imgreaderpgx.java

jpeg2000算法实现

/*
 * CVS identifier:
 *
 * $Id: ImgReaderPGX.java,v 1.10 2001/03/01 09:11:28 grosbois Exp $
 *
 * Class:                   ImgReaderPGX
 *
 * Description:             Image Reader for PGX files (custom file format
 *                          for VM3A)
 *
 *
 *
 * 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.image.input;

import jj2000.j2k.image.*;
import jj2000.j2k.io.*;
import jj2000.j2k.*;

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

/**
 * This class extends the ImgReader abstract class for reading PGX files. PGX
 * is a custom monochrome file format invented specifically to simplify the
 * use of JPEG 2000 with images of different bit-depths in the range 1 to 31
 * bits per pixel.
 *
 * <P>The file consists of a one line text header followed by the binary data.
 * <P><u>Header:</u><br>
 * <tt>"PG"+ <i>ws</i> +&lt;<i>endianess</i>&gt;+ <i>ws</i> +<i>[sign]</i>+ 
 * <i>ws</i> + &lt;<i>bit-depth</i>&gt;+" "+&lt;<i>width</i>&gt;+" "+
 * &lt;<i>height</i>&gt;+'\n'</tt><br>
 * where:<br>
 * - <i>ws</i>(white-spaces) is any combination of characters <tt>' '</tt> and 
 * <tt>'\t'</tt>.<br>
 * - <i>endianess</i> equals <tt>"LM"</tt> or <tt>"ML"</tt>(resp. little-endian
 * or big-endian).<br>
 * - <i>sign</i> equals "+" or "-" (resp. unsigned or signed). If ommited, 
 * default value is unsigned.<br>
 * - <i>bit-depth</i> can be any number between 1 and 31.<br>
 * - <i>width</i> and <i>height</i> are the image dimensions (in pixels).<br>
 * <u>Datas:</u><br>
 * The image binary datas appear one after the other(in raster order) 
 * immediatly after the last header character('\n') and are byte-aligned (they
 * are packed into 1,2 or 4 bytes per sample, depending upon the 
 * <i>bit-depth</i> value).
 *
 * <P> If the data is unisigned, level shifting is applied subtracting
 * 2^(bitdepth - 1)
 *
 * <P>Since it is not possible to know the input file byte-ordering
 * before reading its header, this class can not be construct from a
 * RandomAccessIO. So, the constructor has to open first the input file,
 * to read only its header, and then it can create the appropriate 
 * BufferedRandomAccessFile (Big-Endian or Little-Endian byte-ordering).
 *
 * <P>NOTE: This class is not thread safe, for reasons of internal buffering.
 *
 * @see ImgData
 * @see RandomAccessIO
 * @see BufferedRandomAccessFile
 * @see BEBufferedRandomAccessFile
 * */
public class ImgReaderPGX extends ImgReader implements EndianType{

    /** The offset of the raw pixel data in the PGX file */
    private int offset;

    /** The RandomAccessIO where to get datas from */
    private RandomAccessFile in;

    /** The bit-depth of the input file (must be between 1 and 31)*/
    private int bitDepth;

    /** Whether the input datas are signed or not */
    private boolean isSigned;


    /** The pack length of one sample (in bytes, according to the output
        bit-depth */
    private int packBytes;

    /** The byte ordering to use, as defined in EndianType */
    private int byteOrder;
    
    /** The line buffer. */
    // This makes the class not thrad safe
    // (but it is not the only one making it so)
    private byte buf[];

    /** Temporary DataBlkInt object (needed when encoder uses floating-point
        filters). This avoid allocating new DataBlk at each time */
    private DataBlkInt intBlk;

    /**
     * Creates a new PGX file reader from the specified File object.
     *
     * @param in The input file as File object.
     *
     * @exception IOException If an I/O error occurs.
     * */
    public ImgReaderPGX(File in) throws IOException{
        String header;

        // Check if specified file exists
        if(!in.exists()) {
            throw new IllegalArgumentException("PGX file "+in.getName()+
                                               " does not exist");
        }

        //Opens the given file
        this.in = new RandomAccessFile(in,"r");
        try{
            header = this.in.readLine();
        }
        catch(IOException e){
            throw new IOException(in.getName()+" is not a PGX file");
        }
        if (header == null) {
            throw new IOException(in.getName()+" is an empty file");
        }
        offset = (header.length()+1);

        //Get informations from header
        StringTokenizer st = new StringTokenizer(header);
        try{
            int nTokens = st.countTokens();

            // Magic Number
            if(!(st.nextToken()).equals("PG"))
                throw new IOException(in.getName()+" is not a PGX file");

            // Endianess
            String tmp = st.nextToken();
            if(tmp.equals("LM"))
                byteOrder = LITTLE_ENDIAN;
            else if(tmp.equals("ML"))
                byteOrder = BIG_ENDIAN;
            else
                throw new IOException(in.getName()+" is not a PGX file");

            // Unsigned/signed if present in the header
            if (nTokens==6) {
                tmp = st.nextToken();
                if(tmp.equals("+"))
                isSigned = false;
            else if(tmp.equals("-"))
                isSigned = true;
            else
                throw new IOException(in.getName()+" is not a PGX file");
            }

            // bit-depth, width, height
            try{
                bitDepth = (new Integer(st.nextToken())).intValue();
                // bitDepth must be between 1 and 31
                if((bitDepth<=0)||(bitDepth>31))
                throw new IOException(in.getName()+
                    " is not a valid PGX file");

                w = (new Integer(st.nextToken())).intValue();
                h = (new Integer(st.nextToken())).intValue();
            }
            catch(NumberFormatException e){
                throw new IOException(in.getName()+" is not a PGX file");
            }
        }
        catch(NoSuchElementException e){
            throw new IOException(in.getName()+" is not a PGX file");
        }

        // Number of component
        nc = 1;

        // Number of bytes per data
        if(bitDepth<=8)
            packBytes = 1;
        else if(bitDepth<=16)
            packBytes = 2;
        else // <= 31
            packBytes = 4;
    }

    /**
     * Creates a new PGX file reader from the specified file name.
     *
     * @param inName The input file name.
     * */
    public ImgReaderPGX(String inName) throws IOException{
        this(new File(inName));
    }

    /**
     * Closes the underlying RandomAccessIO from where the image data is being
     * read. No operations are possible after a call to this method.
     *
     * @exception IOException If an I/O error occurs.
     * */
    public void close() throws IOException {
        in.close();
        in = null;
        buf = null;
    }

    /**
     * Returns the number of bits corresponding to the nominal range of the
     * data in the specified component. This is the value of bitDepth which is
     * read in the PGX file header.
     *
     * <P>If this number is <i>b</b> then the nominal range is between
     * -2^(b-1) and 2^(b-1)-1, for originally signed or unsigned data
     * (unsigned data is level shifted to have a nominal average of 0).
     *
     * @param c The index of the component.
     *
     * @return The number of bits corresponding to the nominal range of the
     * data.
     * */
    public int getNomRangeBits(int c) {
        // Check component index
        if (c != 0)
            throw new IllegalArgumentException();

        return bitDepth;
    }

    /**
     * Returns the position of the fixed point in the specified component
     * (i.e. the number of fractional bits), which is always 0 for this
     * ImgReader.
     *
     * @param c The index of the component.
     *
     * @return The position of the fixed-point (i.e. the number of fractional
     * bits). Always 0 for this ImgReader.
     * */
    public int getFixedPoint(int c) {
        // Check component index
        if (c != 0)
            throw new IllegalArgumentException();
        return 0;
    }
  
    /**
     * Returns, in the blk argument, the block of image data containing the
     * specifed rectangular area, in the specified component. The data is
     * returned, as a reference to the internal data, if any, instead of as a
     * copy, therefore the returned data should not be modified.
     *
     * <P> After being read the coefficients are level shifted by subtracting
     * 2^(nominal bit range - 1)
     *
     * <P>The rectangular area to return is specified by the 'ulx', 'uly', 'w'
     * and 'h' members of the 'blk' argument, relative to the current
     * tile. These members are not modified by this method. The 'offset' and
     * 'scanw' of the returned data can be arbitrary. See the 'DataBlk' class.
     *
     * <P>If the data array in <tt>blk</tt> is <tt>null</tt>, then a new one
     * is created if necessary. The implementation of this interface may
     * choose to return the same array or a new one, depending on what is more
     * efficient. Therefore, the data array in <tt>blk</tt> prior to the
     * method call should not be considered to contain the returned data, a
     * new array may have been created. Instead, get the array from
     * <tt>blk</tt> after the method has returned.
     *
     * <P>The returned data always has its 'progressive' attribute unset
     * (i.e. false).
     *
     * <P>When an I/O exception is encountered the JJ2KExceptionHandler is
     * used. The exception is passed to its handleException method. The action