The photographs of celebrities and models in fashion advertisements and magazines are routinely buffed with a helping of digital polish. The retouching can be slight — colors brightened, a stray hair put in place, a pimple healed. Or it can be drastic — shedding 10 or 20 pounds, adding a few inches in height and erasing all wrinkles and blemishes, done using Adobe’s Photoshop software, the photo retoucher’s magic wand.