How to white out a background on photos?

Is there a way to get an all white background, white it all out behind the picture, is there an app? For iPhone.

Also what app can you add the smudge grey/white tint over your pictures.

If you want an all white background shoot against a white wall. Or shoot on a very bright day in the shadows and expose for the subject, so the rest of the scene is very overexposed.