pdstream.java

非常有用的操作pdf文件的java源码

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 * Copyright (c) 2004-2005, www.pdfbox.org
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
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 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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package org.pdfbox.pdmodel.common;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.pdfbox.cos.COSArray;
import org.pdfbox.cos.COSBase;
import org.pdfbox.cos.COSDictionary;
import org.pdfbox.cos.COSName;
import org.pdfbox.cos.COSStream;

import org.pdfbox.filter.Filter;
import org.pdfbox.filter.FilterManager;

import org.pdfbox.pdmodel.PDDocument;

import org.pdfbox.pdmodel.common.filespecification.PDFileSpecification;

/**
 * A PDStream represents a stream in a PDF document.  Streams are tied to a single
 * PDF document.
 *
 * @author <a href="mailto:[e-mail]">Ben Litchfield</a>
 * @version $Revision: 1.16 $
 */
public class PDStream implements COSObjectable
{
    private COSStream stream;
    
    /**
     * This will create a new PDStream object.
     */
    protected PDStream()
    {
        //should only be called by PDMemoryStream
    }
    
    /**
     * This will create a new PDStream object.
     * 
     * @param document The document that the stream will be part of.
     */
    public PDStream( PDDocument document )
    {
        stream = new COSStream( document.getDocument().getScratchFile() );
    }
    
    /**
     * Constructor.
     *
     * @param str The stream parameter.
     */
    public PDStream( COSStream str )
    {
        stream = str;
    }
    
    /**
     * Constructor.  Reads all data from the input stream and embeds it into the
     * document, this will close the InputStream.
     *
     * @param doc The document that will hold the stream.
     * @param str The stream parameter.
     * @throws IOException If there is an error creating the stream in the document.
     */
    public PDStream( PDDocument doc, InputStream str ) throws IOException
    {
        this( doc, str, false );
    }
    
    /**
     * Constructor.  Reads all data from the input stream and embeds it into the
     * document, this will close the InputStream.
     *
     * @param doc The document that will hold the stream.
     * @param str The stream parameter.
     * @param filtered True if the stream already has a filter applied.
     * @throws IOException If there is an error creating the stream in the document.
     */
    public PDStream( PDDocument doc, InputStream str, boolean filtered ) throws IOException
    {
        OutputStream output = null;
        try
        {
            stream = new COSStream( doc.getDocument().getScratchFile() );
            if( filtered )
            {
                output = stream.createFilteredStream();
            }
            else
            {
                output = stream.createUnfilteredStream();
            }
            byte[] buffer = new byte[ 1024 ];
            int amountRead = -1;
            while( (amountRead = str.read(buffer)) != -1 )
            {
                output.write( buffer, 0, amountRead );
            }
        }
        finally
        {
            if( output != null )
            {
                output.close();
            }
            if( str != null )
            {
                str.close();
            }
        }
    }
    
    /**
     * If there are not compression filters on the current stream then this
     * will add a compression filter, flate compression for example.
     */
    public void addCompression()
    {
        List filters = getFilters();
        if( filters == null )
        {
            filters = new ArrayList();
            filters.add( COSName.FLATE_DECODE );
            setFilters( filters );
        }
    }
    
    /**
     * Create a pd stream from either a regular COSStream on a COSArray of cos streams.
     * @param base Either a COSStream or COSArray.
     * @return A PDStream or null if base is null.
     * @throws IOException If there is an error creating the PDStream.
     */
    public static PDStream createFromCOS( COSBase base ) throws IOException
    {
        PDStream retval = null;
        if( base instanceof COSStream )
        {
            retval = new PDStream( (COSStream)base );
        }
        else if( base instanceof COSArray )
        {
            retval = new PDStream( new COSStreamArray( (COSArray)base ) );
        }
        else
        {
            if( base != null )
            {
                throw new IOException( "Contents are unknown type:" + base.getClass().getName() );
            }
        }
        return retval;
    }


    /**
     * Convert this standard java object to a COS object.
     *
     * @return The cos object that matches this Java object.
     */
    public COSBase getCOSObject()
    {
        return stream;
    }
    
    /**
     * This will get a stream that can be written to.
     * 
     * @return An output stream to write data to.
     * 
     * @throws IOException If an IO error occurs during writing.
     */
    public OutputStream createOutputStream() throws IOException
    {
        return stream.createUnfilteredStream();
    }
    
    /**
     * This will get a stream that can be read from.
     * 
     * @return An input stream that can be read from.
     * 
     * @throws IOException If an IO error occurs during reading.
     */
    public InputStream createInputStream() throws IOException
    {
        return stream.getUnfilteredStream();
    }
    
    /**
     * This will get a stream with some filters applied but not others.  This is useful
     * when doing images, ie filters = [flate,dct], we want to remove flate but leave dct
     * 
     * @param stopFilters A list of filters to stop decoding at.
     * @return A stream with decoded data.
     * @throws IOException If there is an error processing the stream.
     */
    public InputStream getPartiallyFilteredStream( List stopFilters ) throws IOException
    {
        FilterManager manager = stream.getFilterManager();
        InputStream is = stream.getFilteredStream();
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        List filters = getFilters();
        Iterator iter = filters.iterator();
        String nextFilter = null;
        boolean done = false;
        while( iter.hasNext() && !done )
        {
            os.reset();
            nextFilter = (String)iter.next();
            if( stopFilters.contains( nextFilter ) )
            {
                done = true;
            }
            else
            {
                Filter filter = manager.getFilter( COSName.getPDFName(nextFilter) );
                filter.decode( is, os, stream );
                is = new ByteArrayInputStream( os.toByteArray() );
            }
        }
        return is;
    }
    
    /**
     * Get the cos stream associated with this object.
     *
     * @return The cos object that matches this Java object.
     */
    public COSStream getStream()
    {