org.freehep.graphicsio.png
Class PNGEncoder

java.lang.Object
  org.freehep.graphicsio.png.PNGEncoder

All Implemented Interfaces:

ImageObserver

public class PNGEncoder

extends Object

implements ImageObserver

Source Code:

PNGEncoder.java

Field Summary

protected int	bytePos
protected int	bytesPerPixel
protected int	compressionLevel
protected CRC32	crc
protected long	crcValue
protected int	dataPos
static boolean	ENCODE_ALPHA Constant specifying that alpha channel should be encoded.
protected boolean	encodeAlpha
protected int	endPos
protected int	filter
static int	FILTER_LAST
static int	FILTER_NONE Constants for filters
static int	FILTER_SUB
static int	FILTER_UP
protected int	hdrPos
protected int	height
protected Image	image
protected List	keys
protected byte[]	leftBytes
protected int	maxPos
static boolean	NO_ALPHA Constant specifying that alpha channel should not be encoded.
protected byte[]	pngBytes
protected byte[]	priorRow
protected List	text
protected int	width

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

PNGEncoder()

PNGEncoder(Image image)
Class constructor specifying Image to encode, with no alpha channel encoding.

PNGEncoder(Image image, boolean encodeAlpha)
Class constructor specifying Image to encode, and whether to encode alpha.

PNGEncoder(Image image, boolean encodeAlpha, int whichFilter)
Class constructor specifying Image to encode, whether to encode alpha, and filter to use.

PNGEncoder(Image image, boolean encodeAlpha, int whichFilter, int compLevel)
Class constructor specifying Image source to encode, whether to encode alpha, filter to use, and compression level.

Method Summary

void	addText(String key, String value)
protected void	filterSub(byte[] pixels, int startPos, int width) Perform "sub" filtering on the given row.
protected void	filterUp(byte[] pixels, int startPos, int width) Perform "up" filtering on the given row.
int	getCompressionLevel() Retrieve compression level
boolean	getEncodeAlpha() Retrieve alpha encoding status.
int	getFilter() Retrieve filtering scheme
boolean	imageUpdate(Image image, int flags, int x, int y, int width, int height)
byte[]	pngEncode() Creates an array of bytes that is the PNG equivalent of the current image.
byte[]	pngEncode(boolean encodeAlpha) Creates an array of bytes that is the PNG equivalent of the current image, specifying whether to encode alpha or not.
protected byte[]	resizeByteArray(byte[] array, int newLength) Increase or decrease the length of a byte array.
void	setCompressionLevel(int level) Set the compression level to use
void	setEncodeAlpha(boolean encodeAlpha) Set the alpha encoding on or off.
void	setFilter(int whichFilter) Set the filter to use
void	setImage(Image image) Set the image to be encoded
protected int	writeByte(int b, int offset) Write a single byte into the pngBytes array at a given position.
protected int	writeBytes(byte[] data, int offset) Write an array of bytes into the pngBytes array.
protected int	writeBytes(byte[] data, int nBytes, int offset) Write an array of bytes into the pngBytes array, specifying number of bytes to write.
protected void	writeEnd() Write a PNG "IEND" chunk into the pngBytes array.
protected void	writeHeader() Write a PNG "IHDR" chunk into the pngBytes array.
protected boolean	writeImageData() Write the image data into the pngBytes array.
protected int	writeInt2(int n, int offset) Write a two-byte integer into the pngBytes array at a given position.
protected int	writeInt4(int n, int offset) Write a four-byte integer into the pngBytes array at a given position.
protected int	writeString(String s, int offset) Write a string into the pngBytes array at a given position.
protected void	writeText(String key, String value)

Methods inherited from class java.lang.Object

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

Field Detail

ENCODE_ALPHA

public static final boolean ENCODE_ALPHA

Constant specifying that alpha channel should be encoded.

See Also:

Constant Field Values

NO_ALPHA

public static final boolean NO_ALPHA

Constant specifying that alpha channel should not be encoded.

See Also:

Constant Field Values

FILTER_NONE

public static final int FILTER_NONE

Constants for filters

See Also:

Constant Field Values

FILTER_SUB

public static final int FILTER_SUB

See Also:

Constant Field Values

FILTER_UP

public static final int FILTER_UP

See Also:

Constant Field Values

FILTER_LAST

public static final int FILTER_LAST

See Also:

Constant Field Values

pngBytes

protected byte[] pngBytes

priorRow

protected byte[] priorRow

leftBytes

protected byte[] leftBytes

image

protected Image image

width

protected int width

height

protected int height

bytePos

protected int bytePos

maxPos

protected int maxPos

hdrPos

protected int hdrPos

dataPos

protected int dataPos

endPos

protected int endPos

crc

protected CRC32 crc

crcValue

protected long crcValue

encodeAlpha

protected boolean encodeAlpha

filter

protected int filter

bytesPerPixel

protected int bytesPerPixel

compressionLevel

protected int compressionLevel

keys

protected List keys

text

protected List text

Constructor Detail

PNGEncoder

public PNGEncoder()

PNGEncoder

public PNGEncoder(Image image)

Class constructor specifying Image to encode, with no alpha channel encoding.

Parameters:

image - A Java Image object which uses the DirectColorModel

See Also:

Image

PNGEncoder

public PNGEncoder(Image image,
                  boolean encodeAlpha)

Class constructor specifying Image to encode, and whether to encode alpha.

Parameters:

image - A Java Image object which uses the DirectColorModel

encodeAlpha - Encode the alpha channel? false=no; true=yes

See Also:

Image

PNGEncoder

public PNGEncoder(Image image,
                  boolean encodeAlpha,
                  int whichFilter)

Class constructor specifying Image to encode, whether to encode alpha, and filter to use.

Parameters:

image - A Java Image object which uses the DirectColorModel

encodeAlpha - Encode the alpha channel? false=no; true=yes

whichFilter - 0=none, 1=sub, 2=up

See Also:

Image

PNGEncoder

public PNGEncoder(Image image,
                  boolean encodeAlpha,
                  int whichFilter,
                  int compLevel)

Class constructor specifying Image source to encode, whether to encode alpha, filter to use, and compression level.

Parameters:

image - A Java Image object

encodeAlpha - Encode the alpha channel? false=no; true=yes

whichFilter - 0=none, 1=sub, 2=up

compLevel - 0..9

See Also:

Image

Method Detail

addText

public void addText(String key,
                    String value)

setImage

public void setImage(Image image)

Set the image to be encoded

Parameters:

image - A Java Image object which uses the DirectColorModel

See Also:

Image

imageUpdate

public boolean imageUpdate(Image image,
                           int flags,
                           int x,
                           int y,
                           int width,
                           int height)

Specified by:

imageUpdate in interface ImageObserver

pngEncode

public byte[] pngEncode(boolean encodeAlpha)

Creates an array of bytes that is the PNG equivalent of the current image, specifying whether to encode alpha or not.

Parameters:

encodeAlpha - boolean false=no alpha, true=encode alpha

Returns:

an array of bytes, or null if there was a problem

pngEncode

public byte[] pngEncode()

Creates an array of bytes that is the PNG equivalent of the current image. Alpha encoding is determined by its setting in the constructor.

Returns:

an array of bytes, or null if there was a problem

setEncodeAlpha

public void setEncodeAlpha(boolean encodeAlpha)

Set the alpha encoding on or off.

Parameters:

encodeAlpha - false=no, true=yes

getEncodeAlpha

public boolean getEncodeAlpha()

Retrieve alpha encoding status.

Returns:

boolean false=no, true=yes

setFilter

public void setFilter(int whichFilter)

Set the filter to use

Parameters:

whichFilter - from constant list

getFilter

public int getFilter()

Retrieve filtering scheme

Returns:

int (see constant list)

setCompressionLevel

public void setCompressionLevel(int level)

Set the compression level to use

Parameters:

level - 0 through 9

getCompressionLevel

public int getCompressionLevel()

Retrieve compression level

Returns:

int in range 0-9

resizeByteArray

protected byte[] resizeByteArray(byte[] array,
                                 int newLength)

Increase or decrease the length of a byte array.

Parameters:

array - The original array.

newLength - The length you wish the new array to have.

Returns:

Array of newly desired length. If shorter than the original, the trailing elements are truncated.

writeBytes

protected int writeBytes(byte[] data,
                         int offset)

Write an array of bytes into the pngBytes array. Note: This routine has the side effect of updating maxPos, the largest element written in the array. The array is resized by 1000 bytes or the length of the data to be written, whichever is larger.

Parameters:

data - The data to be written into pngBytes.

offset - The starting point to write to.

Returns:

The next place to be written to in the pngBytes array.

writeBytes

protected int writeBytes(byte[] data,
                         int nBytes,
                         int offset)

Write an array of bytes into the pngBytes array, specifying number of bytes to write. Note: This routine has the side effect of updating maxPos, the largest element written in the array. The array is resized by 1000 bytes or the length of the data to be written, whichever is larger.

Parameters:

data - The data to be written into pngBytes.

nBytes - The number of bytes to be written.

offset - The starting point to write to.

Returns:

The next place to be written to in the pngBytes array.

writeInt2

protected int writeInt2(int n,
                        int offset)

Write a two-byte integer into the pngBytes array at a given position.

Parameters:

n - The integer to be written into pngBytes.

offset - The starting point to write to.

Returns:

The next place to be written to in the pngBytes array.

writeInt4

protected int writeInt4(int n,
                        int offset)

Write a four-byte integer into the pngBytes array at a given position.

Parameters:

n - The integer to be written into pngBytes.

offset - The starting point to write to.

Returns:

The next place to be written to in the pngBytes array.

writeByte

protected int writeByte(int b,
                        int offset)

Write a single byte into the pngBytes array at a given position.

Parameters:

b - The integer to be written into pngBytes.

offset - The starting point to write to.

Returns:

The next place to be written to in the pngBytes array.

writeString

protected int writeString(String s,
                          int offset)

Write a string into the pngBytes array at a given position. This uses the getBytes method, so the encoding used will be its default.

Parameters:

s - The String to be written into pngBytes.

offset - The starting point to write to.

Returns:

The next place to be written to in the pngBytes array.

See Also:

String.getBytes()

writeHeader

protected void writeHeader()

Write a PNG "IHDR" chunk into the pngBytes array.

writeText

protected void writeText(String key,
                         String value)

filterSub

protected void filterSub(byte[] pixels,
                         int startPos,
                         int width)

Perform "sub" filtering on the given row. Uses temporary array leftBytes to store the original values of the previous pixels. The array is 16 bytes long, which will easily hold two-byte samples plus two-byte alpha.

Parameters:

pixels - The array holding the scan lines being built

startPos - Starting position within pixels of bytes to be filtered.

width - Width of a scanline in pixels.

filterUp

protected void filterUp(byte[] pixels,
                        int startPos,
                        int width)

Perform "up" filtering on the given row. Side effect: refills the prior row with current row

Parameters:

pixels - The array holding the scan lines being built

startPos - Starting position within pixels of bytes to be filtered.

width - Width of a scanline in pixels.

writeImageData

protected boolean writeImageData()

Write the image data into the pngBytes array. This will write one or more PNG "IDAT" chunks. In order to conserve memory, this method grabs as many rows as will fit into 32K bytes, or the whole image; whichever is less.

Returns:

true if no errors; false if error grabbing pixels

writeEnd

protected void writeEnd()

Write a PNG "IEND" chunk into the pngBytes array.