Resizing Just Parts of Your Image Using Content-aware Scaling in Adobe Photoshop CS5
We’ve all run into situations where our image is a little smaller than the area where we need it to fit. For example, if you resize a digital camera image so it fits within a traditional 8×10″ image area, you’ll have extra space either above or below your image (or both). That’s where Content-Aware Scaling comes in—it lets you resize one part of your image, while keeping the important parts intact (basically, it analyzes the image and stretches, or shrinks, parts of the image it thinks aren’t as important). Here’s how to use it:
Create a new document at 8×10″ and 240 ppi. Open a digital camera image, get the Move tool (V), and drag-and-drop it onto the new document, then press Command-T (PC: Ctrl-T) to bring up Free Transform. Press-and-hold the Shift key, then grab a corner point and drag inward to scale the image down, so it fits within the 8×10″ area (as shown here), and press Return (PC: Enter). Go under the Edit menu and choose Content-Aware Scale (or press Command-Option-Shift-C [PC: Ctrl-Alt-Shift-C]).
Grab the top handle, drag straight upward, and notice that it stretches the sky upward, but pretty much leaves the man intact, without stretching or bloating him. If you keep dragging upward, it will start dragging him, so you can’t drag forever, but luckily you see a live onscreen preview, so you’ll know how far you can drag. When you’ve dragged far enough, press Return to lock in your change. (Note: The button that looks like a person in the Options Bar tells Content-Aware Scale that there are people in the photo, so it avoids anything with a skin tone. It doesn’t always work, but it’s worth a try.)
There are two more controls you need to know about: First, if you try Content-Aware Scale and it stretches your subject more than you want, go get the Lasso tool (L) and drag a selection around your subject (as shown here, top left), then go under the Select menu and choose Save Selection. When the Save Selection dialog appears, just click OK. Then bring up Content-Aware Scale again, but this time, go up in the Options Bar and choose your selection from the Protect pop-up menu (as shown here) to tell Photoshop where your subject is. Now you can drag to the right to fill the empty space with the least stretching.
There’s also an Amount control up in the Options Bar, which determines how much stretching protection is provided. At its default of 100%, it’s protecting as much as possible. At 50%, it’s a mix of protected resizing and regular Free Transform, and for some photos that works best. The nice thing is the Amount control is live, so as long as your handles are still in place, you can lower the Amount and see live onscreen how it affects your resizing.