Tutorial: Leveling a Horizon
This tutorial was last tested for the Gimp 2.2.13
Humans are very good at picking a horizon that is not level. However when we are taking photographs we don't always get it right. This tutorial is a simple method of correcting that. The before and after views:
I will be using the original photo on the left than can be downloaded here.
- Select the "Measure distances and angles" tool.
- Click and hold a point right on the horizon, drag to another point on the horizon.
- GIMP will draw a line right on the horizon between the first click point and the release point.
- At the bottom of the window it will give you two pieces of information, the distance between the points and the angle, we are interested in the angle.
- Go to <Image> / Layer / Transform / Arbitrary Rotation (or use Shift + R)
- Rotate the image using the Angle field by the amount shown, a positive number will rotate the photo clockwise, a negative number will turn it the other way.
- The problem now is that the image has transparent corners.
- To remove them you have several choices:
- Clone nearby image into them.
- Crop the photo (my preference is to crop).