Art-Repair Software May Also Aid Hollywood, Military

Bijal P. Trivedi
National Geographic Today
September 17, 2002

In many ancient churches in Europe, scaffolding stands before crumbling frescoes. Atop the steel skeletons, conservators using techniques as old as the frescoes themselves can spend months if not years painstakingly filling in chips and cracks to return a work to its former glory—a process called inpainting.

Now Guillermo Sapiro, a professor of electrical and computer engineering at the University of Minnesota at Minneapolis–St. Paul, has developed a computer program that can dramatically speed up the inpainting process.

The program has applications beyond old masterpieces: Hollywood and the U.S. Navy, among others, have expressed interest in a technology that can fill in blanks and restore missing pieces.

"The goal of inpainting is to restore an image in a way not detectable by the viewer," Sapiro says. "It just has to look natural."

Sapiro was inspired to work on the program after attending an imaging conference in France several years ago. On a field trip, he went to the Minneapolis Institute of Arts to watch professional conservators at work.

Translating Art to Math

Elizabeth Buschor, a conservator with the Upper Midwest Conservation Association who specializes in art on paper, "began inpainting by first establishing boundaries and lines and then went back to fill in the color," Sapiro recalls. "We tried to translate her work into a mathematical language and imitate what she was doing."

When done by hand, inpainting is laborious and subjective. One conservator's decisions will differ from another. But Sapiro's program takes a scientific approach.

Once a damaged or incomplete picture is in digital format, a numerical value is assigned to each pixel, the smallest unit of an image. A set of algorithms—step-by-step mathematical procedures—use colors, lines and brightness to calculate the exact value of pixels surrounding the damage or gap.

Like interpolating trends from a graph, the program extends the cut-off lines and borders, then fills in the missing areas with color, working from the edges inward.

"It looks like a wonderful tool," says Dan Kushel, distinguished teaching professor at the Art Conservation Department at Buffalo State College in New York. "It won't take over what we do, but it could certainly speed it up. We can work things out and do a virtual reconstruction first before applying real materials to the original works."

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