Ooops - Didn't mean to do that but turned out great anyway

I was just working on a photos, actually quite a few, this is why I was using shortcuts; I typed this (thinking it would brink the image size box) but it gave me a nice unexpected effect instead...now I just need to find out what it is...!

Ctrl+I

From this

To This

I know what it is now, it's invert...