Im a professional photographer who does a lot of architectural and real estate work, and I am always correcting perspective skews. There have been some other apps that have done this, but they were always clumsy and difficult. This is a terrific solution and I use it virtually every day. And to clarify, the problem with other de-skewing apps referenced in other reviews is that they will only work if youre skew is completely evenly balanced from left to right or top to bottom. This app however allows you to completely tailor your skew correction (e.g. the left side a little less than the right side, while raising just the top right a little bit, etc.) and as far as I know is the only app that does that.