Adjust Image size while printing on Zebra Barcode Printer in ASP.Net

I am using this code but Printing image is not clear on Zebra barcode printer, while same image in folder is clear.

private void SendToPrinter(string ff)
{
    string ff = Server.MapPath("~/FinalQRCode/") + filename;
    ProcessStartInfo info = new ProcessStartInfo();
    info.Verb = "print";
    info.FileName = ff;
    info.CreateNoWindow = true;
    info.WindowStyle = ProcessWindowStyle.Hidden;            
    Process.Start(info);
    Process p = new Process();
    p.StartInfo = info;
    p.Start();
}