Among the Photoshop features that fall into the category of "love it or hate it" falls Extract. Introduced with Photoshop 5.5, this featured is designed to separate a subject from its background. Unfortunately, it is a "destructive" process, you lose image data because the background is deleted. Let's look at one way around that.
When you work with Edit> extract, you identify the border between your subject and the background, tell Extract which part you want to keep, and Photoshop does the rest. It determines, based on pixel color, which pixels are part of the subject and should stay, and which pixels are part of the background and should go. And by "go" I mean deleted. Vanished. Into the sunset, never to return. Unless we bring them back, that is.
Our subject image is PhotoSpin Image #PS003009.
We prepare the image in Extract by using the Edge Highlighter tool to identify the edge and then filling the subject area with the Fill tool.
Clicking the Preview button gives us a good look at what Extract will do. (Note that I've set the Preview Display to Gray Matte. This affects only the preview, not the extracted image.)
When we use Extract, you'll see that the image is separated (more or less) from the background, but that the background is completely deleted.
Working on a copy of the image is, as always, a good idea. But you may find need for the background later in your creative process. For example, at a later stage of development, you might decide to add back in a specific object or section from the original background. For this reason, it's handy to have the background retained with the image (although you can always clone from the original).
Here's one way to make Extract a less destructive technique: Make a copy of the background layer and hide the original before you use Extract. That way your image retains all of the info. At the end of the creative process, if you no longer need the background, you can delete the hidden layer.
Here's a touch-up trick. As soon as you've used extract, zoom in and use the History Brush to add back anything inadvertently deleted along the edges. (In the History palette, click in the left column next to the history state immediately prior to extract.)
However, as you can see, it's a little tough to determine where the original edge was. That's another great reason to have the original background available. By making it visible, we know exactly where to paint with the History Brush. It doesn't matter if we paint over pixels that don't need to be restored, as long as we do a good job of painting back in only the subject.
And, of course, we can always hide that background again to check our progress.
Copying the background layer before extracting is just one technique for preventing Extract from throwing away pixels that we may need later.
Pete
Bauer is the Help Desk Director for NAPP, as well
as a Contributing Writer for Photoshop User and Mac Design
magazines. His books include "Special Edition Using
Adobe Photoshop 7" (with Jeff Foster), "Special
Edition Using Adobe Illustrator 10," "Sams Teach
Yourself Adobe Illustrator 10 in 24 Hours" (with Mordy
Golding), and "Special Edition Using Adobe Illustrator
9." Pete writes documentation for a variety of computer
graphics related products, as well as testing software
for a number of companies. As a computer graphics efficiency
consultant, Pete specializes in customized training programs.
He is based in Columbus, Ohio, and can be contacted via
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