C# Winform实现炫酷的透明动画片界面

protected   override  CreateParams CreateParams
           {
              get 
                  {
                 CreateParams cp  =   base .CreateParams;
                 cp.ExStyle  |=   0x00080000 ;  //  WS_EX_LAYERED 扩展样式 
                  return  cp;
             } 
         } 

          public   void  SetBitmap(Bitmap bitmap,  byte  opacity)
             {
              if  (bitmap.PixelFormat  !=  PixelFormat.Format32bppArgb)
                  throw   new  ApplicationException( "位图必须是32位包含alpha 通道" );
 
             IntPtr screenDc  =  Win32.GetDC(IntPtr.Zero);
             IntPtr memDc  =  Win32.CreateCompatibleDC(screenDc);
             IntPtr hBitmap  =  IntPtr.Zero;
             IntPtr oldBitmap  =  IntPtr.Zero;
 
              try  
                  {
                 hBitmap  =  bitmap.GetHbitmap(Color.FromArgb( 0 ));   // 创建GDI位图句柄，效率较低
                 oldBitmap  =  Win32.SelectObject(memDc, hBitmap);
 
                 Win32.Size size  =   new  Win32.Size(bitmap.Width, bitmap.Height);
                 Win32.Point pointSource  =   new  Win32.Point( 0 ,  0 );
                 Win32.Point topPos  =   new  Win32.Point(Left, Top);
                 Win32.BLENDFUNCTION blend  =   new  Win32.BLENDFUNCTION();
                 blend.BlendOp              =  Win32.AC_SRC_OVER;
                 blend.BlendFlags           =   0 ;
                 blend.SourceConstantAlpha  =  opacity;
                 blend.AlphaFormat          =  Win32.AC_SRC_ALPHA;
 
                 Win32.UpdateLayeredWindow(Handle, screenDc,  ref  topPos,  ref  size, memDc,  ref  pointSource,  0 ,  ref  blend, Win32.ULW_ALPHA);
             } 
              finally  
                  {
                 Win32.ReleaseDC(IntPtr.Zero, screenDc);
                  if  (hBitmap  !=  IntPtr.Zero) 
                       {
                     Win32.SelectObject(memDc, oldBitmap);
                     
                     Win32.DeleteObject(hBitmap);
                 } 
                 Win32.DeleteDC(memDc);
             } 
         } 

      class  Win32
         {
          public   enum  Bool
             {
             False  =   0 ,
             True
         } ;
 
 
         [StructLayout(LayoutKind.Sequential)]
          public   struct  Point
              {
              public  Int32 x;
              public  Int32 y;
 
               public  Point(Int32 x, Int32 y)  
               {  this .x  =  x;  this .y  =  y; } 
         } 
 
 
         [StructLayout(LayoutKind.Sequential)]
          public   struct  Size
              {
              public  Int32 cx;
              public  Int32 cy;
 
               public  Size(Int32 cx, Int32 cy)  
                 {  this .cx  =  cx;  this .cy  =  cy; } 
         } 
 
 
         [StructLayout(LayoutKind.Sequential, Pack  =   1 )]
          struct  ARGB
             {
              public   byte  Blue;
              public   byte  Green;
              public   byte  Red;
              public   byte  Alpha;
         } 
 
 
         [StructLayout(LayoutKind.Sequential, Pack  =   1 )]
          public   struct  BLENDFUNCTION
              {
              public   byte  BlendOp;
              public   byte  BlendFlags;
              public   byte  SourceConstantAlpha;
              public   byte  AlphaFormat;
         } 
 
 
          public   const  Int32 ULW_COLORKEY  =   0x00000001 ;
          public   const  Int32 ULW_ALPHA  =   0x00000002 ;
          public   const  Int32 ULW_OPAQUE  =   0x00000004 ;
 
          public   const   byte  AC_SRC_OVER  =   0x00 ;
          public   const   byte  AC_SRC_ALPHA  =   0x01 ;
 
 
         [DllImport( " user32.dll " , ExactSpelling  =   true , SetLastError  =   true )]
          public   static   extern  Bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst,  ref  Point pptDst,  ref  Size psize, IntPtr hdcSrc,  ref  Point pprSrc, Int32 crKey,  ref  BLENDFUNCTION pblend, Int32 dwFlags);

         [DllImport( " user32.dll " , ExactSpelling  =   true , SetLastError  =   true )]
          public   static   extern  IntPtr GetDC(IntPtr hWnd);
 
         [DllImport( " user32.dll " , ExactSpelling  =   true )]
          public   static   extern   int  ReleaseDC(IntPtr hWnd, IntPtr hDC);
 
         [DllImport( " gdi32.dll " , ExactSpelling  =   true , SetLastError  =   true )]
          public   static   extern  IntPtr CreateCompatibleDC(IntPtr hDC);
 
         [DllImport( " gdi32.dll " , ExactSpelling  =   true , SetLastError  =   true )]
          public   static   extern  Bool DeleteDC(IntPtr hdc);
 
         [DllImport( " gdi32.dll " , ExactSpelling  =   true )]
          public   static   extern  IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
 
         [DllImport( " gdi32.dll " , ExactSpelling  =   true , SetLastError  =   true )]
          public   static   extern  Bool DeleteObject(IntPtr hObject);
 
         [DllImport( " user32.dll " , EntryPoint  =   " SendMessage " )]
          public   static   extern   int  SendMessage( int  hWnd,  int  wMsg,  int  wParam,  int  lParam);
         [DllImport( " user32.dll " , EntryPoint  =   " ReleaseCapture " )]
 
          public   static   extern   int  ReleaseCapture();
          public   const   int  WM_SysCommand  =   0x0112 ;
          public   const   int  SC_MOVE  =   0xF012 ;
 
          public   const   int  SC_MAXIMIZE  =   61488 ;
          public   const   int  SC_MINIMIZE  =   61472 ;
     }