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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="geometry.quickstart"></a><a class="link" href="quickstart.html" title="Quick Start">Quick Start</a> |
| </h2></div></div></div> |
| <p> |
| This Quick Start section shows some of the features of Boost.Geometry in the |
| form of annotated, relatively simple, code snippets. |
| </p> |
| <p> |
| 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, |
| 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> |
| is used. Boost.Geometry is header only, so including headerfiles is enough. |
| There is no linking with any library necessary. |
| </p> |
| <p> |
| </p> |
| <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> |
| <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> |
| <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> |
| |
| <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> |
| </pre> |
| <p> |
| </p> |
| <h4> |
| <a name="geometry.quickstart.h0"></a> |
| <span class="phrase"><a name="geometry.quickstart.cartesian"></a></span><a class="link" href="quickstart.html#geometry.quickstart.cartesian">Cartesian</a> |
| </h4> |
| <p> |
| It is possible to use only a small part of the library. For example: the distance |
| between two points is a common use case. Boost.Geometry can calculate it from |
| various types. Using one of its own types: |
| </p> |
| <p> |
| </p> |
| <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> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| If the right headers are included and the types are bound to a coordinate system, |
| various other types can be used as points: plain C array's, Boost.Array's, |
| Boost.Tuple's, Boost.Fusion imported structs, your own classes... |
| </p> |
| <p> |
| Registering and using a C array: |
| </p> |
| <p> |
| </p> |
| <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> |
| |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| </p> |
| <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> |
| <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> |
| <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> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Another often used algorithm is point-in-polygon. It is implemented in Boost.Geometry |
| under the name <code class="computeroutput"><span class="identifier">within</span></code>. We show |
| its usage here checking a Boost.Tuple (as a point) located within a polygon, |
| filled with C Array point pairs. |
| </p> |
| <p> |
| But it is first necessary to register a Boost.Tuple, like the C array: |
| </p> |
| <p> |
| </p> |
| <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> |
| |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| </p> |
| <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> |
| <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> |
| <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> |
| <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> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| We can calculate the area of a polygon: |
| </p> |
| <p> |
| </p> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| By the nature of a template library, it is possible to mix point types. We |
| calculate distance again, now using a C array point and a Boost.Tuple point: |
| </p> |
| <p> |
| </p> |
| <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> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The snippets listed above generate the following output: |
| </p> |
| <pre class="programlisting">Distance p1-p2 is: 1.41421 |
| Distance a-b is: 2.23607 |
| Point p is in polygon? true |
| Area: 3.015 |
| Distance a-p is: 2.87924 |
| </pre> |
| <h4> |
| <a name="geometry.quickstart.h1"></a> |
| <span class="phrase"><a name="geometry.quickstart.non_cartesian"></a></span><a class="link" href="quickstart.html#geometry.quickstart.non_cartesian">Non-Cartesian</a> |
| </h4> |
| <p> |
| It is also possible to use non-Cartesian points. For example: points on a sphere. |
| When then an algorithm such as distance is used the library "inspects" |
| that it is handling spherical points and calculates the distance over the sphere, |
| instead of applying the Pythagorean theorem. |
| </p> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| Boost.Geometry supports a geographical coordinate system, but that is in |
| an extension and not released in the current Boost release. |
| </p></td></tr> |
| </table></div> |
| <p> |
| We approximate the Earth as a sphere and calculate the distance between Amsterdam |
| and Paris: |
| </p> |
| <p> |
| </p> |
| <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> |
| <span class="special"><</span> |
| <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> |
| <span class="special">></span> <span class="identifier">spherical_point</span><span class="special">;</span> |
| |
| <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> |
| <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> |
| |
| <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> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| It writes: |
| </p> |
| <pre class="programlisting">Distance in miles: 267.02</pre> |
| <h4> |
| <a name="geometry.quickstart.h2"></a> |
| <span class="phrase"><a name="geometry.quickstart.adapted_structs"></a></span><a class="link" href="quickstart.html#geometry.quickstart.adapted_structs">Adapted |
| structs</a> |
| </h4> |
| <p> |
| Finally an example from a totally different domain: developing window-based |
| applications, for example using QtWidgets. As soon as Qt classes are registered |
| in Boost.Geometry we can use them. We can, for example, check if two rectangles |
| overlap and if so, move the second one to another place: |
| </p> |
| <p> |
| </p> |
| <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> |
| <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> |
| <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> |
| <span class="special">{</span> |
| <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> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <h4> |
| <a name="geometry.quickstart.h3"></a> |
| <span class="phrase"><a name="geometry.quickstart.more"></a></span><a class="link" href="quickstart.html#geometry.quickstart.more">More</a> |
| </h4> |
| <p> |
| In the reference many more examples can be found. |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2009-2015 Barend Gehrels, Bruno Lalande, |
| Mateusz Loskot, Adam Wulkiewicz, Oracle and/or its affiliates<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
| </tr></table> |
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