Binaryworld - MaxSystemColors - The number of screen colors ... [ VB -> Windows ]

Private Declare Function GetDesktopWindow Lib "user32" () As Long
Private Declare Function GetDC Lib "user32" (ByVal hWnd As Long) As Long
Private Declare Function ReleaseDC Lib "user32" (ByVal hWnd As Long, _
  ByVal hDC As Long) As Long
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hDC As Long, _
  ByVal nIndex As Long) As Long
Private Const BITSPIXEL = 12
Private Const PLANES = 14

' returns the max number of colors supported by the video card

Function MaxSystemColors() As Long
  Dim hWnd As Long
  Dim hDC As Long
  Dim bitsPerPixel As Long
  Dim colorPlanes As Long
  Dim bits As Integer

  ' get the device context of the desktop window
  hWnd = GetDesktopWindow()
  hDC = GetDC(hWnd)
  ' the number of bits per pixels
  bitsPerPixel = GetDeviceCaps(hDC, BITSPIXEL)
  ' the number of color planes
  colorPlanes = GetDeviceCaps(hDC, PLANES)
  ' number of bits for each pixel
  bits = bitsPerPixel * colorPlanes
  ' no video card has more than 1.6 million colors
  If bits > 24 Then bits = 24
  ' evaluate the result
  MaxSystemColors = 2 ^ bits
  ' release the device context
  ReleaseDC hWnd, hDC
End Function