Per Pixel Alpha Blend in C#

<br />
Imports System<br />
Imports System.Drawing<br />
Imports System.Drawing.Imaging<br />
Imports System.Windows.Forms<br />
Imports System.Runtime.InteropServices<br />
'Translation from C# by Dj Den4ik<br />
Public Class PerPixelAlphaForm<br />
    'Implements Windows.Forms.IWin32Window<br />
<br />
    Public Structure ARGB<br />
        Public Blue As Byte<br />
        Public Green As Byte<br />
        Public Red As Byte<br />
        Public Alpha As Byte<br />
    End Structure<br />
<br />
    Public Structure BLENDFUNCTION<br />
        Public BlendOp As Byte<br />
        Public BlendFlags As Byte<br />
        Public SourceConstantAlpha As Byte<br />
        Public AlphaFormat As Byte<br />
    End Structure<br />
<br />
    Public Const ULW_COLORKEY As Int32 = &H1<br />
    Public Const ULW_ALPHA As Int32 = &H2<br />
    Public Const ULW_OPAQUE As Int32 = &H4<br />
<br />
    Public Const AC_SRC_OVER As Byte = &H0<br />
    Public Const AC_SRC_ALPHA As Byte = &H1<br />
<br />
    Public Declare Function UpdateLayeredWindow Lib "user32" Alias "UpdateLayeredWindow" (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 Boolean<br />
    Public Declare Function GetDC Lib "user32" Alias "GetDC" (ByVal hWnd As IntPtr) As IntPtr<br />
    Public Declare Function ReleaseDC Lib "user32" Alias "ReleaseDC" (ByVal hWnd As IntPtr, ByVal hDC As IntPtr) As Integer<br />
    Public Declare Function CreateCompatibleDC Lib "gdi32.dll" Alias "CreateCompatibleDC" (ByVal hDC As IntPtr) As IntPtr<br />
    Public Declare Function DeleteDC Lib "gdi32.dll" Alias "DeleteDC" (ByVal hDC As IntPtr) As Boolean<br />
    Public Declare Function SelectObject Lib "gdi32.dll" Alias "SelectObject" (ByVal hDC As IntPtr, ByVal hObject As IntPtr) As IntPtr<br />
    Public Declare Function DeleteObject Lib "gdi32.dll" Alias "DeleteObject" (ByVal hObject As IntPtr) As Boolean<br />
<br />
    Public Sub SetBitmap(ByVal bitmap As Bitmap, ByVal opacity As Byte, ByVal frm As Form)<br />
        If bitmap.PixelFormat <> PixelFormat.Format32bppArgb Then Throw New ApplicationException("The bitmap must be 32ppp with alpha-channel.")<br />
<br />
        ' The ideia of this is very simple,<br />
        ' 1. Create a compatible DC with screen;<br />
        ' 2. Select the bitmap with 32bpp with alpha-channel in the compatible DC;<br />
        ' 3. Call the UpdateLayeredWindow.<br />
<br />
        Dim screenDc As IntPtr = GetDC(IntPtr.Zero)<br />
        Dim memDc As IntPtr = CreateCompatibleDC(screenDc)<br />
        Dim hBitmap As IntPtr = IntPtr.Zero<br />
        Dim oldBitmap As IntPtr = IntPtr.Zero<br />
<br />
        Try<br />
            hBitmap = bitmap.GetHbitmap(Color.FromArgb(0))  ' grab a GDI handle from this GDI+ bitmap<br />
            oldBitmap = SelectObject(memDc, hBitmap)<br />
            Dim size As New Size(bitmap.Width, bitmap.Height)<br />
            Dim pointSource As New Point(0, 0)<br />
            Dim topPos As New Point(frm.Left, frm.Top)<br />
            Dim blend As New BLENDFUNCTION<br />
            blend.BlendOp = AC_SRC_OVER<br />
            blend.BlendFlags = 0<br />
            blend.SourceConstantAlpha = opacity<br />
            blend.AlphaFormat = AC_SRC_ALPHA<br />
            UpdateLayeredWindow(frm.Handle, screenDc, topPos, size, memDc, pointSource, 0, blend, ULW_ALPHA)<br />
        Finally<br />
            ReleaseDC(IntPtr.Zero, screenDc)<br />
            If hBitmap <> IntPtr.Zero Then<br />
                SelectObject(memDc, oldBitmap)<br />
                DeleteObject(hBitmap)<br />
            End If<br />
            DeleteDC(memDc)<br />
<br />
        End Try<br />
    End Sub<br />

<br />
    Dim ppaf As New PerPixelAlphaForm<br />
    Dim bmp As New Bitmap("D:\Audio\FL Studio 7\Artwork\FL Studio Producer Edition\Title_.png")<br />
<br />
    Protected Overrides ReadOnly Property CreateParams() As System.Windows.Forms.CreateParams<br />
        Get<br />
            Dim SecPerm As New Security.Permissions.SecurityPermission(Security.Permissions.PermissionState.Unrestricted)<br />
            SecPerm.Demand()<br />
<br />
            ' Extend the CreateParams property of the Button class.<br />
            Dim cp As System.Windows.Forms.CreateParams = MyBase.CreateParams<br />
            ' Update the button Style.<br />
            cp.ExStyle = &H80000<br />
<br />
            Return cp<br />
        End Get<br />
    End Property<br />
<br />
    Private Sub frmTest_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load<br />
        Me.FormBorderStyle = Windows.Forms.FormBorderStyle.None<br />
        Me.TopMost = True<br />
        For Each ctrl As Control In Me.Controls<br />
            ctrl.DrawToBitmap(bmp, ctrl.Bounds)<br />
        Next<br />
        Me.Region = New Region()<br />
        ppaf.SetBitmap(bmp, 240, Me)<br />
    End Sub<br />
<br />
<br />
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)<br />
<br />
        Const WM_MOUSEMOVE As Int32 = &H200<br />
        Const WM_NCLBUTTONDOWN As Int32 = &HA1<br />
        Const HTCAPTION As Int32 = 2<br />
<br />
        '// ????????????? WM_MOUSEMOVE <br />
        If m.Msg = WM_MOUSEMOVE Then<br />
<br />
            '// ???????? ReleaseCapture <br />
            MyBase.Capture = False<br />
<br />
            '// ??????? ???? ????????? <br />
            Dim message As New Message<br />
            With message<br />
                .HWnd = Me.Handle<br />
                .Msg = WM_NCLBUTTONDOWN<br />
                .WParam = HTCAPTION<br />
                .LParam = 0&<br />
            End With<br />
<br />
            '// ?????????? ???? ????????? ???? <br />
            MyBase.WndProc(message)<br />
        End If<br />
<br />
        MyBase.WndProc(m)<br />
<br />
    End Sub<br />

<br />
public void SetBitmap(Bitmap bitmap, byte opacity = 255) {<br />
}<br />

partial class MainForm: Form
{
  Bitmap bkgrnd = null;

...

  // Constructor
  public MainForm()
  {
    InitializeComponent();
    bkgrnd = lib.LoadBitmapResource(2005);  // Assign your Bitmap loaded from .dll
    this.BackgroundImage = bkgrnd;
    // StartPosition has no affect so use this instead.
    this.CenterToScreen();
  }

...

private void RefreshFormTimer_Tick(object sender, EventArgs e)
{
  if (bkgrnd != null)
    SetBitmap(bkgrnd);
}