org.opentripplanner.common.geometry

Class CompactLineString

java.lang.Object

org.opentripplanner.common.geometry.CompactLineString

All Implemented Interfaces:

Serializable

public final class CompactLineString
extends Object
implements Serializable

Compact line string. To optimize storage, we use the following tricks:

• Store only intermediate points (end-points are given by the external context, ie from/to vertices)
• For straight-line geometries (sometimes around half of the street geometries), re-use the same static object (since there is nothing to store)
• Store intermediate point in fixed floating points with fixed precision, using delta coding from the previous point, and variable length coding (most of the delta coordinates will thus fits in 1 or 2 bytes).

This trick alone saves around 20% of memory compared to the bulky JTS LineString, which is split on many objects (Coordinates, cached Envelope, Geometry itself). Performance hit should be low as we do not need the geometry during a path search.

Author:

laurent

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected static int[]	STRAIGHT_LINE Singleton representation of a straight-line (where nothing has to be stored), to be re-used.
protected static byte[]	STRAIGHT_LINE_PACKED

Constructor Summary

Constructors

Constructor and Description
CompactLineString()

Method Summary

Modifier and Type	Method and Description
static byte[]	compackLineString(double x0, double y0, double x1, double y1, com.vividsolutions.jts.geom.LineString lineString, boolean reverse) Same as the other version, but in a var-len int packed form (Dlugosz coding).
static int[]	compactLineString(double xa, double ya, double xb, double yb, com.vividsolutions.jts.geom.LineString lineString, boolean reverse) Public factory to create a compact line string.
static com.vividsolutions.jts.geom.LineString	uncompackLineString(double x0, double y0, double x1, double y1, byte[] packedCoords, boolean reverse) Same as the other version, but in a var-len int packed form (Dlugosz coding).
static com.vividsolutions.jts.geom.LineString	uncompactLineString(double xa, double ya, double xb, double yb, int[] coords, boolean reverse) Construct a LineString based on external end-points and compacted int version.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

STRAIGHT_LINE

protected static final int[] STRAIGHT_LINE

Singleton representation of a straight-line (where nothing has to be stored), to be re-used.

STRAIGHT_LINE_PACKED

protected static final byte[] STRAIGHT_LINE_PACKED

Constructor Detail

CompactLineString

public CompactLineString()

Method Detail

compactLineString

public static int[] compactLineString(double xa,
                                      double ya,
                                      double xb,
                                      double yb,
                                      com.vividsolutions.jts.geom.LineString lineString,
                                      boolean reverse)

Public factory to create a compact line string. Optimize for straight-line only line string (w/o intermediate end-points).

Parameters:

xa - X coordinate of end point A

ya - Y coordinate of end point A

xb - X coordinate of end point B

yb - Y coordinate of end point B

lineString - The geometry to compact. Please be aware that we ignore first and last coordinate in the line string, they need to be exactly the same as A and B.

reverse - True if A and B are inverted (B is start, A is end).

Returns:

compackLineString

public static byte[] compackLineString(double x0,
                                       double y0,
                                       double x1,
                                       double y1,
                                       com.vividsolutions.jts.geom.LineString lineString,
                                       boolean reverse)

Same as the other version, but in a var-len int packed form (Dlugosz coding).

Parameters:

x0 -

y0 -

x1 -

y1 -

lineString -

Returns:

uncompactLineString

public static com.vividsolutions.jts.geom.LineString uncompactLineString(double xa,
                                                                         double ya,
                                                                         double xb,
                                                                         double yb,
                                                                         int[] coords,
                                                                         boolean reverse)

Construct a LineString based on external end-points and compacted int version.

Parameters:

xa -

ya -

xb -

yb -

coords - Compact version of coordinates

reverse - True if A and B and the compacted geometry is reversed.

Returns:

uncompackLineString

public static com.vividsolutions.jts.geom.LineString uncompackLineString(double x0,
                                                                         double y0,
                                                                         double x1,
                                                                         double y1,
                                                                         byte[] packedCoords,
                                                                         boolean reverse)

Same as the other version, but in a var-len int packed form (Dlugosz coding).

Parameters:

x0 -

y0 -

x1 -

y1 -

coords -

Returns: