You can combine two images in an impressive way by wrapping one around the contours of another so the first image follows every nook and cranny of the second. To perform this feat, you need to create a displacement map—a grayscale image that Photoshop uses to warp and bend one image to the curvature of another. Applying this technique to photos of friends and family is great fun. For example, you can take a circuit board and wrap it around a body or a face, as shown in Figure 8-29. Here’s what you do:
Open the image you want to map another image onto (like a face), and then hunt down the channel with the greatest contrast.
To make the best possible displacement map, you need the channel with the highest contrast. If you’re in RGB mode (and you probably are), you can cycle through the channels by pressing ⌘-3, 4, and 5 (Ctrl+3, 4, and 5 on a PC). Because digital cameras tend to have so many more green sensors than red or blue ones, you’ll most likely pick the green channel.
Figure 8-29. With a displacement map, you can apply all kinds of wild textures to skin. Know anyone who needs to be turned into a reptile? To follow along with this tutorial, visit this book’s Missing CD page at www.missingmanuals.com/cds and download the practice file Map.zip.
Duplicate the high-contrast channel and send it to a new document.
Open the Channels panel by clicking its icon ...