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<?php
/**
* EGMapPolylineEncoder
*
* Modified version of:
* PolylineEncoder based on Mark McClure's Javascript PolylineEncoder
* and Jim Hribar's PHP version. All nicely melted into a proper PHP5 class.
*
* @package Google Maps Helpers
* @since 2008-12-02
* @author Matthias Bauer <matthias@pulpmedia.at>
* @copyright 2008, Pulpmedia Medientechnik und -design GmbH
* @see http://facstaff.unca.edu/mcmcclur/GoogleMaps/EncodePolyline/
*/
class EGMapPolylineEncoder {
protected $numLevels = 18;
protected $zoomFactor = 2;
protected $verySmall = 0.00001;
protected $forceEndpoints = true;
protected $zoomLevelBreaks = array();
/**
* All parameters are set with useful defaults.
* If you actually want to understand them, see Mark McClure's detailed description.
*
* @see http://facstaff.unca.edu/mcmcclur/GoogleMaps/EncodePolyline/algorithm.html
*/
public function __construct($numLevels = 18, $zoomFactor = 2, $verySmall = 0.00001, $forceEndpoints = true)
{
$this->numLevels = $numLevels;
$this->zoomFactor = $zoomFactor;
$this->verySmall = $verySmall;
$this->forceEndpoints = $forceEndpoints;
for ($i = 0; $i < $this->numLevels; $i++)
{
$this->zoomLevelBreaks[$i] = $this->verySmall * pow($this->zoomFactor, $this->numLevels - $i - 1);
}
}
/**
* Generates all values needed for the encoded Google Maps Polyline.
*
* @param array Multidimensional input array in the form of
* array(array(latitude, longitude), array(latitude, longitude),...)
*
* @return String the encoded points | stdClass Simple object containing three public parameter:
* - points: the points string with escaped backslashes
* - levels: the encoded levels ready to use
* - rawPoints: the points right out of the encoder
* - numLevels: should be used for creating the polyline
* - zoomFactor: should be used for creating the polyline
*/
public function encode($points, $pointsOnly = true)
{
$absMaxDist=0;
$dists = array();
if (count($points) > 2)
{
$stack[] = array(0, count($points) - 1);
while (count($stack) > 0)
{
$current = array_pop($stack);
$maxDist = 0;
for ($i = $current[0] + 1; $i < $current[1]; $i++)
{
$temp = $this->distance($points[$i], $points[$current[0]], $points[$current[1]]);
if ($temp > $maxDist)
{
$maxDist = $temp;
$maxLoc = $i;
if ($maxDist > $absMaxDist)
{
$absMaxDist = $maxDist;
}
}
}
if ($maxDist > $this->verySmall)
{
$dists[$maxLoc] = $maxDist;
array_push($stack, array($current[0], $maxLoc));
array_push($stack, array($maxLoc, $current[1]));
}
}
}
if ($pointsOnly)
return str_replace("\\","\\\\", $this->createEncodings($points, $dists));
$polyline = new stdClass();
$polyline->rawPoints = $this->createEncodings($points, $dists);
$polyline->levels = $this->encodeLevels($points, $dists, $absMaxDist);
$polyline->points = str_replace("\\", "\\\\", $polyline->rawPoints);
$polyline->numLevels = $this->numLevels;
$polyline->zoomFactor = $this->zoomFactor;
return $polyline;
}
/**
*
* @param integer $dd
* @return integer the computed level
*/
private function computeLevel($dd)
{
if ($dd > $this->verySmall)
{
$lev = 0;
while ($dd < $this->zoomLevelBreaks[$lev])
{
$lev++;
}
}
return $lev;
}
/**
* Calculates distance between point locations
*
* @param integer $p0
* @param integer $p1
* @param integer $p2
* @return integer
*/
private function distance($p0, $p1, $p2)
{
if ($p1[0] == $p2[0] && $p1[1] == $p2[1])
{
$out = sqrt(pow($p2[0] - $p0[0], 2) + pow($p2[1] - $p0[1], 2));
} else
{
$u = (($p0[0] - $p1[0]) * ($p2[0] - $p1[0]) + ($p0[1] - $p1[1]) * ($p2[1] - $p1[1])) / (pow($p2[0] - $p1[0], 2) + pow($p2[1] - $p1[1], 2));
if ($u <= 0)
{
$out = sqrt(pow($p0[0] - $p1[0], 2) + pow($p0[1] - $p1[1], 2));
}
if ($u >= 1)
{
$out = sqrt(pow($p0[0] - $p2[0], 2) + pow($p0[1] - $p2[1], 2));
}
if (0 < $u && $u < 1)
{
$out = sqrt(pow($p0[0] - $p1[0] - $u * ($p2[0] - $p1[0]), 2) + pow($p0[1] - $p1[1] - $u * ($p2[1] - $p1[1]), 2));
}
}
return $out;
}
/**
* Encodes a signed number
*
* @param float $num
* @return string
*/
private function encodeSignedNumber($num)
{
$sgn_num = $num << 1;
if ($num < 0)
{
$sgn_num = ~($sgn_num);
}
return $this->encodeNumber($sgn_num);
}
/**
* Encodes points
* @param array $points
* @param array $dists
* @return string the encoded points
*/
private function createEncodings($points, $dists)
{
$encoded_points = '';
$plat = $lng = $plng = $plat = 0;
for ($i = 0; $i < count($points); $i++)
{
if (isset($dists[$i]) || $i == 0 || $i == count($points) - 1)
{
$point = $points[$i];
$lat = $point[0];
$lng = $point[1];
$late5 = floor($lat * 1e5);
$lnge5 = floor($lng * 1e5);
$dlat = $late5 - $plat;
$dlng = $lnge5 - $plng;
$plat = $late5;
$plng = $lnge5;
$encoded_points .= $this->encodeSignedNumber($dlat) . $this->encodeSignedNumber($dlng);
}
}
return $encoded_points;
}
/**
* Encodes levels
*
* @param array $points
* @param array $dists
* @param integer $absMaxDist
* @return string
*/
private function encodeLevels($points, $dists, $absMaxDist)
{
$encoded_levels = '';
if ($this->forceEndpoints)
{
$encoded_levels .= $this->encodeNumber($this->numLevels - 1);
} else
{
$encoded_levels .= $this->encodeNumber($this->numLevels - $this->computeLevel($absMaxDist) - 1);
}
for ($i = 1; $i < count($points) - 1; $i++)
{
if (isset($dists[$i]))
{
$encoded_levels .= $this->encodeNumber($this->numLevels - $this->computeLevel($dists[$i]) - 1);
}
}
if ($this->forceEndpoints)
{
$encoded_levels .= $this->encodeNumber($this->numLevels - 1);
} else
{
$encoded_levels .= $this->encodeNumber($this->numLevels - $this->computeLevel($absMaxDist) - 1);
}
return $encoded_levels;
}
/**
* Encodes a number
*
* @param integer $num
* @return string
*/
private function encodeNumber($num)
{
$encodeString = '';
while ($num >= 0x20)
{
$nextValue = (0x20 | ($num & 0x1f)) + 63;
$encodeString .= chr($nextValue);
$num >>= 5;
}
$finalValue = $num + 63;
$encodeString .= chr($finalValue);
return $encodeString;
}
}
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