Sometimes you may take a photo of a landscape or a beach and later realize that the horizon is crooked. Here’s how you can straighten the horizon:
The first step is to pull the ruler down from the numbered bar at the top and place it over the horizon the way it should be.
Of course, the ruler will not be completely in line with the horizon, so try to place the ruler over the centre of the horizon.
Then use “Rotate” and rotate the photo until the horizon lines up with the ruler. Now crop the phot with the scalpel.