protected void btnUpload_Click(object sender, EventArgs e)
{
    if (fileUpload.HasFile)
    {
        string ghostDllPath = HttpContext.Current.Server.MapPath("~/bin/External");
        GhostscriptRasterizer rasterizer = null;
        GhostscriptVersionInfo vesion = null;
        if (Environment.Is64BitProcess)
            vesion = new Ghostscript.NET.GhostscriptVersionInfo(new Version(0, 0, 0), ghostDllPath + @"gsdll64.dll", string.Empty, Ghostscript.NET.GhostscriptLicense.GPL);
        else
            vesion = new Ghostscript.NET.GhostscriptVersionInfo(new Version(0, 0, 0), ghostDllPath + @"gsdll32.dll", string.Empty, Ghostscript.NET.GhostscriptLicense.GPL);
        using (rasterizer = new Ghostscript.NET.Rasterizer.GhostscriptRasterizer())
        {
            rasterizer.Open(fileUpload.PostedFile.InputStream, vesion, false);
            if (rasterizer.PageCount > 0)
            {
                  int dpi = 90;
                  System.Drawing.Image img = rasterizer.GetPage(dpi, dpi, 1);
                  using (MemoryStream ms = new MemoryStream())
                  {
                       string file = Guid.NewGuid().ToString() + ".png";
                       img.Save(ms, ImageFormat.Png);
                       Response.ContentType = "image/png";
                       byte[] data = ms.ToArray();
                       Response.OutputStream.Write(data, 0, data.Length);
                       Response.AddHeader("Content-Disposition", "attachment;filename=" + file);
                       Response.Flush();
                   }
            }
            rasterizer.Close();
        }
    }
}