entropycoder.java

jpeg2000算法实现

/*
 * CVS identifier:
 *
 * $Id: EntropyCoder.java,v 1.54 2001/02/14 10:47:33 grosbois Exp $
 *
 * Class:                   EntropyCoder
 *
 * Description:             The abstract class for entropy encoders
 *
 *
 *
 * COPYRIGHT:
 * 
 * This software module was originally developed by Rapha雔 Grosbois and
 * Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel
 * Askel鰂 (Ericsson Radio Systems AB); and Bertrand Berthelot, David
 * Bouchard, F閘ix Henry, Gerard Mozelle and Patrice Onno (Canon Research
 * Centre France S.A) in the course of development of the JPEG2000
 * standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This
 * software module is an implementation of a part of the JPEG 2000
 * Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio
 * Systems AB and Canon Research Centre France S.A (collectively JJ2000
 * Partners) agree not to assert against ISO/IEC and users of the JPEG
 * 2000 Standard (Users) any of their rights under the copyright, not
 * including other intellectual property rights, for this software module
 * with respect to the usage by ISO/IEC and Users of this software module
 * or modifications thereof for use in hardware or software products
 * claiming conformance to the JPEG 2000 Standard. Those intending to use
 * this software module in hardware or software products are advised that
 * their use may infringe existing patents. The original developers of
 * this software module, JJ2000 Partners and ISO/IEC assume no liability
 * for use of this software module or modifications thereof. No license
 * or right to this software module is granted for non JPEG 2000 Standard
 * conforming products. JJ2000 Partners have full right to use this
 * software module for his/her own purpose, assign or donate this
 * software module to any third party and to inhibit third parties from
 * using this software module for non JPEG 2000 Standard conforming
 * products. This copyright notice must be included in all copies or
 * derivative works of this software module.
 * 
 * Copyright (c) 1999/2000 JJ2000 Partners.
 * */
package jj2000.j2k.entropy.encoder;

import jj2000.j2k.quantization.quantizer.*;
import jj2000.j2k.codestream.writer.*;
import jj2000.j2k.wavelet.analysis.*;
import jj2000.j2k.wavelet.*;
import jj2000.j2k.encoder.*;
import jj2000.j2k.entropy.*;
import jj2000.j2k.image.*;
import jj2000.j2k.util.*;
import jj2000.j2k.roi.*;

import java.util.*;
import java.io.*;

/**
 * This abstract class provides the general interface for block-based entropy
 * encoders. The input to the entropy coder is the quantized wavelet
 * coefficients, or codewords, represented in sign magnitude. The output is a
 * compressed code-block with rate-distortion information.
 *
 * <P>The source of data for objects of this class are 'CBlkQuantDataSrcEnc'
 * objects.
 *
 * <P>For more details on the sign magnitude representation used see the
 * Quantizer class.
 *
 * <P>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 entropy
 * coder. If that is not the case for a particular implementation then the
 * methods should be overriden.
 *
 * @see Quantizer
 * @see CBlkQuantDataSrcEnc
 * */
public abstract class EntropyCoder extends ImgDataAdapter
    implements CodedCBlkDataSrcEnc, StdEntropyCoderOptions {

    /** The prefix for entropy coder options: 'C' */
    public final static char OPT_PREFIX = 'C';

    /** The list of parameters that is accepted for entropy coding. Options 
     * for entropy coding start with 'C'. */
    private final static String [][] pinfo = {
        {"Cblksiz", "[<tile-component idx>] <width> <height> "+
         "[[<tile-component idx>] <width> <height>]",
         "Specifies the maximum code-block size to use for tile-component. "+
         "The maximum width and height is 1024, however the surface area "+
         "(i.e. width x height) must not exceed 4096. The minimum width and "+
         "height is 4.","64 64"},
        {"Cbypass", "[<tile-component idx>] on|off"+
         "[ [<tile-component idx>] on|off ...]",
         "Uses the lazy coding mode with the entropy coder. This will bypass "+
         "the MQ coder for some of the coding passes, where the distribution "+
         "is often close to uniform. Since the MQ codeword will be "+
         "terminated "+
         "at least once per lazy pass, it is important to use an efficient "+
         "termination algorithm, see the 'Cterm' option."+
         "'on' enables, 'off' disables it.","off"},
        {"CresetMQ", "[<tile-component idx>] on|off"+
         "[ [<tile-component idx>] on|off ...]",
         "If this is enabled the probability estimates of the MQ coder are "+
         "reset after each arithmetically coded (i.e. non-lazy) coding pass. "+
         "'on' enables, 'off' disables it.","off"},
        {"Creg_term", "[<tile-component idx>] on|off"+
         "[ [<tile-component idx>] on|off ...]",
         "If this is enabled the codeword (raw or MQ) is terminated on a "+
         "byte boundary after each coding pass. In this case it is important "+
         "to use an efficient termination algorithm, see the 'Cterm' option. "+
         "'on' enables, 'off' disables it.","off"},
        {"Ccausal","[<tile-component idx>] on|off"+
         "[ [<tile-component idx>] on|off ...]", 
         "Uses vertically stripe causal context formation. If this is "+
         "enabled "+
         "the context formation process in one stripe is independant of the "+
         "next stripe (i.e. the one below it). 'on' "+
         "enables, 'off' disables it.","off"},
        {"Cseg_symbol","[<tile-component idx>] on|off"+
         "[ [<tile-component idx>] on|off ...]",
         "Inserts an error resilience segmentation symbol in the MQ "+
         "codeword at the end of "+
         "each bit-plane (cleanup pass). Decoders can use this "+
         "information to detect and "+
         "conceal errors.'on' enables, 'off' disables "+
         "it.","off"},
        {"Cterm", "[<tile-component idx>] near_opt|easy|predict|full"+
         "[ [<tile-component idx>] near_opt|easy|predict|full ...]",
         "Specifies the algorithm used to terminate the MQ codeword. "+
         "The most efficient one is 'near_opt', which delivers a codeword "+
         "which in almost all cases is the shortest possible. The 'easy' is "+
         "a simpler algorithm that delivers a codeword length that is close "+
         "to the previous one (in average 1 bit longer). The 'predict' is"+
         " almost "+
         "the same as the 'easy' but it leaves error resilient information "+
         "on "+
         "the spare least significant bits (in average 3.5 bits), which can "+
         "be used by a decoder to detect errors. The 'full' algorithm "+
         "performs a full flush of the MQ coder and is highly inefficient.\n"+
         "It is important to use a good termination policy since the MQ "+
         "codeword can be terminated quite often, specially if the 'Cbypass'"+
         " or "+
         "'Creg_term' options are enabled (in the normal case it would be "+
         "terminated once per code-block, while if 'Creg_term' is specified "+
         "it will be done almost 3 times per bit-plane in each code-block).",
	 "near_opt"},
        {"Clen_calc","[<tile-component idx>] near_opt|lazy_good|lazy"+
         "[ [<tile-component idx>] ...]",
         "Specifies the algorithm to use in calculating the necessary MQ "+
         "length for each decoding pass. The best one is 'near_opt', which "+
         "performs a rather sophisticated calculation and provides the best "+
         "results. The 'lazy_good' and 'lazy' are very simple algorithms "+
         "that "+
         "provide rather conservative results, 'lazy_good' one being "+
         "slightly "+
         "better. Do not change this option unless you want to experiment "+
         "the effect of different length calculation algorithms.","near_opt"},
        {"Cpp","[<tile-component idx>] <dim> <dim> [<dim> <dim>] " +
         "[ [<tile-component idx>] ...]",
         "Specifies precinct partition dimensions for tile-component. The "+
         "first "+
         "two values apply to the highest resolution and the following ones "+
         "(if "+
         "any) apply to the remaining resolutions in decreasing order. If "+
         "less "+
         "values than the number of decomposition levels are specified, "+
         "then the "+
         "last two values are used for the remaining resolutions.", null},
    };

    /** The source of quantized wavelet coefficients */
    protected CBlkQuantDataSrcEnc src;

    /**
     * Initializes the source of quantized wavelet coefficients.
     *
     * @param src The source of quantized wavelet coefficients.
     * */
    public EntropyCoder(CBlkQuantDataSrcEnc src) {
        super(src);
        this.src = src;
    }

    /**
     * Returns the code-block width for the specified tile and component.
     *
     * @param t The tile index
     * 
     * @param c the component index
     *
     * @return The code-block width for the specified tile and component
     * */
    public abstract int getCBlkWidth(int t, int c);
    
    /**
     * Returns the code-block height for the specified tile and component.
     *
     * @param t The tile index
     * 
     * @param c the component index
     *
     * @return The code-block height for the specified tile and component
     * */
    public abstract int getCBlkHeight(int t, int c);

    /**
     * Returns the reversibility of the tile-component data that is provided
     * by the object.  Data is reversible when it is suitable for lossless and
     * lossy-to-lossless compression.
     *
     * <P>Since entropy coders themselves are always reversible, it returns
     * the reversibility of the data that comes from the 'CBlkQuantDataSrcEnc'
     * source object (i.e. ROIScaler).
     *
     * @param t Tile index
     *
     * @param c Component index
     *
     * @return true is the data is reversible, false if not.
     *
     * @see jj2000.j2k.roi.encoder.ROIScaler
     * */
    public boolean isReversible(int t,int c) {
        return src.isReversible(t,c);
    }

    /**
     * Returns a reference to the root of subband tree structure representing
     * the subband decomposition for the specified tile-component.
     *
     * @param t The index of the tile.
     *
     * @param c The index of the component.
     *
     * @return The root of the subband tree structure, see Subband.
     *
     * @see SubbandAn
     *
     * @see Subband
     * */
    public SubbandAn getSubbandTree(int t,int c) {
        return src.getSubbandTree(t,c);
    }

    /**
     * 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.
     *
     * @return The horizontal coordinate of the origin of the cell and
     * code-block partitions, with respect to the canvas origin, on the
     * reference grid.
     * */
    public int getPartitionULX() {
        return src.getPartitionULX();
    }

    /**
     * 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.
     *
     * @return The vertical coordinate of the origin of the cell and
     * code-block partitions, with respect to the canvas origin, on the
     * reference grid.
     * */
    public int getPartitionULY() {
        return src.getPartitionULY();
    }

    /**
     * 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.
     *
     * @return the options name, their synopsis and their explanation, 
     * or null if no options are supported.
     * */
    public static String[][] getParameterInfo() {
        return pinfo;
    }

    /**
     * Creates a EntropyCoder object for the appropriate entropy coding
     * parameters in the parameter list 'pl', and having 'src' as the source
     * of quantized data.
     *
     * @param src The source of data to be entropy coded
     *
     * @param encSpec The encoder specifications
     *
     * @param pl The parameter list (or options).
     *
     * @exception IllegalArgumentException If an error occurs while parsing
     * the options in 'pl'
     * */
    public static EntropyCoder createInstance(CBlkQuantDataSrcEnc src,
                                              EncoderSpecs encSpec,
                                              ParameterList pl) {
        // Check parameters
        pl.checkList(OPT_PREFIX,pl.toNameArray(pinfo));
        return new StdEntropyCoder(src, encSpec);
    }
}