I got it.this code has done it
Private Sub btnExport0_Click()
Try
Dim path As String = Server.MapPath(Request.QueryString("imgpath"))
Dim imgin As System.Drawing.Image = System.Drawing.Image.FromFile(path)
Dim bitmap As New System.Drawing.Bitmap(imgin.Width, imgin.Height)
Dim g As Graphics = Graphics.FromImage(bitmap)
g.Clear(Color.Black)
Dim brush As New System.Drawing.TextureBrush(imgin)
g.FillEllipse(brush, New Rectangle(0, 0, imgin.Width, imgin.Height))
g.Dispose()
Response.Clear()
Response.ContentType = "image/pjpeg"
bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg)
Response.End()
bitmap.Dispose()
Catch ex As Exception
End Try
End Sub