Photoshop CC: The Missing Manual, 2nd Edition

Mapping One Image onto Another

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 face, as in Figure 7-29. Here’s what you do:

1. 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 (and thus activate) different channels by pressing ⌘-3, 4, and 5 (Ctrl+3, 4, and 5 on a PC); stop when you land on the one you want to use. (As you learned in the box on Why Are Channels Gray?, Photoshop displays channels in grayscale.) Because digital cameras tend to have so many more green sensors than red or blue ones, you’ll most likely pick the green channel.

2. Duplicate the high-contrast channel, and then send it to a new document.

   Open the Channels panel by clicking its icon in the panel dock or choosing Window→Channels. With the highest contrast channel active, choose Duplicate Channel from the Channels panel’s menu. In the resulting dialog box, choose New from the Destination section’s ...