setting transparancy on png through alphachannel

OrigBitmap.Draw(NewBitmap, 0, 0, _
                           OrigBitmap.Width, OrigBitmap.Height, _
                           Aurigma.GraphicsMill.Transforms.CombineMode.Alpha, 0.2F, _
                           Aurigma.GraphicsMill.Transforms.InterpolationMode.HighQuality)

Option Strict On
Option Explicit On

Imports Aurigma.GraphicsMill
Imports Aurigma.GraphicsMill.Codecs
Imports Aurigma.GraphicsMill.Transforms

Partial Class ImageParse
    Inherits System.Web.UI.Page

    'Dim color As Aurigma.GraphicsMill.RgbColorcolor = Aurigma.GraphicsMill.RgbColor.FromArgb32(&H112233)
    'Dim a As Integer = color.A
    'Dim r As Integer = color.R
    'Dim g As Integer = color.G
    'Dim b As Integer = Color.B

    'Aurigma.GraphicsMill.Bitmap bitmap = new Aurigma.GraphicsMill.Bitmap(@"d:/images/test/embededprofile.png")
    'bitmap.ColorManagement.ColorManagementEnabled = true
    'bitmap.ColorManagement.RgbColorProfile = Aurigma.GraphicsMill.ColorProfile.FromSrgb()
    'bitmap.ColorManagement.ConvertToContinuous(Aurigma.GraphicsMill.ColorSpace.Rgb, false, false)
    'bitmap.Save(@"c:/newembededprofile.jpg")
    'bitmap.Dispose();

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        Dim OrigBitmap As New Aurigma.GraphicsMill.Bitmap(Server.MapPath("~/Images/add.png"))

        'Create new
        'Dim NewBitmap As New Aurigma.GraphicsMill.Bitmap(RgbColor.White, 35, 35, PixelFormat.Format32bppArgb)

        Dim bHasAlpha As Boolean = OrigBitmap.HasAlpha

        If bHasAlpha Then
            
            'Draw foreground image on background with transparency
            'OrigBitmap.Draw(NewBitmap, 0, 0, OrigBitmap.Width, OrigBitmap.Height, Transforms.CombineMode.Alpha, 0.2, Transforms.InterpolationMode.HighQuality)

            'OrigBitmap.ColorAdjustment.AdjustHsl(-0.2, -0.5, 0.5)

            'Somehow 8bpp indexed is stated as supported in the aurigma documentation
            'but still i need to convert to another pixelformat before i can use transparentize??

            'Convert image
            OrigBitmap.ColorManagement.Convert(PixelFormat.Format32bppArgb)

            'After conversion background is smudged!!!??? 
            'This doesnt happen in photoshop when i convert this image to rgb channels
            'and then manually set opacity and then save it to disk

            'After some more testing i came to the conclusion that the background is only smudged in Explorer not in Firefox??!!
            'Then again after i save this generated image through photoshop it displays perfectly in both browsers!!


            'If i convert with 24bpp then background becomes white, i need the *.png to retain its original background
            'OrigBitmap.ColorManagement.Convert(PixelFormat.Format24bppRgb)

            'Now apply transparancy
            OrigBitmap.Channels.Transparentize(Color.FromArgb32(0, 255, 255, 255), 1.0)


            'Try to remove background after 24bpp conversion
            'OrigBitmap.Channels.DiscardAlpha(RgbColor.White)


            'Resize image so i can see it better ;-)
            OrigBitmap.Transforms.Resize(100, 100, InterpolationMode.HighQuality)

            Dim encoderOptions As New PngEncoderOptions

            

            'Save to file to check image inside photoshop
            'OrigBitmap.Save("H:/test.png")

            'When i open *.png in photoshop cs2 everything looks fine
            'But when i open the image inside a browser background looks smudged (happens after conversion)
            'After i save this graphicsmill generated image through photoshop cs2
            'everything is fine again no smudged background !!!!!


            'Save image to response stream
            Response.Clear()
            Response.ContentType = "image/png"
            OrigBitmap.Save(Response.OutputStream, encoderOptions)


            'NewBitmap.Save(Response.OutputStream, encoderOptions)
            Response.End()

            'NewBitmap.Dispose()
            OrigBitmap.Dispose()

        End If


    End Sub

End Class