Option Explicit

Private Declare Function GetDesktopWindow Lib "user32.dll" () _
        As Long

Private Declare Function GetDC Lib "user32.dll" ( _
        ByVal hwnd As Long) As Long

Private Declare Function ReleaseDC Lib "user32.dll" ( _
        ByVal hwnd As Long, _
        ByVal hdc As Long) As Long

Private Declare Function GetSystemMetrics Lib "user32.dll" ( _
        ByVal nIndex As Long) As Long

Private Declare Function BitBlt Lib "gdi32.dll" ( _
        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 StretchBlt Lib "gdi32.dll" ( _
        ByVal hdc 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 nSrcWidth As Long, _
        ByVal nSrcHeight As Long, _
        ByVal dwRop As Long) As Long

Public Enum eCaptureMode
  CropPicture = 0
  SizePicBox = 1
  SizePicture = 2
End Enum

Public Function GetDesktop(ByRef pbPictureBox As PictureBox, _
      Optional ByVal CaptureMode As eCaptureMode = CropPicture) _
      As Boolean

  Dim hDesktop      As Long
  Dim hDesktopDC    As Long
  Dim ScreenWidth   As Long
  Dim ScreenHeight  As Long

  hDesktop = GetDesktopWindow()
  hDesktopDC = GetDC(hDesktop)

  ScreenWidth = GetSystemMetrics(0&)
  ScreenHeight = GetSystemMetrics(1&)

  With pbPictureBox
    If CaptureMode = SizePicBox Then
      .Width = ScreenWidth * Screen.TwipsPerPixelX
      .Height = ScreenHeight * Screen.TwipsPerPixelY
    End If
    .AutoRedraw = True
    .Cls
  End With

  If CaptureMode = CropPicture Or CaptureMode = SizePicBox Then
    Call BitBlt(pbPictureBox.hdc, 0&, 0&, _
                ScreenWidth, ScreenHeight, _
                hDesktopDC, 0&, 0&, vbSrcCopy)

  Else
    Call StretchBlt(pbPictureBox.hdc, 0&, 0&, _
                pbPictureBox.Width \ Screen.TwipsPerPixelX, _
                pbPictureBox.Height \ Screen.TwipsPerPixelY, _
                hDesktopDC, 0&, 0&, _
                ScreenWidth, ScreenHeight, vbSrcCopy)
  End If

  With pbPictureBox
    .AutoRedraw = False
    .Refresh
  End With

  Call ReleaseDC(hDesktop, hDesktopDC)
End Function

Option Explicit

Private Sub cmdDoScreenshot_Click()
  Call Form_Resize

  If chkHideDuringScreenshot.Value = 1 Then
    Me.Hide
  End If
  DoEvents

  GetDesktop picScreenshot, cboScreenshotType.ItemData( _
        cboScreenshotType.ListIndex)

  If chkHideDuringScreenshot.Value = 1 Then
    Me.Show
  End If
End Sub

Private Sub Form_Load()
  With Me.cboScreenshotType
    .Clear
    .AddItem "Bild ggf.abschneiden"
    .ItemData(.NewIndex) = 0
    .AddItem "Picturebox an Bild anpassen"
    .ItemData(.NewIndex) = 1
    .AddItem "Bild an Picturebox anpassen"
    .ItemData(.NewIndex) = 2

    .ListIndex = 0
  End With
End Sub

Private Sub Form_Resize()
  picScreenshot.Width = Me.ScaleWidth - (picScreenshot.Left * 2)
  picScreenshot.Height = Abs(Me.ScaleHeight - picScreenshot.Top)
End Sub