org.elasticsearch.common.geo.GeoLineDecomposer Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of elasticsearch Show documentation
Show all versions of elasticsearch Show documentation
Elasticsearch subproject :distribution:archives:integ-test-zip
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.common.geo;
import org.elasticsearch.geometry.Line;
import org.elasticsearch.geometry.MultiLine;
import java.util.Arrays;
import java.util.List;
import static org.elasticsearch.common.geo.GeoUtils.normalizePoint;
/**
* Splits lines by datelines.
*/
public class GeoLineDecomposer {
private static final double DATELINE = 180;
private GeoLineDecomposer() {
// no instances
}
public static void decomposeMultiLine(MultiLine multiLine, List collector) {
for (Line line : multiLine) {
decomposeLine(line, collector);
}
}
/**
* Splits the specified line by datelines and adds them to the supplied lines array
*/
public static void decomposeLine(Line line, List collector) {
if (line.isEmpty()) {
return;
}
double[] lons = new double[line.length()];
double[] lats = new double[lons.length];
for (int i = 0; i < lons.length; i++) {
double[] lonLat = new double[] { line.getX(i), line.getY(i) };
normalizePoint(lonLat, false, true);
lons[i] = lonLat[0];
lats[i] = lonLat[1];
}
decompose(lons, lats, collector);
}
/**
* Decompose a linestring given as array of coordinates by anti-meridian.
*/
private static void decompose(double[] lons, double[] lats, List collector) {
int offset = 0;
double shift = 0;
int i = 1;
while (i < lons.length) {
// Check where the line is going east (+1), west (-1) or directly north/south (0)
int direction = Double.compare(lons[i], lons[i - 1]);
double newShift = calculateShift(lons[i - 1], direction < 0);
// first point lon + shift is always between -180.0 and +180.0
if (i - offset > 1 && newShift != shift) {
// Jumping over anti-meridian - we need to start a new segment
double[] partLons = Arrays.copyOfRange(lons, offset, i);
double[] partLats = Arrays.copyOfRange(lats, offset, i);
performShift(shift, partLons);
shift = newShift;
offset = i - 1;
collector.add(new Line(partLons, partLats));
} else {
// Check if new point intersects with anti-meridian
shift = newShift;
double t = intersection(lons[i - 1] + shift, lons[i] + shift);
if (Double.isNaN(t) == false) {
// Found intersection, all previous segments are now part of the linestring
double[] partLons = Arrays.copyOfRange(lons, offset, i + 1);
double[] partLats = Arrays.copyOfRange(lats, offset, i + 1);
lons[i - 1] = partLons[partLons.length - 1] = (direction > 0 ? DATELINE : -DATELINE) - shift;
lats[i - 1] = partLats[partLats.length - 1] = lats[i - 1] + (lats[i] - lats[i - 1]) * t;
performShift(shift, partLons);
offset = i - 1;
collector.add(new Line(partLons, partLats));
} else {
// Didn't find intersection - just continue checking
i++;
}
}
}
if (offset == 0) {
performShift(shift, lons);
collector.add(new Line(lons, lats));
} else if (offset < lons.length - 1) {
double[] partLons = Arrays.copyOfRange(lons, offset, lons.length);
double[] partLats = Arrays.copyOfRange(lats, offset, lats.length);
performShift(shift, partLons);
collector.add(new Line(partLons, partLats));
}
}
/**
* shifts all coordinates by shift
*/
private static void performShift(double shift, double[] lons) {
if (shift != 0) {
for (int j = 0; j < lons.length; j++) {
lons[j] = lons[j] + shift;
}
}
}
/**
* Calculates how many degres the given longitude needs to be moved east in order to be in -180 - +180. +180 is inclusive only
* if include180 is true.
*/
private static double calculateShift(double lon, boolean include180) {
double normalized = GeoUtils.centeredModulus(lon, 360);
double shift = Math.round(normalized - lon);
if (include180 == false && normalized == 180.0) {
shift = shift - 360;
}
return shift;
}
/**
* Checks it the segment from p1x to p2x intersects with anti-meridian
* p1x must be with in -180 +180 range
*/
private static double intersection(double p1x, double p2x) {
if (p1x == p2x) {
return Double.NaN;
}
final double t = ((p1x < p2x ? DATELINE : -DATELINE) - p1x) / (p2x - p1x);
if (t >= 1 || t <= 0) {
return Double.NaN;
} else {
return t;
}
}
}