简单的部分透明比较难做，不过可以换个方式考虑一下。
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把本问题转换成在VB.NET 2005环境下创建不规则窗体（＝普通窗体 － 透明部分）问题，解决方法就很多了，网上也有许多例子。如 章立民 的书里就详细讲过。
大致思路如下：
1。将backgroundimage设成一个位图（点阵图）
2.将Transparaencykey设成位图的背景颜色（位图最取背景单纯，单纯部分将成为透明部分）
3.如需要可以将formborderstyle设为none，会移除标题栏，并需要手动编写窗体移动、关闭等动作代码，
PS：一下代码是复制的，因为Google一下就有
‘添加新模块：
Option Explicit
'透明接口调用
Private Declare Function SetwindowLong Lib "user32" _
Alias "SetwindowLongA" _
(ByVal hwnd As Long, _
ByVal nIndex As Long, _
ByVal dwNewLong As Long) _
As Long
Private Declare Function GetwindowLong Lib "user32" _
Alias "GetwindowLongA" ( _
ByVal hwnd As Long, _
ByVal nIndex As Long) _
As Long
Private Declare Function SetLayeredwindowAttributes Lib "user32" ( _
ByVal hwnd As Long, _
ByVal crKey As Long, _
ByVal bAlpha As Long, _
ByVal dwFlags As Long) _
As Long
Private Const GWL_EXSTYLE = (-20)
Private Const LWA_ALPHA As Long = H2
Private Const WS_EX_LAYERED As Long = H80000
'设置窗口透明度
Public Sub SetFormToAlpha(hwnd As Long, lngAlpha As Long)
Dim tmpLog As Long
If hwnd = 0 Then Exit Sub
If lngAlpha = 0 And lngAlpha = 255 Then
tmpLog = GetwindowLong(hwnd, GWL_EXSTYLE) '窗口属性
Call SetwindowLong(hwnd, GWL_EXSTYLE, tmpLog or WS_EX_LAYERED)
Call SetLayeredwindowAttributes(hwnd, 0, lngAlpha, LWA_ALPHA)
End If
End Sub
先建一个标准EXE工程，然后添加一个用户控件，把以下代码复制到控件代码中，再把此控件放置到Form1上。
[vb] view plain copy
Option Explicit
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Private Declare Function GetClientRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As Long
Private Declare Function ClientToScreen Lib "user32" (ByVal hwnd As Long, lpPoint As POINTAPI) As Long
Private Declare Function ScreenToClient Lib "user32" (ByVal hwnd As Long, lpPoint As POINTAPI) As Long
Private Declare Function SetRect Lib "user32" (lpRect As RECT, ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
Private Declare Function OffsetRect Lib "user32" (lpRect As RECT, ByVal X As Long, ByVal Y As Long) As Long
Private Type POINTAPI
X As Long
Y As Long
End Type
Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
Private Declare Function DrawText Lib "user32" Alias "DrawTextA" (ByVal hdc As Long, ByVal lpStr As String, ByVal nCount As Long, lpRect As RECT, ByVal wFormat As Long) As Long
Private Const DT_SINGLELINE = H20
Private Const DT_CENTER = H1
Private Const DT_VCENTER = H4
Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, ByVal hdc As Long) As Long
Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function CreateCompatibleBitmap Lib "gdi32" (ByVal hdc As Long, ByVal nWidth As Long, ByVal nHeight As Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function ShowWindow Lib "user32" (ByVal hwnd As Long, ByVal nCmdShow As Long) As Long
Private Const SW_SHOW = 5
Private Const SW_HIDE = 0
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal X As Long, ByVal Y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Private Declare Function AlphaBlend Lib "msimg32" (ByVal hDestDC As Long, ByVal X As Long, ByVal Y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal widthSrc As Long, ByVal heightSrc As Long, ByVal blendFunct As Long) As Boolean
Dim m_hMemDC As Long
Dim m_hMemBmp As Long, m_hMemBmpPrev As Long
Dim m_rcControl As RECT
Private Sub UserControl_Initialize()
UserControl.AutoRedraw = True
UserControl.BackColor = vbRed
m_hMemDC = CreateCompatibleDC(UserControl.hdc)
End Sub
Private Sub UserControl_Terminate()
If m_hMemBmp 0 Then
DeleteObject SelectObject(m_hMemDC, m_hMemBmpPrev)
End If
DeleteDC m_hMemDC
End Sub
Public Sub Translucence()
Dim hdc As Long
Dim tPt As POINTAPI
'获得控件当前位置和大小
ClientToScreen UserControl.hwnd, tPt
ScreenToClient UserControl.ContainerHwnd, tPt
Call GetClientRect(UserControl.hwnd, m_rcControl)
OffsetRect m_rcControl, tPt.X, tPt.Y
'创建一幅内存位图
If m_hMemBmp 0 Then
DeleteObject (SelectObject(m_hMemDC, m_hMemBmpPrev))
End If
m_hMemBmp = CreateCompatibleBitmap(UserControl.hdc, m_rcControl.Right, m_rcControl.Bottom)
m_hMemBmpPrev = SelectObject(m_hMemDC, m_hMemBmp)
'隐藏控件
ShowWindow UserControl.hwnd, SW_HIDE
DoEvents
'保存控件容器的图像到内存位图中
Dim hDesktopDC As Long
hDesktopDC = GetDC(UserControl.hwnd)
BitBlt m_hMemDC, 0, 0, m_rcControl.Right, m_rcControl.Bottom, hDesktopDC, 0, 0, vbSrcCopy
ReleaseDC 0, hDesktopDC
'通过alpha效果进行半透明渲染
UserControl.AutoRedraw = True
AlphaBlend m_hMemDC, 0, 0, m_rcControl.Right, m_rcControl.Bottom, UserControl.hdc, 0, 0, m_rcControl.Right, m_rcControl.Bottom, 5242880
UserControl.AutoRedraw = False
'显示控件
ShowWindow UserControl.hwnd, SW_SHOW
'将渲染后的结果复制到控件中
BitBlt UserControl.hdc, 0, 0, m_rcControl.Right, m_rcControl.Bottom, m_hMemDC, 0, 0, vbSrcCopy
End Sub
Private Sub UserControl_Paint()
BitBlt UserControl.hdc, 0, 0, m_rcControl.Right, m_rcControl.Bottom, m_hMemDC, 0, 0, vbSrcCopy
End Sub
在Form1的Form_Activate事件里输入以下代码：
[vb] view plain copy
Private Sub Form_Activate()
Me.UserControl11.Translucence
End Sub
最后，你将看到一个粉红色半透明的方块，该方块就是你所需要的半透明的控件。至于控件的其它功能，可以自行扩展。
'函数SetLayeredWindowAttributes ' 使用这个函数，可以轻松的实现半透明窗体。按照微软的要求，透明窗体窗体在创建时应使用WS_EX_LAYERED参数（用CreateWindowEx），或者在创建后设置该参数（用SetWindowLong），我选用后者。全部函数、常量声明如下： Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long ' 其中hwnd是透明窗体的句柄，crKey为颜色值，bAlpha是透明度，取值范围是[0,255]，dwFlags是透明方式，可以取两个值：当取值为LWA_ALPHA时，crKey参数无效，bAlpha参数有效；当取值为LWA_COLORKEY时，bAlpha参数有效而窗体中的所有颜色为crKey的地方将变为透明－－这个功能很有用：我们不必再为建立不规则形状的窗体而调用一大堆区域分析、创建、合并函数了，只需指定透明处的颜色值即可，哈哈哈哈！请看具体代码。 Private Const WS_EX_LAYERED = H80000 Private Const GWL_EXSTYLE = (-20) Private Const LWA_ALPHA = H2 Private Const LWA_COLORKEY = H1 Private Sub Command1_Click() Unload Me End Sub Private Sub Form_Load() Dim rtn As Long rtn = GetWindowLong(hwnd, GWL_EXSTYLE) rtn = rtn Or WS_EX_LAYERED SetWindowLong hwnd, GWL_EXSTYLE, rtn SetLayeredWindowAttributes hwnd, 0, 150, LWA_ALPHA End Sub
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Const WS_EX_LAYERED = H80000
Private Const GWL_EXSTYLE = (-20)
Private Const LWA_ALPHA = H2
Private Const LWA_COLORKEY = H1
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
Private Sub SetFormTranslucency(hwnd As Long, crKey As Long, bAlpha As Byte, dwFlags As Long)'实现半透明窗体
Dim rtn As Long
rtn = GetWindowLong(hwnd, GWL_EXSTYLE)
rtn = rtn Or WS_EX_LAYERED
SetWindowLong hwnd, GWL_EXSTYLE, rtn
SetLayeredWindowAttributes hwnd, crKey, bAlpha, dwFlags
End Sub
Private Sub Form_Load()
Call SetFormTranslucency(Me.hwnd, 0, 200, 2) '窗体半透明，200为透明值
End Sub
可以实现窗体和窗体上的控件全都半透明，透明度可调
