VMs thumbnail image via the Virtual Server COM object

So the first week of App Building has gone well.  I'll write more about my app as soon as it is finished, but I figured I would share a code snippet which you may find helpful.

The Virtual Server 2005 COM API allows you to do a great many things, even get a thumbnail image of the virtual machine's screen.  Unfortunately however that property is returned as an array of integers which are persisted as Object[].  In other words the functionality is there but you need to convert it to something useful yourself.

The following routine does this convertion for you in VB.NET:

''' <summary>
''' Returns the thumbnail for the underlying
''' Virtual Machine.
''' </summary>
''' <remarks>
''' If the Virtual Machine is off then the thumbnail will
''' be solid gray.
''' Also, this code snippet will only work with
''' Visual Studio 2005 codenamed Whidbey since it takes
''' advantage a new VB.NET feature, unsigned integers.
''' </remarks>
Public ReadOnly Property Thumbnail() As Bitmap
   Get
      ' Get the int array from VServer
Dim pixelArrayObj As Object()
pixelArrayObj = CType( _
               m_comVirtualMachine.Display.Thumbnail, _
Object())

      ' Convert it to a bitmap
Dim bmp As New Bitmap(64, 48)

' Pixel index
      Dim i As Integer = 0

' The thumbnail is always 64x48
      For y As Integer = 0 To 47
For x As Integer = 0 To 63

Dim uiPixel As UInteger = CUInt(pixelArrayObj(i))
Dim red, green, blue As Integer

red = CInt((uiPixel >> 8) Mod 256)
green = CInt((uiPixel >> 16) Mod 256)
blue = CInt((uiPixel >> 24) Mod 256)

            bmp.SetPixel(x, y, _
                        Color.FromArgb(red, green, blue))
            i += 1
         Next
      Next

Return bmp
End Get

End Property

Disclaimer: The code snippet is offered 'as is' and offers no warranties, expressed or implied.  If that 40-line function is somehow responsible for your computer becoming self-aware and taking over the human race, sorry, but don’t blame me or Microsoft.

Comments

• Anonymous
  August 10, 2005
  In the past I have posted about using Virtual Servers 'thumbnail' API to perform virtual machine automation...
• Anonymous
  August 16, 2005
  Really nice peace of code, usefull !
  
  Can you explain me briefly what these 'unsigned' integer are? I would like to grab why it's important in this case.
  
  thanks again for this.
  
  
  
• Anonymous
  August 22, 2005
  The comment has been removed
• Anonymous
  September 20, 2005
  well I made it work on older vb.net distribution (2003), by replacing
  
  Dim uiPixel As UInteger = CUInt(pixelArrayObj(i))
  
  with
  
  Dim uiPixel As Double = Convert.ToDouble(pixelArrayObj(i))
  
  
  
  here's the code returning the bitmap:
  
  Private Function Thumbnail1(ByVal m_comVirtualMachine As VMVirtualMachine) As Bitmap
  
  Dim pixelArrayObj As Object()
  pixelArrayObj = CType(m_comVirtualMachine.Display.Thumbnail, Object())
  
  ' Convert it to a bitmap
  Dim bmp As New Bitmap(64, 48)
  
  ' Pixel index
  Dim i As Integer = 0
  
  ' The thumbnail is always 64x48
  For y As Integer = 0 To 47
  For x As Integer = 0 To 63
  
  Dim uiPixel As Double = Convert.ToDouble(pixelArrayObj(i))
  Dim red, green, blue As Integer
  
  red = CInt((uiPixel >> 8) Mod 256)
  green = CInt((uiPixel >> 16) Mod 256)
  blue = CInt((uiPixel >> 24) Mod 256)
  
  bmp.SetPixel(x, y, Color.FromArgb(red, green, blue))
  i += 1
  Next
  Next
  
  Return bmp
  
  End Function