ImageInfo

  		public static ImageInfo ReadPng (string fileName)
		{
			int w, h;
			if (GetPngImageSize (fileName, out w, out h))
				return new ImageInfo { FileName = fileName, Width = w, Height = h };
			
			return new ImageInfo  ();	
		}
		
		public static ImageInfo ReadJpg (string fileName)
		{
			int w, h;
			if (GetJpgImageSize (fileName, out w, out h))
				return new ImageInfo { FileName = fileName, Width = w, Height = h };
			
			return new ImageInfo ();	
		}
		
		public static ImageInfo Read (string fileName)
		{
			ImageInfo info = ReadPng (fileName);
			if (info.FileName == null)
				info = ReadJpg (fileName);
			return info;
		}

		static int ReadInt (BinaryReader reader)
		{
			int result = 0;
			result += (int)reader.ReadByte () << 24;
			result += (int)reader.ReadByte () << 16;
			result += (int)reader.ReadByte () << 8;
			result += (int)reader.ReadByte ();
			return result;
		}
		
		static bool GetPngImageSize (string fileName, out int width, out int height, bool tryReverting = true)
		{
			// PNG file format specification can be found at: http://www.w3.org/TR/PNG
			BinaryReader reader = null;
			try {
				reader = new BinaryReader (File.OpenRead (fileName));
				var pngHeader = reader.ReadBytes (8);
				// Check for valid PNG header.
				if (pngHeader[0] != 137 ||
					pngHeader[1] != 80 || pngHeader[2] != 78 || pngHeader [3] != 71 ||
					pngHeader [4] != 13 || pngHeader [5] != 10 || pngHeader [6] != 26 || pngHeader [7] != 10)
					throw new IOException ("File has no valid PNG header.");
				
				// First chunk is always the IHDR header chunk
				reader.ReadBytes (4); // skip chunk size
				var ihdrID = reader.ReadBytes (4);
				if (ihdrID[0] == 73 && ihdrID[1] == 72 && ihdrID[2] == 68 && ihdrID[3] == 82) {
					width = ReadInt (reader);
					height = ReadInt (reader);
					return true;
				}

				if (tryReverting) {
					// Assumed to be an iOS app at this point, which means pngcrush may have made this file unreadable...
					var pngcrush = AppleSdkSettings.DeveloperRoot.Combine ("Platforms", "iPhoneOS.platform", "Developer", "usr", "bin", "pngcrush");
					if (File.Exists (pngcrush)) {
						var reverted = System.IO.Path.GetTempFileName ();
						var args = new ProcessArgumentBuilder ();
						args.Add ("-revert-iphone-optimizations");
						args.AddQuoted (fileName);
						args.AddQuoted (reverted);

						var output = new StringWriter ();
						MonoDevelop.Core.Runtime.ProcessService.StartProcess (pngcrush, args.ToString (), "", output, output, null).WaitForExit ();
						bool success = GetPngImageSize (reverted, out width, out height, false);
						File.Delete (reverted);
						return success;
					}
				}

				throw new IOException ("IHDR missing or corrupt.");
			} catch (Exception e) {
				LoggingService.LogError ("Error while getting png image size of: " + fileName, e);
				width = height = -1;
				return false;
			} finally {
				if (reader != null)
					reader.Close ();
			}
		}
		
		static bool GetJpgImageSize (string filename, out int width, out int height)
		{
			try {
				var type = Pixbuf.GetFileInfo (filename, out width, out height);
				return type != null && type.Name == "jpeg";
			} catch {
				width = height = -1;
				return false;
			}
		}