1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Quick Start</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../index.html" title="Chapter 1. Geometry"> 8<link rel="up" href="../index.html" title="Chapter 1. Geometry"> 9<link rel="prev" href="design.html" title="Design Rationale"> 10<link rel="next" href="spatial_indexes.html" title="Spatial Indexes"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="design.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="spatial_indexes.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 27<a name="geometry.quickstart"></a><a class="link" href="quickstart.html" title="Quick Start">Quick Start</a> 28</h2></div></div></div> 29<p> 30 This Quick Start section shows some of the features of Boost.Geometry in the 31 form of annotated, relatively simple, code snippets. 32 </p> 33<p> 34 The code below assumes that <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span></code> is included, 35 and that <code class="computeroutput"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span></code> 36 is used. Boost.Geometry is header only, so including headerfiles is enough. 37 There is no linking with any library necessary. 38 </p> 39<p> 40</p> 41<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 42<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">point_xy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 43<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">polygon</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 44 45<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">;</span> 46</pre> 47<p> 48 </p> 49<h4> 50<a name="geometry.quickstart.h0"></a> 51 <span class="phrase"><a name="geometry.quickstart.cartesian"></a></span><a class="link" href="quickstart.html#geometry.quickstart.cartesian">Cartesian</a> 52 </h4> 53<p> 54 It is possible to use only a small part of the library. For example: the distance 55 between two points is a common use case. Boost.Geometry can calculate it from 56 various types. Using one of its own types: 57 </p> 58<p> 59</p> 60<pre class="programlisting"><span class="identifier">model</span><span class="special">::</span><span class="identifier">d2</span><span class="special">::</span><span class="identifier">point_xy</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">p1</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="number">1</span><span class="special">),</span> <span class="identifier">p2</span><span class="special">(</span><span class="number">2</span><span class="special">,</span> <span class="number">2</span><span class="special">);</span> 61<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Distance p1-p2 is: "</span> <span class="special"><<</span> <span class="identifier">distance</span><span class="special">(</span><span class="identifier">p1</span><span class="special">,</span> <span class="identifier">p2</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 62</pre> 63<p> 64 </p> 65<p> 66 If the right headers are included and the types are bound to a coordinate system, 67 various other types can be used as points: plain C array's, Boost.Array's, 68 Boost.Tuple's, Boost.Fusion imported structs, your own classes... 69 </p> 70<p> 71 Registering and using a C array: 72 </p> 73<p> 74</p> 75<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">adapted</span><span class="special">/</span><span class="identifier">c_array</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 76 77<span class="identifier">BOOST_GEOMETRY_REGISTER_C_ARRAY_CS</span><span class="special">(</span><span class="identifier">cs</span><span class="special">::</span><span class="identifier">cartesian</span><span class="special">)</span> 78</pre> 79<p> 80 </p> 81<p> 82</p> 83<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span><span class="special">[</span><span class="number">2</span><span class="special">]</span> <span class="special">=</span> <span class="special">{</span><span class="number">1</span><span class="special">,</span><span class="number">1</span><span class="special">};</span> 84<span class="keyword">int</span> <span class="identifier">b</span><span class="special">[</span><span class="number">2</span><span class="special">]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">};</span> 85<span class="keyword">double</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">distance</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span> <span class="identifier">b</span><span class="special">);</span> 86<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Distance a-b is: "</span> <span class="special"><<</span> <span class="identifier">d</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 87</pre> 88<p> 89 </p> 90<p> 91 Another often used algorithm is point-in-polygon. It is implemented in Boost.Geometry 92 under the name <code class="computeroutput"><span class="identifier">within</span></code>. We show 93 its usage here checking a Boost.Tuple (as a point) located within a polygon, 94 filled with C Array point pairs. 95 </p> 96<p> 97 But it is first necessary to register a Boost.Tuple, like the C array: 98 </p> 99<p> 100</p> 101<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">adapted</span><span class="special">/</span><span class="identifier">boost_tuple</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 102 103<span class="identifier">BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS</span><span class="special">(</span><span class="identifier">cs</span><span class="special">::</span><span class="identifier">cartesian</span><span class="special">)</span> 104</pre> 105<p> 106 </p> 107<p> 108</p> 109<pre class="programlisting"><span class="keyword">double</span> <span class="identifier">points</span><span class="special">[][</span><span class="number">2</span><span class="special">]</span> <span class="special">=</span> <span class="special">{{</span><span class="number">2.0</span><span class="special">,</span> <span class="number">1.3</span><span class="special">},</span> <span class="special">{</span><span class="number">4.1</span><span class="special">,</span> <span class="number">3.0</span><span class="special">},</span> <span class="special">{</span><span class="number">5.3</span><span class="special">,</span> <span class="number">2.6</span><span class="special">},</span> <span class="special">{</span><span class="number">2.9</span><span class="special">,</span> <span class="number">0.7</span><span class="special">},</span> <span class="special">{</span><span class="number">2.0</span><span class="special">,</span> <span class="number">1.3</span><span class="special">}};</span> 110<span class="identifier">model</span><span class="special">::</span><span class="identifier">polygon</span><span class="special"><</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">d2</span><span class="special">::</span><span class="identifier">point_xy</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> <span class="identifier">poly</span><span class="special">;</span> 111<span class="identifier">append</span><span class="special">(</span><span class="identifier">poly</span><span class="special">,</span> <span class="identifier">points</span><span class="special">);</span> 112<span class="identifier">boost</span><span class="special">::</span><span class="identifier">tuple</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="keyword">double</span><span class="special">></span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">make_tuple</span><span class="special">(</span><span class="number">3.7</span><span class="special">,</span> <span class="number">2.0</span><span class="special">);</span> 113<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Point p is in polygon? "</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">boolalpha</span> <span class="special"><<</span> <span class="identifier">within</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">poly</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 114</pre> 115<p> 116 </p> 117<p> 118 We can calculate the area of a polygon: 119 </p> 120<p> 121</p> 122<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Area: "</span> <span class="special"><<</span> <span class="identifier">area</span><span class="special">(</span><span class="identifier">poly</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 123</pre> 124<p> 125 </p> 126<p> 127 By the nature of a template library, it is possible to mix point types. We 128 calculate distance again, now using a C array point and a Boost.Tuple point: 129 </p> 130<p> 131</p> 132<pre class="programlisting"><span class="keyword">double</span> <span class="identifier">d2</span> <span class="special">=</span> <span class="identifier">distance</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span> <span class="identifier">p</span><span class="special">);</span> 133<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Distance a-p is: "</span> <span class="special"><<</span> <span class="identifier">d2</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 134</pre> 135<p> 136 </p> 137<p> 138 The snippets listed above generate the following output: 139 </p> 140<pre class="programlisting">Distance p1-p2 is: 1.41421 141Distance a-b is: 2.23607 142Point p is in polygon? true 143Area: 3.015 144Distance a-p is: 2.87924 145</pre> 146<h4> 147<a name="geometry.quickstart.h1"></a> 148 <span class="phrase"><a name="geometry.quickstart.non_cartesian"></a></span><a class="link" href="quickstart.html#geometry.quickstart.non_cartesian">Non-Cartesian</a> 149 </h4> 150<p> 151 It is also possible to use non-Cartesian points. For example: points on a sphere. 152 When then an algorithm such as distance is used the library "inspects" 153 that it is handling spherical points and calculates the distance over the sphere, 154 instead of applying the Pythagorean theorem. 155 </p> 156<div class="note"><table border="0" summary="Note"> 157<tr> 158<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td> 159<th align="left">Note</th> 160</tr> 161<tr><td align="left" valign="top"><p> 162 Boost.Geometry supports a geographical coordinate system, but that is in 163 an extension and not released in the current Boost release. 164 </p></td></tr> 165</table></div> 166<p> 167 We approximate the Earth as a sphere and calculate the distance between Amsterdam 168 and Paris: 169 </p> 170<p> 171</p> 172<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">point</span> 173 <span class="special"><</span> 174 <span class="keyword">double</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">cs</span><span class="special">::</span><span class="identifier">spherical_equatorial</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">degree</span><span class="special">></span> 175 <span class="special">></span> <span class="identifier">spherical_point</span><span class="special">;</span> 176 177<span class="identifier">spherical_point</span> <span class="identifier">amsterdam</span><span class="special">(</span><span class="number">4.90</span><span class="special">,</span> <span class="number">52.37</span><span class="special">);</span> 178<span class="identifier">spherical_point</span> <span class="identifier">paris</span><span class="special">(</span><span class="number">2.35</span><span class="special">,</span> <span class="number">48.86</span><span class="special">);</span> 179 180<span class="keyword">double</span> <span class="keyword">const</span> <span class="identifier">earth_radius</span> <span class="special">=</span> <span class="number">3959</span><span class="special">;</span> <span class="comment">// miles</span> 181<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Distance in miles: "</span> <span class="special"><<</span> <span class="identifier">distance</span><span class="special">(</span><span class="identifier">amsterdam</span><span class="special">,</span> <span class="identifier">paris</span><span class="special">)</span> <span class="special">*</span> <span class="identifier">earth_radius</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 182</pre> 183<p> 184 </p> 185<p> 186 It writes: 187 </p> 188<pre class="programlisting">Distance in miles: 267.02</pre> 189<h4> 190<a name="geometry.quickstart.h2"></a> 191 <span class="phrase"><a name="geometry.quickstart.adapted_structs"></a></span><a class="link" href="quickstart.html#geometry.quickstart.adapted_structs">Adapted 192 structs</a> 193 </h4> 194<p> 195 Finally an example from a totally different domain: developing window-based 196 applications, for example using QtWidgets. As soon as Qt classes are registered 197 in Boost.Geometry we can use them. We can, for example, check if two rectangles 198 overlap and if so, move the second one to another place: 199 </p> 200<p> 201</p> 202<pre class="programlisting"><span class="identifier">QRect</span> <span class="identifier">r1</span><span class="special">(</span><span class="number">100</span><span class="special">,</span> <span class="number">200</span><span class="special">,</span> <span class="number">15</span><span class="special">,</span> <span class="number">15</span><span class="special">);</span> 203<span class="identifier">QRect</span> <span class="identifier">r2</span><span class="special">(</span><span class="number">110</span><span class="special">,</span> <span class="number">210</span><span class="special">,</span> <span class="number">20</span><span class="special">,</span> <span class="number">20</span><span class="special">);</span> 204<span class="keyword">if</span> <span class="special">(</span><span class="identifier">overlaps</span><span class="special">(</span><span class="identifier">r1</span><span class="special">,</span> <span class="identifier">r2</span><span class="special">))</span> 205<span class="special">{</span> 206 <span class="identifier">assign_values</span><span class="special">(</span><span class="identifier">r2</span><span class="special">,</span> <span class="number">200</span><span class="special">,</span> <span class="number">300</span><span class="special">,</span> <span class="number">220</span><span class="special">,</span> <span class="number">320</span><span class="special">);</span> 207<span class="special">}</span> 208</pre> 209<p> 210 </p> 211<h4> 212<a name="geometry.quickstart.h3"></a> 213 <span class="phrase"><a name="geometry.quickstart.more"></a></span><a class="link" href="quickstart.html#geometry.quickstart.more">More</a> 214 </h4> 215<p> 216 In the reference many more examples can be found. 217 </p> 218</div> 219<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 220<td align="left"></td> 221<td align="right"><div class="copyright-footer">Copyright © 2009-2019 Barend Gehrels, Bruno Lalande, Mateusz Loskot, Adam 222 Wulkiewicz, Oracle and/or its affiliates<p> 223 Distributed under the Boost Software License, Version 1.0. (See accompanying 224 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 225 </p> 226</div></td> 227</tr></table> 228<hr> 229<div class="spirit-nav"> 230<a accesskey="p" href="design.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="spatial_indexes.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 231</div> 232</body> 233</html> 234
