uk.ac.starlink.ttools.plot2.geom

Class SkySurface

java.lang.Object

uk.ac.starlink.ttools.plot2.geom.SkySurface

All Implemented Interfaces:

Surface

public class SkySurface
extends Object
implements Surface

Surface implementation for plotting on the celestial sphere. The data coordinates are direction cosines: 3-element arrays containing normalised X,Y,Z coordinates, where each coordinate is in the range -1..+1 and the sum of squares is 1.

Since:

20 Feb 2013

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
SkySurface(Rectangle plotBounds, Projection projection, double[] rotmat, double zoom, double xoff, double yoff, SkySys viewSystem, SkyAxisLabeller axLabeller, Color gridColor, Color axlabelColor, Color scalebarColor, boolean sexagesimal, double crowd, Captioner captioner, boolean antialias) Constructor.

Method Summary

Modifier and Type	Method and Description
GridLiner	createGridder(Rotation rotation, boolean sexagesimal, double loncrowd, double latcrowd) Attempts to construct a GridLiner object to draw grid lines on this plot.
LabelledLine	createLine(Point2D gp1, Point2D gp2) Returns a labelled line corresponding to the (shorter) great circle arc between two graphics points.
boolean	dataToGraphics(double[] dpos, boolean visibleOnly, Point2D.Double gpos) Converts a data space position to a graphics position.
boolean	dataToGraphicsOffset(double[] dpos0, Point2D.Double gpos0, double[] dpos1, boolean visibleOnly, Point2D.Double gpos1) Converts an offset data space position to a graphics position.
boolean	equals(Object o)
SkyAspect	flatPan(Point2D pos0, Point2D pos1) Pan gesture which just translates the entire graphics plane.
SkyAspect	flatZoom(Point2D pos, double factor) Zoom gesture which just magnifies the entire graphics plane.
String	formatPosition(double[] dpos) Formats the given data space position as a coordinate string.
static String	formatPositionDec(double lonRad, double latRad, double pixRad) Formats a lon/lat position as decimal given the approximate size of a screen pixel.
static String	formatPositionSex(double lonRad, double latRad, double pixRad) Formats a lon/lat position as sexagesimal given the approximate size of a screen pixel.
Captioner	getCaptioner() Returns a captioner suitable for drawing general purpose labels annotating the plot.
int	getDataDimCount() Returns 3.
double	getOffsetX() Returns the dimensionless X offset of the plot centre from the plot bounds centre.
double	getOffsetY() Returns the dimensionless Y offset of the plot centre from the plot bounds centre.
Rectangle	getPlotBounds() Returns the rectangle within which all of the plot data will appear.
Projection	getProjection() Returns the projection used by this sky surface.
double[]	getRotation() Returns the rotation matrix corresponding to this view of the sky.
Point	getSkyCenter() Returns the screen position corresponding to the center of the projection used by this surface.
Shape	getSkyShape() Returns a shape that gives the boundary of the sky projection in graphics coordinates.
Surround	getSurround(boolean withScroll) Returns the surround that this surface would like to reserve outside the plot bounds.
SkySys	getViewSystem() Returns the sky system into which coordinates are projected.
double	getZoom() Returns the zoom factor; 1 means the sky is approximately the same size as the plot bounds.
double[]	graphicsToData(Point2D gpos) Attempts to turn a graphics position into a sky position.
double[]	graphicsToData(Point2D gpos, java.util.function.Supplier<CoordSequence> dposSupplier) Attempts to turn a graphics position into a data position.
int	hashCode()
boolean	isContinuousLine(double[] dpos0, double[] dpos1) Indicates whether a line in graphics space between two given data space positions is continuous.
void	paintBackground(Graphics g) Paints the plot surface background.
void	paintForeground(Graphics g) Paints the plot surface foreground.
double	pixelAreaSteradians() Returns the approximate solid angle covered by a screen pixel in steradians.
double	pixelAreaSteradians(Point2D gpos) Returns the solid angle covered by a given graphics pixel in steradians.
SkyAspect	projPan(Point2D pos0, Point2D pos1) Pan gesture which attempts to rotate the sky while leaving the size and location of the graphics plane unchanged.
SkyAspect	projZoom(Point2D pos, double factor) Zoom gesture which attempts to zoom the sky, with the cursor staying at the same sky position, while leaving the size and location of the graphics plane unchanged.
SkyAspect	reframe(Point2D center, double factor) Returns a plot aspect giving the data region defined by a graphics position and zoom factor adjustment.
double	screenDistanceRadians(Point2D gp1, Point2D gp2) Returns the distance along a great circle in radians between two graphics positions.

Methods inherited from class java.lang.Object

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

Constructor Detail

SkySurface

public SkySurface(Rectangle plotBounds,
                  Projection projection,
                  double[] rotmat,
                  double zoom,
                  double xoff,
                  double yoff,
                  SkySys viewSystem,
                  SkyAxisLabeller axLabeller,
                  Color gridColor,
                  Color axlabelColor,
                  Color scalebarColor,
                  boolean sexagesimal,
                  double crowd,
                  Captioner captioner,
                  boolean antialias)

Constructor.

Parameters:

plotBounds - graphics region within which the plot must fall

projection - sky projection

rotmat - 9-element rotation matrix

zoom - zoom factor; 1 means the sky is approximately the same size as plot bounds

xoff - x offset of plot centre from plot bounds centre in dimensionless units; 0 is centred

yoff - y offset of plot centre from plot bounds centre in dimensionless units; 0 is centred

viewSystem - sky system into which coordinates are projected

axLabeller - sky axis labelling object

gridColor - colour for grid drawing, or null if no grid

axlabelColor - colour for axis labels, or null if no labels

scalebarColor - colour for scale bar, or null if not drawn

sexagesimal - whether to use sexagesimal coordinates

crowd - tick mark crowding factor, 1 is normal

captioner - text rendering object

antialias - whether to antialias grid lines

Method Detail

getDataDimCount

public int getDataDimCount()

Returns 3.

Specified by:

getDataDimCount in interface Surface

Returns:

number of elements in data space coordinate array

getPlotBounds

public Rectangle getPlotBounds()

Description copied from interface: Surface

Returns the rectangle within which all of the plot data will appear. This includes anything that might get drawn by a plot layer, but does not necessarily include axis labels etc.

Specified by:

getPlotBounds in interface Surface

Returns:

plot data area bounds

getSurround

public Surround getSurround(boolean withScroll)

Description copied from interface: Surface

Returns the surround that this surface would like to reserve outside the plot bounds. This is space outside the rectangle returned by Surface.getPlotBounds() to be used for axis labels etc.

If the withScroll parameter is set, then an attempt will be made to return a surround that will not alter if the current plot is scrolled around a moderate amount. For a one-time plot that's not important, but for an interactive plot it prevents the actual plot position jumping around to accommodate more or less space on the axes according to exactly where ticks happen to fall on the axes.

This method is supposed to return only the space that may actually be touched by the plot. The calling code may wish to apply additional padding on top of this for cosmetic reasons.

Specified by:

getSurround in interface Surface

Parameters:

withScroll - true to reserve space for nicer scrolling

Returns:

plot data area surround

paintBackground

public void paintBackground(Graphics g)

Description copied from interface: Surface

Paints the plot surface background. Anything that appears within the plot bounds underneath the data markings must go here.

Specified by:

paintBackground in interface Surface

Parameters:

g - graphics context

paintForeground

public void paintForeground(Graphics g)

Description copied from interface: Surface

Paints the plot surface foreground. Anything that appears on top of the data markings or outside the plot bounds must go here. This may include axes.

Specified by:

paintForeground in interface Surface

Parameters:

g - graphics context

getCaptioner

public Captioner getCaptioner()

Description copied from interface: Surface

Returns a captioner suitable for drawing general purpose labels annotating the plot.

Specified by:

getCaptioner in interface Surface

Returns:

captioner

getProjection

public Projection getProjection()

Returns the projection used by this sky surface.

Returns:

projection

getRotation

public double[] getRotation()

Returns the rotation matrix corresponding to this view of the sky.

Returns:

9-element rotation matrix

getZoom

public double getZoom()

Returns the zoom factor; 1 means the sky is approximately the same size as the plot bounds.

Returns:

zoom factor

getOffsetX

public double getOffsetX()

Returns the dimensionless X offset of the plot centre from the plot bounds centre.

Returns:

dimensionless X offset

getOffsetY

public double getOffsetY()

Returns the dimensionless Y offset of the plot centre from the plot bounds centre.

Returns:

dimensionless Y offset

getViewSystem

public SkySys getViewSystem()

Returns the sky system into which coordinates are projected.

Returns:

view sky system

createGridder

public GridLiner createGridder(Rotation rotation,
                               boolean sexagesimal,
                               double loncrowd,
                               double latcrowd)

Attempts to construct a GridLiner object to draw grid lines on this plot.

The work is done by classes from the SkyView package.

Parameters:

rotation - additional rotation to apply to sky system before grid lines are plotted; may be null for no additional rotation

sexagesimal - true for sexagesimal labels, false for decimal

loncrowd - longitude tick mark crowding factor, 1 is normal

latcrowd - latitude tick mark crowding factor, 1 is normal

Returns:

gridliner, or null on failure

dataToGraphics

public boolean dataToGraphics(double[] dpos,
                              boolean visibleOnly,
                              Point2D.Double gpos)

Description copied from interface: Surface

Converts a data space position to a graphics position. If visibleOnly is true, then if the return value is true, the exit value of gPos is guaranteed to be within the plot bounds of this surface.

If visibleOnly is false, there are no guarantees about the exit value of gPos, and its coordinates could be infinite or NaN. In this case you might want to perform additional checking, for instance with the utility methods PlotUtil.isPointFinite or isPointReal.

Specified by:

dataToGraphics in interface Surface

Parameters:

dpos - dataDimCount-element array containing data space coordinates

visibleOnly - if true, then the conversion will only succeed when the result falls within the plot bounds of this surface

gpos - point object into which the graphics position will be written on success

Returns:

true iff the conversion succeeds

dataToGraphicsOffset

public boolean dataToGraphicsOffset(double[] dpos0,
                                    Point2D.Double gpos0,
                                    double[] dpos1,
                                    boolean visibleOnly,
                                    Point2D.Double gpos1)

Description copied from interface: Surface

Converts an offset data space position to a graphics position. Context is given in the form of an existing converted nearby point (both data and graphics positions).

This (somewhat hacky) method is required for surfaces in which a data position may map to more than one position in graphics space, for instance sky surfaces with discontinuous longitude. The result does not need to be the same as the result of calling Surface.dataToGraphics(double[], boolean, java.awt.geom.Point2D.Double), and is not required to be a legal graphics position, but it must make visual sense, for instance when plotting error bars. The semantics of a "nearby point" is not very well defined. There are probably situations in which calling this will not give the result that's wanted, but they will probably be rare.

Specified by:

dataToGraphicsOffset in interface Surface

Parameters:

dpos0 - context position in data space

gpos0 - context position in graphics space (result of calling dataToGraphics on dpos0)

dpos1 - query position in data space

visibleOnly - if true, the call only succeeds if the result is within the plot bounds of this surface

gpos1 - point object to which the graphics position of dpos1 will be written on success

Returns:

true for success, false for no result

graphicsToData

public double[] graphicsToData(Point2D gpos,
                               java.util.function.Supplier<CoordSequence> dposSupplier)

Description copied from interface: Surface

Attempts to turn a graphics position into a data position. This is not always trivial, for instance in a 3D plot one graphics position maps to a line of data positions. The dposIt argument can optionally be supplied to cope with such instances. If a data pos cannot be determined, null is returned. If dposIt is absent, the method will run quickly. If it's present, it may or may not run slowly.

Specified by:

graphicsToData in interface Surface

Parameters:

gpos - graphics point

dposSupplier - iterable over dataDimCount-element arrays representing all the data space positions plotted, or null

Returns:

dataDimCount-element array giving data space position for gPos, or null if it cannot be determined

graphicsToData

public double[] graphicsToData(Point2D gpos)

Attempts to turn a graphics position into a sky position. This convenience function just calls graphicsToData(gpos,null), since the iterable argument is ignored for the SkySurface.

Parameters:

gpos - graphics position

Returns:

3-element unit vector representing data position, or null if gpos out of range

isContinuousLine

public boolean isContinuousLine(double[] dpos0,
                                double[] dpos1)

Description copied from interface: Surface

Indicates whether a line in graphics space between two given data space positions is continuous.

This is not very well-defined, but if drawing a line in graphics coordinates between the graphics coordinates corresponding to the two data coordinates is likely to do something badly wrong, this method should return false. It is intended to deal with the case where a short offset in data coordinates would lead to a line going the wrong way round the sky when it crosses the longitude=+/-PI boundary in an Aitoff projection.

Specified by:

isContinuousLine in interface Surface

Parameters:

dpos0 - first dataDimCount-element array containing data space coordinates

dpos1 - second dataDimCount-element array containing data space coordinates

Returns:

true if drawing a graphics line between the two positions should be OK

formatPosition

public String formatPosition(double[] dpos)

Description copied from interface: Surface

Formats the given data space position as a coordinate string. If possible the returned string should have the same length and formatting over the whole visible plot surface, so that the representation doesn't jump around when the cursor is moved.

Specified by:

formatPosition in interface Surface

Parameters:

dpos - dataDimCount-element array giving data space position

Returns:

human-readable string representing position

pixelAreaSteradians

public double pixelAreaSteradians()

Returns the approximate solid angle covered by a screen pixel in steradians. It tries to return a representative value for the visible area.

Returns:

approximate area of a screen pixel in steradians

pixelAreaSteradians

public double pixelAreaSteradians(Point2D gpos)

Returns the solid angle covered by a given graphics pixel in steradians.

Parameters:

gpos - position of graphics pixel center

Returns:

approximate area of pixel in steradians, or NaN if pixel is not (all) on the sky

screenDistanceRadians

public double screenDistanceRadians(Point2D gp1,
                                    Point2D gp2)

Returns the distance along a great circle in radians between two graphics positions. The evaluation should be well-conditioned for small or large angles. The given coordinates do not need to be within the graphics bounds, but if they are outside the celestial sphere, NaN will be returned.

Parameters:

gp1 - first position

gp2 - second position

Returns:

separation between positions in radians, or NaN if one of the positions is not on the sky

createLine

public LabelledLine createLine(Point2D gp1,
                               Point2D gp2)

Returns a labelled line corresponding to the (shorter) great circle arc between two graphics points.

Parameters:

gp1 - start point in graphics space

gp2 - end point in graphics space

Returns:

labelled line, or null if it can't be done, for instance if not both points are on the sky

formatPositionSex

public static String formatPositionSex(double lonRad,
                                       double latRad,
                                       double pixRad)

Formats a lon/lat position as sexagesimal given the approximate size of a screen pixel. The pixel size is used to determine how much precision to give.

Parameters:

lonRad - longitude in radians

latRad - latitude in radians

pixRad - approximate size of a screen pixel in radians

formatPositionDec

public static String formatPositionDec(double lonRad,
                                       double latRad,
                                       double pixRad)

Formats a lon/lat position as decimal given the approximate size of a screen pixel. The pixel size is used to determine how much precision to give.

Parameters:

lonRad - longitude in radians

latRad - latitude in radians

pixRad - approximate size of a screen pixel in radians

flatPan

public SkyAspect flatPan(Point2D pos0,
                         Point2D pos1)

Pan gesture which just translates the entire graphics plane.

Parameters:

pos0 - source graphics position

pos1 - destination graphics position

Returns:

panned sky aspect

flatZoom

public SkyAspect flatZoom(Point2D pos,
                          double factor)

Zoom gesture which just magnifies the entire graphics plane.

Parameters:

pos - reference graphics position

factor - zoom factor

Returns:

zoomed sky aspect

projPan

public SkyAspect projPan(Point2D pos0,
                         Point2D pos1)

Pan gesture which attempts to rotate the sky while leaving the size and location of the graphics plane unchanged. If that functionality is not supported by the projection, it will fall back to flat panning.

Parameters:

pos0 - source graphics position

pos1 - destination graphics position

Returns:

panned sky aspect

projZoom

public SkyAspect projZoom(Point2D pos,
                          double factor)

Zoom gesture which attempts to zoom the sky, with the cursor staying at the same sky position, while leaving the size and location of the graphics plane unchanged. If that functionality is not supported by the projection, it will fall back to flat zooming.

Parameters:

pos - reference graphics position

factor - zoom factor

Returns:

zoomed sky aspect

reframe

public SkyAspect reframe(Point2D center,
                         double factor)

Returns a plot aspect giving the data region defined by a graphics position and zoom factor adjustment.

Parameters:

center - position in current graphics coordinates of the sky position requested as the new center

factor - zoom factor (from current)

Returns:

reframed sky aspect

getSkyCenter

public Point getSkyCenter()

Returns the screen position corresponding to the center of the projection used by this surface. That position will typically, but not necessarily, be the least distorted point. The returned position is not necessarily within the currently visible plot bounds.

Returns:

central position in graphics coordinates

getSkyShape

public Shape getSkyShape()

Returns a shape that gives the boundary of the sky projection in graphics coordinates.

Returns:

sky boundary shape

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object