Bileder i asp.net

Hej
jeg har forsøgt mig med at lave et billede med .net egen drawing metoder, men farverne virker lidt gnidret og ikke særlig kønne.
Kan man på en eller anden måde gøre farverne og linier mere "glatte" eller skal man købe et billed modul.
Jeg håber I forstår hvad jeg mener.

Mvh
Henrik

Her er koden:
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Dim objBitmap As New System.Drawing.Bitmap(1200, 840)
        Dim objGraphics As System.Drawing.Graphics
        objGraphics = System.Drawing.Graphics.FromImage(objBitmap)
        objGraphics.Clear(Drawing.Color.White)

        Dim p As New Drawing.Pen(Drawing.Color.Yellow, 0)
        Dim rect As New Drawing.Rectangle(10, 10, 280, 280)
        Dim rect1 As New Drawing.Rectangle(100, 100, 480, 480)
        objGraphics.DrawEllipse(p, rect)
        objGraphics.FillRectangle(Drawing.Brushes.Brown, rect1)


        objGraphics.DrawLine(Drawing.Pens.Black, 100, 100, 400, 400)

        Dim b1 As New Drawing.SolidBrush(Drawing.Color.Red)
        Dim b2 As New Drawing.SolidBrush(Drawing.Color.Green)
        Dim b3 As New Drawing.SolidBrush(Drawing.Color.Blue)
        objGraphics.FillPie(b1, rect, 0.0F, 90.0F)
        objGraphics.FillPie(b2, rect, 90.0F, 60.0F)
        objGraphics.FillPie(b3, rect, 150.0F, 210.0F)

        Dim fontfml As New Drawing.FontFamily(Drawing.Text.GenericFontFamilies.Serif)
        Dim font As New Drawing.Font(fontfml, 14)
        Dim brush As New Drawing.SolidBrush(Drawing.Color.Blue)
        objGraphics.DrawString("Draw Graphics", font, brush, 100, 400)

        objBitmap.Save(Response.OutputStream,Drawing.Imaging.ImageFormat.Gif)
       
        objBitmap.Dispose()
        objGraphics.Dispose()
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