Alpha透明窗口的形式

我得到以下代码来加载一个带alpha通道的PNG到表单上，并重新调整表单以匹配alpha通道。Alpha透明窗口的形式

Public Function applyAlphaForm(ByVal f As Form, ByVal bitmap As Bitmap, Optional ByVal opacity As Byte = 255) As Boolean 
    f.FormBorderStyle = FormBorderStyle.None 
    Dim style As Long 
    style = Win32.GetWindowLong(f.Handle, Win32.GWL_EXSTYLE) 
    If Not (style And Win32.WS_EX_LAYERED = Win32.WS_EX_LAYERED) Then 
     style = style Or Win32.WS_EX_LAYERED 
     Win32.SetWindowLong(f.Handle, Win32.GWL_EXSTYLE, style) 
    End If 
    Return SetBitmap(f, bitmap, opacity) 
End Function 

Public Function SetBitmap(ByVal f As Form, ByVal bitmap As Bitmap, ByVal opacity As Byte) As Boolean 
    f.Height = bitmap.Height 
    f.Width = bitmap.Width 
    If bitmap.PixelFormat <> PixelFormat.Format32bppArgb Then 
     f.BackgroundImage = bitmap 
     f.TransparencyKey = bitmap.GetPixel(0, 0) 
     Return True 
    End If 

    Dim screenDC As IntPtr = Win32.GetDC(IntPtr.Zero) 
    Dim memDC As IntPtr = Win32.CreateCompatibleDC(screenDC) 
    Dim hBitmap As IntPtr = IntPtr.Zero 
    Dim oldBitmap As IntPtr = IntPtr.Zero 

    Try 
     hBitmap = bitmap.GetHbitmap(Color.FromArgb(0)) 'grab a GDI handle from this GDI+ bitmap 
     oldBitmap = Win32.SelectObject(memDC, hBitmap) 

     Dim size As Win32.Size = New Win32.Size(bitmap.Width, bitmap.Height) 
     Dim pointSource As Win32.Point = New Win32.Point(0, 0) 
     Dim topPos As Win32.Point = New Win32.Point(f.Left, f.Top) 
     Dim blend As Win32.BLENDFUNCTION = New Win32.BLENDFUNCTION() 
     blend.BlendOp = Win32.AC_SRC_OVER 
     blend.BlendFlags = 0 
     blend.SourceConstantAlpha = opacity 
     blend.AlphaFormat = Win32.AC_SRC_ALPHA 

     Win32.UpdateLayeredWindow(f.Handle, screenDC, topPos, size, memDC, pointSource, 0, blend, Win32.ULW_ALPHA) 

    Catch ex As Exception 
    Finally 
     Win32.ReleaseDC(IntPtr.Zero, screenDC) 
     If hBitmap <> IntPtr.Zero Then 
      Win32.SelectObject(memDC, oldBitmap) 
      Win32.DeleteObject(hBitmap) 
     End If 
     Win32.DeleteDC(memDC) 
    End Try 
    Return True 
End Function

尼斯和容易的，但如果我把一些控制（按钮，文本框...）的形式，他们就会消失。我的客人UpdateLayeredWindow将画在hDC的形式，所以我们不能看到它背后的任何东西。那么如何在表单上绘制一些表单控件呢？我已经尝试遍历所有控件，并在调用api之前呈现给png位图，但这将是静态图像。

来源

2012-05-22 Trinh Hoang Nhu

为什么你不只是将位图转换为32bpp并摆脱该代码？ –

糟糕！我发现了一个解决方案：http://stackoverflow.com/questions/2979125/how-to-make-the-form-into-fully-transparent-32bit-alpha :( –

@Hans帕桑特：我想要一个来自PNG（某些不透明区域）的半透明数据... –

所以我必须创建两个，背景形式透明的alpha和前景形式与控制它。控制表单将只显示控制区域。

来源

2012-08-01 15:28:17

Alpha透明窗口的形式

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