org.locationtech.jts:jts-core 1.17.0
org.locationtech.jts.shape.fractal

## Class MortonCode

• public class MortonCode
extends Object
Encodes points as the index along the planar Morton (Z-order) curve.

The planar Morton (Z-order) curve is a continuous space-filling curve. The Morton curve defines an ordering of the points in the positive quadrant of the plane. The index of a point along the Morton curve is called the Morton code.

A sequence of subsets of the Morton curve can be defined by a level number. Each level subset occupies a square range. The curve at level n Mn contains 2n + 1 points. It fills the range square of side 2level. Curve points have ordinates in the range [0, 2level - 1]. The code for a given point is identical at all levels. The level simply determines the number of points in the curve subset and the size of the range square.

This implementation represents codes using 32-bit integers. This allows levels 0 to 16 to be handled. The class supports encoding points and decoding the point for a given code value.

The Morton order has the property that it tends to preserve locality. This means that codes which are near in value will have spatially proximate points. The converse is not always true - the delta between codes for nearby points is not always small. But the average delta is small enough that the Morton order is an effective way of linearizing space to support range queries.

Author:
Martin Davis
MortonCurveBuilder, HilbertCode
• ### Field Summary

Fields
Modifier and Type Field and Description
static int MAX_LEVEL
The maximum curve level that can be represented.
• ### Constructor Summary

Constructors
Constructor and Description
MortonCode()
• ### Method Summary

All Methods
Modifier and Type Method and Description
static Coordinate decode(int index)
Computes the point on the Morton curve for a given index.
static int encode(int x, int y)
Computes the index of the point (x,y) in the Morton curve ordering.
static int level(int numPoints)
The level of the finite Morton curve which contains at least the given number of points.
static int maxOrdinate(int level)
The maximum ordinate value for points in the curve for the given level.
static int size(int level)
The number of points in the curve for the given level.
• ### Field Detail

• #### MAX_LEVEL

public static final int MAX_LEVEL
The maximum curve level that can be represented.
Constant Field Values
• ### Constructor Detail

• #### MortonCode

public MortonCode()
• ### Method Detail

• #### size

public static int size(int level)
The number of points in the curve for the given level. The number of points is 22 * level.
Parameters:
level - the level of the curve
Returns:
the number of points
• #### maxOrdinate

public static int maxOrdinate(int level)
The maximum ordinate value for points in the curve for the given level. The maximum ordinate is 2level - 1.
Parameters:
level - the level of the curve
Returns:
the maximum ordinate value
• #### level

public static int level(int numPoints)
The level of the finite Morton curve which contains at least the given number of points.
Parameters:
numPoints - the number of points required
Returns:
the level of the curve
• #### encode

public static int encode(int x,
int y)
Computes the index of the point (x,y) in the Morton curve ordering.
Parameters:
x - the x ordinate of the point
y - the y ordinate of the point
Returns:
the index of the point along the Morton curve
• #### decode

public static Coordinate decode(int index)
Computes the point on the Morton curve for a given index.
Parameters:
index - the index of the point on the curve
Returns:
the point on the curve