Steganography IX - The Cross-Format Solution

/* This class has been written by
 * Corinna John (Hannover, Germany)
 * picturekey@binary-universe.net
 * 
 * You can use the code in any context you like,
 * as long as you do not delete this comment.
 * 
 * Please send me a little feedback about what you're
 * using this code for and what changes you'd like to
 * see in later versions. (And please excuse my bad english)
 * 
 * WARNING: This is experimental code.
 * Some bugs and flaws have been left in there,
 * to keep the code readable to people who want
 * to understand the algorithm.
 * Please do not expect "Release Quality".
 * */

using System;
using System.IO;
using System.Drawing;
using System.Windows.Forms;

namespace SteganoDemo
{
	/// <summary>
	/// Zusammendfassende Beschreibung f�r AviUtility.
	/// </summary>
	public class AviUtility : FileUtility
	{
		private const String TempSourceFileName = "steganodemo_temp1.bmp";
		private const String TempDestinationFileName = "steganodemo_temp2.bmp";

		public override void Hide(Stream messageStream, Stream keyStream){
			AviWriter aviWriter = new AviWriter();
			AviReader aviReader = new AviReader();
			ImageUtility utility = new ImageUtility();

			aviReader.Open(carrierFile.SourceFileName);
			aviWriter.Open(carrierFile.DestinationFileName, aviReader.FrameRate);
			
			String fileName = Application.ExecutablePath;
			int index = fileName.LastIndexOf("\\")+1;
			CarrierFile frameCarrierFile = new CarrierFile(
				fileName.Substring(0, index) + TempSourceFileName,
				fileName.Substring(0, index) + TempDestinationFileName,
				0,
				carrierFile.CountBitsToHidePerCarrierUnit,
				carrierFile.NoisePercent );
			
			//ignore length of entire message
			byte[] buffer = new Byte[messageStream.Length - 4];
			messageStream.Seek(4, SeekOrigin.Begin);
			messageStream.Read(buffer, 0, buffer.Length);
			messageStream.SetLength(buffer.Length);
			messageStream.Seek(0, SeekOrigin.Begin);
			messageStream.Write(buffer, 0, buffer.Length);
			messageStream.Seek(0, SeekOrigin.Begin);
			
			Bitmap bmp;
			Stream messageWithCount = null;
			for(int frameIndex=0; frameIndex<aviReader.CountFrames; frameIndex++){
				//export a frame
                aviReader.ExportBitmap(frameIndex, frameCarrierFile.SourceFileName);

                //pass the frame to ImageUtility
				utility.Initialize(frameCarrierFile);
				frameCarrierFile.CountUseableCarrierUnits = utility.CountUseableUnits(keyStream);
				frameCarrierFile.CountBytesToHide = (Int32)Math.Ceiling( (float)carrierFile.CountBytesToHide * ((float)frameCarrierFile.CountUseableCarrierUnits / carrierFile.CountCarrierUnits) );
				
				messageWithCount = FileUtility.GetMessagePart(messageStream, frameCarrierFile.CountBytesToHide);
				utility.Hide(messageWithCount, keyStream);
			
				//add the new frame
				bmp = (Bitmap)Image.FromFile(frameCarrierFile.DestinationFileName);
				aviWriter.AddFrame(bmp);
				bmp.Dispose();
			}
			messageWithCount.Close();
			
			//delete temporary files
			if(File.Exists(frameCarrierFile.SourceFileName)){ File.Delete(frameCarrierFile.SourceFileName); }
			if(File.Exists(frameCarrierFile.DestinationFileName)){ File.Delete(frameCarrierFile.DestinationFileName); }

			aviReader.Close();
			aviWriter.Close();
		}

		public override void Extract(Stream messageStream, Stream keyStream){
			AviReader aviReader = new AviReader();
			ImageUtility utility = new ImageUtility();

			aviReader.Open(carrierFile.SourceFileName);
			
			String fileName = Application.ExecutablePath;
			int index = fileName.LastIndexOf("\\")+1;
			CarrierFile frameCarrierFile = new CarrierFile(
				fileName.Substring(0, index) + TempSourceFileName,
				fileName.Substring(0, index) + TempDestinationFileName,
				0,
				carrierFile.CountBitsToHidePerCarrierUnit,
				carrierFile.NoisePercent );
			
			Stream messagePart = new MemoryStream();
			byte[] buffer;
			for(int frameIndex=0; frameIndex<aviReader.CountFrames; frameIndex++){
				//export a frame
				aviReader.ExportBitmap(frameIndex, frameCarrierFile.SourceFileName);
				
				//pass the frame to ImageUtility
				frameCarrierFile.CountBytesToHide = 0;
				utility.Initialize(frameCarrierFile);
				/*if(carrierFile.CountBytesToHide > 0){
					frameCarrierFile.CountUseableCarrierUnits = utility.CountUseableUnits(keyStream);
					frameCarrierFile.CountBytesToHide = (Int32)Math.Ceiling( (float)carrierFile.CountBytesToHide * ((float)frameCarrierFile.CountUseableCarrierUnits / carrierFile.CountCarrierUnits) );
				}*/

				messagePart.SetLength(0);
				utility.Extract(messagePart, keyStream);
				
				//copy extracted stream into message
				buffer = new byte[messagePart.Length];
				messagePart.Seek(0, SeekOrigin.Begin);
				messagePart.Read(buffer, 0, buffer.Length);
				messageStream.Write(buffer, 0, buffer.Length);
			}

			//delete temporary files
			if(File.Exists(frameCarrierFile.SourceFileName)){ File.Delete(frameCarrierFile.SourceFileName); }
			
			aviReader.Close();
		}

		public override long CountUnits(){
			AviReader ar = new AviReader();
			ar.Open(carrierFile.SourceFileName);
			Size size = ar.BitmapSize;
			long countPixels = size.Width * size.Height * ar.CountFrames;
			ar.Close();
			return countPixels;
		}
		
		public override FileType GetFileType(){
			return new VideoFileType();
		}


	}
}