Determines whether a given point is inside a given polygon.
/**
* test for getPointOnSurface
*
* @param array $ring array of points forming the ring
*
* @dataProvider providerForTestGetPointOnSurface
* @return void
*/
public function testGetPointOnSurface($ring)
{
$this->assertEquals(
$this->object->isPointInsidePolygon(
$this->object->getPointOnSurface($ring),
$ring
),
true
);
}
/**
* Returns a point that is guaranteed to be on the surface of the ring.
* (for simple closed rings)
*
* @param array $ring array of points forming the ring
*
* @return array|void a point on the surface of the ring
* @access public
* @static
*/
public static function getPointOnSurface($ring)
{
// Find two consecutive distinct points.
for ($i = 0, $nb = count($ring) - 1; $i < $nb; $i++) {
if ($ring[$i]['y'] != $ring[$i + 1]['y']) {
$x0 = $ring[$i]['x'];
$x1 = $ring[$i + 1]['x'];
$y0 = $ring[$i]['y'];
$y1 = $ring[$i + 1]['y'];
break;
}
}
if (!isset($x0)) {
return false;
}
// Find the mid point
$x2 = ($x0 + $x1) / 2;
$y2 = ($y0 + $y1) / 2;
// Always keep $epsilon < 1 to go with the reduction logic down here
$epsilon = 0.1;
$denominator = sqrt(Util::pow($y1 - $y0, 2) + Util::pow($x0 - $x1, 2));
$pointA = array();
$pointB = array();
while (true) {
// Get the points on either sides of the line
// with a distance of epsilon to the mid point
$pointA['x'] = $x2 + $epsilon * ($y1 - $y0) / $denominator;
$pointA['y'] = $y2 + ($pointA['x'] - $x2) * ($x0 - $x1) / ($y1 - $y0);
$pointB['x'] = $x2 + $epsilon * ($y1 - $y0) / (0 - $denominator);
$pointB['y'] = $y2 + ($pointB['x'] - $x2) * ($x0 - $x1) / ($y1 - $y0);
// One of the points should be inside the polygon,
// unless epsilon chosen is too large
if (GISPolygon::isPointInsidePolygon($pointA, $ring)) {
return $pointA;
}
if (GISPolygon::isPointInsidePolygon($pointB, $ring)) {
return $pointB;
}
//If both are outside the polygon reduce the epsilon and
//recalculate the points(reduce exponentially for faster convergence)
$epsilon = Util::pow($epsilon, 2);
if ($epsilon == 0) {
return false;
}
}
}
/**
* Generate the WKT for the data from ESRI shape files.
*
* @param array $row_data GIS data
*
* @return string the WKT for the data from ESRI shape files
* @access public
*/
public function getShape($row_data)
{
// Determines whether each line ring is an inner ring or an outer ring.
// If it's an inner ring get a point on the surface which can be used to
// correctly classify inner rings to their respective outer rings.
foreach ($row_data['parts'] as $i => $ring) {
$row_data['parts'][$i]['isOuter'] = GISPolygon::isOuterRing($ring['points']);
}
// Find points on surface for inner rings
foreach ($row_data['parts'] as $i => $ring) {
if (!$ring['isOuter']) {
$row_data['parts'][$i]['pointOnSurface'] = GISPolygon::getPointOnSurface($ring['points']);
}
}
// Classify inner rings to their respective outer rings.
foreach ($row_data['parts'] as $j => $ring1) {
if ($ring1['isOuter']) {
continue;
}
foreach ($row_data['parts'] as $k => $ring2) {
if (!$ring2['isOuter']) {
continue;
}
// If the pointOnSurface of the inner ring
// is also inside the outer ring
if (GISPolygon::isPointInsidePolygon($ring1['pointOnSurface'], $ring2['points'])) {
if (!isset($ring2['inner'])) {
$row_data['parts'][$k]['inner'] = array();
}
$row_data['parts'][$k]['inner'][] = $j;
}
}
}
$wkt = 'MULTIPOLYGON(';
// for each polygon
foreach ($row_data['parts'] as $ring) {
if (!$ring['isOuter']) {
continue;
}
$wkt .= '(';
// start of polygon
$wkt .= '(';
// start of outer ring
foreach ($ring['points'] as $point) {
$wkt .= $point['x'] . ' ' . $point['y'] . ',';
}
$wkt = mb_substr($wkt, 0, mb_strlen($wkt) - 1);
$wkt .= ')';
// end of outer ring
// inner rings if any
if (isset($ring['inner'])) {
foreach ($ring['inner'] as $j) {
$wkt .= ',(';
// start of inner ring
foreach ($row_data['parts'][$j]['points'] as $innerPoint) {
$wkt .= $innerPoint['x'] . ' ' . $innerPoint['y'] . ',';
}
$wkt = mb_substr($wkt, 0, mb_strlen($wkt) - 1);
$wkt .= ')';
// end of inner ring
}
}
$wkt .= '),';
// end of polygon
}
$wkt = mb_substr($wkt, 0, mb_strlen($wkt) - 1);
$wkt .= ')';
// end of multipolygon
return $wkt;
}
