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