Digital Focus: Straighten Your Crooked Pictures

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Feature: Straighten Your Crooked Pictures

Why is it that a picture looks perfectly straight in the viewfinder when you photograph it, but by the time it makes its way onto your PC, it's tilted like a sinking ship?

The answer is simple: The scene in your viewfinder is as level as the world around you, and your brain ignores the fact that the camera itself is slightly off-kilter when you frame the shot. So, as usual, it's your brain's fault.

But just because you take the occasional crooked picture, that doesn't mean you have to live with it. This week, let's look at straightening pictures in some detail. This is somewhat similar to correcting perspective in photos. I've written about this before, in "Fix Perspective in Your Photos" and "Fix Perspective in Architectural Photos."

But so far, I've never covered plain old straightening. Nor have I touched on some of the problems that come from this type of correction. For example, straightening an image can leave blank spots in the corners of a picture. This week we'll learn how judicious use of the Clone Brush can remedy these defects.

Use the Straighten Tool

In the old days, image editing software didn't come with an easy way to straighten photos; you had to rotate the picture, a little at a time, until it looked about right. Our tools have evolved, making the task far easier. I'll use Jasc Paint Shop Pro to demonstrate my point.

Let's work on a picture of a windmill that I took a while ago. The windmill's tilt is not severe, but the lean to the right is just enough to spoil an otherwise good photo. Save the shot to your hard drive so that you can open it up and work along with me.

Start the correction by selecting the Straighten tool from the second cubby in the toolbar on the left side of the screen. You'll see a horizontal line appear across the picture. Position the line with your mouse over something in the picture that's supposed to be perfectly vertical or horizontal. Simply grab its endpoints and move them to where you want them. This sample picture offers a nice, straight windmill shaft that should be vertical, so I centered the line right over it.

When the line is arranged just the way you like, click the check mark in the Tool Options palette at the top of the screen. If the Tool Options palette isn't already on screen, display it by choosing View, Palettes, Tool Options.

Presto--the windmill is straight.

Clone Away the Emptiness

Unfortunately, by fixing one problem we've created another. By rotating the picture, we've introduced empty space along the edges; you'll probably want to get rid of it.

If you don't mind making the picture smaller and changing the composition slightly, the fix is a snap: Just crop the picture, being careful to eliminate the empty space in the process.

But you can be more creative than that: Try filling in the voids using the Clone Brush. This works great when you have a simple, indistinct background--as in this week's sample picture.

Click the Clone Brush (it's in the eighth cubby in the toolbar) and then, in the Tool Options palette, set the size of the brush to about 40 pixels. You should adjust the size up or down if you're editing pictures that are much larger or smaller than the one we're working with this week. Make sure that the Opacity is set at 100 percent, and you're ready to go.

Now right-click in the sky very near the empty space, but low enough that the entire Clone Brush diameter is in the blue, and paint across the space. You may need to do a bit of "scrubbing" back and forth to get the color consistent, and you may have to sample different bits of the sky to fully and seamlessly cover the empty area.

Repeat the process to paint down the left side. When you reach the clouds, stop and sample a spot in the middle of the thick, bushy clouds near the mountains, then resume painting. When you reach the mountain itself, right-click precisely on the top edge of the mountain, move the brush to the blank space, and paint. The new, cloned mountain should line up with the real mountain perfectly. Finish the cloning in this way.

When you're all done, save the picture.

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