How to Change image from colors to gray scale

I was searching the net for changing the image colors to its gray scale


Color to grayScale with Transparent Background

 I found a good example here
But It changes the background color also
to it's black-white,So it appears in black color.

With simple a change in code to fix the problem
here it is:

Public Function ConvertToGrayScale(ByVal Source As Bitmap) As Bitmap
Dim bm As New Bitmap(Source.Width, Source.Height)
Dim x As IntegerDim y As Integer
Dim FirstPixelColor As Color
FirstPixelColor = Source.GetPixel(0, 0)For y = 0 To bm.Height - 1
  For x = 0 To bm.Width - 1
  Dim c As Color = Source.GetPixel(x, y)
  If c <> FirstPixelColor Then
      Dim luma As Integer = CInt(c.R * 0.3 + c.G * 0.59 + c.B * 0.11)   
      bm.SetPixel(x, y,Color.FromArgb(luma, luma, luma))   Else
      bm.SetPixel(x, y,Color.FromArgb(0, 0, 0, 0))
  End If
  Next
Next
Return bm
End Function

Just copy and paste and try it ,If you have a simpler method tell me.