Print in silent mode on Linux

I need it to do a print in silent mode without opening the openprinterdialog On Linux. On Windows works well, but not on Linux.

I tried this:

lpr -P Brother_QL_570 image.png

but does not print.

How can I do?

You did enter the whole path to image.png? Not only image.png?

Yes. The script was an example. However now it works, but if I make a FOR also for 3, the launch always this command, the label hangs.

      Dim a As Integer
      For  a=0 to 3
        Dim f1 As FolderItem
        imgpic(a).Save(f1,Picture.SaveAsPNG, Picture.QualityDefault)
        Dim sh As New Shell
        sh.execute("lpr -P Brother_QL_570 "+f1.ShellPath)