LocationIndexedLine.java
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.linearref;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.LineString;
import org.locationtech.jts.geom.MultiLineString;
/**
* Supports linear referencing
* along a linear {@link Geometry}
* using {@link LinearLocation}s as the index.
*/
public class LocationIndexedLine
{
private Geometry linearGeom;
/**
* Constructs an object which allows linear referencing along
* a given linear {@link Geometry}.
*
* @param linearGeom the linear geometry to reference along
*/
public LocationIndexedLine(Geometry linearGeom)
{
this.linearGeom = linearGeom;
checkGeometryType();
}
private void checkGeometryType()
{
if (! (linearGeom instanceof LineString || linearGeom instanceof MultiLineString))
throw new IllegalArgumentException("Input geometry must be linear");
}
/**
* Computes the {@link Coordinate} for the point
* on the line at the given index.
* If the index is out of range the first or last point on the
* line will be returned.
* The Z-ordinate of the computed point will be interpolated from
* the Z-ordinates of the line segment containing it, if they exist.
*
* @param index the index of the desired point
* @return the Coordinate at the given index
*/
public Coordinate extractPoint(LinearLocation index)
{
return index.getCoordinate(linearGeom);
}
/**
* Computes the {@link Coordinate} for the point
* on the line at the given index, offset by the given distance.
* If the index is out of range the first or last point on the
* line will be returned.
* The computed point is offset to the left of the line if the offset distance is
* positive, to the right if negative.
*
* The Z-ordinate of the computed point will be interpolated from
* the Z-ordinates of the line segment containing it, if they exist.
*
* @param index the index of the desired point
* @param offsetDistance the distance the point is offset from the segment
* (positive is to the left, negative is to the right)
* @return the Coordinate at the given index
*/
public Coordinate extractPoint(LinearLocation index, double offsetDistance)
{
LinearLocation indexLow = index.toLowest(linearGeom);
return indexLow.getSegment(linearGeom).pointAlongOffset(indexLow.getSegmentFraction(), offsetDistance);
}
/**
* Computes the {@link LineString} for the interval
* on the line between the given indices.
* If the start location is after the end location,
* the computed linear geometry has reverse orientation to the input line.
*
* @param startIndex the index of the start of the interval
* @param endIndex the index of the end of the interval
* @return the linear geometry between the indices
*/
public Geometry extractLine(LinearLocation startIndex, LinearLocation endIndex)
{
return ExtractLineByLocation.extract(linearGeom, startIndex, endIndex);
}
/**
* Computes the index for a given point on the line.
* <p>
* The supplied point does not <i>necessarily</i> have to lie precisely
* on the line, but if it is far from the line the accuracy and
* performance of this function is not guaranteed.
* Use {@link #project} to compute a guaranteed result for points
* which may be far from the line.
*
* @param pt a point on the line
* @return the index of the point
* @see #project(Coordinate)
*/
public LinearLocation indexOf(Coordinate pt)
{
return LocationIndexOfPoint.indexOf(linearGeom, pt);
}
/**
* Finds the index for a point on the line
* which is greater than the given index.
* If no such index exists, returns <tt>minIndex</tt>.
* This method can be used to determine all indexes for
* a point which occurs more than once on a non-simple line.
* It can also be used to disambiguate cases where the given point lies
* slightly off the line and is equidistant from two different
* points on the line.
*
* The supplied point does not <i>necessarily</i> have to lie precisely
* on the line, but if it is far from the line the accuracy and
* performance of this function is not guaranteed.
* Use {@link #project} to compute a guaranteed result for points
* which may be far from the line.
*
* @param pt a point on the line
* @param minIndex the value the returned index must be greater than
* @return the index of the point greater than the given minimum index
*
* @see #project(Coordinate)
*/
public LinearLocation indexOfAfter(Coordinate pt, LinearLocation minIndex)
{
return LocationIndexOfPoint.indexOfAfter(linearGeom, pt, minIndex);
}
/**
* Computes the indices for a subline of the line.
* (The subline must <i>conform</i> to the line; that is,
* all vertices in the subline (except possibly the first and last)
* must be vertices of the line and occur in the same order).
*
* @param subLine a subLine of the line
* @return a pair of indices for the start and end of the subline.
*/
public LinearLocation[] indicesOf(Geometry subLine)
{
return LocationIndexOfLine.indicesOf(linearGeom, subLine);
}
/**
* Computes the index for the closest point on the line to the given point.
* If more than one point has the closest distance the first one along the line
* is returned.
* (The point does not necessarily have to lie precisely on the line.)
*
* @param pt a point on the line
* @return the index of the point
*/
public LinearLocation project(Coordinate pt)
{
return LocationIndexOfPoint.indexOf(linearGeom, pt);
}
/**
* Returns the index of the start of the line
* @return the location index
*/
public LinearLocation getStartIndex()
{
return new LinearLocation();
}
/**
* Returns the index of the end of the line
* @return the location index
*/
public LinearLocation getEndIndex()
{
return LinearLocation.getEndLocation(linearGeom);
}
/**
* Tests whether an index is in the valid index range for the line.
*
* @param index the index to test
* @return <code>true</code> if the index is in the valid range
*/
public boolean isValidIndex(LinearLocation index)
{
return index.isValid(linearGeom);
}
/**
* Computes a valid index for this line
* by clamping the given index to the valid range of index values
*
* @return a valid index value
*/
public LinearLocation clampIndex(LinearLocation index)
{
LinearLocation loc = index.copy();
loc.clamp(linearGeom);
return loc;
}
}