#region UpdateLayeredWindow

        #region 重写窗体的 CreateParams 属性

        protected override CreateParams CreateParams

        {

            get

            {

                CreateParams cp = base.CreateParams;

                cp.ExStyle |= 0x00080000;  //  WS_EX_LAYERED 扩展样式

                //无边框任务栏窗口最小化

                const int WS_MINIMIZEBOX = 0x00020000;  // Winuser.h中定义

                //CreateParams cp = base.CreateParams;

                cp.Style = cp.Style | WS_MINIMIZEBOX;   // 允许最小化操作

                return cp;

            }

        }

        #endregion

        #region API调用

        public void SetBits(Bitmap bitmap)//调用UpdateLayeredWindow（）方法。this.BackgroundImage为你事先准备的带透明图片。

        {

            //if (!haveHandle) return;

            if (!Bitmap.IsCanonicalPixelFormat(bitmap.PixelFormat) || !Bitmap.IsAlphaPixelFormat(bitmap.PixelFormat))

                throw new ApplicationException("图片必须是32位带Alhpa通道的图片。");

            IntPtr oldBits = IntPtr.Zero;

            IntPtr screenDC = Win32.GetDC(IntPtr.Zero);

            IntPtr hBitmap = IntPtr.Zero;

            IntPtr memDc = Win32.CreateCompatibleDC(screenDC);

            try

            {

                Win32.Point topLoc = new Win32.Point(Left, Top);

                Win32.Size bitMapSize = new Win32.Size(bitmap.Width, bitmap.Height);

                Win32.BLENDFUNCTION blendFunc = new Win32.BLENDFUNCTION();

                Win32.Point srcLoc = new Win32.Point(, );

                hBitmap = bitmap.GetHbitmap(Color.FromArgb());

                oldBits = Win32.SelectObject(memDc, hBitmap);

                blendFunc.BlendOp = Win32.AC_SRC_OVER;

                blendFunc.SourceConstantAlpha = ;

                blendFunc.AlphaFormat = Win32.AC_SRC_ALPHA;

                blendFunc.BlendFlags = ;

                Win32.UpdateLayeredWindow(Handle, screenDC, ref topLoc, ref bitMapSize, memDc, ref srcLoc, , ref blendFunc, Win32.ULW_ALPHA);

            }

            finally

            {

                if (hBitmap != IntPtr.Zero)

                {

                    Win32.SelectObject(memDc, oldBits);

                    Win32.DeleteObject(hBitmap);

                }

                Win32.ReleaseDC(IntPtr.Zero, screenDC);

                Win32.DeleteDC(memDc);

            }

        }

        #endregion

        #endregion

        public MainForm()

        {

            InitializeComponent();

            Bitmap bg = new Bitmap(this.Width, this.Height);

            Graphics g = Graphics.FromImage(bg);

            g.DrawImage(img, x, y, img.Width, img.Height);

            g.Dispose();

            SetBits(bg);

        }