Class Dequantizer

  • All Implemented Interfaces:
    CBlkWTDataSrcDec, InvWTData, MultiResImgData
    Direct Known Subclasses:
    StdDequantizer

    public abstract class Dequantizer
    extends MultiResImgDataAdapter
    implements CBlkWTDataSrcDec
    This is the abstract class from which all dequantizers must inherit. This class has the concept of a current tile and all operations are performed on the current tile.

    This class provides default implemenations for most of the methods (wherever it makes sense), under the assumption that the image and component dimensions, and the tiles, are not modifed by the dequantizer. If that 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 input 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 most significat bits. The most significant magnitude bit corresponds to the most significant bit-plane and so on.

    The output data is either in floating-point, or in fixed-point two's complement. In case of floating-point data the the value returned by getFixedPoint() must be 0. If the case of fixed-point data the number of fractional bits must be defined at the constructor of the implementing class and all operations must be performed accordingly. Each component may have a different number of fractional bits.

    • Field Detail

      • OPT_PREFIX

        public static final char OPT_PREFIX
        The prefix for dequantizer options: 'Q'
        See Also:
        Constant Field Values
      • src

        protected CBlkQuantDataSrcDec src
        The entropy decoder from where to get the quantized data (the source).
      • rb

        protected int[] rb
        The "range bits" for each transformed component
      • utrb

        protected int[] utrb
        The "range bits" for each un-transformed component
    • Constructor Detail

      • Dequantizer

        public Dequantizer​(CBlkQuantDataSrcDec src,
                           int[] utrb,
                           DecoderSpecs decSpec)
        Initializes the source of compressed data.
        Parameters:
        src - From where to obtain the quantized data.
        utrb - The number of "range bits" for each component (must be the "range bits" of the un-transformed components. For a definition of "range bits" see the getNomRangeBits() method.
        See Also:
        getNomRangeBits(int)
    • Method Detail

      • getNomRangeBits

        public int getNomRangeBits​(int c)
        Returns the number of bits, referred to as the "range bits", corresponding to the nominal range of the data in the specified component.

        The returned value corresponds to the nominal dynamic range of the reconstructed image data, not of the wavelet coefficients themselves. This is because different subbands have different gains and thus different nominal ranges. To have an idea of the nominal range in each subband the subband analysis gain value from the subband tree structure, returned by the getSynSubbandTree() method, can be used. See the Subband class for more details.

        If this number is b then for unsigned data the nominal range is between 0 and 2^b-1, and for signed data it is between -2^(b-1) and 2^(b-1)-1.

        Specified by:
        getNomRangeBits in interface CBlkWTDataSrcDec
        Parameters:
        c - The index of the component
        Returns:
        The number of bits corresponding to the nominal range of the data.
        See Also:
        Subband
      • getSynSubbandTree

        public SubbandSyn getSynSubbandTree​(int t,
                                            int c)
        Returns the subband tree, for the specified tile-component. This method returns the root element of the subband tree structure, see Subband and SubbandSyn. The tree comprises all the available resolution levels.

        The number of magnitude bits ('magBits' member variable) for each subband may have not been not initialized (it depends on the actual dequantizer and its implementation). However, they are not necessary for the subsequent steps in the decoder chain.

        Specified by:
        getSynSubbandTree in interface InvWTData
        Specified by:
        getSynSubbandTree in interface MultiResImgData
        Parameters:
        t - The index of the tile, from 0 to T-1.
        c - The index of the component, from 0 to C-1.
        Returns:
        The root of the tree structure.
      • getCbULX

        public int getCbULX()
        Returns the horizontal code-block partition origin. Allowable values are 0 and 1, nothing else.
        Specified by:
        getCbULX in interface InvWTData
      • getCbULY

        public int getCbULY()
        Returns the vertical code-block partition origin. Allowable values are 0 and 1, nothing else.
        Specified by:
        getCbULY in interface InvWTData
      • 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 and the third one is a long description of what the parameter is. 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.
      • setTile

        public void setTile​(int x,
                            int y)
        Changes the current tile, given the new indexes. An IllegalArgumentException is thrown if the indexes do not correspond to a valid tile.

        This default implementation changes the tile in the source and re-initializes properly component transformation variables..

        Specified by:
        setTile in interface MultiResImgData
        Overrides:
        setTile in class MultiResImgDataAdapter
        Parameters:
        x - The horizontal index of the tile.
        y - The vertical index of the new tile.
      • nextTile

        public void nextTile()
        Advances to the next tile, in standard scan-line order (by rows then columns). An NoNextElementException is thrown if the current tile is the last one (i.e. there is no next tile).

        This default implementation just advances to the next tile in the source and re-initializes properly component transformation variables.

        Specified by:
        nextTile in interface MultiResImgData
        Overrides:
        nextTile in class MultiResImgDataAdapter