.NET2.0 如何使用透明PNG作为窗体背景
但是VB.NET里面如果直接设置背景图像就会这样
TransparencyKey的方法我试过，没有效果
目前找到一个，但是有严重的BUG，就是不管窗体上面放置什么控件，运行时都完全看不见
下面是代码：AlphaForm.vb
Imports System
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Windows.Forms
Imports System.Runtime.InteropServices
#Region "Win32 Class"
Friend Class Win32
#Region "常量"
Public Const ULW_COLORKEY As Int32 = &H1
Public Const ULW_ALPHA As Int32 = &H2
Public Const ULW_OPAQUE As Int32 = &H4
Public Const WS_EX_LAYERED As Int32 = &H80000
Public Const AC_SRC_OVER As Byte = &H0
Public Const AC_SRC_ALPHA As Byte = &H1
#End Region
#Region "枚举"
Public Enum Bool
[False] = 0
[True]
End Enum
#End Region
#Region "结构"
<StructLayout(LayoutKind.Sequential, Pack:=1)> _
Private Structure ARGB
Public Blue As Byte
Public Green As Byte
Public Red As Byte
Public Alpha As Byte
End Structure
<StructLayout(LayoutKind.Sequential)> _
Public Structure Size
Public cx As Int32
Public cy As Int32
Public Sub New(ByVal cx As Int32, ByVal cy As Int32)
Me.cx = cx
Me.cy = cy
End Sub
End Structure
<StructLayout(LayoutKind.Sequential)> _
Public Structure Point
Public x As Int32
Public y As Int32
Public Sub New(ByVal x As Int32, ByVal y As Int32)
Me.x = x
Me.y = y
End Sub
End Structure
<StructLayout(LayoutKind.Sequential, Pack:=1)> _
Public Structure BLENDFUNCTION
Public BlendOp As Byte
Public BlendFlags As Byte
Public SourceConstantAlpha As Byte
Public AlphaFormat As Byte
End Structure
#End Region
#Region "API"
'该函数检索一指定窗口的客户区域或整个屏幕的显示设备上下文环境的句柄，以后可以在GDI函数中使用该句柄来在设备上下文环境中绘图。
Public Declare Auto Function GetDC Lib "user32.dll" (ByVal hWnd As IntPtr) As IntPtr
'该函数创建一个与指定设备兼容的内存设备上下文环境（DC）。通过GetDc()获取的HDC直接与相关设备沟通，而本函数创建的DC，则是与内存中的一个表面相关联。
Public Declare Auto Function CreateCompatibleDC Lib "gdi32.dll" (ByVal hDC As IntPtr) As IntPtr
'该函数选择一对象到指定的设备上下文环境中，该新对象替换先前的相同类型的对象。
Public Declare Auto Function SelectObject Lib "gdi32.dll" (ByVal hDC As IntPtr, ByVal hObject As IntPtr) As IntPtr
'该函数更新一个分层的窗口的位置，大小，形状，内容和半透明度。
Public Declare Auto Function UpdateLayeredWindow Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal hdcDst As IntPtr, ByRef pptDst As Point, ByRef psize As Size, ByVal hdcSrc As IntPtr, ByRef pprSrc As Point, ByVal crKey As Int32, ByRef pblend As BLENDFUNCTION, ByVal dwFlags As Int32) As Bool
'该函数释放设备上下文环境（DC）供其他应用程序使用。函数的效果与设备上下文环境类型有关。它只释放公用的和设备上下文环境，对于类或私有的则无效。
Public Declare Auto Function ReleaseDC Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal hDC As IntPtr) As Integer
'该函数删除一个逻辑笔、画笔、字体、位图、区域或者调色板，释放所有与该对象有关的系统资源，在对象被删除之后，指定的句柄也就失效了。
Public Declare Auto Function DeleteObject Lib "gdi32.dll" (ByVal hObject As IntPtr) As Bool
'该函数删除指定的设备上下文环境（DC）。
Public Declare Auto Function DeleteDC Lib "gdi32.dll" (ByVal hdc As IntPtr) As Bool
#End Region
End Class
#End Region
Public Class AlphaForm
Inherits Form
Public Sub SetBitmap(ByVal opacity As Byte)
Dim bmp As Bitmap = Me.BackgroundImage
If bmp.PixelFormat <> PixelFormat.Format32bppArgb Then
Throw New ApplicationException("窗体背景必须使用带Alpha通道的32位图片。")
End If
'根据图片大小设置窗体大小 www.2cto.com
Me.Size = bmp.Size
'在内存中创建与当前屏幕兼容的DC
Dim hDC1 As IntPtr = Win32.GetDC(IntPtr.Zero)
Dim hDC2 As IntPtr = Win32.CreateCompatibleDC(hDC1)
Dim hBitmap1 As IntPtr = IntPtr.Zero
Dim hBitmap2 As IntPtr = IntPtr.Zero
Try
hBitmap1 = bmp.GetHbitmap(Color.FromArgb(0))
hBitmap2 = Win32.SelectObject(hDC2, hBitmap1)
Dim blend As New Win32.BLENDFUNCTION()
With blend
.BlendOp = Win32.AC_SRC_OVER
.BlendFlags = 0
.AlphaFormat = Win32.AC_SRC_ALPHA
.SourceConstantAlpha = opacity
End With
Call Win32.UpdateLayeredWindow(Me.Handle, hDC1, New Win32.Point(Left, Top),
New Win32.Size(bmp.Width, bmp.Height), hDC2,
New Win32.Point(0, 0), 0, blend, Win32.ULW_ALPHA)
Finally
Call Win32.ReleaseDC(IntPtr.Zero, hDC1)
If hBitmap1 <> IntPtr.Zero Then
Call Win32.SelectObject(hDC2, hBitmap2)
Call Win32.DeleteObject(hBitmap1)
End If
Call Win32.DeleteDC(hDC2)
End Try
End Sub
Protected Overloads Overrides ReadOnly Property CreateParams() As CreateParams
Get
If Not DesignMode Then
Dim cp As CreateParams = MyBase.CreateParams
cp.ExStyle = cp.ExStyle Or Win32.WS_EX_LAYERED
Return cp
Else
Return MyBase.CreateParams
End If
End Get
End Property
End Class
Public Class MainForm
Inherits AlphaForm
'让窗体继承Alplaform类
Private Sub MainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.BackgroundImage = My.Resources.alphabg
'把窗体背景设置成32位真彩色BMP或PNG
SetBitmap(255)
'传入你想设置的窗体整体透明度值(0~255)
End Sub
End Class
