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Instead of using a proprietary inferior method the way Microsoft did for Windows, Apple adopted the Portable Document Format (PDF) for flawless images at any size.
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Al Fasoldt's reviews and commentaries, continuously available online since 1983

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Spectacular image quality of Mac OS X is built into the operating system


Dec. 31, 2003


By Al Fasoldt
Copyright © 2003, Al Fasoldt
Copyright © 2003, The Post-Standard

   Apple's Mac OS X computers sparkle when they show digital images and videos. Whether you have an OS X Mac with a standard CRT monitor or a flat LCD screen, your Macintosh was designed as a no-compromise graphical computer.
   Part of the credit has to go to the superb software that comes with all modern Macs -- Preview, an exceptionally competent image viewer and converter, and iPhoto, the best all-in-one image viewer and organizer on the planet.
   But you might not realize that something else deserves a cheer, too. With the introduction of OS X, Apple changed the way its computers display everything on the screen. Instead of using a proprietary method of showing graphical items -- images, icons, window borders and so on -- Apple adopted the Portable Document Format, or PDF. The striking advantage of PDF is its uncanny disregard for the size of the items it is displaying. No matter how big or small an object is, PDF shows it as clearly as possible.
   You might be thinking, "So what? Don't Windows computers do the same thing?"
   Not at all. In fact, apart from such obvious differences as total immunity to Windows viruses, the biggest advantage of using an OS X Macintosh for fans of digital photography might well be its incomparable ability to scale any image to any conceivable size without losing sharpness or overall quality.
   You can see this for yourself using a good digital image in iPhoto. Here's how:
   1. Open iPhoto and create a new catalog for testing. (Click the "+" button at the lower left and type TEST as the name, then click the TEST folder to open it. It will be empty.)
   2. Go to the the display of 2003 Stars Magazine digital photo winners on my Technofile Web site. The address is http://technofileonline/2003winners/con031603.html. Click on the photo you'd like to use for this test, then click "Full Size Photo" to see the original.
   3. Drag the full-size image out of the browser window and drop it on the desktop, then drag it from the desktop into iPhoto. It should end up as the only image in the TEST folder.
   Notice that iPhoto has a slider bar at the bottom right. With only one image in the catalog you are viewing, sliding this zoom bar in either direction should immediately scale the photo larger or smaller. (Having many images visible could slow things down.) When you make it smaller, watch how the image shrinks without any deterioration except for overall size. It never becomes blocky or pixelated. When you make it larger, notice how it steadily grows bigger without any sign of exaggerated shapes.
   This amazing capability isn't something iPhoto possesses; it's built into your OS X Mac. Technically, the PDF display sizing Apple uses is called Quartz. A variation in the newest OS X Macs is called Quartz Extreme. Windows is far behind, using a proprietary Microsoft system that can't rescale objects faithfully.
   Apart from impressing friends who haven't yet switched to Mac OS X, what value does Apple's PDF scaling have? It takes much of the work away from programmers when they're developing image-display software, for one thing.
   You can see this in ACDSee 1.6 for the Mac. It does a great job of showing images full-screen. (Be sure to set it up to do that automatically.) Another program that benefits from Quartz scaling is Preview. In Panther, the current version of OS X, Preview is at last fast enough to be used as a primary image viewer, and its newfound speed should also tempt you to choose it instead of Adobe Reader for viewing PDF documents.