org.icepdf.core.pobjects.functions
Class Function

java.lang.Object
  org.icepdf.core.pobjects.functions.Function

Direct Known Subclasses:

Function_0, Function_2, Function_3, Function_4

public abstract class Function
extends java.lang.Object

The class Function is factory responsible for creating the correct function type for the given "FunctionType" dictionary entry.

Functions in PDF represent static, self-contained numerical transformations. In general, a function can take any number (m) of input values and produce any number (n) of output values:

f(x₀,..., x_m-1) = y₀, ... , y_n-1

In PDF functions, all the input values and all the output values are numbers. Each function definition includes a domain, the set of legal values for the input. Some functions also define a range, the set of legal values for the output. Input and output values are clipped to the respective domain and range.

This function factory currently support the following function types:

• type 0 - sampled function, uses a table of sample values to define the function. various techniques are used to interpolate values between the sampled values.
• type 2 - exponential interpolation, defines a set of coefficients for an exponential function.
• type 3 - stitching function, a combination of other functions, partitioned across a domain.
• type 4 - calculator function, uses operators from the PostScript language do describe an arithmetic expression.

Since:

1.0

Field Summary

protected float[]	domain An array of 2 x m numbers, where m is the number of input values.
protected int	functionType Function type associated with this function.
protected float[]	range An array of 2 x n numbers, where n is the number of output values.

Constructor Summary

protected

Function(Dictionary d) Creates a new instance of Function object.

Method Summary

abstract float[]	calculate(float[] m) Evaluates the input values specified by m.
float[]	getDomain()
static Function	getFunction(Library l, java.lang.Object o) Creates a new instance of a Function object.
int	getFunctionType() Gets the function type number.
float[]	getRange()
static float	interpolate(float x, float xmin, float xmax, float ymin, float ymax) Interpolation function.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

domain

protected float[] domain

An array of 2 x m numbers, where m is the number of input values. Input values outside the declared domain are clipped to the nearest boundary value.

range

protected float[] range

An array of 2 x n numbers, where n is the number of output values. Output values outside the declared range are clipped to the nearest boundary value. If this entry is absent, no clipping is done.

functionType

protected int functionType

Function type associated with this function.

Constructor Detail

Function

protected Function(Dictionary d)

Creates a new instance of Function object.

Parameters:

d - dictionary containing a vaild function dictionary.

Method Detail

getFunction

public static Function getFunction(Library l,
                                   java.lang.Object o)

Creates a new instance of a Function object. Possible function types are:

• 0 - sampled funciton.
• 2 - exponential interpolation funciton.

Parameters:

l - document library.

o - dictionary or Hashtable containing Function type entries.

Returns:

Function object for the specified function type, null if the function type is not available or not defined.

getFunctionType

public int getFunctionType()

Gets the function type number.

• type 0 - sampled function, uses a table of sample values to define the function. various techniques are used to interpolate values between the sampled values.
• type 2 - exponential interpolation, defines a set of coeffiecients for an exponential function.
• type 3 - stitching function, a combination of other functions, partitioned across a domain.
• type 4 - calculator function, uses operators from the PostScript language do describe an arithmetic expression.

interpolate

public static float interpolate(float x,
                                float xmin,
                                float xmax,
                                float ymin,
                                float ymax)

Interpolation function. For the given value of x, the interpolate calculates the y value on the line defined by the two points (x_min, y_min) and (x_max, y_max).

Parameters:

x - value we want to find a y value for.

xmin - point 1, x value.

xmax - point 2, x value.

ymin - point 1, y value.

ymax - oint 2, y value.

Returns:

y value for the given x value on the point define by (x_min, y_min) and (x_max, y_max).

calculate

public abstract float[] calculate(float[] m)

Evaluates the input values specified by m. In general, a function can take any number (m) of input values and produce any number (n) of output values:

f(x₀,..., x_m-1) = y₀, ... , y_n-1

Parameters:

m - input values to put through function.

Returns:

n output values.

getDomain

public float[] getDomain()

getRange

public float[] getRange()