Rotate
figure 1: The Rotate Button
The rotate button allows you to rotate an image in Snappy. When you click on this button, you can rotate an image left or right. You can also invert the image (top becomes bottom, bottom becomes top). Finally, if you select the None option, any rotations you may have already applied will be removed. The None option is the default setting for rotation.
The Custom option allows you to control exactly how the image will be rotated. When you select this option, a green and red square will appear on the left and right sides of your image. (They are connected by a dotted line.) These tabs, and the line, represent where you want the new horizon of your image to be. Simply click-and-drag on these tabs to position the horizon. When you're finished, click the Process button. Snappy will then produce a new image with the new horizon.
The custom rotate feature is great for those times when your camera just wasn't straight, because you may have been on a boat, or you just weren't paying attention. By setting a new horizon, the image won't look like it was taken at a Mystery Spot.