Package skyview.geometry
Class Projecter
java.lang.Object
skyview.geometry.Transformer
skyview.geometry.Projecter
 All Implemented Interfaces:
java.io.Serializable
,Component
 Direct Known Subclasses:
Ait
,Arc
,Cah
,Car
,Csc
,Hpx
,Mer
,Mol
,Sfl
,Sin
,Stg
,Tan
,Tea
,Toa
,Tot
,Zea
,Zpn
public abstract class Projecter extends Transformer
This class is the parent class for Transformers that project a point from the celestial sphere
to a projection plane.
Implementation within SkyView of a projection requires:
 Creation of the Xxx projection class where Xxx is the three letter
WCS name for the class (e.g., Tan, Sin, Mer, ...) The projecter class file normally includes
* The mathematical transformation between the sphere and plane.
* The associated deprojecter as an embedded class.
* Where feasible the methods that implement straddling lines in the projection
and shadow points. An associated straddler class may be defined.
* Information as to whether the projection may be extended in the X and Y directions.
 For fixed projections, an entry in the fixedPoints hash of the Projecter class.
 For projections that are intended to be available as output projections in the Web interface
* an entry in the basic query form to allow the selection of this projection for output
* an update of the JavaScript classes that enable users to see the coordinates
associated with an image point in the image output.
 See Also:
 Serialized Form

Constructor Summary
Constructors Constructor Description Projecter()

Method Summary
Modifier and Type Method Description boolean
allValid()
Are all points in the projection plane valid?protected int
getInputDimension()
What is the input dimensionality of a projecter?protected int
getOutputDimension()
What is the output dimensionality of a projecter?double
getXTiling()
Some projections can tile the projection plane with repeated copies.double
getYTiling()
The tiling period in Yabstract Deprojecter
inverse()
Get the inversedouble[]
shadowPoint(double x, double y)
Return a shadowpoint for the input location.boolean
straddle(double[][] pnts)
Does this pixel go wrap around the standard region of the image? E.g., does it straddle the 180 deg in a Car or Ait projection?boolean
straddleable()
Is it possible for a pixel to straddle the valid region.double[][][]
straddleComponents(double[][] pnts)
If this is a straddling pixel, then return the straddle componentsdouble[]
tissot(double x, double y)
Return the Tissot ellipse parameters for the projection.boolean
validPosition(double[] pos)
Is this a valid position in the projection plane for this image.Methods inherited from class skyview.geometry.Transformer
isInverse, transform, transform, transform

Constructor Details

Projecter
public Projecter()


Method Details

inverse
Get the inverse Specified by:
inverse
in classTransformer

getOutputDimension
protected int getOutputDimension()What is the output dimensionality of a projecter? Specified by:
getOutputDimension
in classTransformer

getInputDimension
protected int getInputDimension()What is the input dimensionality of a projecter? Specified by:
getInputDimension
in classTransformer

getXTiling
public double getXTiling()Some projections can tile the projection plane with repeated copies. This method gives the vectors along which the tiles repeat. Note that for azimuthal like (e.g., Mercator) projections, the tiling may be possible in the longitudinal direction, but not in the latitudinal direction. Some projections (e.g., CAR) can tile in both directions (but note that the periodicity for tiling is 360 degrees in both directions in the CAR projection since the latitudes will run ... 90 80 ...0 ... 80 90 80 ... 0 ... 80 90 80 .... Returns:
 The period in X in radians. A value of 0 means that there is not periodicity.

getYTiling
public double getYTiling()The tiling period in Y Returns:
 The tiling period in radians. A value of 0 means that there is no period.

validPosition
public boolean validPosition(double[] pos)Is this a valid position in the projection plane for this image. This default is appropriate for all projections where the projection plane is infinite. 
allValid
public boolean allValid()Are all points in the projection plane valid? 
straddleable
public boolean straddleable()Is it possible for a pixel to straddle the valid region. 
straddle
public boolean straddle(double[][] pnts)Does this pixel go wrap around the standard region of the image? E.g., does it straddle the 180 deg in a Car or Ait projection? 
straddleComponents
public double[][][] straddleComponents(double[][] pnts)If this is a straddling pixel, then return the straddle components 
shadowPoint
public double[] shadowPoint(double x, double y)Return a shadowpoint for the input location. Shadowpoints are not defined for all projections. 
tissot
public double[] tissot(double x, double y)Return the Tissot ellipse parameters for the projection. This gives the axes and position angle of an ellipse that reflects the distotortion at the given point. If there is no distortion or rotation, then the values (1,1,0) are returned. If the major axis is aligned with latitude, then the angle (the third parameter) will be 0, or pi/2 if greater aligned with longitude. If the projection is equalarea then the first two parameters are multiplicative inverses. This implementation is a place holder which should be overriden by specific projections. It returns a set of NaNs to indicate that the calculation has not been done. Parameters:
x
 The Xvalue at which the Tissot indicatrix is to be calculated.y
 The Yvalue at which the Tissot indicatrix is to be calculated. Returns:
 A three element double vector [Semimajor, semiminor, position angle] with the axes size and positional angle of the ellipse.
