jj2000.j2k.quantization.quantizer
Class Quantizer

java.lang.Object
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  +--jj2000.j2k.image.ImgDataAdapter
        |
        +--jj2000.j2k.quantization.quantizer.Quantizer
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
static char OPT_PREFIX
          The prefix for quantizer options: 'Q'
private static java.lang.String[][] pinfo
          The list of parameters that is accepted for quantization.
protected  CBlkWTDataSrc src
          The source of wavelet transform coefficients
 
Fields inherited from class jj2000.j2k.image.ImgDataAdapter
imgdatasrc, tIdx
 
Constructor Summary
Quantizer(CBlkWTDataSrc src)
          Initializes the source of wavelet transform coefficients.
 
Method Summary
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, EncoderSpecs encSpec)
          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.
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 java.lang.String[][] getParameterInfo()
          Returns the parameters that are used in this class and implementing classes.
 int getPartitionULX()
          Returns the horizontal coordinate of the origin of the cell and code-block partition, with respect to the canvas origin, on the reference grid.
 int getPartitionULY()
          Returns the vertical coordinate of the origin of the cell and code-block partition, with respect to the canvas origin, on the reference grid.
 SubbandAn getSubbandTree(int t, int c)
          Returns a reference to the subband tree structure representing the subband decomposition for the specified tile-component.
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
getCompHeight, getCompImgHeight, getCompImgWidth, getCompSubsX, getCompSubsY, getCompWidth, getHeight, getImgHeight, getImgULX, getImgULY, getImgWidth, getNomRangeBits, getNumComps, getNumTiles, getNumTiles, getTile, getTileIdx, getTileOff, getULX, getULY, getWidth, nextTile, setTile
 
Methods inherited from class java.lang.Object
, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait
 

Field Detail

OPT_PREFIX

public static final char OPT_PREFIX
The prefix for quantizer options: 'Q'

pinfo

private static final java.lang.String[][] pinfo
The list of parameters that is accepted for quantization. Options for quantization start with 'Q'.

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

getSubbandTree

public SubbandAn getSubbandTree(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().

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)

getPartitionULX

public int getPartitionULX()
Returns the horizontal coordinate of the origin of the cell and code-block partition, with respect to the canvas origin, on the reference grid. Allowable values are 0 and 1, nothing else.
Returns:
The horizontal coordinate of the origin of the cell and code-block partitions, with respect to the canvas origin, on the reference grid.

getPartitionULY

public int getPartitionULY()
Returns the vertical coordinate of the origin of the cell and code-block partition, with respect to the canvas origin, on the reference grid. Allowable values are 0 and 1, nothing else.
Returns:
The vertical coordinate of the origin of the cell and code-block partitions, with respect to the canvas origin, on the reference grid.

getParameterInfo

public static java.lang.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,
                                       EncoderSpecs encSpec)
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:
java.lang.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.