org.geotools.referencing.operation

Class DefaultMathTransformFactory

Object

AbstractFactory

ReferencingFactory

DefaultMathTransformFactory

All Implemented Interfaces:

Factory, RegistrableFactory, MathTransformFactory

public class DefaultMathTransformFactory
extends ReferencingFactory
implements MathTransformFactory

Low level factory for creating math transforms. Many high level GIS applications will never need to use this factory directly; they can use a coordinate operation factory instead. However, the MathTransformFactory interface can be used directly by applications that wish to transform other types of coordinates (e.g. color coordinates, or image pixel coordinates).

A math transform is an object that actually does the work of applying formulae to coordinate values. The math transform does not know or care how the coordinates relate to positions in the real world. This lack of semantics makes implementing MathTransformFactory significantly easier than it would be otherwise.

For example the affine transform applies a matrix to the coordinates without knowing how what it is doing relates to the real world. So if the matrix scales Z values by a factor of 1000, then it could be converting meters into millimeters, or it could be converting kilometers into meters.

Because math transforms have low semantic value (but high mathematical value), programmers who do not have much knowledge of how GIS applications use coordinate systems, or how those coordinate systems relate to the real world can implement MathTransformFactory. The low semantic content of math transforms also means that they will be useful in applications that have nothing to do with GIS coordinates. For example, a math transform could be used to map color coordinates between different color spaces, such as converting (red, green, blue) colors into (hue, light, saturation) colors.

Since a math transform does not know what its source and target coordinate systems mean, it is not necessary or desirable for a math transform object to keep information on its source and target coordinate systems.

Since:

2.1

Author:

Martin Desruisseaux (IRD)

Field Summary

Fields inherited from class ReferencingFactory

LOGGER

Fields inherited from class AbstractFactory

hints, MAXIMUM_PRIORITY, MINIMUM_PRIORITY, NORMAL_PRIORITY, priority

Constructor Summary

Constructors

Constructor and Description
DefaultMathTransformFactory() Constructs a default math transform factory.

Method Summary

Modifier and Type	Method and Description
static void	cleanupThreadLocals() Cleans up the thread local set in this thread.
MathTransform	createAffineTransform(Matrix matrix) Creates an affine transform from a matrix.
MathTransform	createBaseToDerived(CoordinateReferenceSystem baseCRS, MathTransform projection, CoordinateSystem derivedCS) Creates a transform from a base CRS to a derived CS.
MathTransform	createBaseToDerived(CoordinateReferenceSystem baseCRS, ParameterValueGroup parameters, CoordinateSystem derivedCS) Creates a parameterized transform from a base CRS to a derived CS.
MathTransform	createConcatenatedTransform(MathTransform transform1, MathTransform transform2) Creates a transform by concatenating two existing transforms.
MathTransform	createFromWKT(String text) Creates a math transform object from a Well Known Text (WKT).
MathTransform	createFromXML(String xml) Creates a math transform object from a XML string.
MathTransform	createParameterizedTransform(ParameterValueGroup parameters) Creates a transform from a group of parameters.
MathTransform	createPassThroughTransform(int firstAffectedOrdinate, MathTransform subTransform, int numTrailingOrdinates) Creates a transform which passes through a subset of ordinates to another transform.
Set<OperationMethod>	getAvailableMethods(Class<? extends Operation> type) Returns a set of available methods for math transforms.
ParameterValueGroup	getDefaultParameters(String method) Returns the default parameter values for a math transform using the given method.
OperationMethod	getLastMethodUsed() Returns the operation method used for the latest call to createParameterizedTransform in the currently running thread.
OperationMethod	getOperationMethod(String name) Returns the operation method for the specified name.
Citation	getVendor() Returns the vendor responsible for creating this factory implementation.
static void	main(String[] args) Dump to the standard output stream a list of available operation methods.
void	scanForPlugins() Scans for factory plug-ins on the application class path.

Methods inherited from class ReferencingFactory

ensureNonNull

Methods inherited from class AbstractFactory

addImplementationHints, equals, getImplementationHints, getPriority, hashCode, onDeregistration, onRegistration, toString

Methods inherited from class Object

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

Constructor Detail

DefaultMathTransformFactory

public DefaultMathTransformFactory()

Constructs a default math transform factory.

Method Detail

getVendor

public Citation getVendor()

Returns the vendor responsible for creating this factory implementation. Many implementations may be available for the same factory interface. The default implementation returns Geotools.

Overrides:

getVendor in class ReferencingFactory

Returns:

The vendor for this factory implementation.

getAvailableMethods

public Set<OperationMethod> getAvailableMethods(Class<? extends Operation> type)

Returns a set of available methods for math transforms. For each element in this set, the operation method name must be known to the getDefaultParameters(java.lang.String) method in this factory. The set of available methods is implementation dependent.

Specified by:

getAvailableMethods in interface MathTransformFactory

Parameters:

type - Operation.class for fetching all operation methods, or Projection.class for fetching only map projection methods.

Returns:

All math transform methods available in this factory.

See Also:

getDefaultParameters(java.lang.String), createParameterizedTransform(org.opengis.parameter.ParameterValueGroup)

getLastMethodUsed

public OperationMethod getLastMethodUsed()

Returns the operation method used for the latest call to createParameterizedTransform in the currently running thread. Returns null if not applicable.

Specified by:

getLastMethodUsed in interface MathTransformFactory

Returns:

The last method used, or null if unknown of unsupported.

Since:

2.5

See Also:

createParameterizedTransform(org.opengis.parameter.ParameterValueGroup)

getOperationMethod

public OperationMethod getOperationMethod(String name)
                                   throws NoSuchIdentifierException

Returns the operation method for the specified name.

Parameters:

name - The case insensitive identifier code of the operation method to search for (e.g. "Transverse_Mercator").

Returns:

The operation method.

Throws:

NoSuchIdentifierException - if there is no operation method registered for the specified name.

Since:

2.2

getDefaultParameters

public ParameterValueGroup getDefaultParameters(String method)
                                         throws NoSuchIdentifierException

Returns the default parameter values for a math transform using the given method. The method argument is the name of any operation method returned by the getAvailableMethods(java.lang.Class<? extends org.opengis.referencing.operation.Operation>) method. A typical example is "Transverse_Mercator" ).

This method creates new parameter instances at every call. It is intented to be modified by the user before to be passed to createParameterizedTransform(parameters).

Specified by:

getDefaultParameters in interface MathTransformFactory

Parameters:

method - The case insensitive name of the method to search for.

Returns:

The default parameter values.

Throws:

NoSuchIdentifierException - if there is no transform registered for the specified method.

See Also:

getAvailableMethods(java.lang.Class<? extends org.opengis.referencing.operation.Operation>), createParameterizedTransform(org.opengis.parameter.ParameterValueGroup), AbstractMathTransform.getParameterValues()

createBaseToDerived

public MathTransform createBaseToDerived(CoordinateReferenceSystem baseCRS,
                                         ParameterValueGroup parameters,
                                         CoordinateSystem derivedCS)
                                  throws NoSuchIdentifierException,
                                         FactoryException

Creates a parameterized transform from a base CRS to a derived CS. If the "semi_major" and "semi_minor" parameters are not explicitly specified, they will be inferred from the ellipsoid and added to parameters. In addition, this method performs axis switch as needed.

The operation method used can be obtained by a call to #getLastUsedMethod.

Specified by:

createBaseToDerived in interface MathTransformFactory

Parameters:

baseCRS - The source coordinate reference system.

parameters - The parameter values for the transform.

derivedCS - the target coordinate system.

Returns:

The parameterized transform.

Throws:

NoSuchIdentifierException - if there is no transform registered for the method.

FactoryException - if the object creation failed. This exception is thrown if some required parameter has not been supplied, or has illegal value.

createBaseToDerived

public MathTransform createBaseToDerived(CoordinateReferenceSystem baseCRS,
                                         MathTransform projection,
                                         CoordinateSystem derivedCS)
                                  throws FactoryException

Creates a transform from a base CRS to a derived CS. This method expects a "raw" transform without unit conversion or axis switch, typically a map projection working on (longitude, latitude) axes in degrees and (x, y) axes in metres. This method inspects the coordinate systems and prepend or append the unit conversions and axis switchs automatically.

Parameters:

baseCRS - The source coordinate reference system.

projection - The "raw" base to derived transform.

derivedCS - the target coordinate system.

Returns:

The parameterized transform.

Throws:

FactoryException - if the object creation failed. This exception is thrown if some required parameter has not been supplied, or has illegal value.

Since:

2.5

createParameterizedTransform

public MathTransform createParameterizedTransform(ParameterValueGroup parameters)
                                           throws NoSuchIdentifierException,
                                                  FactoryException

Creates a transform from a group of parameters. The method name is inferred from the parameter group name. Example:

 ParameterValueGroup p = factory.getDefaultParameters("Transverse_Mercator");
 p.parameter("semi_major").setValue(6378137.000);
 p.parameter("semi_minor").setValue(6356752.314);
 MathTransform mt = factory.createParameterizedTransform(p);
 

Specified by:

createParameterizedTransform in interface MathTransformFactory

Parameters:

parameters - The parameter values.

Returns:

The parameterized transform.

Throws:

NoSuchIdentifierException - if there is no transform registered for the method.

FactoryException - if the object creation failed. This exception is thrown if some required parameter has not been supplied, or has illegal value.

See Also:

getDefaultParameters(java.lang.String), getAvailableMethods(java.lang.Class<? extends org.opengis.referencing.operation.Operation>), #getLastUsedMethod

createAffineTransform

public MathTransform createAffineTransform(Matrix matrix)
                                    throws FactoryException

Creates an affine transform from a matrix. If the transform's input dimension is M, and output dimension is N, then the matrix will have size [N+1][M+1]. The +1 in the matrix dimensions allows the matrix to do a shift, as well as a rotation. The [M][j] element of the matrix will be the j'th ordinate of the moved origin. The [i][N] element of the matrix will be 0 for i less than M, and 1 for i equals M.

Specified by:

createAffineTransform in interface MathTransformFactory

Parameters:

matrix - The matrix used to define the affine transform.

Returns:

The affine transform.

Throws:

FactoryException - if the object creation failed.

createConcatenatedTransform

public MathTransform createConcatenatedTransform(MathTransform transform1,
                                                 MathTransform transform2)
                                          throws FactoryException

Creates a transform by concatenating two existing transforms. A concatenated transform acts in the same way as applying two transforms, one after the other.

The dimension of the output space of the first transform must match the dimension of the input space in the second transform. If you wish to concatenate more than two transforms, then you can repeatedly use this method.

Specified by:

createConcatenatedTransform in interface MathTransformFactory

Parameters:

transform1 - The first transform to apply to points.

transform2 - The second transform to apply to points.

Returns:

The concatenated transform.

Throws:

FactoryException - if the object creation failed.

createPassThroughTransform

public MathTransform createPassThroughTransform(int firstAffectedOrdinate,
                                                MathTransform subTransform,
                                                int numTrailingOrdinates)
                                         throws FactoryException

Creates a transform which passes through a subset of ordinates to another transform. This allows transforms to operate on a subset of ordinates. For example, if you have (Lat,Lon,Height) coordinates, then you may wish to convert the height values from meters to feet without affecting the (Lat,Lon) values.

Specified by:

createPassThroughTransform in interface MathTransformFactory

Parameters:

firstAffectedOrdinate - The lowest index of the affected ordinates.

subTransform - Transform to use for affected ordinates.

numTrailingOrdinates - Number of trailing ordinates to pass through. Affected ordinates will range from firstAffectedOrdinate inclusive to dimTarget-numTrailingOrdinates exclusive.

Returns:

A pass through transform with the following dimensions:

 Source: firstAffectedOrdinate + subTransform.getSourceDimensions() + numTrailingOrdinates
 Target: firstAffectedOrdinate + subTransform.getTargetDimensions() + numTrailingOrdinates
     

Throws:

FactoryException - if the object creation failed.

createFromXML

public MathTransform createFromXML(String xml)
                            throws FactoryException

Creates a math transform object from a XML string. The default implementation always throws an exception, since this method is not yet implemented.

Specified by:

createFromXML in interface MathTransformFactory

Parameters:

xml - Math transform encoded in XML format.

Returns:

The math transform (never null).

Throws:

FactoryException - if the object creation failed.

createFromWKT

public MathTransform createFromWKT(String text)
                            throws FactoryException

Creates a math transform object from a Well Known Text (WKT).

Specified by:

createFromWKT in interface MathTransformFactory

Parameters:

text - Math transform encoded in Well-Known Text format.

Returns:

The math transform (never null).

Throws:

FactoryException - if the Well-Known Text can't be parsed, or if the math transform creation failed from some other reason.

scanForPlugins

public void scanForPlugins()

Scans for factory plug-ins on the application class path. This method is needed because the application class path can theoretically change, or additional plug-ins may become available. Rather than re-scanning the classpath on every invocation of the API, the class path is scanned automatically only on the first invocation. Clients can call this method to prompt a re-scan. Thus this method need only be invoked by sophisticated applications which dynamically make new plug-ins available at runtime.

main

public static void main(String[] args)

Dump to the standard output stream a list of available operation methods. This method can be invoked from the command line. It provides a mean to verify which transforms were found in the classpath. The syntax is:

java org.geotools.referencing.operation.DefaultMathTransformFactory <options> <method>

where options are:

-projections	List only projections
-conversions	List only conversions
-all	List the parameters for all transforms
-encoding <code>	Set the character encoding
-locale <language>	Set the language for the output (e.g. "fr" for French)

and <method> is the optional name of an operation method (e.g. "Affine", "EPSG:9624" or just "9624" for the affine transform method).

Note for Windows users: If the output contains strange symbols, try to supply an "-encoding" argument. Example:

java org.geotools.referencing.operation.DefaultMathTransformFactory -encoding Cp850

The codepage number (850 in the previous example) can be obtained from the DOS commande line using the "chcp" command with no arguments.

Parameters:

args - Command line arguments.

cleanupThreadLocals

public static void cleanupThreadLocals()

Cleans up the thread local set in this thread. They can prevent web applications from proper shutdown