# Class TransferFunction

Object
TransferFunction

All Implemented Interfaces:
  `Serializable`, `Cloneable`

public class TransferFunction extends Object implements Cloneable, Serializable
The function converting raster sample values to geophysics values. The function is usually linear, but can sometimes be logarithmic or exponential. The latter occur most often when measuring concentration of something.

Supported transfer function types
Type | Equation
--- | ---
`LINEAR` | y = scale⋅x + offset
`LOGARITHMIC` | y = scale⋅logbase(x) + offset
`EXPONENTIAL` | y = scale⋅basex + offset

## Missing values

This `TransferFunction` class handles only the continuous part of transfer functions. This class does not handle missing values other than `NaN`. For a more complete class with support for non-NaN missing values, see `org​.apache​.sis​.coverage​.SampleDimension`.

## Serialization

Serialized instances of this class are not guaranteed to be compatible with future SIS versions. Serialization should be used only for short term storage or RMI between applications running the same SIS version.

Since:
  0.5
See Also:
  - `SampleDimension​.getTransferFunction()`
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `TransferFunction()`
  Creates a transfer function initialized to the identity transform.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `TransferFunction`
  `clone()`
  Returns a clone of this transfer function.
  `MathTransform`
  `createTransform(MathTransformFactory factory)`
  Creates a transform from sample values to geophysics values using the given factory.
  `double`
  `getBase()`
  Returns the logarithm or exponent base in the transfer function.
  `double`
  `getOffset()`
  Returns the offset of the transfer function.
  `double`
  `getScale()`
  Returns the scale factor of the transfer function.
  `MathTransform1D`
  `getTransform()`
  Returns the transform from sample values to geophysics values, as specified by the current properties of this `TransferFunction`.
  `TransferFunctionType`
  `getType()`
  Returns the transfer function type (linear, logarithmic or exponential).
  `boolean`
  `isIdentity()`
  Returns `true` if this transfer function is identity.
  `void`
  `setBase(double base)`
  Sets the logarithm or exponent base in the transfer function.
  `void`
  `setOffset(double offset)`
  Sets the offset of the transfer function.
  `void`
  `setScale(double scale)`
  Sets the scale factor of the transfer function.
  `void`
  `setTransform(MathTransform1D function)`
  Sets the transform from sample values to geophysics values.
  `void`
  `setType(TransferFunctionType type)`
  Sets the transfer function type.
  `String`
  `toString()`
  Returns a string representation of this transfer function for debugging purpose.

  ### Methods inherited from class Object

  `equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### TransferFunction

    public TransferFunction()
    Creates a transfer function initialized to the identity transform.
    See Also:
      - `isIdentity()`

- ## Method Details

  - ### isIdentity

    public boolean isIdentity()
    Returns `true` if this transfer function is identity. The function is identity if its type is linear, its scale is 1 and its offset is 0.
    Returns:
      whether this transfer function is identity.
    Since:
      1.0

  - ### getType

    public TransferFunctionType getType()
    Returns the transfer function type (linear, logarithmic or exponential).
    Returns:
      the transfer function type.

  - ### setType

    public void setType(TransferFunctionType type)
    Sets the transfer function type. The default value is `TransferFunctionType​.LINEAR`.
    Parameters:
      `type` - the transfer function type.

  - ### getBase

    public double getBase()
    Returns the logarithm or exponent base in the transfer function. This value is always 1 for `TransferFunctionType​.LINEAR`, and usually (but not necessarily) 10 for the logarithmic and exponential types.
    Returns:
      the logarithmic or exponent base.

  - ### setBase

    public void setBase(double base)
    Sets the logarithm or exponent base in the transfer function. This value is ignored for `TransferFunctionType​.LINEAR`. For other supported types, the default value is 10.
    Parameters:
      `base` - the new logarithm or exponent base.
    Throws:
      `IllegalArgumentException` - if the given base is NaN, negative, zero or infinite.

  - ### getScale

    public double getScale()
    Returns the scale factor of the transfer function.
    Returns:
      the scale factor.

  - ### setScale

    public void setScale(double scale)
    Sets the scale factor of the transfer function. The default value is 1.
    Parameters:
      `scale` - the new scale factor.
    Throws:
      `IllegalArgumentException` - if the given scale is NaN, zero or infinite.

  - ### getOffset

    public double getOffset()
    Returns the offset of the transfer function.
    Returns:
      the offset.

  - ### setOffset

    public void setOffset(double offset)
    Sets the offset of the transfer function. The default value is 0.
    Parameters:
      `offset` - the new offset.
    Throws:
      `IllegalArgumentException` - if the given scale is NaN or infinite.

  - ### createTransform

    public MathTransform createTransform(MathTransformFactory factory) throws FactoryException
    Creates a transform from sample values to geophysics values using the given factory. This method constructs a transform mathematically equivalent to the one returned by `getTransform()`, but allows to specify another factory than the default one.
    Parameters:
      `factory` - the factory to use for creating a transform.
    Returns:
      the transform from sample to geophysics values.
    Throws:
      `FactoryException` - if the given factory failed to create a transform.
    Since:
      1.0

  - ### getTransform

    public MathTransform1D getTransform()
    Returns the transform from sample values to geophysics values, as specified by the current properties of this `TransferFunction`.
    Returns:
      the transform from sample to geophysics values.

  - ### setTransform

    public void setTransform(MathTransform1D function) throws IllegalArgumentException
    Sets the transform from sample values to geophysics values. This method infers the base, scale and offset values from the given transform.
    Parameters:
      `function` - the transform to set.
    Throws:
      `IllegalArgumentException` - if this method does not recognize the given transform.

  - ### clone

    public TransferFunction clone()
    Returns a clone of this transfer function.
    Overrides:
      `clone` in class `Object`
    Returns:
      a clone of this transfer function.
    Since:
      0.8

  - ### toString

    public String toString()
    Returns a string representation of this transfer function for debugging purpose. The string returned by this method may change in any future SIS version.
    Overrides:
      `toString` in class `Object`
    Returns:
      a string representation of this transfer function.