Added image conversion parts from commonwin32.

NTwain/ImageTools.cs

@@ -0,0 +1,119 @@
+using Microsoft.Win32.SafeHandles;
+using NTwain.Interop;
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Text;
+using System.Windows.Media.Imaging;
+
+namespace NTwain
+{
+    public static class ImageTools
+    {
+        internal static Bitmap ReadBitmapImage(IntPtr dibBitmap)
+        {
+            Bitmap finalImg = null;
+            Bitmap tempImg = null;
+            if (IsDib(dibBitmap))
+            {
+                try
+                {
+                    var header = (BITMAPINFOHEADER)Marshal.PtrToStructure(dibBitmap, typeof(BITMAPINFOHEADER));
+
+                    if (header.Validate())
+                    {
+                        PixelFormat format = header.GetDrawingPixelFormat();
+                        tempImg = new Bitmap(header.biWidth, Math.Abs(header.biHeight), header.GetStride(), format, header.GetScan0(dibBitmap));
+                        ColorPalette pal = header.GetDrawingPalette(dibBitmap);
+                        if (pal != null)
+                        {
+                            tempImg.Palette = pal;
+                        }
+                        float xdpi = header.GetXDpi();
+                        float ydpi = header.GetYDpi();
+                        if (xdpi != 0 && ydpi == 0)
+                        {
+                            ydpi = xdpi;
+                        }
+                        else if (ydpi != 0 && xdpi == 0)
+                        {
+                            xdpi = ydpi;
+                        }
+                        if (xdpi != 0)
+                        {
+                            tempImg.SetResolution(xdpi, ydpi);
+                        }
+                        if (header.IsBottomUpImage)
+                        {
+                            tempImg.RotateFlip(RotateFlipType.RotateNoneFlipY);
+                        }
+                        finalImg = tempImg;
+                        tempImg = null;
+                    }
+                }
+                finally
+                {
+                    if (tempImg != null)
+                    {
+                        tempImg.Dispose();
+                    }
+                }
+            }
+            return finalImg;
+        }
+
+        static bool IsDib(IntPtr dibBitmap)
+        {
+            // a quick check not guaranteed correct,
+            // compare first byte to size of struct (which is also the first field)
+            var test = Marshal.ReadInt32(dibBitmap);
+            // should be 40
+            return test == BITMAPINFOHEADER.GetByteSize();
+        }
+
+        /// <summary>
+        /// Converts a <see cref="Bitmap"/> to WPF <see cref="BitmapSource"/>.
+        /// </summary>
+        /// <param name="image">The image to convert.</param>
+        /// <returns></returns>
+        public static BitmapSource ConvertToWpfBitmap(this Bitmap image)
+        {
+            if (image != null)
+            {
+                using (var hbm = new SafeHBitmapHandle(image.GetHbitmap(), true))
+                {
+                    return System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
+                       hbm.DangerousGetHandle(),
+                       IntPtr.Zero,
+                       System.Windows.Int32Rect.Empty,
+                       BitmapSizeOptions.FromEmptyOptions());
+                }
+            }
+            return null;
+        }
+
+        class SafeHBitmapHandle : SafeHandleZeroOrMinusOneIsInvalid
+        {
+            [SecurityCritical]
+            public SafeHBitmapHandle(IntPtr preexistingHandle, bool ownsHandle)
+                : base(ownsHandle)
+            {
+                SetHandle(preexistingHandle);
+            }
+
+            protected override bool ReleaseHandle()
+            {
+                return NativeMethods.DeleteObject(handle);
+            }
+        }
+
+        internal static Bitmap ReadTiffImage(IntPtr data)
+        {
+            return null;
+        }
+    }
+}