/*
* Geopaparazzi - Digital field mapping on Android based devices
* Copyright (C) 2016 HydroloGIS (www.hydrologis.com)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package eu.geopaparazzi.library.routing.osmbonuspack;
import java.util.ArrayList;
/**
* Methods to encode and decode a polyline with Google polyline encoding/decoding scheme.
* @see <a href="https://developers.google.com/maps/documentation/utilities/polylinealgorithm">Google polyline algorithm</a>
*/
public class PolylineEncoder {
private static StringBuffer encodeSignedNumber(int num) {
int sgn_num = num << 1;
if (num < 0) {
sgn_num = ~(sgn_num);
}
return(encodeNumber(sgn_num));
}
private static StringBuffer encodeNumber(int num) {
StringBuffer encodeString = new StringBuffer();
while (num >= 0x20) {
int nextValue = (0x20 | (num & 0x1f)) + 63;
encodeString.append((char)(nextValue));
num >>= 5;
}
num += 63;
encodeString.append((char)(num));
return encodeString;
}
/**
* Encode a polyline with Google polyline encoding method
* @param polyline the polyline
* @param precision 1 for a 6 digits encoding, 10 for a 5 digits encoding.
* @return the encoded polyline, as a String
*/
public static String encode(ArrayList<GeoPoint> polyline, int precision) {
StringBuffer encodedPoints = new StringBuffer();
int prev_lat = 0, prev_lng = 0;
for (GeoPoint trackpoint:polyline) {
int lat = trackpoint.getLatitudeE6() / precision;
int lng = trackpoint.getLongitudeE6() / precision;
encodedPoints.append(encodeSignedNumber(lat - prev_lat));
encodedPoints.append(encodeSignedNumber(lng - prev_lng));
prev_lat = lat;
prev_lng = lng;
}
return encodedPoints.toString();
}
/**
* Decode a "Google-encoded" polyline
* @param encodedString
* @param precision 1 for a 6 digits encoding of lat and lon, 10 for a 5 digits encoding.
* @param hasAltitude if the polyline also contains altitude (GraphHopper routes, with altitude in cm).
* @return the polyline.
*/
public static ArrayList<GeoPoint> decode(String encodedString, int precision, boolean hasAltitude) {
int index = 0;
int len = encodedString.length();
int lat = 0, lng = 0, alt = 0;
ArrayList<GeoPoint> polyline = new ArrayList<>(len / 3);
//capacity estimate: polyline size is roughly 1/3 of string length for a 5digits encoding, 1/5 for 10digits.
while (index < len) {
int b, shift, result;
shift = result = 0;
do {
b = encodedString.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = result = 0;
do {
b = encodedString.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
if (hasAltitude){
shift = result = 0;
do {
b = encodedString.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dalt = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
alt += dalt;
}
GeoPoint p = new GeoPoint(lat*precision, lng*precision, alt/100);
polyline.add(p);
}
//Log.d("BONUSPACK", "decode:string="+len+" points="+polyline.size());
return polyline;
}
}