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 );
}
}
}
}