Perspective ++ photo editor and Photos Extension is the missing link to mobile photo editing.
With Perspective++ users can:
Adjust horizon.
Adjust horizontal and verticle perspective.
Crop using rule of thirds method.
Create "Fisheye" and distortions to any point in your image.
Users can set the horizon and adjust the perspective with out exporting to complicated image editing applications. 
Available as both a stand alone application and a Photos Extension Perspective ++ users have the ability the adjust the perspective of images including panoramas right inside the Photos app.
Adjusting the perspective is particularly useful when editing architectural images and large panoramas where the edges can become distorted.
Adjusting the perspective can also let the image place a larger emphasis on the sky or objects in the foreground.
Fisheye adjustment not only makes for cool landscape and panorama images but also can be used selectively to place greater emphasis on specify portions of the image being edited. This is shown in the app screenshots, just look at the emblem behind the statue.

Convenient image sharing with sister application "Canvas Art" allows recent edits from both applications to be shared and accessed within the application.
Take your iPhone and iPad photography to a new level with Perspective ++.