jj2000.j2k.quantization.quantizer

Class Quantizer

java.lang.Object

jj2000.j2k.image.ImgDataAdapter

jj2000.j2k.quantization.quantizer.Quantizer

All Implemented Interfaces:

ImgData, CBlkQuantDataSrcEnc, ForwWTDataProps

Direct Known Subclasses:

StdQuantizer

public abstract class Quantizer
extends ImgDataAdapter
implements CBlkQuantDataSrcEnc

This abstract class provides the general interface for quantizers. The input of a quantizer is the output of a wavelet transform. The output of the quantizer is the set of quantized wavelet coefficients represented in sign-magnitude notation (see below).

This class provides default implementation for most of the methods (wherever it makes sense), under the assumption that the image, component dimensions, and the tiles, are not modifed by the quantizer. If it is not the case for a particular implementation, then the methods should be overriden.

Sign magnitude representation is used (instead of two's complement) for the output data. The most significant bit is used for the sign (0 if positive, 1 if negative). Then the magnitude of the quantized coefficient is stored in the next M most significat bits. The rest of the bits (least significant bits) can contain a fractional value of the quantized coefficient. This fractional value is not to be coded by the entropy coder. However, it can be used to compute rate-distortion measures with greater precision.

The value of M is determined for each subband as the sum of the number of guard bits G and the nominal range of quantized wavelet coefficients in the corresponding subband (Rq), minus 1:

M = G + Rq -1

The value of G should be the same for all subbands. The value of Rq depends on the quantization step size, the nominal range of the component before the wavelet transform and the analysis gain of the subband (see Subband).

The blocks of data that are requested should not cross subband boundaries.

NOTE: At the moment only quantizers that implement the 'CBlkQuantDataSrcEnc' interface are supported.

See Also:

Subband

Field Summary

Fields

Modifier and Type	Field and Description
static char	OPT_PREFIX The prefix for quantizer options: 'Q'
protected CBlkWTDataSrc	src The source of wavelet transform coefficients

Fields inherited from class jj2000.j2k.image.ImgDataAdapter

imgdatasrc, tIdx

Constructor Summary

Constructors

Constructor and Description
Quantizer(CBlkWTDataSrc src) Initializes the source of wavelet transform coefficients.

Method Summary

Modifier and Type	Method and Description
protected abstract void	calcSbParams(SubbandAn sb, int n) Calculates the parameters of the SubbandAn objects that depend on the Quantizer.
static Quantizer	createInstance(CBlkWTDataSrc src, J2KImageWriteParamJava wp) Creates a Quantizer object for the appropriate type of quantization specified in the options in the parameter list 'pl', and having 'src' as the source of data to be quantized.
SubbandAn	getAnSubbandTree(int t, int c) Returns a reference to the subband tree structure representing the subband decomposition for the specified tile-component.
int	getCbULX() Returns the horizontal offset of the code-block partition.
int	getCbULY() Returns the vertical offset of the code-block partition.
abstract int	getMaxMagBits(int c) Returns the maximum number of magnitude bits in any subband in the current tile.
abstract int	getNumGuardBits(int t, int c) Returns the number of guard bits used by this quantizer in the given tile-component.
static String[][]	getParameterInfo() Returns the parameters that are used in this class and implementing classes.
abstract boolean	isDerived(int t, int c) Returns true if the quantizer of given tile-component uses derived quantization step sizes.

Methods inherited from class jj2000.j2k.image.ImgDataAdapter

getCompImgHeight, getCompImgWidth, getCompSubsX, getCompSubsY, getCompULX, getCompULY, getImgHeight, getImgULX, getImgULY, getImgWidth, getNomRangeBits, getNomTileHeight, getNomTileWidth, getNumComps, getNumTiles, getNumTiles, getTile, getTileCompHeight, getTileCompWidth, getTileHeight, getTileIdx, getTilePartULX, getTilePartULY, getTileWidth, nextTile, setTile

Methods inherited from class java.lang.Object

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

Methods inherited from interface jj2000.j2k.quantization.quantizer.CBlkQuantDataSrcEnc

getNextCodeBlock, getNextInternCodeBlock

Methods inherited from interface jj2000.j2k.wavelet.analysis.ForwWTDataProps

isReversible

Methods inherited from interface jj2000.j2k.image.ImgData

getCompImgHeight, getCompImgWidth, getCompSubsX, getCompSubsY, getCompULX, getCompULY, getImgHeight, getImgULX, getImgULY, getImgWidth, getNomRangeBits, getNomTileHeight, getNomTileWidth, getNumComps, getNumTiles, getNumTiles, getTile, getTileCompHeight, getTileCompWidth, getTileHeight, getTileIdx, getTilePartULX, getTilePartULY, getTileWidth, nextTile, setTile

Field Detail

OPT_PREFIX

public static final char OPT_PREFIX

The prefix for quantizer options: 'Q'

See Also:

Constant Field Values

src

protected CBlkWTDataSrc src

The source of wavelet transform coefficients

Constructor Detail

Quantizer

public Quantizer(CBlkWTDataSrc src)

Initializes the source of wavelet transform coefficients.

Parameters:

src - The source of wavelet transform coefficients.

Method Detail

getNumGuardBits

public abstract int getNumGuardBits(int t,
                                    int c)

Returns the number of guard bits used by this quantizer in the given tile-component.

Parameters:

t - Tile index

c - Component index

Returns:

The number of guard bits

isDerived

public abstract boolean isDerived(int t,
                                  int c)

Returns true if the quantizer of given tile-component uses derived quantization step sizes.

Parameters:

t - Tile index

c - Component index

Returns:

True if derived quantization is used.

calcSbParams

protected abstract void calcSbParams(SubbandAn sb,
                                     int n)

Calculates the parameters of the SubbandAn objects that depend on the Quantizer. The 'stepWMSE' field is calculated for each subband which is a leaf in the tree rooted at 'sb', for the specified component. The subband tree 'sb' must be the one for the component 'n'.

Parameters:

sb - The root of the subband tree.

n - The component index.

See Also:

SubbandAn.stepWMSE

getAnSubbandTree

public SubbandAn getAnSubbandTree(int t,
                                  int c)

Returns a reference to the subband tree structure representing the subband decomposition for the specified tile-component.

This method gets the subband tree from the source and then calculates the magnitude bits for each leaf using the method calcSbParams().

Specified by:

getAnSubbandTree in interface ForwWTDataProps

Parameters:

t - The index of the tile.

c - The index of the component.

Returns:

The subband tree structure, see SubbandAn.

See Also:

SubbandAn, Subband, calcSbParams(jj2000.j2k.wavelet.analysis.SubbandAn, int)

getCbULX

public int getCbULX()

Returns the horizontal offset of the code-block partition. Allowable values are 0 and 1, nothing else.

Specified by:

getCbULX in interface ForwWTDataProps

getCbULY

public int getCbULY()

Returns the vertical offset of the code-block partition. Allowable values are 0 and 1, nothing else.

Specified by:

getCbULY in interface ForwWTDataProps

getParameterInfo

public static String[][] getParameterInfo()

Returns the parameters that are used in this class and implementing classes. It returns a 2D String array. Each of the 1D arrays is for a different option, and they have 3 elements. The first element is the option name, the second one is the synopsis, the third one is a long description of what the parameter is and the fourth is its default value. The synopsis or description may be 'null', in which case it is assumed that there is no synopsis or description of the option, respectively. Null may be returned if no options are supported.

Returns:

the options name, their synopsis and their explanation, or null if no options are supported.

createInstance

public static Quantizer createInstance(CBlkWTDataSrc src,
                                       J2KImageWriteParamJava wp)

Creates a Quantizer object for the appropriate type of quantization specified in the options in the parameter list 'pl', and having 'src' as the source of data to be quantized. The 'rev' flag indicates if the quantization should be reversible. NOTE: At the moment only sources of wavelet data that implement the 'CBlkWTDataSrc' interface are supported.

Parameters:

src - The source of data to be quantized

encSpec - Encoder specifications

Throws:

IllegalArgumentException - If an error occurs while parsing the options in 'pl'

getMaxMagBits

public abstract int getMaxMagBits(int c)

Returns the maximum number of magnitude bits in any subband in the current tile.

Parameters:

c - the component number

Returns:

The maximum number of magnitude bits in all subbands of the current tile.