nextapp.echoservlet.image
Class PngEncoder

java.lang.Object
  nextapp.echoservlet.image.PngEncoder

public class PngEncoder

extends java.lang.Object

Encodes a java.awt.Image into PNG format. For more information on the PNG specification, see the W3C PNG page at http://www.w3.org/TR/REC-png.html.

Nested Class Summary

private static class	PngEncoder.AverageFilter An implementation of an "Average" filter.
private class	PngEncoder.ByteTranslator Translates byte-based rasters.
static interface	PngEncoder.Filter An interface for PNG filters.
private class	PngEncoder.IntTranslator Translates integer-based rasters.
private static class	PngEncoder.PaethFilter An implementation of a "Paeth" filter.
private static class	PngEncoder.SubFilter An implementation of a "Sub" filter.
(package private) static interface	PngEncoder.Translator An interface for translators, which translate pixel data from a writable raster into an R/G/B/A ordering required by the PNG specification.
private static class	PngEncoder.UpFilter An implementation of an "Up" filter.

Field Summary

static PngEncoder.Filter	AVERAGE_FILTER
private static int	AVERAGE_FILTER_TYPE
private static byte	BIT_DEPTH
private static byte	COLOR_TYPE_INDEXED
private static byte	COLOR_TYPE_RGB
private static byte	COLOR_TYPE_RGBA
private int	compressionLevel
private boolean	encodeAlpha
private PngEncoder.Filter	filter
private int	height
private static byte[]	IDAT
private static byte[]	IEND
private static byte[]	IHDR
private java.awt.image.BufferedImage	image
private int	inputBpp
private static int[]	INT_TRANSLATOR_CHANNEL_MAP
private int	outputBpp
static PngEncoder.Filter	PAETH_FILTER
private static int	PAETH_FILTER_TYPE
private static byte[]	PLTE
private java.awt.image.Raster	raster
private static byte[]	SIGNATURE
static PngEncoder.Filter	SUB_FILTER
private static int	SUB_FILTER_TYPE
private int	transferType
private PngEncoder.Translator	translator
static PngEncoder.Filter	UP_FILTER
private static int	UP_FILTER_TYPE
private int	width

Constructor Summary

PngEncoder(java.awt.Image image, boolean encodeAlpha, PngEncoder.Filter filter, int compressionLevel)
Creates a PNG encoder for an image.

Method Summary

void	encode(java.io.OutputStream out) Encodes the image.
private void	writeIdatChunks(java.io.OutputStream out, java.util.zip.Checksum csum) Writes the IDAT (Image data) chunks to the output stream.
private void	writeIendChunk(java.io.OutputStream out, java.util.zip.Checksum csum) Writes the IEND (End-of-file) chunk to the output stream.
private void	writeIhdrChunk(java.io.OutputStream out, java.util.zip.Checksum csum) Writes the IHDR (Image Header) chunk to the output stream.
private static void	writeInt(java.io.OutputStream out, int i) Writes an 32-bit integer value to the output stream.
private void	writePlteChunk(java.io.OutputStream out, java.util.zip.Checksum csum) Writes the PLTE (Palette) chunk to the output stream.

Methods inherited from class java.lang.Object

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

Field Detail

SUB_FILTER

public static final PngEncoder.Filter SUB_FILTER

UP_FILTER

public static final PngEncoder.Filter UP_FILTER

AVERAGE_FILTER

public static final PngEncoder.Filter AVERAGE_FILTER

PAETH_FILTER

public static final PngEncoder.Filter PAETH_FILTER

SIGNATURE

private static final byte[] SIGNATURE

IHDR

private static final byte[] IHDR

PLTE

private static final byte[] PLTE

IDAT

private static final byte[] IDAT

IEND

private static final byte[] IEND

SUB_FILTER_TYPE

private static final int SUB_FILTER_TYPE

See Also:

Constant Field Values

UP_FILTER_TYPE

private static final int UP_FILTER_TYPE

See Also:

Constant Field Values

AVERAGE_FILTER_TYPE

private static final int AVERAGE_FILTER_TYPE

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Constant Field Values

PAETH_FILTER_TYPE

private static final int PAETH_FILTER_TYPE

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Constant Field Values

BIT_DEPTH

private static final byte BIT_DEPTH

See Also:

Constant Field Values

COLOR_TYPE_INDEXED

private static final byte COLOR_TYPE_INDEXED

See Also:

Constant Field Values

COLOR_TYPE_RGB

private static final byte COLOR_TYPE_RGB

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Constant Field Values

COLOR_TYPE_RGBA

private static final byte COLOR_TYPE_RGBA

See Also:

Constant Field Values

INT_TRANSLATOR_CHANNEL_MAP

private static final int[] INT_TRANSLATOR_CHANNEL_MAP

image

private java.awt.image.BufferedImage image

encodeAlpha

private boolean encodeAlpha

filter

private PngEncoder.Filter filter

compressionLevel

private int compressionLevel

width

private int width

height

private int height

transferType

private int transferType

raster

private java.awt.image.Raster raster

inputBpp

private int inputBpp

outputBpp

private int outputBpp

translator

private PngEncoder.Translator translator

Constructor Detail

PngEncoder

public PngEncoder(java.awt.Image image,
                  boolean encodeAlpha,
                  PngEncoder.Filter filter,
                  int compressionLevel)

Creates a PNG encoder for an image.

Parameters:

image - The image to be encoded.

encodeAlpha - True if the image's alpha channel should be encoded.

filter - The filter to be applied to the image data, one of the following values:

• SUB_FILTER
• UP_FILTER
• AVERAGE_FILTER
• PAETH_FILTER

If a null value is specified, no filtering will be performed.

compressionLevel - The deflater compression level that will be used for compressing the image data. Valid values range from 0 to 9. Higher values result in smaller files and therefore decrease network traffic, but require more CPU time to encode. The normal compromise value is 3.

Method Detail

writeInt

private static void writeInt(java.io.OutputStream out,
                             int i)
                      throws java.io.IOException

Writes an 32-bit integer value to the output stream.

Parameters:

out - The OutputStream to write the integer value to.

i - The integer to write tot he output stream.

Throws:

java.io.IOException

encode

public void encode(java.io.OutputStream out)
            throws java.io.IOException

Encodes the image.

Parameters:

out - An OutputStream to which the encoded image will be written.

Throws:

java.io.IOException - if a problem is encountered writing the output.

writeIdatChunks

private void writeIdatChunks(java.io.OutputStream out,
                             java.util.zip.Checksum csum)
                      throws java.io.IOException

Writes the IDAT (Image data) chunks to the output stream.

Parameters:

out - The OutputStream to write the chunk to.

csum - The Checksum that is updated as data is written to the passed-in OutputStream.

Throws:

java.io.IOException - if a problem is encountered writing the output.

writeIendChunk

private void writeIendChunk(java.io.OutputStream out,
                            java.util.zip.Checksum csum)
                     throws java.io.IOException

Writes the IEND (End-of-file) chunk to the output stream.

Parameters:

out - The OutputStream to write the chunk to.

csum - The Checksum that is updated as data is written to the passed-in OutputStream.

Throws:

java.io.IOException - if a problem is encountered writing the output.

writeIhdrChunk

private void writeIhdrChunk(java.io.OutputStream out,
                            java.util.zip.Checksum csum)
                     throws java.io.IOException

Writes the IHDR (Image Header) chunk to the output stream.

Parameters:

out - The OutputStream to write the chunk to.

csum - The Checksum that is updated as data is written to the passed-in OutputStream.

Throws:

java.io.IOException - if a problem is encountered writing the output.

writePlteChunk

private void writePlteChunk(java.io.OutputStream out,
                            java.util.zip.Checksum csum)
                     throws java.io.IOException

Writes the PLTE (Palette) chunk to the output stream.

Parameters:

out - The OutputStream to write the chunk to.

csum - The Checksum that is updated as data is written to the passed-in OutputStream.

Throws:

java.io.IOException - if a problem is encountered writing the output.