Hi,Ben!
Thank you for your posting! From your post,my understanding on this issue
is How to set the "opacity"of a windows form control "panel". If I'm off
base,please feel free to let me know.
Actually there's no such a relevant atrribute for a panel's opacity in
vs.net. But we can do this using GDI+. we could contruct a custom control
derived from "Panel" class adding a special OnPaint method, and use this
custom control in your windows applications.
Here is a sample:
Option Explicit On
Option Strict On
Imports System.ComponentModel
Imports System.Drawing.Imaging
Imports System.Drawing.Drawing2D
Public Class TransPanel
Inherits System.Windows.Forms.Panel
#Region " Component Designer generated code "
Public Sub New(ByVal Container As System.ComponentModel.IContainer)
MyClass.New()
'Required for Windows.Forms Class Composition Designer support
Container.Add(Me)
Me.SetStyle(ControlStyles.DoubleBuffer, True)
Me.SetStyle(ControlStyles.AllPaintingInWmPaint, True)
Me.SetStyle(ControlStyles.UserPaint, True)
End Sub
Public Sub New()
MyBase.New()
'This call is required by the Component Designer.
InitializeComponent()
'Add any initialization after the InitializeComponent() call
End Sub
'Component overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
'Required by the Component Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Component Designer
'It can be modified using the Component Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()
components = New System.ComponentModel.Container
End Sub
#End Region
Private _opacity As Double = 0.1
<Category("Appearance"), DefaultValue(GetType(Double), "0.1"),
Description("Gets or Sets the opacity level of the panel.")> _
Public Property Opacity() As Double
Get
Return _opacity
End Get
Set(ByVal Value As Double)
If Value < 0 OrElse Value > 1 Then
Throw New ArgumentException("Value must be between 0.00 and 1.00")
End If
_opacity = Value
Me.Invalidate()
End Set
End Property
Protected Overrides Sub OnMove(ByVal e As System.EventArgs)
Me.Invalidate()
End Sub
Protected Overrides Sub OnPaint(ByVal e As
System.Windows.Forms.PaintEventArgs)
If Me.BackgroundImage Is Nothing Then
If Not (Parent.BackgroundImage Is Nothing) Then
e.Graphics.DrawImage(Parent.BackgroundImage, _
New Rectangle(0, 0, Me.Width, Me.Height), _
Me.Left, Me.Top, Me.Width, Me.Height, GraphicsUnit.Pixel)
Else
e.Graphics.FillRectangle(New SolidBrush(Parent.BackColor), _
New Rectangle(0, 0, Me.Width, Me.Height))
End If
End If
Dim attributes As New ImageAttributes
Dim matrixElements As Single()() = { _
New Single() {1.0F, 0.0F, 0.0F, 0.0F, 0.0F}, _
New Single() {0.0F, 1.0F, 0.0F, 0.0F, 0.0F}, _
New Single() {0.0F, 0.0F, 1.0F, 0.0F, 0.0F}, _
New Single() {0.0F, 0.0F, 0.0F, CSng(_opacity), 0.0F}, _
New Single() {0.0F, 0.0F, 0.0F, 0.0F, 1.0F}}
Dim matrix As ColorMatrix
matrix = New ColorMatrix(matrixElements)
attributes.SetColorMatrix(matrix, ColorMatrixFlag.Default,
ColorAdjustType.Bitmap)
Dim bitmap As Bitmap = New Bitmap(Me.Width, Me.Height,
PixelFormat.Format24bppRgb)
Dim g As Graphics = Graphics.FromImage(bitmap)
Dim brush As Brush = New SolidBrush(Me.BackColor)
g.FillRectangle(brush, New RectangleF(0, 0, Me.Width, Me.Height))
brush.Dispose()
e.Graphics.DrawImage(bitmap, _
New Rectangle(0, 0, Me.Width, Me.Height), _
0, 0, Me.Width, Me.Height, GraphicsUnit.Pixel, attributes)
End Sub
End Class
Please let me know if you have any other concerns, or need anything else.
Luke Zhang
Microsoft Online Community Support
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