view
Class OrthographicMorpher

java.lang.Object
  view.OrthographicMorpher

All Implemented Interfaces:

Morphing

public class OrthographicMorpher
extends Object
implements Morphing

This morphing instance translates ra/dec to pixels under the rule of an orthogonal projection. It requires a center of projection in ra,dec and a field-of-view size, i.e. the size of the projected area in degrees. Setting a new component size can then be performed at will. The defining equations are:

   x = k_x cos(δ) sin(Δα),
   y = k_y [sin(δ)cos(δ_c)-cos(δ)sin(δ_c)cos(Δα)],
   sin(δ)=y/k_y cos(δ_c)+r sin(δ_c),
   tan(Δα)=x/[r cos(δ_c)-y sin(δ_c)]
   

where r is a radius,

   r^2 = (1-x^2/k_x^2-y^2/k_y^2)
   

The scaling factors k_x and k_y can be calculated using

   k_x = w/2 sin(δ_c)/[tan(a/2)*(1-sin^2(δ_c)cos^2(a/2))^0.5],
   k_y = h/2 1/sin(b/2)
   

with w and h being the width and height of the field-of-view in pixel.

Note that above formulars render the center of projection at (0,0). To allow direct conversion into component pixels, the pixels are translated for half the component's width and side, respectively.

Field Summary

private double	cosdc The cosine of the declination of the center of projection.
private double	dec The center of projection, declination in degrees.
private Dimension	fov The size of the field of view in pixel.
private boolean	hemisphere If true we only consider points on the front side.
private double	kx The scaling factor in x for fov-pixel size one.
private double	ky The scaling factor in y for fov-pixel size one.
private double	rac The center of projection, right ascension in degrees.
private double	sindc The sine of the declination of the center of projection.

Constructor Summary

OrthographicMorpher(double ra, double de, double width, double height)
The center of the projcetion and the extend of the field-of-view in x and y directions must be specified.

OrthographicMorpher(double ra, double de, double width, double height, boolean half)
The center of the projcetion and the extend of the field-of-view in x and y directions must be specified.

Method Summary

void	setFieldSize(Dimension size) Sets the current size of the field of view in pixels.
Point2D	toPrimary(Point2D radec) Converts a point from the secondary system to the primary.
Point2D	toSecondary(Point2D pixel) This conversation is non-unique, but we assume the solution closer to the center of projection to be the correct one.

Methods inherited from class java.lang.Object

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

Field Detail

rac

private double rac

The center of projection, right ascension in degrees.

dec

private double dec

The center of projection, declination in degrees.

sindc

private double sindc

The sine of the declination of the center of projection.

cosdc

private double cosdc

The cosine of the declination of the center of projection.

kx

private double kx

The scaling factor in x for fov-pixel size one.

ky

private double ky

The scaling factor in y for fov-pixel size one.

fov

private Dimension fov

The size of the field of view in pixel.

hemisphere

private boolean hemisphere

If true we only consider points on the front side.

Constructor Detail

OrthographicMorpher

public OrthographicMorpher(double ra,
                           double de,
                           double width,
                           double height)

The center of the projcetion and the extend of the field-of-view in x and y directions must be specified. All units are in degrees. Scaling factors are calculated, but only for a 1pxl x 1pxl field. All angles are in degrees. Only considers points on the positive hemisphere

OrthographicMorpher

public OrthographicMorpher(double ra,
                           double de,
                           double width,
                           double height,
                           boolean half)

The center of the projcetion and the extend of the field-of-view in x and y directions must be specified. All units are in degrees. Scaling factors are calculated, but only for a 1pxl x 1pxl field. All angles are in degrees.

Method Detail

setFieldSize

public void setFieldSize(Dimension size)

Sets the current size of the field of view in pixels.

toSecondary

public Point2D toSecondary(Point2D pixel)

This conversation is non-unique, but we assume the solution closer to the center of projection to be the correct one.

Specified by:

toSecondary in interface Morphing

Parameters:

pixel - The image coordinates.

Returns:

A Point in the secondary system, i.e. ra/dec

Throws:

UnsupportedOperationException

toPrimary

public Point2D toPrimary(Point2D radec)

Converts a point from the secondary system to the primary. Converts ra/dec into pixel. Note that under a orthographic projection, two positions on the sphere exist that convert to the same pixel. If hemisphere is true, then null is returned if the ra/dec point handed over is on the 'backside'.

Specified by:

toPrimary in interface Morphing

Parameters:

radec - A point in the secondary system.

Returns:

Pixel coordinates.

Throws:

UnsupportedOperationException