com.twelvemonkeys.io.enc

Class PackBitsEncoder

java.lang.Object

com.twelvemonkeys.io.enc.PackBitsEncoder

All Implemented Interfaces:

Encoder

public final class PackBitsEncoder
extends Object
implements Encoder

Encoder implementation for Apple PackBits run-length encoding.

From Wikipedia, the free encyclopedia
PackBits is a fast, simple compression scheme for run-length encoding of data.

Apple introduced the PackBits format with the release of MacPaint on the Macintosh computer. This compression scheme is one of the types of compression that can be used in TIFF-files.

A PackBits data stream consists of packets of one byte of header followed by data. The header is a signed byte; the data can be signed, unsigned, or packed (such as MacPaint pixels).

PackBits

Header byte	Data
0 to 127	1 + n literal bytes of data
0 to -127	One byte of data, repeated 1 - n times in the decompressed output
-128	No operation

Note that interpreting 0 as positive or negative makes no difference in the output. Runs of two bytes adjacent to non-runs are typically written as literal data.

Version:

$Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/enc/PackBitsEncoder.java#1 $

Author:

Harald Kuhr

See Also:

Understanding PackBits

Constructor Summary

Constructors

Constructor and Description
PackBitsEncoder() Creates a PackBitsEncoder.

Method Summary

Modifier and Type	Method and Description
void	encode(OutputStream stream, ByteBuffer buffer) Encodes up to buffer.remaining() bytes into the given input stream, from the given buffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

PackBitsEncoder

public PackBitsEncoder()

Creates a PackBitsEncoder.

Method Detail

encode

public void encode(OutputStream stream,
                   ByteBuffer buffer)
            throws IOException

Description copied from interface: Encoder

Encodes up to buffer.remaining() bytes into the given input stream, from the given buffer.

Specified by:

encode in interface Encoder

Parameters:

stream - the output stream to encode data to

buffer - buffer to read data from

Throws:

IOException - if an I/O error occurs