vb.net screenshot tutorial

Dim _myBitmap as new Bitmap(50,50) '' 50,50 is the size: width, height, few diff. overloads
Dim _gr As Graphics = Graphics.FromImage(_myBitmap) '' we need the gr object for copyfromscreen

_gr.CopyFromScreen(***,***) '' not actual paremeters.
_gr.Dispose() ''don't forget about this later

    Public Shared Function CopyFromScreen(ByVal tl As Point, ByVal width As Int32, ByVal height As Int32) As Bitmap
        Dim _rtnBmp As New Bitmap(width, height)
        Dim _gr As Graphics = Graphics.FromImage(_rtnBmp)
        _gr.CopyFromScreen(tl, New Point(0, 0), New Size(width, height), CopyPixelOperation.SourceCopy) '' sourcecopy or ____ ?
        _gr.Dispose()
        Return _rtnBmp
    End Function

    Public Shared Function GetWindowScreen(ByVal windowTitle As String, Optional ByVal includeBorders As Boolean = True) As Bitmap
        Dim _targetWindowHandle As IntPtr = FindWindow(Nothing, windowTitle) 'try to find window based on title.
        If _targetWindowHandle = 0 Then
            ''window not found
            MessageBox.Show("ScreenShotManager::GetScreenOfApp windowTitle not found! --> '" & windowTitle & "'" & Environment.NewLine _
                            & "Are you sure that program is running?")
            Return New Bitmap(2, 2) ''why not (1,1). choice.
        Else
            ''window found
            Dim _targetWindowInfo As WINDOWINFO
            GetWindowInfo(_targetWindowHandle, _targetWindowInfo)
            If includeBorders Then
                Dim _tl As New Point(_targetWindowInfo.rcWindow.Left, _targetWindowInfo.rcWindow.Top)
                Return CopyFromScreen(_tl, _targetWindowInfo.rcWindow.Width, _targetWindowInfo.rcWindow.Height)
            Else
                Dim _tl As New Point(_targetWindowInfo.rcClient.Left, _targetWindowInfo.rcClient.Top)
                Return CopyFromScreen(_tl, _targetWindowInfo.rcClient.Width, _targetWindowInfo.rcClient.Height)
            End If
        End If
    End Function

Public Sub RunFPSTest()

        If MessageBox.Show("Open pinball.exe before you click OK") = DialogResult.OK Then

            Dim _ss As Bitmap
            Dim _timeLapse As TimeSpan
            Dim _startTime As DateTime = Date.Now
            Dim _aColor As Color
            Dim _ctr As Int32 = 0

            For jj = 1 To 15
                _ss = GetWindowScreen("3D Pinball for Windows - Space Cadet", True)
                For xx As Int32 = 0 To _ss.Width - 1
                    For yy As Int32 = 0 To _ss.Height - 1
                        _aColor = _ss.GetPixel(xx, yy)
                        If _aColor.R = 0 And _aColor.G = 0 And _aColor.B = 0 Then
                            'white/black
                            _ctr += 1
                        End If
                    Next
                Next
            Next
            _timeLapse = Date.Now.Subtract(_startTime)
            MsgBox("It took " + _timeLapse.TotalSeconds.ToString & "s to scan 15 times, that's..." & Environment.NewLine _
                   & (15 / _timeLapse.TotalSeconds).ToString + " / second " & Environment.NewLine _
                   * "Image size: " & _ss.Width & "x" & _ss.Height & " pixels" & Environment.NewLine _
                   & "black_pixel_ctr: " & _ctr.ToString)
        End If

    End Sub

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
Private Declare Function GetWindowInfo Lib "user32" (ByVal hWnd As IntPtr, ByRef pWinInfo As WINDOWINFO) As Boolean

    Private Structure WINDOWINFO
        Dim cbSize As Integer
        Dim rcWindow As RECT_win32 ''entire form, including border
        Dim rcClient As RECT_win32 ''client window, no border
        Dim dwStyle As Integer 
        Dim dwExStyle As Integer
        Dim dwWindowStatus As UInt32 ''fullscreen? minimized?
        Dim cxWindowBorders As UInt32
        Dim cyWindowBorders As UInt32''not sure
        Dim atomWindowType As UInt16
        Dim wCreatorVersion As Short
    End Structure

''' <summary>
    ''' NOT bit compatible with system.drawing.rectangle
    ''' </summary>
    Private Structure RECT_win32 'not bit compatible with system.drawing.rectangle.
        Dim Left As Integer
        Dim Top As Integer
        Dim Right As Integer
        Dim Bottom As Integer
        Public Property Height() As Integer
            Get
                Return Bottom - Top
            End Get
            Set(ByVal value As Integer)
                Bottom = value - Top
            End Set
        End Property
        Public Property Width() As Integer
            Get
                Return Right - Left
            End Get
            Set(ByVal value As Integer)
                Right = value + Left
            End Set
        End Property
    End Structure