I need help finding a photography app for the iPhone. Description is below?

[asdfghjkl]

I always see people using this app on instagram and tumblr but i can't find it. I have this picture and over it i want to put words. I want the words to be the negative space where the picture would show through and the words to have like a solid color around it. I know its kind of confusing, but does anyone know the name of the app I'm talking about?

[razz]

go to instagram
sign up
download app
now accept the fact that you will never have a normal life again due to this app.