How do I blur in distance

Hello everybody I was searching on the scirra forums but didn't find what I was looking for. What I was looking for is how do I blur the map if the player is far away from that side of the map so the player couldn't see what is in front of him. So basically like in in the game that came out called This War of Mine When you spawn you cant see anything that is far away or the if the door is closed. But you can see that there is something so you will be still able to see through the blur that something is moving there!

Thank you for your attention!

You might find something useful here

Hmm procrastinator didn't find what I needed it's fog only... But is there a way creating a shadow as a second image (which is with blur) so it's not black? So like here:

So in basic meaning how do you make the black shadow to show the image that it covers and blur it so you cant see if you are behind the wall but you can still see what there is!

Thank you for your time!