cds.healpix.fillingcurve

Interface FillingCurve2D

public interface FillingCurve2D

Interface defining a two-dimensional space-filling curve. It provides method to transform a pair of 2d-coordinates in a single index in the curve. The index value is here called hash value since the intput parameters are discritized coordinates, and information is lost during the discretization.

Author:

F.-X. Pineau

Method Summary

Modifier and Type	Method and Description
long	hash2i0(long hash) Special case of hash2ij(long) in which the discretized coordinate along the vertical axis equals zero.
long	hash2ij(long hash) Transforms the given space filling curve index (or hash value) into a single value from which it is straightforward to extract the associated 2d-coordinates using methods ij2i(long) and ij2j(long).
long	i02hash(int i) Special case of ij2hash(int, int) in which the discretized coordinate along the vertical axis equals zero.
long	ij2hash(int i, int j) Transforms coordinates in a discretized 2d-plane into a space filling curve index.
int	ij2i(long ij) Extract the discretized horizontal coordinates from the result of the method hash2ij(long).
int	ij2j(long ij) Extract the discretized vertical coordinates from the result of the method hash2ij(long).
long	xy2hash(double x, double y) The default implementation (not implemented to stay compatible with Java Version < 8) should be: return ij2hash((int) x, (int) y).

Method Detail

xy2hash

long xy2hash(double x,
             double y)

The default implementation (not implemented to stay compatible with Java Version < 8) should be: return ij2hash((int) x, (int) y).

Parameters:

x - coordinate along the horizontal axis

y - coordinate along the vertical axis

Returns:

the space filling curve index (or hash value) associated to the given 2d-coordinates.

ij2hash

long ij2hash(int i,
             int j)

Transforms coordinates in a discretized 2d-plane into a space filling curve index. This can be thought of as computing a hash value from 2d-coordinates.

Parameters:

i - discretized coordinate along the horizontal axis

j - discretized coordinate along the vertical axis

Returns:

the space filling curve index (or hash value) associated to the given discretized 2d-coordinates.

i02hash

long i02hash(int i)

Special case of ij2hash(int, int) in which the discretized coordinate along the vertical axis equals zero.

Parameters:

i - discretized coordinate along the horizontal axis

Returns:

the space filling curve index (or hash value) associated to the given discretized horizontal coordinate, assuming the discretized vertical coordinate equal zero.

hash2ij

long hash2ij(long hash)

Transforms the given space filling curve index (or hash value) into a single value from which it is straightforward to extract the associated 2d-coordinates using methods ij2i(long) and ij2j(long).

Parameters:

hash - the space filling curve index (or hash value)

Returns:

a single value from which it is straightforward to extract the associated 2d-coordinates using methods ij2i(long) and ij2j(long).

hash2i0

long hash2i0(long hash)

Special case of hash2ij(long) in which the discretized coordinate along the vertical axis equals zero.

Parameters:

hash - the space filling curve index (or hash value)

Returns:

a single value, knowing the vertical coordinate equals zero, from which it is straightforward to extract the associated horizontal coordinate using method ij2i(long).

ij2i

int ij2i(long ij)

Extract the discretized horizontal coordinates from the result of the method hash2ij(long).

Parameters:

ij - result of the method hash2ij(long)

Returns:

the discretized horizontal coordinate stored in the given parameter ij

ij2j

int ij2j(long ij)

Extract the discretized vertical coordinates from the result of the method hash2ij(long).

Parameters:

ij - result of the method hash2ij(long)

Returns:

the discretized horizontal coordinate stored in the given parameter ij