Grayscale

enum SmoothingMode{
  SmoothingModeInvalid     = QualityModeInvalid,
  SmoothingModeDefault     = QualityModeDefault,
  SmoothingModeHighSpeed   = QualityModeLow,
  SmoothingModeHighQuality = QualityModeHigh,
     SmoothingModeNone,
  SmoothingModeAntiAlias
};

В данный момент фактически нет разницы между режимами SmoothingModeDefault, SmoothingModeHighSpeed и SmoothingModeNone: все они  выключают  антиалиасинг примитивов. Изображение при этом приобретает привычные ступенчатые края:

http://www.codeguru.com/forum/showthread.php?threadid=465347

• Public Shared Function MakeGrayscale3(ByVal original As Bitmap) As Bitmap
•     'create a blank bitmap the same size as original
•     Dim newBitmap As New Bitmap(original.Width, original.Height)
•    
•     'get a graphics object from the new image
•     Dim g As Graphics = Graphics.FromImage(newBitmap)
•    
•     'create the grayscale ColorMatrix
•     Dim colorMatrix As New ColorMatrix(New Single()() {New Single() {0.3, 0.3, 0.3, 0, 0}, New Single() {0.59, 0.59, 0.59, 0, 0}, New Single() {0.11, 0.11, 0.11, 0, 0}, New Single() {0, 0, 0, 1, 0}, New Single() {0, 0, 0, 0, 1}})
•    
•     'create some image attributes
•     Dim attributes As New ImageAttributes()
•    
•     'set the color matrix attribute
•     attributes.SetColorMatrix(colorMatrix)
•    
•     'draw the original image on the new image
•     'using the grayscale color matrix
•     g.DrawImage(original, New Rectangle(0, 0, original.Width, original.Height), 0, 0, original.Width, original.Height, _
•     GraphicsUnit.Pixel, attributes)
•    
•     'dispose the Graphics object
•     g.Dispose()
•     Return newBitmap
• End Function