Learn how to scale an image

Most image editors can help you make an image bigger or smaller. Here are few guidelines that you can use to get better results.

By Paul Anderson

Making an image bigger or smaller is a relatively simple operation with most image editors. But following a few guidelines can help you get better results.

With raster images—which you use most of the time—scaling up just doesn't work. Photographic images can grow a bit and still look convincing, but anything else quickly begins to look like a checkerboard. The exceptions are fully aliased images composed entirely of rectangles, which can scale up indefinitely.

When shrinking an image, you'll want to use an image editor that supports antialiasing, such as Photoshop or Paint Shop Pro. (Microsoft Paint—the image program built into Windows—does scaling, but it retains alias.) With antialiasing, the smaller version will still look like the original despite working with fewer pixels. In fact, scaling down is the easiest way to smooth out a jagged image.

Finally, before you scale anything, make sure that the image is in true color. A common mistake is to scale down an indexed-color image. Because not enough colors are available to antialias properly, the results look terrible. Switching to true color solves this problem. Look for RGB, 24-Bit, or Millions Of Colors in the menus of your image editor.

Paul Anderson is associate technical editor for CNET His responsibilities don't include handling graphics, so naturally, he handles them all the time.

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