diff --git a/project/vc12/Nvidia.TextureTools.UnitTests/Test.cs b/project/vc12/Nvidia.TextureTools.UnitTests/Test.cs
index d09b778..e3b3e03 100644
--- a/project/vc12/Nvidia.TextureTools.UnitTests/Test.cs
+++ b/project/vc12/Nvidia.TextureTools.UnitTests/Test.cs
@@ -1,6 +1,8 @@
 using NUnit.Framework;
 using System;
 using Nvidia.TextureTools;
+using System.Runtime.InteropServices;
+
 namespace Nvidia.TextureTools.UnitTests {
 	[TestFixture ()]
 	public class Test {
@@ -11,8 +13,56 @@ namespace Nvidia.TextureTools.UnitTests {
 			var outputOptions = new OutputOptions ();
 			var compressionOptions = new CompressionOptions ();
 			var compressor = new Compressor ();
+			inputOptions.SetAlphaMode (AlphaMode.Premultiplied);
+			inputOptions.SetTextureLayout (TextureType.Texture2D, 128, 128, 1);
+			byte [] sourceData = new byte [128*128*4];
+			var dataHandle = GCHandle.Alloc (sourceData, GCHandleType.Pinned);
+			var BeginImage = new OutputOptions.BeginImageHandler (BeginImageInternal);
+			var WriteData = new OutputOptions.OutputHandler (WriteDataInternal);
+			var EndImage = new OutputOptions.EndImageHandler (EndImageInternal);
+			var a = GCHandle.Alloc (BeginImage);
+			var b = GCHandle.Alloc (WriteData);
+			var c = GCHandle.Alloc (EndImage);
+			try {
+				var dataPtr = dataHandle.AddrOfPinnedObject ();
+				inputOptions.SetMipmapData (dataPtr, 128, 128, 1, 0, 0);
+				inputOptions.SetMipmapGeneration (false);
+				inputOptions.SetGamma (1.0f, 1.0f);
+				outputOptions.SetOutputHeader (false);
+				outputOptions.SetOutputOptionsOutputHandler (BeginImage, WriteData, EndImage);
+				var estsize = compressor.EstimateSize (inputOptions, compressionOptions);
+				Assert.True (compressor.Compress (inputOptions, compressionOptions, outputOptions));
+			}finally {
+				a.Free ();
+				b.Free ();
+				c.Free ();
+				dataHandle.Free ();
+			}
+		}
 
-			compressor.Compress (inputOptions, compressionOptions, outputOptions);
+		byte [] buffer;
+		int offset;
+
+		void BeginImageInternal (int size, int width, int height, int depth, int face, int miplevel)
+		{
+			buffer = new byte [size];
+			offset = 0;
+		}
+
+		bool WriteDataInternal (IntPtr data, int length)
+		{
+			Marshal.Copy (data, buffer, offset, length);
+			offset += length;
+			if (offset == buffer.Length)
+			{
+				
+			}
+			return true;
+		}
+
+		void EndImageInternal ()
+		{
+			Console.WriteLine ("EndImageInternal");
 		}
 	}
 }
diff --git a/project/vc12/Nvidia.TextureTools/TextureTools.cs b/project/vc12/Nvidia.TextureTools/TextureTools.cs
index 3894da3..5aa0349 100644
--- a/project/vc12/Nvidia.TextureTools/TextureTools.cs
+++ b/project/vc12/Nvidia.TextureTools/TextureTools.cs
@@ -422,8 +422,9 @@ namespace Nvidia.TextureTools
 	{
 		#region Delegates
 		public delegate void ErrorHandler(Error error);
-		private delegate void WriteDataDelegate(IntPtr data, int size);
-		private delegate void ImageDelegate(int size, int width, int height, int depth, int face, int miplevel);
+		public delegate bool OutputHandler(IntPtr data, int size);
+		public delegate void EndImageHandler();
+		public delegate void BeginImageHandler (int size, int width, int height, int depth, int face, int miplevel);
 		#endregion
 
 		#region Bindings
@@ -447,8 +448,8 @@ namespace Nvidia.TextureTools
 		[DllImport("nvtt"), SuppressUnmanagedCodeSecurity]
 		private extern static void nvttSetOutputOptionsOutputHeader(IntPtr outputOptions, bool b);
 
-		//[DllImport("nvtt"), SuppressUnmanagedCodeSecurity]
-		//private extern static void nvttSetOutputOptionsOutputHandler(IntPtr outputOptions, WriteDataDelegate writeData, ImageDelegate image);
+		[DllImport("nvtt"), SuppressUnmanagedCodeSecurity]
+		private extern static void nvttSetOutputOptionsOutputHandler(IntPtr outputOptions, IntPtr beginImageHandler, IntPtr outputHandler, IntPtr endImageHandler);
 
 		#endregion
 
@@ -477,6 +478,18 @@ namespace Nvidia.TextureTools
 		}
 
 		// @@ Add OutputHandler interface.
+		public void SetOutputOptionsOutputHandler (BeginImageHandler beginImageHandler, OutputHandler outputHandler, EndImageHandler endImageHandler)
+		{
+			IntPtr writeData = IntPtr.Zero;
+			IntPtr beginImage = IntPtr.Zero;
+			IntPtr endImage = IntPtr.Zero;
+			if (beginImageHandler != null || outputHandler != null || endImageHandler != null) {
+				writeData = Marshal.GetFunctionPointerForDelegate (outputHandler);
+				beginImage = Marshal.GetFunctionPointerForDelegate (beginImageHandler);
+				endImage = Marshal.GetFunctionPointerForDelegate (endImageHandler);
+			}
+			nvttSetOutputOptionsOutputHandler (this.options, beginImage, writeData, endImage);
+		}
 	}
 	#endregion