PageStamper.cs :  » PDF » PDF-Clown » it » stefanochizzolini » clown » tools » C# / CSharp Open Source

/*
  Copyright 2007 Stefano Chizzolini. http://clown.stefanochizzolini.it

  Contributors:
    * Stefano Chizzolini (original code developer, http://www.stefanochizzolini.it)

  This file should be part of the source code distribution of "PDF Clown library"
  (the Program): see the accompanying README files for more info.

  This Program is free software; you can redistribute it and/or modify it under
  the terms of the GNU General Public License as published by the Free Software
  Foundation; either version 2 of the License, or (at your option) any later version.

  This Program is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY, either expressed or implied; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the License for more details.

  You should have received a copy of the GNU General Public License along with this
  Program (see README files); if not, go to the GNU website (http://www.gnu.org/).

  Redistribution and use, with or without modification, are permitted provided that such
  redistributions retain the above copyright notice, license and disclaimer, along with
  this list of conditions.
*/

using it.stefanochizzolini.clown.documents;
using it.stefanochizzolini.clown.documents.contents;
using it.stefanochizzolini.clown.documents.contents.composition;
using it.stefanochizzolini.clown.documents.contents.objects;
using it.stefanochizzolini.clown.files;
using it.stefanochizzolini.clown.objects;

namespace it.stefanochizzolini.clown.tools{
  /**
    <summary>Tool for content insertion inside an existing page.</summary>
  */
  public class PageStamper
  {
    #region dynamic
    #region fields
    private Page page;

    private PrimitiveFilter background;
    private PrimitiveFilter foreground;
    #endregion

    #region constructors
    public PageStamper(
      ) : this(null)
    {}

    public PageStamper(
      Page page
      )
    {Page = page;}
    #endregion

    #region interface
    #region public
    public void Flush(
      )
    {
      // Ensuring that there's room for the new content chunks inside the page's content stream...
      /*
        NOTE: This specialized stamper is optimized for content insertion without modifying
        existing content representations, leveraging the peculiar feature of page structures
        to express their content streams as arrays of data streams.
      */
      PdfArray streams;
      {
        PdfDirectObject contentsObject = page.BaseDataObject[PdfName.Contents];
        PdfDataObject contentsDataObject = File.Resolve(contentsObject);
        // Single data stream?
        if(contentsDataObject is PdfStream)
        {
          /*
            NOTE: Content stream MUST be expressed as an array of data streams in order to host
            background- and foreground-stamped contents.
          */
          streams = new PdfArray();
          streams.Add(contentsObject);
          page.BaseDataObject[PdfName.Contents] = streams;

          page.Update(); // Fundamental to override original page contents collection.
        }
        else
        {
          streams = (PdfArray)contentsDataObject;

          if(!File.Update(contentsObject))
          {page.Update();} // Fundamental to override original page contents collection.
        }
      }

      // Background.
      // Serialize the content!
      background.Flush();
      // Insert the serialized content into the page's content stream!
      streams.Insert(
        0,
        (PdfReference)background.Scanner.Contents.BaseObject
        );

      // Foreground.
      // Serialize the content!
      foreground.Flush();
      // Append the serialized content into the page's content stream!
      streams.Add(
        (PdfReference)foreground.Scanner.Contents.BaseObject
        );
    }

    public PrimitiveFilter Background
    {get{return background;}}

    public PrimitiveFilter Foreground
    {get{return foreground;}}

    public Page Page
    {
      get{return page;}
      set
      {
        page = value;
        if(page == null)
        {
          background = null;
          foreground = null;
        }
        else
        {
          // Background.
          background = CreateFilter();
          // Open the background local state!
          background.Add(SaveGraphicsState.Value);
          // Close the background local state!
          background.Add(RestoreGraphicsState.Value);
          // Open the middleground local state!
          background.Add(SaveGraphicsState.Value);
          // Move into the background!
          background.Scanner.MoveFirst();

          // Foregrond.
          foreground = CreateFilter();
          // Close the middleground local state!
          foreground.Add(RestoreGraphicsState.Value);
        }
      }
    }
    #endregion

    #region private
    private PrimitiveFilter CreateFilter(
      )
    {
      PdfReference reference = page.File.Register(new PdfStream());

      return new PrimitiveFilter(
        new ContentScanner(
          new Contents(
            reference,
            reference.IndirectObject,
            page
            )
          )
        );
    }
    #endregion
    #endregion
    #endregion
  }
}