To begin, lets choose your picture or you can choose whether its your boyfriend, hollywood celebrities or your lovely pet. I use brad pitt as my reference
choose filter > Blur > Smart Blur
at 'mode' option, choose edge only
slide the bar until you satisfid with the result
Your photos still in black background. You just need to choose Image > Adjustment and select inverse (mac shortcut : command + I )
Here's the final result. You can erased some messy lines with eraser tools .