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.

“Fix one thing, then another and pretty soon you end up with Barbie,” said Hany Farid, a professor of computer science and a digital forensics expert at Dartmouth.

And that is a problem, feminist legislators in France, Britain and Norway say, and they want digitally altered photos to be labeled. In June, the American Medical Association adopted a policy on body image and advertising that urged advertisers and others to “discourage the altering of photographs in a manner that could promote unrealistic expectations of appropriate body image.”

Dr. Farid said he became intrigued by the problem after reading about the photo-labeling proposals in Europe. Categorizing photos as either altered or not altered seemed too blunt an approach, he said.