1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>centroid</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="../centroid.html" title="centroid"> 9<link rel="prev" href="centroid_3_with_strategy.html" title="centroid (with strategy)"> 10<link rel="next" href="return_centroid_1.html" title="return_centroid"> 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="centroid_3_with_strategy.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../centroid.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="return_centroid_1.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="geometry.reference.algorithms.centroid.centroid_2"></a><a class="link" href="centroid_2.html" title="centroid">centroid</a> 28</h5></div></div></div> 29<p> 30 <a class="indexterm" name="idm45635705649744"></a> 31Calculates the centroid of a geometry. 32 </p> 33<h6> 34<a name="geometry.reference.algorithms.centroid.centroid_2.h0"></a> 35 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.description"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.description">Description</a> 36 </h6> 37<p> 38 The free function centroid calculates the geometric center (or: center 39 of mass) of a geometry. It uses the default strategy, based on the coordinate 40 system of the geometry. 41 </p> 42<h6> 43<a name="geometry.reference.algorithms.centroid.centroid_2.h1"></a> 44 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.synopsis"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.synopsis">Synopsis</a> 45 </h6> 46<p> 47</p> 48<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Geometry</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Point</span><span class="special">></span> 49<span class="keyword">void</span> <span class="identifier">centroid</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">geometry</span><span class="special">,</span> <span class="identifier">Point</span> <span class="special">&</span> <span class="identifier">c</span><span class="special">)</span></pre> 50<p> 51 </p> 52<h6> 53<a name="geometry.reference.algorithms.centroid.centroid_2.h2"></a> 54 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.parameters"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.parameters">Parameters</a> 55 </h6> 56<div class="informaltable"><table class="table"> 57<colgroup> 58<col> 59<col> 60<col> 61<col> 62</colgroup> 63<thead><tr> 64<th> 65 <p> 66 Type 67 </p> 68 </th> 69<th> 70 <p> 71 Concept 72 </p> 73 </th> 74<th> 75 <p> 76 Name 77 </p> 78 </th> 79<th> 80 <p> 81 Description 82 </p> 83 </th> 84</tr></thead> 85<tbody> 86<tr> 87<td> 88 <p> 89 Geometry const & 90 </p> 91 </td> 92<td> 93 <p> 94 Any type fulfilling a Geometry Concept 95 </p> 96 </td> 97<td> 98 <p> 99 geometry 100 </p> 101 </td> 102<td> 103 <p> 104 A model of the specified concept 105 </p> 106 </td> 107</tr> 108<tr> 109<td> 110 <p> 111 Point & 112 </p> 113 </td> 114<td> 115 <p> 116 Any type fulfilling a Point Concept 117 </p> 118 </td> 119<td> 120 <p> 121 c 122 </p> 123 </td> 124<td> 125 <p> 126 The calculated centroid will be assigned to this point reference 127 </p> 128 </td> 129</tr> 130</tbody> 131</table></div> 132<h6> 133<a name="geometry.reference.algorithms.centroid.centroid_2.h3"></a> 134 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.header"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.header">Header</a> 135 </h6> 136<p> 137 Either 138 </p> 139<p> 140 <code class="computeroutput"><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></code> 141 </p> 142<p> 143 Or 144 </p> 145<p> 146 <code class="computeroutput"><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">algorithms</span><span class="special">/</span><span class="identifier">centroid</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> 147 </p> 148<h6> 149<a name="geometry.reference.algorithms.centroid.centroid_2.h4"></a> 150 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.conformance"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.conformance">Conformance</a> 151 </h6> 152<p> 153 The function centroid implements function Centroid from the <a href="http://www.opengeospatial.org/standards/sfa" target="_top">OGC 154 Simple Feature Specification</a>. 155 </p> 156<h6> 157<a name="geometry.reference.algorithms.centroid.centroid_2.h5"></a> 158 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.behavior"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.behavior">Behavior</a> 159 </h6> 160<div class="informaltable"><table class="table"> 161<colgroup> 162<col> 163<col> 164</colgroup> 165<thead><tr> 166<th> 167 <p> 168 Case 169 </p> 170 </th> 171<th> 172 <p> 173 Behavior 174 </p> 175 </th> 176</tr></thead> 177<tbody> 178<tr> 179<td> 180 <p> 181 Point 182 </p> 183 </td> 184<td> 185 <p> 186 Returns the point itself as the centroid 187 </p> 188 </td> 189</tr> 190<tr> 191<td> 192 <p> 193 Multi Point 194 </p> 195 </td> 196<td> 197 <p> 198 Calculates centroid (based on average) 199 </p> 200 </td> 201</tr> 202<tr> 203<td> 204 <p> 205 linear (e.g. linestring) 206 </p> 207 </td> 208<td> 209 <p> 210 Calculates centroid (based on weighted length) 211 </p> 212 </td> 213</tr> 214<tr> 215<td> 216 <p> 217 areal (e.g. polygon) 218 </p> 219 </td> 220<td> 221 <p> 222 Calculates centroid 223 </p> 224 </td> 225</tr> 226<tr> 227<td> 228 <p> 229 Empty (e.g. polygon without points) 230 </p> 231 </td> 232<td> 233 <p> 234 Throws a <a class="link" href="../../exceptions/centroid_exception.html" title="centroid_exception">centroid_exception</a> 235 </p> 236 </td> 237</tr> 238<tr> 239<td> 240 <p> 241 Cartesian 242 </p> 243 </td> 244<td> 245 <p> 246 Implemented 247 </p> 248 </td> 249</tr> 250<tr> 251<td> 252 <p> 253 Spherical 254 </p> 255 </td> 256<td> 257 <p> 258 Calculates the centroid as if based on Cartesian coordinates 259 </p> 260 </td> 261</tr> 262</tbody> 263</table></div> 264<h6> 265<a name="geometry.reference.algorithms.centroid.centroid_2.h6"></a> 266 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.supported_geometries"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.supported_geometries">Supported 267 geometries</a> 268 </h6> 269<div class="informaltable"><table class="table"> 270<colgroup> 271<col> 272<col> 273<col> 274</colgroup> 275<thead><tr> 276<th> 277 </th> 278<th> 279 <p> 280 2D 281 </p> 282 </th> 283<th> 284 <p> 285 3D 286 </p> 287 </th> 288</tr></thead> 289<tbody> 290<tr> 291<td> 292 <p> 293 Point 294 </p> 295 </td> 296<td> 297 <p> 298 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 299 </p> 300 </td> 301<td> 302 <p> 303 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 304 </p> 305 </td> 306</tr> 307<tr> 308<td> 309 <p> 310 Segment 311 </p> 312 </td> 313<td> 314 <p> 315 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 316 </p> 317 </td> 318<td> 319 <p> 320 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 321 </p> 322 </td> 323</tr> 324<tr> 325<td> 326 <p> 327 Box 328 </p> 329 </td> 330<td> 331 <p> 332 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 333 </p> 334 </td> 335<td> 336 <p> 337 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 338 </p> 339 </td> 340</tr> 341<tr> 342<td> 343 <p> 344 Linestring 345 </p> 346 </td> 347<td> 348 <p> 349 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 350 </p> 351 </td> 352<td> 353 <p> 354 <span class="inlinemediaobject"><img src="../../../../img/nyi.png" alt="nyi"></span> 355 </p> 356 </td> 357</tr> 358<tr> 359<td> 360 <p> 361 Ring 362 </p> 363 </td> 364<td> 365 <p> 366 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 367 </p> 368 </td> 369<td> 370 <p> 371 <span class="inlinemediaobject"><img src="../../../../img/nyi.png" alt="nyi"></span> 372 </p> 373 </td> 374</tr> 375<tr> 376<td> 377 <p> 378 Polygon 379 </p> 380 </td> 381<td> 382 <p> 383 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 384 </p> 385 </td> 386<td> 387 <p> 388 <span class="inlinemediaobject"><img src="../../../../img/nyi.png" alt="nyi"></span> 389 </p> 390 </td> 391</tr> 392<tr> 393<td> 394 <p> 395 MultiPoint 396 </p> 397 </td> 398<td> 399 <p> 400 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 401 </p> 402 </td> 403<td> 404 <p> 405 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 406 </p> 407 </td> 408</tr> 409<tr> 410<td> 411 <p> 412 MultiLinestring 413 </p> 414 </td> 415<td> 416 <p> 417 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 418 </p> 419 </td> 420<td> 421 <p> 422 <span class="inlinemediaobject"><img src="../../../../img/nyi.png" alt="nyi"></span> 423 </p> 424 </td> 425</tr> 426<tr> 427<td> 428 <p> 429 MultiPolygon 430 </p> 431 </td> 432<td> 433 <p> 434 <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span> 435 </p> 436 </td> 437<td> 438 <p> 439 <span class="inlinemediaobject"><img src="../../../../img/nyi.png" alt="nyi"></span> 440 </p> 441 </td> 442</tr> 443</tbody> 444</table></div> 445<h6> 446<a name="geometry.reference.algorithms.centroid.centroid_2.h7"></a> 447 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.complexity"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.complexity">Complexity</a> 448 </h6> 449<p> 450 Linear 451 </p> 452<h6> 453<a name="geometry.reference.algorithms.centroid.centroid_2.h8"></a> 454 <span class="phrase"><a name="geometry.reference.algorithms.centroid.centroid_2.example"></a></span><a class="link" href="centroid_2.html#geometry.reference.algorithms.centroid.centroid_2.example">Example</a> 455 </h6> 456<p> 457 Shows calculation of a centroid of a polygon 458 </p> 459<p> 460</p> 461<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 462<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">list</span><span class="special">></span> 463 464<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> 465<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> 466<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> 467 468 469<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> 470<span class="special">{</span> 471 <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">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="identifier">point_type</span><span class="special">;</span> 472 <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">polygon</span><span class="special"><</span><span class="identifier">point_type</span><span class="special">></span> <span class="identifier">polygon_type</span><span class="special">;</span> 473 474 <span class="identifier">polygon_type</span> <span class="identifier">poly</span><span class="special">;</span> 475 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span> 476 <span class="string">"POLYGON((2 1.3,2.4 1.7,2.8 1.8,3.4 1.2,3.7 1.6,3.4 2,4.1 3,5.3 2.6,5.4 1.2,4.9 0.8,2.9 0.7,2 1.3)"</span> 477 <span class="string">"(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))"</span><span class="special">,</span> <span class="identifier">poly</span><span class="special">);</span> 478 479 <span class="identifier">point_type</span> <span class="identifier">p</span><span class="special">;</span> 480 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">centroid</span><span class="special">(</span><span class="identifier">poly</span><span class="special">,</span> <span class="identifier">p</span><span class="special">);</span> 481 482 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"centroid: "</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">dsv</span><span class="special">(</span><span class="identifier">p</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> 483 484 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 485<span class="special">}</span> 486</pre> 487<p> 488 </p> 489<p> 490 Output: 491 </p> 492<pre class="programlisting">centroid: (4.04663, 1.6349) 493<img src="../../../../img/algorithms/centroid.png" alt="centroid"> 494</pre> 495<p> 496 Note that the centroid might be located in a hole or outside a polygon, 497 easily. 498 </p> 499</div> 500<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 501<td align="left"></td> 502<td align="right"><div class="copyright-footer">Copyright © 2009-2019 Barend Gehrels, Bruno Lalande, Mateusz Loskot, Adam 503 Wulkiewicz, Oracle and/or its affiliates<p> 504 Distributed under the Boost Software License, Version 1.0. (See accompanying 505 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>) 506 </p> 507</div></td> 508</tr></table> 509<hr> 510<div class="spirit-nav"> 511<a accesskey="p" href="centroid_3_with_strategy.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../centroid.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="return_centroid_1.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 512</div> 513</body> 514</html> 515
