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。

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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
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