org.gridfour.lsop

Class LsDecoder08

java.lang.Object

org.gridfour.lsop.LsDecoder08

All Implemented Interfaces:

ICompressionDecoder

public class LsDecoder08
extends Object
implements ICompressionDecoder

Provides methods and data elements used to decode data compressed using the Gridfour LSOP format based on the methods of Smith and Lewis' Optimal Predictors.

The LS decoder and encoder are separated into separate packages and separate modules in order to manage code dependencies. The encoding process requires solving a 9-variable linear system. Doing so requires the use of a 3rd party Java library, so an implementation that uses the LS format introduces an additional dependency to the code base. But the decoding process does not use any operations that would require an external dependency. Thus the decoder is specified as part of the Gridfour core module, while the encoder is not.

Constructor Summary

Constructors

Constructor and Description
LsDecoder08()

Method Summary

Modifier and Type	Method and Description
void	analyze(int nRows, int nColumns, byte[] packing) Analyzes the content of the packing to collect statistics on the compression.
void	clearAnalysisData() Clears all accumulated analysis data.
int[]	decode(int nRows, int nColumns, byte[] packing) Decodes the content of the packing and populates an integer array to store the data.
float[]	decodeFloats(int nRows, int nColumns, byte[] packing) Decodes the content of the packing and populates an integer array to store the data.
void	reportAnalysisData(PrintStream ps, int nTilesInRaster) Prints analysis results (if any) to specified print stream

Methods inherited from class java.lang.Object

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

Constructor Detail

LsDecoder08

public LsDecoder08()

Method Detail

decode

public int[] decode(int nRows,
                    int nColumns,
                    byte[] packing)
             throws IOException

Description copied from interface: ICompressionDecoder

Decodes the content of the packing and populates an integer array to store the data.

Specified by:

decode in interface ICompressionDecoder

Parameters:

nRows - a value of 1 or greater giving the number of rows in the tile

nColumns - a value of 1 or greater giving the number of columns in the

packing - an array of bytes containing the encoded data to be decompressed

Returns:

if successful, a valid integer array giving content for the tile in row-major order

Throws:

IOException - in the event of an incompatible packing

analyze

public void analyze(int nRows,
                    int nColumns,
                    byte[] packing)
             throws IOException

Description copied from interface: ICompressionDecoder

Analyzes the content of the packing to collect statistics on the compression.

This method is intended to be used when assessing the results of data compression. It may be used for a single tile or for a collection of multiple tiles. When used for multiple tiles, the results are assumed to be cumulative. Thus an implementation is expected to maintain statistics as state data (class member data).

Specified by:

analyze in interface ICompressionDecoder

Parameters:

nRows - the number of rows in the tile to be analyzed.

nColumns - the number of columns in the tile to be analyzed.

packing - a valid packing for the associated codec implementation

Throws:

IOException - in the event of an incompatible packing

reportAnalysisData

public void reportAnalysisData(PrintStream ps,
                               int nTilesInRaster)

Description copied from interface: ICompressionDecoder

Prints analysis results (if any) to specified print stream

Specified by:

reportAnalysisData in interface ICompressionDecoder

Parameters:

ps - a valid print stream.

nTilesInRaster - the number of tiles in the raster

clearAnalysisData

public void clearAnalysisData()

Description copied from interface: ICompressionDecoder

Clears all accumulated analysis data.

Specified by:

clearAnalysisData in interface ICompressionDecoder

decodeFloats

public float[] decodeFloats(int nRows,
                            int nColumns,
                            byte[] packing)
                     throws IOException

Description copied from interface: ICompressionDecoder

Decodes the content of the packing and populates an integer array to store the data.

Specified by:

decodeFloats in interface ICompressionDecoder

Parameters:

nRows - a value of 1 or greater giving the number of rows in the tile

nColumns - a value of 1 or greater giving the number of columns in the

packing - an array of bytes containing the encoded data to be decompressed

Returns:

if successful, a valid integer array giving content for the tile in row-major order

Throws:

IOException - in the event of an incompatible packing