Kim Kardashian has practically made a living off her curvaceous figure. But the E! network celeb was looking less shapely in Complex magazine in April, her body reduced about a dress size, her legs smoothed to near-perfection.

How did readers know? Complex accidentally posted a pre-Photoshopped image of Kardashian on its Web site — before her thighs, arms and waist had been digitally sculpted. In a matter of hours the photo was gone. But in that brief time span, those who spotted it got a little reminder that we should think twice about taking photographs at face value.

“My belief,” says Scott Kelby, president of the Florida-based National Association of Photoshop Professionals, “is that every single major magazine cover is retouched. I don’t know how they couldn’t be.” But don’t stop there. Aside from U.S. newspapers, most of which do not permit photos to be manipulated, it’s quite possible that the vast majority of images seen in the public arena have been altered.

Photoshop, the go-to graphics editing program that got a foothold in the 1990s, has become so ubiquitous that most of us gaze at faces, bodies and landscapes not even registering that wrinkles have been diminished, legs lengthened and the sky honed to a dreamlike shade of blue. And, unlike its predecessor, airbrushing, anyone can use it.

But Photoshop’s popularity has proved divisive. While some laud it for its ability to allow people — and things — to look their best in a photograph, others see it as a vehicle for feeding our culture’s desire for uber-perfection.

“I think the perfect bodies we’re seeing in magazines that are Photoshopped have a terrible effect on how women feel about their own bodies,” says Montana Miller, assistant professor in the department of popular culture at Bowling Green State University in Ohio.

One theory about retouching in advertisements is that it’s done to create an aspirational concept of beauty that inspires women to buy more products. Miller has heard another: that the goal of showing perfect images is to make women feel bad about themselves — also making them buy more beauty products.

Kelby, who writes a blog about Photoshop, doesn’t believe it’s a malevolent force; he sees it as practical and cites the example of singer Faith Hill.

In 2007, the fashion Web site Jezebel posted unaltered images of Hill that were shot for a Redbook magazine cover. In comparing them with the finished product, it appeared that Hill got a makeover, including erased crow’s-feet, excised back fat and a slimmer arm.

The fallout was huge — the Jezebel post generated more than 1.3 million views and was picked up by ABCNews.com, VH1.com, TMZ.com and a number of blogs. Many commenters were angry that an already attractive woman had her image altered to appear on the cover of a national magazine. (Redbook declined to comment for this story.)

“If you met Faith Hill in person,” Kelby says, “you would think she’s absolutely beautiful. And when you take her picture, you will see every flaw that you never saw in person. Those flaws not only become visible, but magnified….”

What the brain perceives in a still photo is vastly different from what it perceives in real life, according to Dr. Dale Purves, director of the Center for Cognitive Neuroscience at Duke University in Durham, N.C. Up close and personal, “every second you’re getting a series of images of a person that you’re kind of blending together, and that would be a little more forgiving.” What we’re taking in, he adds, is a load of stuff, including clothing, personality and smells — elements that don’t necessarily translate to two dimensions.

At Complex magazine, editor-in-chief Noah Callahan-Bever says he tries to sit in on every cover shoot.

“I want to make sure that person is represented in a fair way,” he says. “If their flesh tone ends up looking flat and dead, and it doesn’t look true to who they are, then it goes back for more retouching.”

Ask Ladies’ Home Journal creative director Jeffrey Saks if magazines are consciously manipulating images to foster readers’ poor self-images and he says no.

“We’re not trying to make women feel bad,” he says. “We’re trying to show women looking like real people, and whatever cleaning up we do is basically about the quality of the photograph more than trying to do plastic surgery.”