coswriter.java

非常有用的操作pdf文件的java源码

        {
            addObjectToWrite( root );
        }
        if( info != null )
        {
            addObjectToWrite( info );
        }
        

        while( objectsToWrite.size() > 0 )
        {
            COSBase nextObject = (COSBase)objectsToWrite.remove( 0 );
            doWriteObject( nextObject );
        }
        
        
        willEncrypt = false;
        
        if( encrypt != null )
        {
            addObjectToWrite( encrypt );
        }
        
        while( objectsToWrite.size() > 0 )
        {
            COSBase nextObject = (COSBase)objectsToWrite.remove( 0 );
            doWriteObject( nextObject );
        }

        // write all objects
        /**
        for (Iterator i = doc.getObjects().iterator(); i.hasNext();)
        {
            COSObject obj = (COSObject) i.next();
            doWriteObject(obj);
        }**/
    }

    private void addObjectToWrite( COSBase object )
    {
        COSBase actual = object;
        if( actual instanceof COSObject )
        {  
            actual = ((COSObject)actual).getObject();
        }
        
        if( !writtenObjects.contains( object ) &&
            !objectsToWrite.contains( object ) &&
            !actualsAdded.contains( actual ) )
        {
            objectsToWrite.add( object );
            if( actual != null )
            {
                actualsAdded.add( actual );
            }
        }
    }

    /**
     * This will write a COS object.
     *
     * @param obj The object to write.
     *
     * @throws COSVisitorException If there is an error visiting objects.
     */
    public void doWriteObject( COSBase obj ) throws COSVisitorException
    {
        try
        {
            writtenObjects.add( obj );
            // find the physical reference
            currentObjectKey = getObjectKey( obj );
            // add a x ref entry
            addXRefEntry( new COSWriterXRefEntry(getStandardOutput().getPos(), obj, currentObjectKey));
            // write the object
            getStandardOutput().write(String.valueOf(currentObjectKey.getNumber()).getBytes());
            getStandardOutput().write(SPACE);
            getStandardOutput().write(String.valueOf(currentObjectKey.getGeneration()).getBytes());
            getStandardOutput().write(SPACE);
            getStandardOutput().write(OBJ);
            getStandardOutput().writeEOL();
            obj.accept( this );
            getStandardOutput().writeEOL();
            getStandardOutput().write(ENDOBJ);
            getStandardOutput().writeEOL();
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * This will write the header to the PDF document.
     *
     * @param doc The document to get the data from.
     *
     * @throws IOException If there is an error writing to the stream.
     */
    protected void doWriteHeader(COSDocument doc) throws IOException
    {
        getStandardOutput().write( doc.getHeaderString().getBytes() );
        getStandardOutput().writeEOL();
        getStandardOutput().write(COMMENT);
        getStandardOutput().write(GARBAGE);
        getStandardOutput().writeEOL();
    }


    /**
     * This will write the trailer to the PDF document.
     *
     * @param doc The document to create the trailer for.
     *
     * @throws IOException If there is an IOError while writing the document.
     * @throws COSVisitorException If there is an error while generating the data.
     */
    protected void doWriteTrailer(COSDocument doc) throws IOException, COSVisitorException
    {
        getStandardOutput().write(TRAILER);
        getStandardOutput().writeEOL();

        COSDictionary trailer = doc.getTrailer();
        //sort xref, needed only if object keys not regenerated
        Collections.sort(getXRefEntries());
        COSWriterXRefEntry lastEntry = (COSWriterXRefEntry)getXRefEntries().get( getXRefEntries().size()-1);
        trailer.setInt(COSName.getPDFName("Size"), (int)lastEntry.getKey().getNumber()+1);
        trailer.removeItem( COSName.PREV );
        /**
        COSObject catalog = doc.getCatalog();
        if (catalog != null)
        {
            trailer.setItem(COSName.getPDFName("Root"), catalog);
        }
        */
        trailer.accept(this);

        getStandardOutput().write(STARTXREF);
        getStandardOutput().writeEOL();
        getStandardOutput().write(String.valueOf(getStartxref()).getBytes());
        getStandardOutput().writeEOL();
        getStandardOutput().write(EOF);
    }

    /**
     * write the x ref section for the pdf file
     *
     * currently, the pdf is reconstructed from the scratch, so we write a single section
     *
     * todo support for incremental writing?
     *
     * @param doc The document to write the xref from.
     *
     * @throws IOException If there is an error writing the data to the stream.
     */
    protected void doWriteXRef(COSDocument doc) throws IOException
    {
        String offset;
        String generation;

        // sort xref, needed only if object keys not regenerated
        Collections.sort(getXRefEntries());
        COSWriterXRefEntry lastEntry = (COSWriterXRefEntry)getXRefEntries().get( getXRefEntries().size()-1 );

        // remember the position where x ref is written
        setStartxref(getStandardOutput().getPos());
        //
        getStandardOutput().write(XREF);
        getStandardOutput().writeEOL();
        // write start object number and object count for this x ref section
        // we assume starting from scratch
        getStandardOutput().write(String.valueOf(0).getBytes());
        getStandardOutput().write(SPACE);
        getStandardOutput().write(String.valueOf(lastEntry.getKey().getNumber() + 1).getBytes());
        getStandardOutput().writeEOL();
        // write initial start object with ref to first deleted object and magic generation number
        offset = formatXrefOffset.format(0);
        generation = formatXrefGeneration.format(65535);
        getStandardOutput().write(offset.getBytes());
        getStandardOutput().write(SPACE);
        getStandardOutput().write(generation.getBytes());
        getStandardOutput().write(SPACE);
        getStandardOutput().write(XREF_FREE);
        getStandardOutput().writeCRLF();
        // write entry for every object
        long lastObjectNumber = 0;
        for (Iterator i = getXRefEntries().iterator(); i.hasNext();)
        {
            COSWriterXRefEntry entry = (COSWriterXRefEntry) i.next();
            while( lastObjectNumber<entry.getKey().getNumber()-1 )
            {
                offset = formatXrefOffset.format(0);
                generation = formatXrefGeneration.format(65535);
                getStandardOutput().write(offset.getBytes());
                getStandardOutput().write(SPACE);
                getStandardOutput().write(generation.getBytes());
                getStandardOutput().write(SPACE);
                getStandardOutput().write(XREF_FREE);
                getStandardOutput().writeCRLF();
                lastObjectNumber++;
            }
            lastObjectNumber = entry.getKey().getNumber();
            offset = formatXrefOffset.format(entry.getOffset());
            generation = formatXrefGeneration.format(entry.getKey().getGeneration());
            getStandardOutput().write(offset.getBytes());
            getStandardOutput().write(SPACE);
            getStandardOutput().write(generation.getBytes());
            getStandardOutput().write(SPACE);
            getStandardOutput().write(entry.isFree() ? XREF_FREE : XREF_USED);
            getStandardOutput().writeCRLF();
        }
    }

    /**
     * This will get the object key for the object.
     *
     * @param obj The object to get the key for.
     *
     * @return The object key for the object.
     */
    private COSObjectKey getObjectKey( COSBase obj )
    {
        COSBase actual = obj;
        if( actual instanceof COSObject )
        {
            actual = ((COSObject)obj).getObject();
        }
        COSObjectKey key = null;
        if( actual != null )
        {
            key = (COSObjectKey)objectKeys.get(actual);
        }
        if( key == null )
        {
            key = (COSObjectKey)objectKeys.get(obj);
        }
        if (key == null)
        {
            setNumber(getNumber()+1);
            key = new COSObjectKey(getNumber(),0);
            objectKeys.put(obj, key);
            if( actual != null )
            {
                objectKeys.put(actual, key);
            }
        }
        return key;
    }

    /**
     * visitFromArray method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromArray( COSArray obj ) throws COSVisitorException
    {
        try
        {
            int count = 0;
            getStandardOutput().write(ARRAY_OPEN);
            for (Iterator i = obj.iterator(); i.hasNext();)
            {
                COSBase current = (COSBase) i.next();
                if( current instanceof COSDictionary )
                {
                    addObjectToWrite( current );
                    writeReference( current );
                }
                else if( current instanceof COSObject )
                {
                    COSBase subValue = ((COSObject)current).getObject();
                    if( subValue instanceof COSDictionary || subValue == null )
                    {
                        addObjectToWrite( current );
                        writeReference( current );
                    }
                    else
                    {
                        subValue.accept( this );
                    }
                }
                else if( current == null )
                {
                    COSNull.NULL.accept( this );
                }
                else
                {
                    current.accept(this);
                }
                count++;
                if (i.hasNext())
                {
                    if (count % 10 == 0)
                    {
                        getStandardOutput().writeEOL();
                    }
                    else
                    {
                        getStandardOutput().write(SPACE);
                    }
                }
            }
            getStandardOutput().write(ARRAY_CLOSE);
            getStandardOutput().writeEOL();
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromBoolean method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromBoolean(COSBoolean obj) throws COSVisitorException
    {
        
        try
        {
            obj.writePDF( getStandardOutput() );
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromDictionary method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromDictionary(COSDictionary obj) throws COSVisitorException
    {
        try
        {
            getStandardOutput().write(DICT_OPEN);
            getStandardOutput().writeEOL();
            for (Iterator i = obj.keyList().iterator(); i.hasNext();)
            {
                COSName name = (COSName) i.next();
                COSBase value = obj.getItem(name);
                if (value != null)
                {
                    name.accept(this);
                    getStandardOutput().write(SPACE);