1 // Boost.Geometry (aka GGL, Generic Geometry Library)
2 //
3 // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
4 // Use, modification and distribution is subject to the Boost Software License,
5 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
6 // http://www.boost.org/LICENSE_1_0.txt)
7 //
8 // GD example
9
10 // GD is a well-known and often used graphic library to write GIF (and other formats)
11
12 // To build and run this example:
13 // 1) download GD from http://www.libgd.org (currently gd-2.0.35 is assumed)
14 // 2) add 11 files
15 // gd.c, gd_gd.c, gd_gif_out.c, gd_io*.c, gd_security.c, gd_topal.c, gdhelpers.c, gdtables.c
16 // to the project or makefile or jamfile
17 // 3) for windows, add define NONDLL to indicate GD is not used as a DLL
18 // (Note that steps 2 and 3 are done in the MSVC gd_example project file and property sheets)
19
20 #include <cmath>
21 #include <cstdio>
22 #include <vector>
23
24 #include <fstream>
25 #include <sstream>
26
27
28 #include <boost/foreach.hpp>
29
30 #include <boost/geometry.hpp>
31 #include <boost/geometry/geometries/multi_polygon.hpp>
32
33 #include <boost/geometry/extensions/gis/latlong/latlong.hpp>
34 #include <boost/geometry/extensions/gis/geographic/strategies/area_huiller_earth.hpp>
35
36
37 #include <gd.h>
38
39 namespace bg = boost::geometry;
40
41
42 // ----------------------------------------------------------------------------
43 // Read an ASCII file containing WKT's
44 // (note this function is shared by various examples)
45 // ----------------------------------------------------------------------------
46 template <typename Geometry>
read_wkt(std::string const & filename,std::vector<Geometry> & geometries)47 inline void read_wkt(std::string const& filename, std::vector<Geometry>& geometries)
48 {
49 std::ifstream cpp_file(filename.c_str());
50 if (cpp_file.is_open())
51 {
52 while (! cpp_file.eof() )
53 {
54 std::string line;
55 std::getline(cpp_file, line);
56 if (! line.empty())
57 {
58 Geometry geometry;
59 bg::read_wkt(line, geometry);
60 geometries.push_back(geometry);
61 }
62 }
63 }
64 }
65
66
main()67 int main()
68 {
69 // Adapt if necessary
70 std::string filename = "../data/world.wkt";
71
72
73 // The world is measured in latlong (degrees), so latlong is appropriate.
74 // We ignore holes in this sample (below)
75 typedef bg::model::ll::point<bg::degree> point_type;
76 typedef bg::model::polygon<point_type> polygon_type;
77 typedef bg::model::multi_polygon<polygon_type> country_type;
78
79 std::vector<country_type> countries;
80
81 // Read (for example) world countries
82 read_wkt(filename, countries);
83
84
85 // Create a GD image.
86 // A world map, as world.shp, is usually mapped in latitude-longitude (-180..180 and -90..90)
87 // For this example we use a very simple "transformation"
88 // mapping to 0..720 and 0..360
89 const double factor = 2.0;
90 gdImagePtr im = gdImageCreateTrueColor(int(360 * factor), int(180 * factor));
91
92 // Allocate three colors
93 int blue = gdImageColorResolve(im, 0, 52, 255);
94 int green = gdImageColorResolve(im, 0, 255, 0);
95 int black = gdImageColorResolve(im, 0, 0, 0);
96
97 // Paint background in blue
98 gdImageFilledRectangle(im, 0, 0, im->sx, im->sy, blue);
99
100 // Paint all countries in green
101 BOOST_FOREACH(country_type const& country, countries)
102 {
103 BOOST_FOREACH(polygon_type const& polygon, country)
104 {
105 // Ignore holes, so take only exterior ring
106 bg::model::ring<point_type> const& ring = bg::exterior_ring(polygon);
107
108 // If wished, suppress too small polygons.
109 // (Note that even in latlong, area is calculated in square meters)
110 double const a = bg::area(ring);
111 if (std::fabs(a) > 5000.0e6)
112 {
113 int const n = ring.size();
114 gdPoint* points = new gdPoint[n];
115
116 for (int i = 0; i < n; i++)
117 {
118 // Translate lon/lat or x/y to GD x/y points
119 points[i].x = int(factor * (bg::get<0>(ring[i]) + 180.0));
120 points[i].y = im->sy - int(factor * (bg::get<1>(ring[i]) + 90.0));
121 }
122
123 // Draw the polygon...
124 gdImageFilledPolygon(im, points, n, green);
125 // .. and the outline in black...
126 gdImagePolygon(im, points, n, black);
127
128 delete[] points;
129 }
130 }
131 }
132
133 // Use GD to create a GIF file
134 std::FILE* out = std::fopen("world.gif", "wb");
135 if (out != NULL)
136 {
137 gdImageGif(im, out);
138 std::fclose(out);
139 }
140
141 gdImageDestroy(im);
142
143 return 0;
144 }
145