In some sense, the iconic photograph of Rosa Parks recreating her quiet act of rebellion on a bus in Montgomery, Ala., belongs to every American. But as a practical matter, it belongs to Bill Gates .

Anyone wanting to use that image in a book or on a Web site must first license it from Corbis, a corporation founded and owned by Mr. Gates, who is better known for starting Microsoft . The photo is among the 11 million prints and negatives in the legendary Bettmann archive, which Corbis bought in 1995.

Since that first purchase, Corbis has spent tens of millions of dollars acquiring image collections and other companies, hired more than 1,000 people and set up two dozen offices worldwide. Although Corbis says it brings in some $250 million a year in sales, it has yet to turn a profit.

Now the company is shuffling its top executives as it takes on new challenges, building up a business in rights management and plotting its response to the rise of low-cost online photo services that threaten to undermine its lucrative stock photo sales.

The company plans to announce Tuesday that Gary Shenk, the president, is being made chief executive as well. Mr. Shenk, 36, is an expert in rights licensing who has risen rapidly through the Corbis ranks since he was hired in 2003 from Universal Studios, where he started a small licensing unit.

The move into rights clearance, which involves sorting out the questions of who owns what material and how much they should be paid for its use, is a departure from the original vision for the company.

Mr. Gates started Corbis in 1989 with the idea that people would someday decorate their homes with a revolving display of digital artwork — interspersing, say, Cecil Stoughton's shot of John F. Kennedy Jr. playing under the desk in the Oval Office with photos of their own families at play.

That is not how things have worked out. But meanwhile Corbis has built up a formidable stash of historical photos, including those in the Bettmann Archive. In 1999, Corbis acquired the licensing rights to the Sygma collection in France, and two years ago it did the same with a German stock image company called Zefa. It licenses those images for an average of about $250 apiece.

Corbis also owns digital reproduction rights for art from the Hermitage Museum in St. Petersburg, Russia, the Philadelphia Museum of Art and the National Gallery in London.

In all, Corbis represents or owns the rights to more than 100 million images, including some of the most famous photographs ever — Arthur Sasse's photo of Einstein sticking his tongue out and Marilyn Monroe on the subway grate. And Corbis handles the licensing of millions of other images on behalf of thousands of photographers.

The archival photos bring in about half of Corbis's sales, but the company also has a stable of professional photographers who generate stock photos for advertising and media clients — images of children on playgrounds, people sitting in business meetings and men in khakis swinging golf clubs.

Over the past few years, Corbis has moved beyond newspaper and magazine clients to pursue advertising and graphic design agencies, as well as corporate marketing departments, which are turning increasingly to high-quality stock photography rather than doing their own expensive photo shoots.

Those customers are also buying from Corbis's growing library of 30,000 short video clips — mostly generic scenes of, say, people shopping or running down the beach.

What Corbis did not foresee was the rise of so-called microstock agencies like Fotolia and iStockPhoto. These sites take advantage of the phenomenon known as crowdsourcing, or turning to the online masses for free or low-cost submissions. Thousands of amateur and semiprofessional photographers armed with high-quality digital cameras and a copy of Photoshop contribute photographs to microstock sites, which often charge $1 to $5 an image.

Although the microstock business still represents a small fraction of the $2 billion market for stock photos, analysts say it is possible that low micropayment prices could take business away from the higher-priced images Corbis relies on for the bulk of its revenues.

The rise of the microstock companies has been of particular concern to Corbis. For all its new lines of business, the company still gets some 88 percent of its revenues from image licenses, yet commands only about 11 percent of that market. Getty Images dominates the market with a 40 percent share.

Getty, which has grown quickly since its start in 1995 with the backing of its wealthy co-founder, Mark Getty, has a foothold in microstock thanks to iStockPhoto, which it bought last year for $50 million.

Mr. Shenk said Corbis would announce its plans for the microstock business sometime this quarter. As for the question of how a high-end company enters that business without cannibalizing its more expensive products, Mr. Shenk said the idea was to find a new kind of customer, people who would never envision buying pictures from a Corbis or Getty.

In that vein, Mr. Shenk said Corbis would make its service as easy to use as the iTunes store of Apple and hinted that Corbis would also be following the crowdsourcing model.

Corbis is also betting heavily on its Creative Resources division, which includes rights services and recorded 44 percent growth in revenue last year, to $30.1 million.

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