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PDF Image Caching (Performance and size improvement)
http://forum.pdfsharp.net/viewtopic.php?f=4&t=2416
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Author:  zanadar [ Wed Apr 24, 2013 2:25 am ]
Post subject:  PDF Image Caching (Performance and size improvement)

Okay so i can't attach the code... here it is (ridiculous forum!!!).
It uses a MD5 hash of the gif version of the image for uniqueness.

PS: Why on earth is this project not open source so that we can contribute properly?

Code file PdfSharp.Pdf.Advanced\PdfImageTable.cs
Code:
#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange (mailto:Stefan.Lange@pdfsharp.com)
//
// Copyright (c) 2005-2009 empira Software GmbH, Cologne (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
#endregion

using System;
using System.Diagnostics;
using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.IO;
using PdfSharp.Drawing;
using PdfSharp.Internal;

namespace PdfSharp.Pdf.Advanced
{
  /// <summary>
  /// Contains all used images of a document.
  /// </summary>
  internal sealed class PdfImageTable : PdfResourceTable
  {
    /// <summary>
    /// Initializes a new instance of this class, which is a singleton for each document.
    /// </summary>
    public PdfImageTable(PdfDocument document)
      : base(document)
    { }

    /// <summary>
    /// Gets a PdfImage from an XImage. If no PdfImage already exists, a new one is created.
    /// </summary>
    public PdfImage GetImage(XImage image)
    {
      PdfImageTable.ImageSelector selector = image.selector;
      if (selector == null)
      {
        selector = new ImageSelector(image);
        image.selector = selector;
      }
      PdfImage pdfImage;
      if (!this.images.TryGetValue(selector, out pdfImage))
      {
        pdfImage = new PdfImage(this.owner, image);
        //pdfImage.Document = this.document;
        Debug.Assert(pdfImage.Owner == this.owner);
        this.images[selector] = pdfImage;
        //if (this.document.EarlyWrite)
        //{
        //  //pdfFont.Close(); delete
        //  //pdfFont.AssignObjID(ref this.document.ObjectID); // BUG just test code!!!!
        //  //pdfFont.WriteObject(null);
        //}
      }
      return pdfImage;
    }

    /// <summary>
    /// Map from ImageSelector to PdfImage.
    /// </summary>
   readonly SortedList<ImageSelector, PdfImage> images = new SortedList<ImageSelector, PdfImage>();

    /// <summary>
    /// A collection of information that uniquely identifies a particular PdfImage.
    /// </summary>
    public class ImageSelector : IComparable<ImageSelector>
    {
      private string hash = null;

      /// <summary>
      /// Initializes a new instance of ImageSelector from an XImage.
      /// </summary>
      public ImageSelector(XImage image)
     {
      using( MemoryStream stream = new MemoryStream() )
      {
         // use the image in gif format for uniqueness check
         image.gdiImage.Save( stream, System.Drawing.Imaging.ImageFormat.Gif );
         stream.Seek( 0, SeekOrigin.Begin );
         System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create();
         byte[] hashBytes = md5.ComputeHash( stream );
         StringBuilder sb = new StringBuilder();
         for( int i = 0; i < hashBytes.Length; i++ )
         {
            sb.Append( hashBytes[ i ].ToString( "X2" ) );
         }
         this.hash = sb.ToString();
      }
     }

     public string GetHash()
     {
        return this.hash;
     }

     public int CompareTo( ImageSelector selector )
     {
        if( selector == null )
           return -1;
        return string.Compare( this.hash, selector.GetHash(), true );
     }
    }
  }
}

Author:  Thomas Hoevel [ Wed Apr 24, 2013 8:12 am ]
Post subject:  Re: PDF Image Caching (Performance and size improvement)

zanadar wrote:
Okay so i can't attach the code... here it is (ridiculous forum!!!).
Well, you can attach code in ZIP files. And you can use the CODE tag to make code in posts more readable.
See also:
viewtopic.php?f=2&t=832

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