Preview began life as Mac OS X's built-in graphics viewer—but in Tiger, it's much more than that. It's now the program you use to view incoming faxes (Chapter 14), as well as a nearly full-blown clone of Adobe Reader (formerly Acrobat Reader), the free program that most people use to read PDF files.
In fact, because Preview now includes searching PDF documents, copying text out of them, adding comments, filling in forms, and clicking live hyperlinks—features that used to be available only in Adobe Reader—Apple doesn't even include Adobe Reader with Mac OS X.
Preview's hallmark is its surprising versatility. It can display and manipulate pictures saved in a wide variety of formats, including common painting formats like JPEG, TIFF, PICT, and GIF; less commonly used formats like BMP, PNG, SGI, TGA, and MacPaint; and even Photoshop, EPS, and PDF graphics. You can even open animated GIFs by adding a Play button to the toolbar, as described below.
To crop graphics in Preview, drag across the part of the graphic that you want to keep. To back out or redraw, click outside the highlighted area; or, to proceed with the crop, choose Tools → Crop Image. (The keyboard shortcut is ⌘-K, just as it is in iMovie.)
If you don't think you'll ever need the original again, save the document. Otherwise, choose File → Save As to spin the cropped image out as a separate file, preserving the original in the process.
You can also rotate an image—even a PDF ...