imgwriterpgm.java

jpeg2000算法实现

/*
 * CVS identifier:
 *
 * $Id: ImgWriterPGM.java,v 1.10 2001/01/24 15:01:27 grosbois Exp $
 *
 * Class:                   ImgWriterRawPGM
 *
 * Description:             Image writer for unsigned 8 bit data in
 *                          PGM file format.
 *
 *
 *
 * 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.output;

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

/**
 * This class writes a component from an image in 8 bit unsigned data to a
 * binary PGM file. The size of the image that is written to the file is the
 * size of the component from which to get the data, not the size of the
 * source image (they differ if there is some sub-sampling).
 *
 * <P>Before writing, all coefficients are inversly level shifted and then
 * "saturated" (they are limited to the nominal dynamic range).<br> <u>Ex:</u>
 * if the nominal range is 0-255, the following algorithm is applied:<br>
 * <tt>if coeff<0, output=0<br> if coeff>255, output=255<br> else
 * output=coeff</tt>
 *
 * <P>The write() methods of an object of this class may not be called
 * concurrently from different threads.
 *
 * <P>NOTE: This class is not thread safe, for reasons of internal buffering.
 * */
public class ImgWriterPGM extends ImgWriter {

    /** Value used to inverse level shift */
    private int levShift;

    /** Where to write the data */
    private RandomAccessFile out;

    /** The index of the component from where to get the data */
    private int c;

    /** The number of fractional bits in the source data */
    private int fb;

    /** A DataBlk, just used to avoid allocating a new one each time
        it is needed */
    private DataBlkInt db = new DataBlkInt();

    /** The offset of the raw pixel data in the PGM file */
    private int offset;
    
    /** The line buffer. */
    // This makes the class not thrad safe
    // (but it is not the only one making it so)
    private byte buf[];

    /**
     * Creates a new writer to the specified File object, to write data from
     * the specified component.
     *
     * <P>The size of the image that is written to the file is the size of the
     * component from which to get the data, specified by b, not the size of
     * the source image (they differ if there is some sub-sampling).
     *
     * @param out The file where to write the data
     *
     * @param imgSrc The source from where to get the image data to
     * write.
     *
     * @param c The index of the component from where to get the data.
     * */
    public ImgWriterPGM(File out, 
			BlkImgDataSrc imgSrc, int c) throws IOException{
        // Check that imgSrc is of the correct type
        // Check that the component index is valid
        if( (c<0) || ( c>=imgSrc.getNumComps() ) || 
            ( imgSrc.getNomRangeBits(c)>8 ) )
            throw new IllegalArgumentException();

        // Initialize
        if( out.exists() && !out.delete() ){
            throw new IOException("Could not reset file");
        }
        this.out = new RandomAccessFile(out,"rw");
        src = imgSrc;
        this.c = c;
        w = imgSrc.getCompImgWidth(c);
        h = imgSrc.getCompImgHeight(c);
        fb = imgSrc.getFixedPoint(c);
        levShift = 1<< (imgSrc.getNomRangeBits(c)-1);

        writeHeaderInfo();
    }

    /**
     * Creates a new writer to the specified file, to write data from the
     * specified component.
     *
     * <P>The size of the image that is written to the file is the size of the
     * component from which to get the data, specified by b, not the size of
     * the source image (they differ if there is some sub-sampling).
     *
     * @param fname The name of the file where to write the data
     *
     * @param imgSrc The source from where to get the image data to
     * write.
     *
     * @param c The index of the component from where to get the data.
     * */
    public ImgWriterPGM(String fname, 
                        BlkImgDataSrc imgSrc, int c) throws IOException{
        this(new File(fname), imgSrc, c);
    }
              
    /**
     * Closes the underlying file or netwrok connection to where the data is
     * written. Any call to other methods of the class become illegal after a
     * call to this one.
     *
     * @exception IOException If an I/O error occurs.
     * */
    public void close() throws IOException {
        int i;
        // Finish writing the file, writing 0s at the end if the data at end
        // has not been written.
        if (out.length() != w*h+offset) {
            // Goto end of file
            out.seek(out.length());
            // Fill with 0s
            for (i = offset+w*h-(int)out.length(); i >0; i--) {
                out.writeByte(0);
            }
        }
        out.close();
        src = null;
        out = null;
        db = null;
    }

    /**
     * Writes all buffered data to the file or resource.
     *
     * @exception IOException If an I/O error occurs.
     * */
    public void flush() throws IOException {
        // No flush needed here since we are using a RandomAccessFile
        // Get rid of line buffer (is this a good choice?)
        buf = null;
    }

    /**
     * Writes the data of the specified area to the file, coordinates are
     * relative to the current tile of the source. Before writing, the
     * coefficients are limited to the nominal range.
     *
     * <P>This method may not be called concurrently from different threads.
     *
     * <P>If the data returned from the BlkImgDataSrc source is progressive,
     * then it is requested over and over until it is not progressive anymore.
     *
     * @param ulx The horizontal coordinate of the upper-left corner of the
     * area to write, relative to the current tile.
     *
     * @param uly The vertical coordinate of the upper-left corner of the area
     * to write, relative to the current tile.
     *
     * @param width The width of the area to write.
     *
     * @param height The height of the area to write.
     *
     * @exception IOException If an I/O error occurs.
     * */
    public void write(int ulx, int uly, int w, int h) throws IOException{
        int k,i,j;
        int fracbits = fb;     // In local variable for faster access
        int tOffx, tOffy;      // Active tile offset in the X and Y direction

        // Initialize db
        db.ulx = ulx;
        db.uly = uly;
        db.w = w;
        db.h = h;
        // Get the current active tile offset
        tOffx = src.getULX(c)-
            (src.getImgULX()+src.getCompSubsX(c)-1)/src.getCompSubsX(c);
        tOffy = src.getULY(c)-
            (src.getImgULY()+src.getCompSubsY(c)-1)/src.getCompSubsY(c);
        // Check the array size
        if (db.data != null && db.data.length < w*h) {
            // A new one will be allocated by getInternCompData()
            db.data = null;
        }
        // Request the data and make sure it is not
        // progressive
        do {
            db = (DataBlkInt)src.getInternCompData(db,c);
        } while (db.progressive);

        // variables used during coeff saturation
        int 
            tmp, 
            maxVal= (1<<src.getNomRangeBits(c))-1;

        // Check line buffer
        if (buf == null || buf.length < w) {
            buf = new byte[w]; // Expand buffer
        }

        // Write line by line
        for (i = 0; i < h; i++) {
            // Skip to beggining of line in file
            out.seek(this.offset+this.w*(uly+tOffy+i)+ulx+tOffx);
            // Write all bytes in the line
            if (fracbits == 0) {
                for (k = db.offset+i*db.scanw+w-1, j = w-1; j >= 0; j--, k--) {
                    tmp = db.data[k]+levShift;
                    buf[j] = (byte)((tmp < 0) ? 0 : ((tmp > maxVal) ?
                                                     maxVal : tmp));
                }
            }
            else {
                for (k = db.offset+i*db.scanw+w-1, j = w-1; j >= 0; j--, k--) {
                    tmp = (db.data[k]>>fracbits)+levShift;
                    buf[j] = (byte)((tmp < 0) ? 0 : ((tmp > maxVal) ?
                                                     maxVal : tmp));
                }
            }
            out.write(buf,0,w);
        }
    }
    
    /**
     * Writes the source's current tile to the output. The requests of data
     * issued to the source BlkImgDataSrc object are done by strips, in order
     * to reduce memory usage.
     *
     * <P>If the data returned from the BlkImgDataSrc source is progressive,
     * then it is requested over and over until it is not progressive anymore.
     *
     * @exception IOException If an I/O error occurs.
     *
     * @see DataBlk
     * */
    public void write() throws IOException {
        int i;
        int tw = src.getCompWidth(c);  // Tile width
        int th = src.getCompHeight(c);  // Tile height
        // Write in strips
        for (i=0; i <th ; i+=DEF_STRIP_HEIGHT) {
            write(0,i,tw,(th-i < DEF_STRIP_HEIGHT) ? th-i : DEF_STRIP_HEIGHT);
        }
    }
    
    /**
     * Writes the header info of the PGM file :
     *
     * P5
     * width height
     * 255
     *
     * @exception IOException If there is an IOException
     * */
     private void writeHeaderInfo() throws IOException{
        byte[] byteVals;
        int i;
        String val;
        
        // write 'P5' to file
        out.writeByte('P'); // 'P'
        out.write('5'); // '5'
        out.write('\n'); // newline
        offset=3;
        // Write width in ASCII
        val=String.valueOf(w);
        byteVals=val.getBytes();
        for(i=0;i<byteVals.length;i++){
            out.writeByte(byteVals[i]);
            offset++;
        }
        out.write(' '); // blank
        offset++;
        // Write height in ASCII
        val=String.valueOf(h);
        byteVals=val.getBytes();
        for(i=0;i<byteVals.length;i++){
            out.writeByte(byteVals[i]);
            offset++;
        }
        // Write maxval
        out.write('\n'); // newline
        out.write('2'); // '2'
        out.write('5'); // '5'
        out.write('5'); // '5'
        out.write('\n'); // newline
        offset+=5;
     }
     
    /**
     * Returns a string of information about the object, more than 1 line
     * long. The information string includes information from the underlying
     * RandomAccessFile (its toString() method is called in turn).
     *
     * @return A string of information about the object.
     * */
    public String toString() {
        return "ImgWriterPGM: WxH = " + w + "x" + h + ", Component = " +
            c + "\nUnderlying RandomAccessFile:\n" + out.toString();
    }
}