org.opengis.ct
Interface CT_MathTransform

All Superinterfaces:

java.rmi.Remote

All Known Implementing Classes:

MathTransformExport

public interface CT_MathTransform

extends java.rmi.Remote

Transforms multi-dimensional coordinate points. If a client application wishes to query the source and target coordinate systems of a transformation, then it should keep hold of the CT_CoordinateTransformation interface, and use the contained math transform object whenever it wishes to perform a transform.

Since:

1.00

Version:

1.01

Author:

Martin Daly

Method Summary

PT_Matrix	derivative(PT_CoordinatePoint cp) Gets the derivative of this transform at a point.
double[]	getCodomainConvexHull(double[] ord) Gets transformed convex hull.
int	getDimSource() Gets the dimension of input points.
int	getDimTarget() Gets the dimension of output points.
CT_DomainFlags	getDomainFlags(double[] ord) Gets flags classifying domain points within a convex hull.
java.lang.String	getWKT() Gets a Well-Known text representation of this object.
java.lang.String	getXML() Gets an XML representation of this object.
CT_MathTransform	inverse() Creates the inverse transform of this object.
boolean	isIdentity() Tests whether this transform does not move any points.
PT_CoordinatePoint	transform(PT_CoordinatePoint cp) Transforms a coordinate point.
double[]	transformList(double[] ord) Transforms a list of coordinate point ordinal values.

Method Detail

getDomainFlags

public CT_DomainFlags getDomainFlags(double[] ord)
                              throws java.rmi.RemoteException

Gets flags classifying domain points within a convex hull. The supplied ordinates are interpreted as a sequence of points, which generates a convex hull in the source space. Conceptually, each of the (usually infinite) points inside the convex hull is then tested against the source domain. The flags of all these tests are then combined. In practice, implementations of different transforms will use different short-cuts to avoid doing an infinite number of tests.

Parameters:

ord - Packed ordinates of points used to generate convex hull.

Returns:

flags classifying domain points within the convex hull.

Throws:

java.rmi.RemoteException - if a remote method call failed.

getCodomainConvexHull

public double[] getCodomainConvexHull(double[] ord)
                               throws java.rmi.RemoteException

Gets transformed convex hull. The supplied ordinates are interpreted as a sequence of points, which generates a convex hull in the source space. The returned sequence of ordinates represents a convex hull in the output space. The number of output points will often be different from the number of input points. Each of the input points should be inside the valid domain (this can be checked by testing the points' domain flags individually). However, the convex hull of the input points may go outside the valid domain. The returned convex hull should contain the transformed image of the intersection of the source convex hull and the source domain.

A convex hull is a shape in a coordinate system, where if two positions A and B are inside the shape, then all positions in the straight line between A and B are also inside the shape. So in 3D a cube and a sphere are both convex hulls. Other less obvious examples of convex hulls are straight lines, and single points. (A single point is a convex hull, because the positions A and B must both be the same - i.e. the point itself. So the straight line between A and B has zero length.) Some examples of shapes that are NOT convex hulls are donuts, and horseshoes.

Parameters:

ord - Packed ordinates of points used to generate convex hull.

Returns:

The transformed convex hull.

Throws:

java.rmi.RemoteException - if a remote method call failed.

getWKT

public java.lang.String getWKT()
                        throws java.rmi.RemoteException

Gets a Well-Known text representation of this object.

Throws:

java.rmi.RemoteException - if a remote method call failed.

getXML

public java.lang.String getXML()
                        throws java.rmi.RemoteException

Gets an XML representation of this object.

Throws:

java.rmi.RemoteException - if a remote method call failed.

transform

public PT_CoordinatePoint transform(PT_CoordinatePoint cp)
                             throws java.rmi.RemoteException

Transforms a coordinate point. The passed parameter point should not be modified.

Parameters:

cp - Point to transform.

Returns:

The transformed point.

Throws:

java.rmi.RemoteException - if a remote method call failed.

transformList

public double[] transformList(double[] ord)
                       throws java.rmi.RemoteException

Transforms a list of coordinate point ordinal values. This method is provided for efficiently transforming many points. The supplied array of ordinal values will contain packed ordinal values. For example, if the source dimension is 3, then the ordinals will be packed in this order: (x₀,y₀,z₀, x₁,y₁,z₁ ...). The size of the passed array must be an integer multiple of DimSource. The returned ordinal values are packed in a similar way. In some DCPs. the ordinals may be transformed in-place, and the returned array may be the same as the passed array. So any client code should not attempt to reuse the passed ordinal values (although they can certainly reuse the passed array). If there is any problem then the server implementation will throw an exception. If this happens then the client should not make any assumptions about the state of the ordinal values.

Parameters:

ord - Packed ordinates of points to transform.

Returns:

The packed transformed points. May be ord.

Throws:

java.rmi.RemoteException - if a remote method call failed.

derivative

public PT_Matrix derivative(PT_CoordinatePoint cp)
                     throws java.rmi.RemoteException

Gets the derivative of this transform at a point. If the transform does not have a well-defined derivative at the point, then this function should fail in the usual way for the DCP. The derivative is the matrix of the non-translating portion of the approximate affine map at the point. The matrix will have dimensions corresponding to the source and target coordinate systems. If the input dimension is M, and the output dimension is N, then the matrix will have size [M][N]. The elements of the matrix {elt[n][m] : n=0..(N-1)} form a vector in the output space which is parallel to the displacement caused by a small change in the m'th ordinate in the input space.

Parameters:

cp - Point in domain at which to get derivative.

Returns:

The derivative of this transform at the suplied point.

Throws:

java.rmi.RemoteException - if a remote method call failed.

inverse

public CT_MathTransform inverse()
                         throws java.rmi.RemoteException

Creates the inverse transform of this object. This method may fail if the transform is not one to one. However, all cartographic projections should succeed.

Returns:

The inverse transform.

Throws:

java.rmi.RemoteException - if a remote method call failed.

getDimSource

public int getDimSource()
                 throws java.rmi.RemoteException

Gets the dimension of input points.

Throws:

java.rmi.RemoteException - if a remote method call failed.

getDimTarget

public int getDimTarget()
                 throws java.rmi.RemoteException

Gets the dimension of output points.

Throws:

java.rmi.RemoteException - if a remote method call failed.

isIdentity

public boolean isIdentity()
                   throws java.rmi.RemoteException

Tests whether this transform does not move any points.

Returns:

true if this MathTransform is an identity transform; false otherwise.

Throws:

java.rmi.RemoteException - if a remote method call failed.