org.geotools.referencing.operation.transform
Class AbstractMathTransform

Object
  Formattable
      AbstractMathTransform

All Implemented Interfaces:

MathTransform

Direct Known Subclasses:

AbstractMathTransform.Inverse, ConcatenatedTransform, ExponentialTransform1D, GeocentricTransform, IdentityTransform, LinearTransform1D, LogarithmicTransform1D, MapProjection, MolodenskiTransform, NADCONTransform, PassThroughTransform, ProjectiveTransform, VerticalTransform, WarpTransform2D

public abstract class AbstractMathTransform
extends Formattable
implements MathTransform

Provides a default implementation for most methods required by the MathTransform interface. AbstractMathTransform provides a convenient base class from which other transform classes can be easily derived. In addition, AbstractMathTransform implements methods required by the MathTransform2D interface, but does not implements MathTransform2D. Subclasses must declare implements MathTransform2D themself if they know to maps two-dimensional coordinate systems.

Since:

2.0

Author:

Martin Desruisseaux

Tutorial:

Coordinate Transformation Parameters

Module:

modules/library/referencing (gt2-referencing.jar) (Maven report) (SVN head)

Nested Class Summary

protected class

AbstractMathTransform.Inverse Default implementation for inverse math transform.

Constructor Summary

protected

AbstractMathTransform() Constructs a math transform.

Method Summary

Shape	createTransformedShape(Shape shape) Transform the specified shape.
Matrix	derivative(DirectPosition point) Gets the derivative of this transform at a point.
Matrix	derivative(Point2D point) Gets the derivative of this transform at a point.
protected static void	ensureNonNull(String name, Object object) Makes sure that an argument is non-null.
boolean	equals(Object object) Compares the specified object with this math transform for equality.
protected String	formatWKT(Formatter formatter) Format the inner part of a Well Known Text (WKT) element.
ParameterDescriptorGroup	getParameterDescriptors() Returns the parameter descriptors for this math transform, or null if unknow.
ParameterValueGroup	getParameterValues() Returns the parameter values for this math transform, or null if unknow.
abstract int	getSourceDimensions() Gets the dimension of input points.
abstract int	getTargetDimensions() Gets the dimension of output points.
int	hashCode() Returns a hash value for this transform.
MathTransform	inverse() Creates the inverse transform of this object.
boolean	isIdentity() Tests whether this transform does not move any points.
protected static boolean	needCopy(int srcOff, int dimSource, int dstOff, int dimTarget, int numPts) Checks if source coordinates need to be copied before to apply the transformation.
protected static double	rollLongitude(double x) Ensures that the specified longitude stay within ±π radians.
DirectPosition	transform(DirectPosition ptSrc, DirectPosition ptDst) Transforms the specified ptSrc and stores the result in ptDst.
void	transform(float[] srcPts, int srcOff, float[] dstPts, int dstOff, int numPts) Transforms a list of coordinate point ordinal values.
Point2D	transform(Point2D ptSrc, Point2D ptDst) Transforms the specified ptSrc and stores the result in ptDst.

Methods inherited from class Formattable

toString, toWKT, toWKT, toWKT

Methods inherited from class Object

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

Methods inherited from interface MathTransform

toWKT, transform

Constructor Detail

AbstractMathTransform

protected AbstractMathTransform()

Constructs a math transform.

Method Detail

getSourceDimensions

public abstract int getSourceDimensions()

Gets the dimension of input points.

Specified by:

getSourceDimensions in interface MathTransform

getTargetDimensions

public abstract int getTargetDimensions()

Gets the dimension of output points.

Specified by:

getTargetDimensions in interface MathTransform

getParameterDescriptors

public ParameterDescriptorGroup getParameterDescriptors()

Returns the parameter descriptors for this math transform, or null if unknow. This method is similar to OperationMethod.getParameters(), except that MathTransform returns parameters in standard units (usually meters or decimal degrees).

Returns:

The parameter descriptors for this math transform, or null.

See Also:

OperationMethod.getParameters()

getParameterValues

public ParameterValueGroup getParameterValues()

Returns the parameter values for this math transform, or null if unknow. This method is similar to Operation.getParameterValues(), except that MathTransform returns parameters in standard units (usually meters or decimal degrees). Since this method returns a copy of the parameter values, any change to a value will have no effect on this math transform.

Returns:

A copy of the parameter values for this math transform, or null.

See Also:

Operation.getParameterValues()

isIdentity

public boolean isIdentity()

Tests whether this transform does not move any points. The default implementation always returns false.

Specified by:

isIdentity in interface MathTransform

transform

public Point2D transform(Point2D ptSrc,
                         Point2D ptDst)
                  throws TransformException

Transforms the specified ptSrc and stores the result in ptDst. The default implementation invokes MathTransform.transform(double[],int,double[],int,int) using a temporary array of doubles.

Parameters:

ptSrc - the specified coordinate point to be transformed.

ptDst - the specified coordinate point that stores the result of transforming ptSrc, or null.

Returns:

the coordinate point after transforming ptSrc and storing the result in ptDst.

Throws:

MismatchedDimensionException - if this transform doesn't map two-dimensional coordinate systems.

TransformException - if the point can't be transformed.

See Also:

MathTransform2D.transform(Point2D,Point2D)

transform

public DirectPosition transform(DirectPosition ptSrc,
                                DirectPosition ptDst)
                         throws TransformException

Transforms the specified ptSrc and stores the result in ptDst. The default implementation invokes MathTransform.transform(double[],int,double[],int,int).

Specified by:

transform in interface MathTransform

Throws:

TransformException

transform

public void transform(float[] srcPts,
                      int srcOff,
                      float[] dstPts,
                      int dstOff,
                      int numPts)
               throws TransformException

Transforms a list of coordinate point ordinal values. The default implementation invokes MathTransform.transform(double[],int,double[],int,int) using a temporary array of doubles.

Specified by:

transform in interface MathTransform

Throws:

TransformException

createTransformedShape

public Shape createTransformedShape(Shape shape)
                             throws TransformException

Transform the specified shape. The default implementation computes quadratic curves using three points for each shape segments.

Parameters:

shape - Shape to transform.

Returns:

Transformed shape, or shape if this transform is the identity transform.

Throws:

IllegalStateException - if this transform doesn't map 2D coordinate systems.

TransformException - if a transform failed.

See Also:

MathTransform2D.createTransformedShape(Shape)

derivative

public Matrix derivative(Point2D point)
                  throws TransformException

Gets the derivative of this transform at a point. The default implementation always throw an exception. Subclasses that implement the MathTransform2D interface should override this method. Other subclasses should override derivative(DirectPosition) instead.

Parameters:

point - The coordinate point where to evaluate the derivative.

Returns:

The derivative at the specified point as a 2×2 matrix.

Throws:

MismatchedDimensionException - if the input dimension is not 2.

TransformException - if the derivative can't be evaluated at the specified point.

See Also:

MathTransform2D.derivative(Point2D)

derivative

public Matrix derivative(DirectPosition point)
                  throws TransformException

Gets the derivative of this transform at a point. The default implementation ensure that point has a valid dimension. Next, it try to delegate the work to an other method:

• If the input dimension is 2, then this method delegates the work to derivative(Point2D).
• If this object is an instance of MathTransform1D, then this method delegates the work to derivative(double).

Otherwise, a TransformException is thrown.

Specified by:

derivative in interface MathTransform

Parameters:

point - The coordinate point where to evaluate the derivative.

Returns:

The derivative at the specified point (never null).

Throws:

NullPointerException - if the derivative dependents on coordinate and point is null.

MismatchedDimensionException - if point doesn't have the expected dimension.

TransformException - if the derivative can't be evaluated at the specified point.

inverse

public MathTransform inverse()
                      throws NoninvertibleTransformException

Creates the inverse transform of this object. The default implementation returns this if this transform is an identity transform, and throws a NoninvertibleTransformException otherwise. Subclasses should override this method.

Specified by:

inverse in interface MathTransform

Throws:

NoninvertibleTransformException

hashCode

public int hashCode()

Returns a hash value for this transform.

Overrides:

hashCode in class Object

equals

public boolean equals(Object object)

Compares the specified object with this math transform for equality. The default implementation checks if object is an instance of the same class than this and use the same parameter descriptor. Subclasses should override this method in order to compare internal fields.

Overrides:

equals in class Object

formatWKT

protected String formatWKT(Formatter formatter)

Format the inner part of a Well Known Text (WKT) element. The default implementation formats all parameter values returned by getParameterValues(). The parameter group name is used as the math transform name.

Overrides:

formatWKT in class Formattable

Parameters:

formatter - The formatter to use.

Returns:

The WKT element name, which is "PARAM_MT" in the default implementation.

See Also:

Formattable.toWKT(), Formattable.toString()

ensureNonNull

protected static void ensureNonNull(String name,
                                    Object object)
                             throws IllegalArgumentException

Makes sure that an argument is non-null. This is a convenience method for subclass constructors.

Parameters:

name - Argument name.

object - User argument.

Throws:

InvalidParameterValueException - if object is null.

IllegalArgumentException

needCopy

protected static boolean needCopy(int srcOff,
                                  int dimSource,
                                  int dstOff,
                                  int dimTarget,
                                  int numPts)

Checks if source coordinates need to be copied before to apply the transformation. This convenience method is provided for transform(...) method implementation. This method make the following assumptions:

• Coordinates will be iterated from lower index to upper index.
• Coordinates are read and writen in shrunk. For example (longitude,latitude,height) values for one coordinate are read together, and the transformed (x,y,z) values are written together only after.

However, this method does not assumes that source and target dimension are the same (in the special case where source and target dimension are always the same, a simplier and more efficient check is possible). The following example prepares a transformation from 2 dimensional points to three dimensional points:

 public void transform(double[] srcPts, int srcOff,
                       double[] dstPts, int dstOff, int numPts)
 {
     if (srcPts==dstPts && needCopy(srcOff, 2, dstOff, 3, numPts) {
         final double[] old = srcPts;
         srcPts = new double[numPts*2];
         System.arraycopy(old, srcOff, srcPts, 0, srcPts.length);
         srcOff = 0;
     }
 }

rollLongitude

protected static double rollLongitude(double x)

Ensures that the specified longitude stay within ±π radians. This method is typically invoked after geographic coordinates are transformed. This method may add or substract some amount of 2π radians to x.

Parameters:

x - The longitude in radians.

Returns:

The longitude in the range ±π radians.