Saturday, June 7, 2014

Google Directions Points Decode

https://maps.googleapis.com/maps/api/directions/json?.....

Google Direction API membantu kita untuk mendapatkan laluan dari point A ke point B.

Kalau kita baca balik JSON(prefered) data yang google return, google akan bagi steps start & end location point. dimana kalau kita translate terus diatas peta akan nampak cacat sedikit sebab polyline tak ikut exactly atas jalan.

Goole ada sertakan detail point diantara start & end point, melalui atribute routes->legs->steps[$_]->polyline->points

Cuma, 'cuma' ia telah di encode kan supaya size data nya tidak besar. saya agak sahaja. sebab google ada bagi tips/cara yg digunakan untuk encode points ni. cuma dia tak bagi complete function kat kita.... hampeh kan?... hehehhe

Saya nak buat sendiri x reti... bila cari kat internet diaorg kata dah ada org buat guna javascript tapi saya cari x jumpa... link broken... yang saya jumpa mamat ni dah convert ker PHP code. dia translate dr javascript... saya plak nak kan yg javascript... bila cari tak jumpa... saya translate balik ke javascript.... hahahhaa.... . may be ada mistake.. tapi saya test ok jer... hehehhe

ini code nya dlm javascript function

/*
 * Copyright (c) 2008 Peter Chng, http://unitstep.net/
 * 
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * convert to javascipt by [email protected]@ayun, http://blog.mbek.net 
*/

function decodePolylineToArray(encoded){
  var length = encoded.length;
  var index = 0;
  var points = [];
  var lat = 0;
  var lng = 0;

  while (index < length)
  {
    // Temporary variable to hold each ASCII byte.
    var b = 0;

    // The encoded polyline consists of a latitude value followed by a
    // longitude value.  They should always come in pairs.  Read the
    // latitude value first.
    var shift = 0;
    var result = 0;
    do
    {
      // The `ord(substr(encoded, $index++))` statement returns the ASCII
      //  code for the character at $index.  Subtract 63 to get the original
      // value. (63 was added to ensure proper ASCII characters are displayed
      // in the encoded polyline string, which is `human` readable)
      //b = ord(substr(encoded, index++)) - 63;
      b = encoded.charCodeAt(index++) - 63;

      // AND the bits of the byte with 0x1f to get the original 5-bit `chunk.
      // Then left shift the bits by the required amount, which increases
      // by 5 bits each time.
      // OR the value into $results, which sums up the individual 5-bit chunks
      // into the original value.  Since the 5-bit chunks were reversed in
      // order during encoding, reading them in this way ensures proper
      // summation.
      result |= (b & 0x1f) << shift;
      shift += 5;
    }
    // Continue while the read byte is >= 0x20 since the last `chunk`
    // was not OR'd with 0x20 during the conversion process. (Signals the end)
    while (b >= 0x20);

    // Check if negative, and convert. (All negative values have the last bit
    // set)
    dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));

    // Compute actual latitude since value is offset from previous value.
    lat += dlat;

    // The next values will correspond to the longitude for this point.
    shift = 0;
    result = 0;
    do
    {
      //b = ord(substr(encoded, index++)) - 63;
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    }
    while (b >= 0x20);

    dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lng += dlng;

    // The actual latitude and longitude values were multiplied by
    // 1e5 before encoding so that they could be converted to a 32-bit
    // integer representation. (With a decimal accuracy of 5 places)
    // Convert back to original values.
    points.push([lat * 1e-5, lng * 1e-5]);
  }

  return points;
}

2 comments:

logistic-solutions said...
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