Module org.apache.sis.referencing
Package org.apache.sis.referencing.operation.transform

Class TransformSeparator

Object
TransformSeparator
public class TransformSeparator extends Object
Extracts a sub-transform from a given Math­Transform and source or target dimension indices. Given an arbitrary Math­Transform, this class tries to return a new math transform that operates only on a given set of source or target dimensions.

Example

If the supplied transform has (x,y,z) inputs and (λ,φ,h) outputs, then the following code: 
TransformSeparator s = new TransformSeparator(theTransform);
s.addSourceDimensionRange(0, 2);
MathTransform mt = s.separate();
will return a transform with (x,y) inputs and (probably) (λ,φ) outputs. The output dimensions can be verified with a call to get­Target­Dimensions().
Since:
0.7

  • Field Details

    • transform

      protected final MathTransform transform
      The transform to separate.

    • sourceDimensions

      protected int[] sourceDimensions
      Indices of transform input dimensions to keep, or null if not yet defined. If non-null, the indices in the array must be sorted in strictly increasing order. This sequence can contain any integers in the range 0 inclusive to Math­Transform​.get­Source­Dimensions() exclusive.

      Values in this array should never be modified. For adding, removing or editing indices, new arrays should be created and assigned to this field. This approach makes easier to keep snapshots of indices arrays at various stages during the process of separating a Math­Transform.

      See Also:

    • targetDimensions

      protected int[] targetDimensions
      Indices of transform output dimensions to keep, or null if not yet defined. If non-null, the indices in the array must be sorted in strictly increasing order. This sequence can contain any integers in the range 0 inclusive to Math­Transform​.get­Target­Dimensions() exclusive.

      Values in this array should never be modified. For adding, removing or editing indices, new arrays should be created and assigned to this field. This approach makes easier to keep snapshots of indices arrays at various stages during the process of separating a Math­Transform.

      See Also:

  • Constructor Details

    • TransformSeparator

      public TransformSeparator(MathTransform transform)
      Constructs a separator for the given transform.
      Parameters:
      transform - the transform to separate.

    • TransformSeparator

      public TransformSeparator(MathTransform transform, MathTransformFactory factory)
      Constructs a separator for the given transform and using the given factory.
      Parameters:
      transform - the transform to separate.
      factory - the factory to use for creating new math transforms, or null if none.

  • Method Details

    • clear

      public void clear()
      Resets this transform separator in the same state than after construction. This method clears any source and target dimensions settings and disables source expansion. This method can be invoked when the same Math­Transform needs to be separated in more than one part, for example an horizontal and a vertical component.

    • addSourceDimensions

      public void addSourceDimensions(int... dimensions) throws IllegalArgumentException
      Adds input dimensions to keep in the separated transform. The given values are source dimension indices of the transform given to the constructor.

      Constraints:

      • All numbers shall be in the range 0 inclusive to Math­Transform​.get­Source­Dimensions() exclusive.
      • The dimensions values shall be in strictly increasing order.
      • The dimensions values shall be greater than all values specified by all previous calls of this method since construction or since the last call to clear().
      Parameters:
      dimensions - a sequence of source dimensions to keep, in strictly increasing order.
      Throws:
      Illegal­Argument­Exception - if dimensions contains negative values or if values are not in a strictly increasing order.

    • addSourceDimensionRange

      public void addSourceDimensionRange(int lower, int upper) throws IllegalArgumentException
      Adds a range of input dimensions to keep in the separated transform. The lower and upper values define a range of source dimension indices of the transform given to the constructor.
      Parameters:
      lower - the lower dimension, inclusive. Shall not be smaller than 0.
      upper - the upper dimension, exclusive. Shall be smaller than Math­Transform​.get­Source­Dimensions().
      Throws:
      Illegal­Argument­Exception - if lower or upper are out of bounds.

    • getSourceDimensions

      public int[] getSourceDimensions() throws IllegalStateException
      Returns the input dimensions to keep or kept in the separated transform. This method performs the first applicable action in the following list:
      1. Source dimensions have been explicitly set by at least one call to add­Source­Dimensions(int...) or add­Source­Dimension­Range(int, int) since construction or since last call to clear(). In such case, this method returns all specified source dimensions.
      2. No source dimensions were set but separate() has been invoked. In such case, this method returns the sequence of source dimensions that separate() chooses to retain. It may be all source dimensions of the transform given at construction time, but not necessarily.
      3. Otherwise an exception is thrown.
      If source dimensions have not been set explicitly, Transform­Separator tries to reduce the set of source dimensions to the smallest set required for computing the target dimensions.
      Returns:
      the input dimension as a sequence of strictly increasing values.
      Throws:
      Illegal­State­Exception - if input dimensions have not been set and separate() has not yet been invoked.

    • addTargetDimensions

      public void addTargetDimensions(int... dimensions) throws IllegalArgumentException
      Adds output dimensions to keep in the separated transform. The given values are target dimension indices of the transform given to the constructor.

      Constraints:

      • All numbers shall be in the range 0 inclusive to Math­Transform​.get­Target­Dimensions() exclusive.
      • The dimensions values shall be in strictly increasing order.
      • The dimensions values shall be greater than all values specified by all previous calls of this method since construction or since the last call to clear().
      Parameters:
      dimensions - a sequence of target dimensions to keep, in strictly increasing order.
      Throws:
      Illegal­Argument­Exception - if dimensions contains negative values or if values are not in a strictly increasing order.

    • addTargetDimensionRange

      public void addTargetDimensionRange(int lower, int upper) throws IllegalArgumentException
      Adds a range of output dimensions to keep in the separated transform. The lower and upper values define a range of target dimension indices of the transform given to the constructor.
      Parameters:
      lower - the lower dimension, inclusive. Shall not be smaller than 0.
      upper - the upper dimension, exclusive. Shall be smaller than Math­Transform​.get­Target­Dimensions().
      Throws:
      Illegal­Argument­Exception - if lower or upper are out of bounds.

    • getTargetDimensions

      public int[] getTargetDimensions() throws IllegalStateException
      Returns the output dimensions to keep or kept in the separated transform. This method performs the first applicable action in the following list:
      1. Target dimensions have been explicitly set by at least one call to add­Target­Dimensions(int...) or add­Target­Dimension­Range(int, int) since construction or since last call to clear(). In such case, this method returns all specified target dimensions.
      2. No target dimensions were set but separate() has been invoked. In such case, the target dimensions are inferred automatically from the source dimensions and the transform.
      3. Otherwise an exception is thrown.
      Returns:
      the output dimension as a sequence of strictly increasing values.
      Throws:
      Illegal­State­Exception - if output dimensions have not been set and separate() has not yet been invoked.

    • isSourceExpandable

      public boolean isSourceExpandable()
      Returns whether separate() is allowed to expand the list of source dimensions. The default value is false, which means that separate() either returns a Math­Transform having exactly the requested source dimensions, or throws a Factory­Exception.
      Returns:
      whether separate() is allowed to add new source dimensions instead of throwing a Factory­Exception.
      Since:
      1.1

    • setSourceExpandable

      public void setSourceExpandable(boolean enabled)
      Sets whether separate() is allowed to expand the list of source dimensions. The default value is false, which means that separate() will throw a Factory­Exception if some target dimensions cannot be computed without inputs that are not in the list of source dimensions. If this flag is set to true, then separate() will be allowed to augment the list of source dimensions with any inputs that are essential for producing all requested outputs.
      Parameters:
      enabled - whether to allow source dimensions expansion.
      Since:
      1.1

    • separate

      public MathTransform separate() throws FactoryException
      Separates the math transform specified at construction time for given dimension indices. This method creates a math transform that use only the specified source dimensions and return only the specified target dimensions. If the source or target dimensions were not specified, then they will be inferred as below:
      • If source dimensions were unspecified, then the returned transform will keep only the source dimensions needed for computing the specified target dimensions. If all source dimensions need to be kept, then they should be specified explicitly.
      • If target dimensions were unspecified, then the returned transform will expect only the specified source dimensions as inputs, and the target dimensions will be inferred automatically.
      • If neither source and target positions were specified, then the returned transform will have the same set of target dimensions, but only the set of source dimensions required for computing those targets. In other words, this method drops unused source dimensions.
      The source and target dimensions actually used can be queried by calls to get­Source­Dimensions() or get­Target­Dimensions() after this separate() method.
      Returns:
      the separated math transform.
      Throws:
      Factory­Exception - if the transform cannot be separated.

    • filterSourceDimensions

      protected MathTransform filterSourceDimensions(MathTransform step, int[] dimensions) throws FactoryException
      Creates a transform for the same mathematic than the given step but expecting only the given dimensions as inputs. This method is invoked by separate() when user-specified source dimensions need to be taken in account. The given step and dimensions are typically the values of transform and source­Dimensions fields respectively, but not necessarily. In particular those arguments will differ when this method is invoked recursively for processing concatenated or sub-transforms.

      Subclasses can override this method if they need to handle some Math­Transform implementations in a special way. However, all implementations of this method shall obey to the following contract:

      • source­Dimensions and target­Dimensions should not be assumed accurate since they may be temporarily outdated or modified during recursive calls to this method.
      • source­Dimensions should not be modified by this method.
      • target­Dimensions must be overwritten (not updated) by this method to the sequence of all target dimensions of step that are also target dimensions of the returned transform. The indices shall be in strictly increasing order from 0 inclusive to step​.get­Target­Dimensions() exclusive.
      Parameters:
      step - the transform for which to retain only a subset of the source dimensions.
      dimensions - indices of the source dimensions of step to retain.
      Returns:
      a transform expecting only the given source dimensions.
      Throws:
      Factory­Exception - if the given transform is not separable.

    • filterTargetDimensions

      protected MathTransform filterTargetDimensions(MathTransform step, int[] dimensions) throws FactoryException
      Creates a transform for the same mathematic than the given step but producing only the given dimensions as outputs. This method is invoked by separate() when user-specified target dimensions need to be taken in account. The given step and dimensions are typically the values of transform and target­Dimensions fields respectively, but not necessarily.

      Subclasses can override this method if they need to handle some Math­Transform implementations in a special way. However, all implementations of this method shall obey to the following contract:

      The number and nature of inputs stay unchanged. For example if the supplied transform has (longitude, latitude, height) outputs, then a filtered transform may keep only the (longitude, latitude) part for the same inputs. In most cases, the filtered transform is non-invertible since it looses information.
      Parameters:
      step - the transform for which to retain only a subset of the target dimensions.
      dimensions - indices of the target dimensions of step to retain.
      Returns:
      a transform producing only the given target dimensions.
      Throws:
      Factory­Exception - if the given transform is not separable.