Got it ! Download application "Spark" Open "Spark".Choose File/New Hotkey/Applescript .Then enter a shortcut key(that isn't used already , like F16) , put in a name and put in this applescript :
Push "Create" at bottom right and
don't forget to activate "Start Spark Deamon" at the bottom of window. Then close "Spark".
And your shortkey will let you make any selection on your screen and save it to desktop AND opens it directly .(and only Spark deamon is active at background)