1<?php
2
3/**
4 * Polygon: A polygon is a plane figure that is bounded by a closed path,
5 * composed of a finite sequence of straight line segments
6 */
7class Polygon extends Collection
8{
9  protected $geom_type = 'Polygon';
10
11  // The boundary of a polygin is it's outer ring
12  public function boundary() {
13    return $this->exteriorRing();
14  }
15
16  public function area($exterior_only = FALSE, $signed = FALSE) {
17    if ($this->isEmpty()) return 0;
18
19    if ($this->geos() && $exterior_only == FALSE) {
20      return $this->geos()->area();
21    }
22
23    $exterior_ring = $this->components[0];
24    $pts = $exterior_ring->getComponents();
25
26    $c = count($pts);
27    if((int)$c == '0') return NULL;
28    $a = '0';
29    foreach($pts as $k => $p){
30      $j = ($k + 1) % $c;
31      $a = $a + ($p->getX() * $pts[$j]->getY()) - ($p->getY() * $pts[$j]->getX());
32    }
33
34    if ($signed) $area = ($a / 2);
35    else $area = abs(($a / 2));
36
37    if ($exterior_only == TRUE) {
38      return $area;
39    }
40    foreach ($this->components as $delta => $component) {
41      if ($delta != 0) {
42        $inner_poly = new Polygon(array($component));
43        $area -= $inner_poly->area();
44      }
45    }
46    return $area;
47  }
48
49  public function centroid() {
50    if ($this->isEmpty()) return NULL;
51
52    if ($this->geos()) {
53      return geoPHP::geosToGeometry($this->geos()->centroid());
54    }
55
56    $exterior_ring = $this->components[0];
57    $pts = $exterior_ring->getComponents();
58
59    $c = count($pts);
60    if((int)$c == '0') return NULL;
61    $cn = array('x' => '0', 'y' => '0');
62    $a = $this->area(TRUE, TRUE);
63
64    // If this is a polygon with no area. Just return the first point.
65    if ($a == 0) {
66      return $this->exteriorRing()->pointN(1);
67    }
68
69    foreach($pts as $k => $p){
70      $j = ($k + 1) % $c;
71      $P = ($p->getX() * $pts[$j]->getY()) - ($p->getY() * $pts[$j]->getX());
72      $cn['x'] = $cn['x'] + ($p->getX() + $pts[$j]->getX()) * $P;
73      $cn['y'] = $cn['y'] + ($p->getY() + $pts[$j]->getY()) * $P;
74    }
75
76    $cn['x'] = $cn['x'] / ( 6 * $a);
77    $cn['y'] = $cn['y'] / ( 6 * $a);
78
79    $centroid = new Point($cn['x'], $cn['y']);
80    return $centroid;
81  }
82
83	/**
84	 * Find the outermost point from the centroid
85	 *
86	 * @returns Point The outermost point
87	 */
88  public function outermostPoint() {
89		$centroid = $this->getCentroid();
90
91		$max = array('length' => 0, 'point' => null);
92
93		foreach($this->getPoints() as $point) {
94			$lineString = new LineString(array($centroid, $point));
95
96			if($lineString->length() > $max['length']) {
97				$max['length'] = $lineString->length();
98				$max['point'] = $point;
99			}
100		}
101
102		return $max['point'];
103  }
104
105  public function exteriorRing() {
106    if ($this->isEmpty()) return new LineString();
107    return $this->components[0];
108  }
109
110  public function numInteriorRings() {
111    if ($this->isEmpty()) return 0;
112    return $this->numGeometries()-1;
113  }
114
115  public function interiorRingN($n) {
116    return $this->geometryN($n+1);
117  }
118
119  public function dimension() {
120    if ($this->isEmpty()) return 0;
121    return 2;
122  }
123
124  public function isSimple() {
125    if ($this->geos()) {
126      return $this->geos()->isSimple();
127    }
128
129    $segments = $this->explode();
130
131    foreach ($segments as $i => $segment) {
132      foreach ($segments as $j => $check_segment) {
133        if ($i != $j) {
134          if ($segment->lineSegmentIntersect($check_segment)) {
135            return FALSE;
136          }
137        }
138      }
139    }
140    return TRUE;
141  }
142
143  /**
144   * For a given point, determine whether it's bounded by the given polygon.
145   * Adapted from http://www.assemblysys.com/dataServices/php_pointinpolygon.php
146   * @see http://en.wikipedia.org/wiki/Point%5Fin%5Fpolygon
147   *
148   * @param Point $point
149   * @param boolean $pointOnBoundary - whether a boundary should be considered "in" or not
150   * @param boolean $pointOnVertex - whether a vertex should be considered "in" or not
151   * @return boolean
152   */
153  public function pointInPolygon($point, $pointOnBoundary = true, $pointOnVertex = true) {
154    $vertices = $this->getPoints();
155
156    // Check if the point sits exactly on a vertex
157    if ($this->pointOnVertex($point, $vertices)) {
158      return $pointOnVertex ? TRUE : FALSE;
159    }
160
161    // Check if the point is inside the polygon or on the boundary
162    $intersections = 0;
163    $vertices_count = count($vertices);
164
165    for ($i=1; $i < $vertices_count; $i++) {
166      $vertex1 = $vertices[$i-1];
167      $vertex2 = $vertices[$i];
168      if ($vertex1->y() == $vertex2->y()
169      && $vertex1->y() == $point->y()
170      && $point->x() > min($vertex1->x(), $vertex2->x())
171      && $point->x() < max($vertex1->x(), $vertex2->x())) {
172        // Check if point is on an horizontal polygon boundary
173        return $pointOnBoundary ? TRUE : FALSE;
174      }
175      if ($point->y() > min($vertex1->y(), $vertex2->y())
176      && $point->y() <= max($vertex1->y(), $vertex2->y())
177      && $point->x() <= max($vertex1->x(), $vertex2->x())
178      && $vertex1->y() != $vertex2->y()) {
179        $xinters =
180          ($point->y() - $vertex1->y()) * ($vertex2->x() - $vertex1->x())
181          / ($vertex2->y() - $vertex1->y())
182          + $vertex1->x();
183        if ($xinters == $point->x()) {
184          // Check if point is on the polygon boundary (other than horizontal)
185          return $pointOnBoundary ? TRUE : FALSE;
186        }
187        if ($vertex1->x() == $vertex2->x() || $point->x() <= $xinters) {
188          $intersections++;
189        }
190      }
191    }
192    // If the number of edges we passed through is even, then it's in the polygon.
193    if ($intersections % 2 != 0) {
194      return TRUE;
195    }
196    else {
197      return FALSE;
198    }
199  }
200
201  public function pointOnVertex($point) {
202    foreach($this->getPoints() as $vertex) {
203      if ($point->equals($vertex)) {
204        return true;
205      }
206    }
207  }
208
209
210  // Not valid for this geometry type
211  // --------------------------------
212  public function length() { return NULL; }
213
214}
215
216