做过.NET Winform窗体美化的人应该都很熟悉UpdateLayeredWindow吧，UpdateLayeredWindow可以实现窗体的任意透明，效果很好，不会有毛边。不过使用这个API之后，会有一个问题就是无法使用普通控件，而且没有Paint消息。为了解决这个问题，有两种方法。
一、使用双层窗体，底层窗体使用UpdateLayeredWindow作为背景，上层窗体用普通窗体，并且可以使用TransparencyKey或者Region来实现去除不需要的窗体内容，让上层窗体能看到底层的窗体。
二、直接单层窗体，使用控件的DrawToBitmap把控件图像绘制到UpdateLayeredWindow 的窗体上，这样就可以看到普通控件了。不过这个也有问题：1.控件内容不能自动更新 2.效率低，很多控件使用DrawToBitmap绘制出的图像不完整，甚至绘制不出图像。比如TextBox无法显示光标，WebBrowser无法 显示内容。
三、采用DirectUI技术，重写所有基础控件。效果最好，不过工作量巨大。
使用UpdateLayeredWindow时，一般是需要对Bitmap缓存起来，通过设置剪辑区域，局部重绘来提高效率。另外还可以异步重绘，模拟Winform的失效到重绘。
有些人会说为什么不直接用WPF啊，Wpf和Winform各有优缺点，适应不同的场合。Winform相对于使用更简单一些，系统要求更低。当然需要看人的习惯了和擅长的。
UpdateLayeredWindow 基本使用方法：
- protected override CreateParams CreateParams
- {
- get
- {
- CreateParams cp = base .CreateParams;
- cp.ExStyle |= 0x00080000 ; // WS_EX_LAYERED 扩展样式
- return cp;
- }
- }
重写窗体的 CreateParams 属性
API调用：
- 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);
- }
- }
API声明：
- 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 ;
- }
需要呈现图像的时候调用 SetBitmap 方法。只要优化好，呈现效率比普通的Paint重绘方式高很多，并且不卡不闪烁，支持任意透明。
下面是自己开发出来的效果：
这个是用OpenGL绘制的
