
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#include <cmath>
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#include <cstdio>
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#include <vector>
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#include <boost/geometry/geometry.hpp>
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#include <boost/geometry/algorithms/area.hpp>
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#include <boost/geometry/geometries/cartesian2d.hpp>
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#include <boost/geometry/extensions/gis/latlong/latlong.hpp>
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#include <gd.h>
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#include "shapelib_common.hpp"
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int main()
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{
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std::string filename = "c:/data/spatial/shape/world_free/world.shp";
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// The world is measured in latlong (degrees), so latlong (point_ll_deg, ring_ll_deg) is appropriate.
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// (It is possible to change this in point_xy)
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// We ignore holes in this sample.
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// So declare a ring_ll_deg (= closed ring, polygon without holes)
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std::vector<boost::geometry::ring_ll_deg> rings;
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// Open a shapefile, for example world countries
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try
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{
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read_shapefile(filename, rings);
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}
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catch(const std::string& s)
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{
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std::cout << s << std::endl;
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return 1;
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}
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// Create a GD image.
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// A world map, as world.shp, is usually mapped in latitude-longitude (-180..180 and -90..90)
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// For this sample we use a very simple "transformation"
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// mapping to 0..720 and 0..360
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const double factor = 2.0;
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gdImagePtr im = gdImageCreateTrueColor(int(360 * factor), int(180 * factor));
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// Allocate three colors
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int blue = gdImageColorResolve(im, 0, 52, 255);
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int green = gdImageColorResolve(im, 0, 255, 0);
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int black = gdImageColorResolve(im, 0, 0, 0);
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// Paint background
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gdImageFilledRectangle(im, 0, 0, im->sx, im->sy, blue);
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// Paint all rings
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for (std::vector<boost::geometry::ring_ll_deg>::const_iterator it = rings.begin(); it != rings.end(); ++it)
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{
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const boost::geometry::ring_ll_deg& ring = *it;
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// If wished, suppress too small polygons.
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// (Note that even in latlong, area is calculated in square meters)
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const double a = boost::geometry::area(ring);
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if (std::fabs(a) > 5000.0e6)
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{
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const int n = ring.size();
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gdPoint* points = new gdPoint[n];
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for (int i = 0; i < n; i++)
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{
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// Translate lon/lat or x/y to GD x/y points
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points[i].x = int(factor * (boost::geometry::get<0>(ring[i]) + 180.0));
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points[i].y = im->sy - int(factor * (boost::geometry::get<1>(ring[i]) + 90.0));
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}
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// Draw the polygon...
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gdImageFilledPolygon(im, points, n, green);
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// .. and the outline...
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gdImagePolygon(im, points, n, black);
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delete[] points;
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}
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}
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// Use GD to create a GIF file
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std::FILE* out = std::fopen("world.gif", "wb");
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if (out != NULL)
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{
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gdImageGif(im, out);
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std::fclose(out);
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}
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gdImageDestroy(im);
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return 0;
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}
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