CORBIS, the photo library owned by Bill Gates, has beaten a rival backed by the Getty family fortune to acquire Zefa of Germany, the world’s third-largest image catalogue.

The deal, estimated at €56 million (£39 million), shores up Corbis’s status as the secondbiggest photograph owner, amid speculation that Mr Gates, the founder of Microsoft, is poised to announce a flotation of the company with a valuation that could exceed $1 billion (£530.7 million).

Annual sales at Corbis, which owns more than 70 million images, will rise above $200 million following the acquisition of Zefa. The German catalogue, which is the last major independent image library in the world, has sales of about €32.5 million.

Steve Davis, chief executive of Corbis, said that the deal would “dramatically improve” the company’s market share in Germany, France and Britain.

A flotation announcement could come as soon as this month, when Corbis holds its annual meeting in New York.

Getty Images, the market leader headed by Mark Getty, the grandson of J. Paul Getty, the oil magnate, had annual sales of $523 million in 2003. The company, which is about 20 per cent owned by the Getty Trust, is worth $4 billion — implying a valuation for Corbis of between a third and a half of Getty Images.

Zefa was jointly owned by Erwin Fey, 3i, the UK venture capital group, and its management. Herr Fey will take about €28 million for his 51 per cent stake, while 3i has more than trebled its initial investment of about €8 million, which it made in 1998.