Adding a shutdown button

Is there a way to add a shutdown button to the log in screen so that I do not have to log back in to shutdown my iMac? In other words, after I have logged in and then the system logs me out due to inactivity, I have to enter my password to be able to shutdown the computer. Is there a way to get the shutdown buttons and restart buttons to appear on the bottom of the screen after the system has logged me out due to inactivity like they appear on the initial log in page? Thanks so much for your help.