org.apache.pdfbox.pdmodel.graphics.predictor

Class PredictorAlgorithm

java.lang.Object

org.apache.pdfbox.pdmodel.graphics.predictor.PredictorAlgorithm

Direct Known Subclasses:

Average, None, Optimum, Paeth, Sub, Up

public abstract class PredictorAlgorithm
extends Object

Implements different PNG predictor algorithms that is used in PDF files.

Version:

$Revision: 1.4 $

Author:

xylifyx@yahoo.co.uk

See Also:

PNG Filters

Constructor Summary

Constructors

Constructor and Description
PredictorAlgorithm()

Method Summary

Methods

Modifier and Type	Method and Description
int	aboveLeftPixel(byte[] buf, int offset, int dy, int x) Get the above-left pixel from the buffer.
int	abovePixel(byte[] buf, int offset, int dy, int x) Get the above pixel from the buffer.
void	checkBufsiz(byte[] src, byte[] dest) check that buffer sizes matches width,height,bpp.
void	decode(byte[] src, byte[] dest) decode a byte array full of image data using the filter that this object implements.
abstract void	decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset, int destDy, int destOffset) decode line of pixel data in src from src_offset and width*bpp bytes forward, put the decoded bytes into dest.
void	encode(byte[] src, byte[] dest) encode a byte array full of image data using the filter that this object implements.
abstract void	encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset, int destDy, int destOffset) encode line of pixel data in src from srcOffset and width*bpp bytes forward, put the decoded bytes into dest.
int	getBpp()
static PredictorAlgorithm	getFilter(int predictor)
int	getHeight()
int	getWidth()
int	leftPixel(byte[] buf, int offset, int dy, int x) Get the left pixel from the buffer.
static void	main(String[] args) Simple command line program to test the algorithm.
void	setBpp(int newBpp)
void	setHeight(int newHeight)
void	setWidth(int newWidth)

Methods inherited from class java.lang.Object

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

Constructor Detail

PredictorAlgorithm

public PredictorAlgorithm()

Method Detail

checkBufsiz

public void checkBufsiz(byte[] src,
               byte[] dest)

check that buffer sizes matches width,height,bpp. This implementation is used by most of the filters, but not Uptimum.

Parameters:

src - The source buffer.

dest - The destination buffer.

encodeLine

public abstract void encodeLine(byte[] src,
              byte[] dest,
              int srcDy,
              int srcOffset,
              int destDy,
              int destOffset)

encode line of pixel data in src from srcOffset and width*bpp bytes forward, put the decoded bytes into dest.

Parameters:

src - raw image data

dest - encoded data

srcDy - byte offset between lines

srcOffset - beginning of line data

destDy - byte offset between lines

destOffset - beginning of line data

decodeLine

public abstract void decodeLine(byte[] src,
              byte[] dest,
              int srcDy,
              int srcOffset,
              int destDy,
              int destOffset)

decode line of pixel data in src from src_offset and width*bpp bytes forward, put the decoded bytes into dest.

Parameters:

src - encoded image data

dest - raw data

srcDy - byte offset between lines

srcOffset - beginning of line data

destDy - byte offset between lines

destOffset - beginning of line data

main

public static void main(String[] args)

Simple command line program to test the algorithm.

Parameters:

args - The command line arguments.

leftPixel

public int leftPixel(byte[] buf,
            int offset,
            int dy,
            int x)

Get the left pixel from the buffer.

Parameters:

buf - The buffer.

offset - The offset into the buffer.

dy - The dy value.

x - The x value.

Returns:

The left pixel.

abovePixel

public int abovePixel(byte[] buf,
             int offset,
             int dy,
             int x)

Get the above pixel from the buffer.

Parameters:

buf - The buffer.

offset - The offset into the buffer.

dy - The dy value.

x - The x value.

Returns:

The above pixel.

aboveLeftPixel

public int aboveLeftPixel(byte[] buf,
                 int offset,
                 int dy,
                 int x)

Get the above-left pixel from the buffer.

Parameters:

buf - The buffer.

offset - The offset into the buffer.

dy - The dy value.

x - The x value.

Returns:

The above-left pixel.

getBpp

public int getBpp()

Returns:

Returns the bpp.

setBpp

public void setBpp(int newBpp)

Parameters:

newBpp - The bpp to set.

getHeight

public int getHeight()

Returns:

Returns the height.

setHeight

public void setHeight(int newHeight)

Parameters:

newHeight - The height to set.

getWidth

public int getWidth()

Returns:

Returns the width.

setWidth

public void setWidth(int newWidth)

Parameters:

newWidth - The width to set.

encode

public void encode(byte[] src,
          byte[] dest)

encode a byte array full of image data using the filter that this object implements.

Parameters:

src - buffer

dest - buffer

decode

public void decode(byte[] src,
          byte[] dest)

decode a byte array full of image data using the filter that this object implements.

Parameters:

src - buffer

dest - buffer

getFilter

public static PredictorAlgorithm getFilter(int predictor)

Parameters:

predictor -

• 1 No prediction (the default value)
• 2 TIFF Predictor 2
• 10 PNG prediction (on encoding, PNG None on all rows)
• 11 PNG prediction (on encoding, PNG Sub on all rows)
• 12 PNG prediction (on encoding, PNG Up on all rows)
• 13 PNG prediction (on encoding, PNG Average on all rows)
• 14 PNG prediction (on encoding, PNG Paeth on all rows)
• 15 PNG prediction (on encoding, PNG optimum)

Returns:

The predictor class based on the predictor code.