如何根据IntPtr直接转换成.net里的System.Drawing.Image对象？

[昵称这是个问题]

我用扫描仪，采用Twain协议方式，扫描后获取了一个IntPtr，如何把它转换为Image呢？求解，谢谢！

[全栈极简]

   IntPtr bmpptr = GlobalLock(img);
                            IntPtr pixptr = GetPixelInfo(bmpptr);
                            Bitmap bitmap = BitmapFromDIB(bmpptr, pixptr);

 [DllImport("kernel32.dll", ExactSpelling = true)]
        internal static extern IntPtr GlobalLock(IntPtr handle);

/// <summary>
        /// 获得内存图片像素信息
        /// </summary>
        /// <param name="bmpptr">内存图片指针</param>
        /// <returns></returns>
        protected IntPtr GetPixelInfo(IntPtr bmpptr)
        {
            BITMAPINFOHEADER bmi = new BITMAPINFOHEADER();
            Marshal.PtrToStructure(bmpptr, bmi);
            Rectangle bmprect = new Rectangle(0, 0, 0, 0); ;
            bmprect.X = bmprect.Y = 0;
            bmprect.Width = bmi.biWidth;
            bmprect.Height = bmi.biHeight;

            if (bmi.biSizeImage == 0)
                bmi.biSizeImage = ((((bmi.biWidth * bmi.biBitCount) + 31) & ~31) >> 3) * bmi.biHeight;

            int p = bmi.biClrUsed;
            if ((p == 0) && (bmi.biBitCount <= 8))
                p = 1 << bmi.biBitCount;
            p = (p * 4) + bmi.biSize + (int)bmpptr;
            return (IntPtr)p;
        }

/// <summary>
        /// 从DIB获得图片指针
        /// </summary>
        /// <param name="pDIB"></param>
        /// <param name="pPix"></param>
        /// <returns></returns>
        public static Bitmap BitmapFromDIB(IntPtr pDIB, IntPtr pPix)
        {
            MethodInfo mi = typeof(Bitmap).GetMethod("FromGDIplus",
                            BindingFlags.Static | BindingFlags.NonPublic);

            if (mi == null)
                return null; // (permission problem) 

            IntPtr pBmp = IntPtr.Zero;
            int status = GdipCreateBitmapFromGdiDib(pDIB, pPix, out pBmp);

            if ((status == 0) && (pBmp != IntPtr.Zero)) // success 
                return (Bitmap)mi.Invoke(null, new object[] { pBmp });
            else
                return null; // failure 
        }

[全栈极简]

我记得codeproject上面有完整的可应用的程序的，可以找找看。