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What Is Preview (and Why You Should Use It)

by Giles Turnbull
Running Mac OS X on Windows
Apple's Preview application (which is included as part of Mac OS X Tiger) is best known as a PDF viewer and a Macintosh alternative to Adobe Reader. You can bookmark PDF pages, add comments, fill out PDF forms, and copy text selections from within the file. This software, however, is also a capable image viewer for file formats such as JPEG, GIF, PNG, PSD, PICT, TIFF, and others, and it even allows you to edit those images. Preview can capture screenshots by selecting the Grab utility under its File menu. Many Mac users prefer using Preview over Adobe Reader because it takes less time to open and renders file pages very quickly.

Many people only know Preview as Apple's humble PDF viewer. Rather than mess about waiting for Adobe Reader to launch itself, plugins and all, Preview opens faster and does the job just as well.

But there's so much more to this application.

It turns out that Preview, especially the most recent version shipping with Mac OS X 10.4 Tiger, has plenty of extra features that can elevate it to one of your favorite utilities. Its usefulness is further enhanced by the fact that it's AppleScriptable, meaning that it can perform many tasks within an Automator workflow.

Here's a quick guide to some of the useful chores you can accomplish with this software.

Preview Is a Photo Editor!

Who knew? It's not like there's even a toolbar button you can use to access this feature, but believe it or not, hidden away under the Tools menu is a little thing called Image Correction (you can call it up with the keyboard shortcut Option+Command+C).

Lo and behold, it's a list of sliders that lets you change all sorts of aspects of your image, such as saturation, sharpness, exposure, and more. Looks kind of familiar, doesn't it?

Hmmm. Preview's image editing panel, and iPhoto's. Separated at birth? Hmmm. Preview's image editing panel, and iPhoto's. Separated at birth?Hmmm. Preview's image editing panel, and iPhoto's. Separated at birth?

Yup, this bunch of editing controls is almost identical to the (much slicker-looking) image editing controls that appeared in iPhoto 5. It's all thanks to the system-level Core Image code. The result is that they look very similar, and do the same sort of tasks.

Interestingly, iPhoto 5 won't even load these advanced controls on anything less than a G4 machine. There simply won't be sufficient processing power to use them. Preview is happy to display the controls even on an old G3, but don't expect it to achieve much except on the smallest and most basic images. Trying to change the exposure and saturation of a large photo on a G3 machine only brings up the spinning beach ball of doom, so don't bother.

On a G4 and above, though, Preview suddenly becomes a very useful little image editor, one that comes without what some people might consider the "bloat" of iPhoto.

While sliders are not the user-interface widget that most professionals would choose for changing things like exposure settings, the controls are more than adequate for editing casual snapshots, photos for the web, or other nonprint pictures.

Preview lets you crop, flip, and rotate images. You can convert from one image type to another just by using Save As... It's got many of the essential features you'd find in dozens of other image editing applications, but has the benefit of being free and closely tied in to the rest of Mac OS X. Preview is starting to look a lot like iPhoto in terms of the image manipulation features it offers. We'll see more similarities as we go on.

Another feature borrowed from iPhoto is the chance to add keywords, although it is a bit unwieldy. Hit Command+I to call up the Info panel for any picture, and you'll see a Keywords tab. Adding keywords requires too many mouse clicks for my liking. A simple empty field into which you could type space-separated keywords would be much simpler, especially if it were a toolbar control that could be slotted in above every image. But the feature is there, if you want to take the time to use it.

Adding keywords in Preview
Adding keywords in Preview

Keywords added this way are instantly searchable in Spotlight, which make them useful for archiving. Sadly they don't show up if you drag the image into iPhoto and call up its Info panel there.

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