libgeos++-dev 3.6.2-1build2 / usr / include / geos / linearref / LengthIndexedLine.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2011 Sandro Santilli <strk@keybit.net>
 * Copyright (C) 2005-2006 Refractions Research Inc.
 * Copyright (C) 2001-2002 Vivid Solutions Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 **********************************************************************
 *
 * Last port: linearref/LengthIndexedLine.java r463
 *
 **********************************************************************/

#ifndef GEOS_LINEARREF_LENGTHINDEXEDLINE_H
#define GEOS_LINEARREF_LENGTHINDEXEDLINE_H

#include <geos/export.h>
#include <geos/geom/Coordinate.h>
#include <geos/geom/Geometry.h>
#include <geos/linearref/LinearLocation.h>

namespace geos
{
namespace linearref   // geos::linearref
{

/** \brief
 * Supports linear referencing along a linear {@link Geometry}
 * using the length along the line as the index.
 * Negative length values are taken as measured in the reverse direction
 * from the end of the geometry.
 * Out-of-range index values are handled by clamping
 * them to the valid range of values.
 * Non-simple lines (i.e. which loop back to cross or touch
 * themselves) are supported.
 */

class GEOS_DLL LengthIndexedLine
{
private:
	const geom::Geometry *linearGeom;
	LinearLocation locationOf(double index) const;
	LinearLocation locationOf(double index, bool resolveLower) const;
	double positiveIndex(double index) const;

public:

	/** \brief
	 * Constructs an object which allows a linear {@link Geometry}
	 * to be linearly referenced using length as an index.
	 *
	 * @param linearGeom the linear geometry to reference along
	 */

	LengthIndexedLine(const geom::Geometry *linearGeom);

	/** \brief
	 * 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
	 */
	geom::Coordinate extractPoint(double index) const;


	/**
	 * \brief
	 * 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
	 */
	geom::Coordinate extractPoint(double index, double offsetDistance) const;

	/**
	 * Computes the {@link LineString} for the interval
	 * on the line between the given indices.
	 * If the endIndex lies before the startIndex,
	 * the computed geometry is reversed.
	 *
	 * @param startIndex the index of the start of the interval
	 * @param endIndex the index of the end of the interval
	 * @return the linear interval between the indices
	 */
	geom::Geometry *extractLine(double startIndex, double endIndex) const;


	/**
	 * Computes the minimum index for a point on the line.
	 * If the line is not simple (i.e. loops back on itself)
	 * a single point may have more than one possible index.
	 * In this case, the smallest index is returned.
	 *
	 * 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 minimum index of the point
	 *
	 * @see project
	 */
	double indexOf(const geom::Coordinate& pt) const;

	/**
	 * 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
	 */
	double indexOfAfter(const geom::Coordinate& pt, double minIndex) const;

	/**
	 * Computes the indices for a subline of the line.
	 * (The subline must <b>conform</b> to the line; that is,
	 * all vertices in the subline (except possibly the first and last)
	 * must be vertices of the line and occcur in the same order).
	 *
	 * @param subLine a subLine of the line
	 * @return a pair of indices for the start and end of the subline.
	 */
	double* indicesOf(const geom::Geometry *subLine) const;


	/**
	 * 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
	 */
	double project(const geom::Coordinate& pt) const;

	/**
	 * Returns the index of the start of the line
	 * @return the start index
	 */
	double getStartIndex() const;

	/**
	 * Returns the index of the end of the line
	 * @return the end index
	 */
	double getEndIndex() const;

	/**
	 * Tests whether an index is in the valid index range for the line.
	 *
	 * @param length the index to test
	 * @return <code>true</code> if the index is in the valid range
	 */
	bool isValidIndex(double index) const;


	/**
	 * Computes a valid index for this line
	 * by clamping the given index to the valid range of index values
	 *
	 * @return a valid index value
	 */
	double clampIndex(double index) const;
};
}
}
#endif