Straightening Your Horizons

There are several ways to straighten out a line in your image. The two most common situations where you may need this technique are squaring up an image that is slightly rotated (perhaps not aligned perfectly at scan time) or to straighten out an errant horizon line.

Our favorite method of rotating an image is to use the ruler tool in combination with the Rotate Canvas command.

Select the Ruler tool (which is now hidden in Photoshop 6 under the Eyedropper tool). Holding down the mouse, select a starting point on one end of as long a portion of the axis you want to rotate along as possible and draw to the other end of that axis. The longer the segment you choose, the more accurate your rotation is likely to be. You also want to select a starting and ending point in which you can clearly see the difference between the pixels on either side of where you click the mouse. This is because you want to start and end the ruler line at the same relative position along the line, ideally almost to the level of a pixel.