Quick image straightening with Photoshop

Microsoft Digital Image Suite, for all its limitations, does a few things really well:

  • Fix red-eye
  • Stitch together panoramas
  • Make straightening images brain-dead easy

I love Photoshop.  It’s definitely my image editor of choice but I always used to launch Digital Image to straighten pictures, then I’d go back to Photoshop for the rest of my tweaks.  It wasn’t until I bought The Photoshop Book for Digital Photographers by Scott Kelby (also in flavors for CS2 and CS3) that I learned the Photoshop method.

Straightening images is actually a pretty simple process, but nowhere in the Photoshop UI does it say “straighten”.  I suppose I could have read the manual, but where’s the fun in that?

The basic steps are:

  1. Use the measure tool to figure out the angle to rotate
  2. Perform an “arbitrary” rotation
  3. Crop your picture

Let’s say you’re in a hurry (or drunk) and snap a quick photo at a wonky angle.

The first step (after opening the picture with Photoshop, of course) is to select the measure tool from your tools palate.  The measure tool is the ruler buried under the eyedropper tool and can be accessed by clicking and holding or by hitting shift-i repeatedly until the measure tool is selected (I’m a big fan of keyboard shortcuts in Photoshop, they save me a bunch of time and make me feel like a power user).

Once you have your measure tool selected you need to pick a line in the picture you think should be horizontal or vertical.  If you’re straightening a landscape the horizon is a good bet.  If you are shooting buildings using a wide angle lens you’ll want to pick a line near the center of the picture and probably a vertical one.

Use the measure tool to draw along the line you think should be vertical.

Rotating the picture is now a fairly automatic process.  From the Image menu select Rotate Canvas -> Arbitrary.  When the dialog pops up you’ll note Photoshop has already filled in a number.  The software has looked at the line you drew using the measure tool and input the number of degrees to rotate automatically.  All you have to do is press OK.

Your image is now straight but you have some extra gunk you need to trim off.  Grab the crop tool from your palate (or hit “c” on your keyboard) and pick out the part of the picture you want to keep.  Hitting enter on your keyboard will crop the picture and after you save you’re done.

 

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