Vb6只有Label控件可以设置背景透明，VB.net基本上都可以，可以按住CTRL多选，或者用鼠标框选，选中多个控件后，设置它们的backcolor属性为透明，或者用代码：
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For Each ctl As Control In Me.Controls
ctl.BackColor = Color.Transparent
Next
示例：背景为纯白色
执行后：
代码：
'========================================
'声明作用：透明化PictureBox，注意设置其背景颜色为纯白
'========================================
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long) As Long
Private Declare Function SetWindowRgn Lib "user32" (ByVal hwnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long
Private Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
Private Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn As Long, ByVal hSrcRgn1 As Long, ByVal hSrcRgn2 As Long, ByVal nCombineMode As Long) As Long
Private Declare Sub ReleaseCapture Lib "user32" ()
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Const RGN_DIFF = 4
Dim CurRgn As Long, TempRgn As Long ' Region variables
'========================================
'函数名称：ShapeMe
'函数作用：透明化PictureBox背景
'========================================
Public Sub ShapeMe(Color As Long, HorizontalScan As Boolean, Optional Name1 As Form = Nothing, Optional Name2 As PictureBox = Nothing)
Dim X As Integer, Y As Integer 'points on form
Dim dblHeight As Double, dblWidth As Double 'height and width of object
Dim lngHDC As Long 'the hDC property of the object
Dim booMiddleOfSet As Boolean 'used during the gathering of transparent points
Dim colPoints As Collection 'this will hold all usrPoints
Set colPoints = New Collection
Dim Z As Variant 'used during iteration through collection
Dim dblTransY As Double 'these 3 variables hold each point that will be made transparent
Dim dblTransStartX As Double
Dim dblTransEndX As Double
Dim Name As Object 'will hold the name of the object. Late-bound and slower, but allows different types (in this case Form or PictureBox)
'check out the name or names passed into the subroutine
If Name1 Is Nothing Xor Name2 Is Nothing Then 'we know there is a name in one of them
If Name1 Is Nothing Then 'set the name
Set Name = Picture1
Else
Set Name = Picture1
End If
Else 'both or none hold valid names
MsgBox "Must pass in the name of either a Form OR a PictureBox. TransForm received NONE or BOTH. Function failed.", vbOKOnly, "ShapeMe Subroutine"
Exit Sub
End If
'initialization
With Name
.AutoRedraw = True 'object must have this setting
.ScaleMode = 3 'object must have this setting
lngHDC = .hdc 'faster to use a variable; VB help recommends using the property, but I didn't encounter any problems
If HorizontalScan = True Then 'look for lines of transparency horizontally
dblHeight = .ScaleHeight 'faster to use a variable
dblWidth = .ScaleWidth 'faster to use a variable
Else 'look vertically (note that the names "dblHeight" and "dblWidth" are non-sensical now, but this was an easy way to do this
dblHeight = .ScaleWidth 'faster to use a variable
dblWidth = .ScaleHeight 'faster to use a variable
End If 'HorizontalScan = True
End With
booMiddleOfSet = False
'gather all points that need to be made transparent
For Y = 0 To dblHeight ' Go through each column of pixels on form
dblTransY = Y
For X = 0 To dblWidth ' Go through each line of pixels on form
'note that using GetPixel appears to be faster than using VB's Point
If TypeOf Name Is Form Then 'check to see if this is a form and use GetPixel function which is a little faster
If GetPixel(lngHDC, X, Y) = Color Then ' If the pixel's color is the transparency color, record it
If booMiddleOfSet = False Then
dblTransStartX = X
dblTransEndX = X
booMiddleOfSet = True
Else
dblTransEndX = X
End If 'booMiddleOfSet = False
Else
If booMiddleOfSet Then
colPoints.Add Array(dblTransY, dblTransStartX, dblTransEndX)
booMiddleOfSet = False
End If 'booMiddleOfSet = True
End If 'GetPixel(lngHDC, X, Y) = Color
ElseIf TypeOf Name Is PictureBox Then 'if a PictureBox then use Point; a little slower but works when GetPixel doesn't
If Name.Point(X, Y) = Color Then
If booMiddleOfSet = False Then
dblTransStartX = X
dblTransEndX = X
booMiddleOfSet = True
Else
dblTransEndX = X
End If 'booMiddleOfSet = False
Else
If booMiddleOfSet Then
colPoints.Add Array(dblTransY, dblTransStartX, dblTransEndX)
booMiddleOfSet = False
End If 'booMiddleOfSet = True
End If 'Name.Point(X, Y) = Color
End If 'TypeOf Name Is Form
Next X
Next Y
CurRgn = CreateRectRgn(0, 0, dblWidth, dblHeight) ' Create base region which is the current whole window
For Each Z In colPoints 'now make it transparent
TempRgn = CreateRectRgn(Z(1), Z(0), Z(2) + 1, Z(0) + 1) ' Create a temporary pixel region for this pixel
CombineRgn CurRgn, CurRgn, TempRgn, RGN_DIFF ' Combine temp pixel region with base region using RGN_DIFF to extract the pixel and make it transparent
DeleteObject (TempRgn) ' Delete the temporary region and free resources
Next
SetWindowRgn Name.hwnd, CurRgn, True ' Finally set the windows region to the final product
'I do not use DeleteObject on the CurRgn, going with the advice in Dan Appleman's book:
'once set to a window using SetWindowRgn, do not delete the region.
Set colPoints = Nothing
End Sub
Private Sub Command1_Click()
Picture1.BackColor = RGB(0, 0, 0) '需要透明的颜色(纯白色)
ShapeMe RGB(255, 255, 255), True, , Picture1 '透明底色
End Sub
窗体半透明: FormXX.Opacity=0.5或者: SetStyle(ControlStyles.SupportsTransparentBackColor, True)ControlXX.BackColor = Color.Transparent '或者是带Alpha的颜色ControlXX.BackColor = Color.FromArgb(128,Color.Red)