Activist investor Trillium Capital on Thursday asked stock photo company Getty Images Holding Inc to evaluate strategic alternatives, including a sale.

Trillium issued an open letter to Getty on Tuesday, saying a sale to either private equity or strategic players could boost the company's shares to more than $12 and add more than $1 billion to its market capitalization.

The investor, which said it owns "hundreds of thousand shares of common stock and common stock equivalents of Getty", put forth its proposal before the company's board, demanding it hire an investment bank to evaluate strategic alternatives.

"We have extensive relationships with global investment banking and private equity firms. We would be happy to make introductions for the Company to expedite this process," Scott Murray, managing partner of Trillium Capital, said in a statement.

Getty Images remains open to constructive insights and engagement with investors, a company spokesperson said.

Getty shares were trading at $6.23, valuing the company at about $2.45 billion, a far cry from its market valuation of $15 billion in August.

The company, a supplier of stock photos and videos, went public for a second time in July last year after 13 years as a privately held entity through a merger deal with a blank-check firm that was backed by Neuberger Berman and CC Capital.

Founded in 1995 by Mark Getty and Jonathan Klein, Getty competes with Reuters News and Associated Press to provide photos and videos for editorial use.

(Reporting by Chavi Mehta in Bengaluru; Editing by Shinjini Ganguli and Anil D'Silva)