com.sun.pdfview.function
Class PDFFunction

java.lang.Object
  com.sun.pdfview.function.PDFFunction

Direct Known Subclasses:

FunctionType0, FunctionType2, FunctionType3, FunctionType4

public abstract class PDFFunction
extends java.lang.Object

PDF Functions are defined in the reference as Section 3.9.

A PDF function maps some set of m inputs into some set of n outputs. There are 4 types of functions:

• Type 0: Sampled functions. (PDF 1.2)
  A sampled function (type 0) uses a table of sample values to define the function. Various techniques are used to interpolate values between the sample values (see Section 3.9.1, "Type 0 (Sampled) Functions").
• Type 2: Exponential Interpolation. (PDF 1.3)
  An exponential interpolation function (type 2) defines a set of coefficients for an exponential function (see Section 3.9.2, "Type 2 (Exponential Interpolation) Functions").
• Type 3: Stitching functions. (PDF 1.3)
  A stitching function (type 3) is a combination of other functions, partitioned across a domain (see Section 3.9.3, "Type 3 (Stitching) Functions").
• Type 4: Postscript calculations. (PDF 1.3)
  A PostScript calculator function (type 4) uses operators from the PostScript language to describe an arithmetic expression (see Section 3.9.4, "Type 4 (PostScript Calculator) Functions").

The function interface contains a single method, calculate which takes an array of m floats an interprets them into an array of n floats.

PDFFunctions do not have accessible constructors. Instead, use the static getFunction() method to read a functions from a PDF Object.

Field Summary

static int	TYPE_0 Sampled function
static int	TYPE_2 Exponential interpolation function
static int	TYPE_3 Stitching function.
static int	TYPE_4 PostScript calculator function.

Constructor Summary

protected

PDFFunction(int type) Creates a new instance of PDFFunction

Method Summary

float[]	calculate(float[] inputs) Map from m input values to n output values.
float[]	calculate(float[] inputs, int inputOffset, float[] outputs, int outputOffset) Map from m input values to n output values.
protected abstract void	doFunction(float[] inputs, int inputOffset, float[] outputs, int outputOffset) Subclasses must implement this method to perform the actual function on the given set of data.
protected float	getDomain(int i) Get a component of the domain of this function
static PDFFunction	getFunction(PDFObject obj) Get a PDFFunction from a PDFObject
int	getNumInputs() Get the number of inputs, m, required by this function
int	getNumOutputs() Get the number of outputs, n, returned by this function
protected float	getRange(int i) Get a component of the range of this function
int	getType() Get the type of this function
protected abstract void	parse(PDFObject obj) Read the function information from a PDF Object
protected void	setDomain(float[] domain) Set the domain of this function
protected void	setRange(float[] range) Set the range of this function

Methods inherited from class java.lang.Object

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

Field Detail

TYPE_0

public static final int TYPE_0

Sampled function

See Also:

Constant Field Values

TYPE_2

public static final int TYPE_2

Exponential interpolation function

See Also:

Constant Field Values

TYPE_3

public static final int TYPE_3

Stitching function.

See Also:

Constant Field Values

TYPE_4

public static final int TYPE_4

PostScript calculator function.

See Also:

Constant Field Values

Constructor Detail

PDFFunction

protected PDFFunction(int type)

Creates a new instance of PDFFunction

Method Detail

getFunction

public static PDFFunction getFunction(PDFObject obj)
                               throws java.io.IOException

Get a PDFFunction from a PDFObject

Throws:

java.io.IOException

getType

public int getType()

Get the type of this function

Returns:

one of the types of function (0-4)

getNumInputs

public int getNumInputs()

Get the number of inputs, m, required by this function

Returns:

the number of input values expected by this function

getNumOutputs

public int getNumOutputs()

Get the number of outputs, n, returned by this function

Returns:

the number of output values this function will return

getDomain

protected float getDomain(int i)

Get a component of the domain of this function

Parameters:

i - the index into the domain array, which has size 2 * m. the ith entry in the array has index 2i, 2i + 1

Returns:

the ith entry in the domain array

setDomain

protected void setDomain(float[] domain)

Set the domain of this function

getRange

protected float getRange(int i)

Get a component of the range of this function

Parameters:

i - the index into the range array, which has size 2 * n. the ith entry in the array has index 2i, 2i + 1

Returns:

the ith entry in the range array

setRange

protected void setRange(float[] range)

Set the range of this function

calculate

public float[] calculate(float[] inputs)

Map from m input values to n output values. The number of inputs m must be exactly one half the size of the domain. The number of outputs should match one half the size of the range.

Parameters:

inputs - an array of >= m input values

Returns:

the array of n output values

calculate

public float[] calculate(float[] inputs,
                         int inputOffset,
                         float[] outputs,
                         int outputOffset)

Map from m input values to n output values. The number of inputs m must be exactly one half the size of the domain. The number of outputs should match one half the size of the range.

Parameters:

inputs - an array of >= m input values

inputOffset - the offset into the input array to read from

outputs - an array of size >= n which will be filled with the output values

outputOffset - the offset into the output array to write to

Returns:

the array of n output values

doFunction

protected abstract void doFunction(float[] inputs,
                                   int inputOffset,
                                   float[] outputs,
                                   int outputOffset)

Subclasses must implement this method to perform the actual function on the given set of data. Note that the inputs are guaranteed to be clipped to the domain, while the outputs will be automatically clipped to the range after being returned from this function.

Parameters:

inputs - guaranteed to be at least as big as getNumInputs() and all values within range

inputOffset - the offset into the inputs array to read from

outputs - guaranteed to be at least as big as getNumOutputs(), but not yet clipped to domain

outputOffset - the offset into the output array to write to

parse

protected abstract void parse(PDFObject obj)
                       throws java.io.IOException

Read the function information from a PDF Object

Throws:

java.io.IOException