org.osmdroid.util

Class PointReducer

java.lang.Object

org.osmdroid.util.PointReducer

public class PointReducer
extends Object

Reduces the number of points in a shape using the Douglas-Peucker algorithm.
From: http://www.phpriot.com/articles/reducing-map-path-douglas-peucker-algorithm/4
Ported from PHP to Java. "marked" array added to optimize.

Since:

6.0.0

Constructor Summary

Constructors

Constructor and Description
PointReducer()

Method Summary

Modifier and Type	Method and Description
static double	orthogonalDistance(GeoPoint point, GeoPoint lineStart, GeoPoint lineEnd) Calculate the orthogonal distance from the line joining the lineStart and lineEnd points to point
static ArrayList<GeoPoint>	reduceWithTolerance(ArrayList<GeoPoint> shape, double tolerance) Reduce the number of points in a shape using the Douglas-Peucker algorithm Suggested usage

Methods inherited from class java.lang.Object

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

Constructor Detail

PointReducer

public PointReducer()

Method Detail

reduceWithTolerance

public static ArrayList<GeoPoint> reduceWithTolerance(ArrayList<GeoPoint> shape,
                                                      double tolerance)

Reduce the number of points in a shape using the Douglas-Peucker algorithm Suggested usage

 

 //get the screen bounds
 BoundingBox boundingBox = map.getBoundingBox();
 final double latSpanDegrees = boundingBox.getLatitudeSpan();
 //get the degree difference, divide by dpi
 double tolerance = latSpanDegrees /densityDpi;
 //each latitude degree on screen is represented by this many dip
 points = PointReducer.reduceWithTolerance(points, tolerance);

 

 

Parameters:

tolerance - The tolerance to decide whether or not to keep a point, in the coordinate system of the points (micro-degrees here)

shape - The shape to reduce

Returns:

the reduced shape

orthogonalDistance

public static double orthogonalDistance(GeoPoint point,
                                        GeoPoint lineStart,
                                        GeoPoint lineEnd)

Calculate the orthogonal distance from the line joining the lineStart and lineEnd points to point

Parameters:

point - The point the distance is being calculated for

lineStart - The point that starts the line

lineEnd - The point that ends the line

Returns:

The distance in points coordinate system