InterpolateFunction (Geotools modules 20-SNAPSHOT API)

Object
- InterpolateFunction

All Implemented Interfaces:

Expression, Function
```
public class InterpolateFunction
extends Object
implements Function
```
This is an implemenation of the Interpolate function as defined by OGC Symbology Encoding (SE) 1.1 specification.
The first parameter should be either the name of a numeric feature property or, if this function is being used as a raster colormap, the String "RasterData" (case-insensitive).
Following this there should be a sequence of interpolation points, each of which is described by two parameters: the first a datum and the second a return value. In the SE speicification these parameters are expected to be Literals but in this implementation more general Expressions are also supported.
Two optional parameters can be provided following the interpolation points: A "method" parameter which can take the values "numeric" or "color" and a "mode" parameter which can take the values "linear", "cosine" or "cubic" (Note: it would make more sense if these terms were reversed but we are adhering to their use as published in the OGC specification).
Number of points and interpolation modes
- Linear and cosine interpolation each require at least two interpolation points to be supplied.
- Cubic interpolation normally requires at least four points with at least two points either side of the value being interpolated. In this function, deal generously with values that lie in the first or last interpolation segment by adding a duplicate of the first or last point as an extra point. This means that it is allowed (though not necessarily sensible) to use cubic interpolation with only three points.
- If only two points are supplied but cubic interpolation is specified, the function will fall back to linear interpolation.
- For all interpolation modes, incoming values outside the range of the interpolation points will be mapped to the value of the closest point (min or max).
- The function will accept a single interpolation point, but all incoming values will simply be mapped to the value of that point regardless of the type of interpolation requested.
- If no interpolation points are supplied, an Exception is thrown.
Author:

Michael Bedward, Johann Sorel (Geomatys)

Field Summary

Fields
Modifier and Type	Field and Description
`static String`	`METHOD_COLOR` Use as a literal value to indicate interpolation method
`static String`	`METHOD_NUMERIC` Use as a literal value to indicate interpolation method
`static String`	`MODE_COSINE` Use as a literal value to indicate interpolation mode
`static String`	`MODE_CUBIC` Use as a literal value to indicate interpolation mode
`static String`	`MODE_LINEAR` Use as a literal value to indicate interpolation mode
`static FunctionName`	`NAME` Make the instance of FunctionName available in a consistent spot.
`static String`	`RASTER_DATA` Use as a PropertyName when defining a color map.

Fields inherited from interface Expression
NIL

Constructor Summary

Constructors
Constructor and Description

InterpolateFunction()

InterpolateFunction(List<Expression> parameters, Literal fallback)

Constructors
Constructor and Description
`InterpolateFunction()`
`InterpolateFunction(List<Expression> parameters, Literal fallback)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Object`	`accept(ExpressionVisitor visitor, Object extraData)` Accepts a visitor.
`Object`	`evaluate(Object object)` Evaluates the given expression based on the content of the given object.
`<T> T`	`evaluate(Object object, Class<T> context)` Evaluates the given expressoin based on the content of the given object and the context type.
`Literal`	`getFallbackValue()` The value of the fallbackValue attribute is used as a default value, if the SE implementation does not support the function.
`FunctionName`	`getFunctionName()` Access to the FunctionName description as used in a FilterCapabilities document.
`String`	`getName()` Returns the name of the function to be called.
`List<Expression>`	`getParameters()` Returns the list subexpressions that will be evaluated to provide the parameters to the function.
`String`	`toString()` Creates a String representation of this Function with the function name and the arguments.

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - MODE_LINEAR
```
public static final String MODE_LINEAR
```
    Use as a literal value to indicate interpolation mode
    
    See Also:
    
    Constant Field Values
  - MODE_COSINE
```
public static final String MODE_COSINE
```
    Use as a literal value to indicate interpolation mode
    
    See Also:
    
    Constant Field Values
  - MODE_CUBIC
```
public static final String MODE_CUBIC
```
    Use as a literal value to indicate interpolation mode
    
    See Also:
    
    Constant Field Values
  - METHOD_NUMERIC
```
public static final String METHOD_NUMERIC
```
    Use as a literal value to indicate interpolation method
    
    See Also:
    
    Constant Field Values
  - METHOD_COLOR
```
public static final String METHOD_COLOR
```
    Use as a literal value to indicate interpolation method
    
    See Also:
    
    Constant Field Values
  - RASTER_DATA
```
public static final String RASTER_DATA
```
    Use as a PropertyName when defining a color map. The "Raterdata" is expected to apply to only a single band;
    
    See Also:
    
    Constant Field Values
  - NAME
```
public static final FunctionName NAME
```
    Make the instance of FunctionName available in a consistent spot.
- Constructor Detail
  - InterpolateFunction
```
public InterpolateFunction()
```
  - InterpolateFunction
```
public InterpolateFunction(List<Expression> parameters,
                           Literal fallback)
```
- Method Detail
  - getName
```
public String getName()
```
    Description copied from interface: Function
    
    Returns the name of the function to be called. For example, this might be "cos" or "atan2".
    You can use this name to look up the number of required parameters in a FilterCapabilities data structure. For the specific meaning of the required parameters you will need to consult the documentation.
    
    Specified by:
    
    getName in interface Function
  - getFunctionName
```
public FunctionName getFunctionName()
```
    Description copied from interface: Function
    
    Access to the FunctionName description as used in a FilterCapabilities document.
    
    Specified by:
    
    getFunctionName in interface Function
    
    Returns:
    
    FunctionName description, if available.
  - getParameters
```
public List<Expression> getParameters()
```
    Description copied from interface: Function
    
    Returns the list subexpressions that will be evaluated to provide the parameters to the function.
    
    Specified by:
    
    getParameters in interface Function
  - accept
```
public Object accept(ExpressionVisitor visitor,
                     Object extraData)
```
    Description copied from interface: Expression
    Accepts a visitor. Subclasses must implement with a method whose content is the following:
```
return visitor.visit(this, extraData);
```
    Specified by:
    
    accept in interface Expression
  - evaluate
```
public Object evaluate(Object object)
```
    Description copied from interface: Expression
    
    Evaluates the given expression based on the content of the given object.
    
    Specified by:
    
    evaluate in interface Expression
  - evaluate
```
public <T> T evaluate(Object object,
                      Class<T> context)
```
    Description copied from interface: Expression
    Evaluates the given expressoin based on the content of the given object and the context type.
    The context parameter is used to control the type of the result of the expression. A particular expression may not be able to evaluate to an instance of context. Therefore to be safe calling code should do a null check on the return value of this method, and call Expression.evaluate(Object) if neccessary. Example:
```
  Object input = ...;
  String result = expression.evaluate( input, String.class );
  if ( result == null ) {
     result = expression.evalute( input ).toString();
  }
  ...
 
```
    Implementations that can not return a result as an instance of context should return null.
    Specified by:
    
    evaluate in interface Expression
    
    Type Parameters:
    
    T - The type of the returned object.
    
    Parameters:
    
    object - The object to evaluate the expression against.
    
    context - The type of the resulting value of the expression.
    
    Returns:
    
    Evaluates the given expression based on the content of the given object an an instance of context.
  - getFallbackValue
```
public Literal getFallbackValue()
```
    Description copied from interface: Function
    
    The value of the fallbackValue attribute is used as a default value, if the SE implementation does not support the function. If the implementation supports the function, then the result value is determined by executing the function.
    
    Specified by:
    
    getFallbackValue in interface Function
    
    Returns:
    
    Optional literal to use if an implementation for this function is not available.
  - toString
```
public String toString()
```
    Creates a String representation of this Function with the function name and the arguments.
    
    Overrides:
    
    toString in class Object

Class InterpolateFunction

Field Summary

Fields inherited from interface Expression

Constructor Summary

Method Summary

Methods inherited from class Object

Field Detail

MODE_LINEAR

MODE_COSINE

MODE_CUBIC

METHOD_NUMERIC

METHOD_COLOR

RASTER_DATA

NAME

Constructor Detail

InterpolateFunction

InterpolateFunction

Method Detail

getName

getFunctionName

getParameters

accept

evaluate

evaluate

getFallbackValue

toString