Former U.S. President Barack Obama speaks during the unveiling of his portrait at the Smithsonian’s National Portrait Gallery in Washington, U.S., February 12, 2018. REUTERS/Jim Bourg

Former U.S. President George W. Bush unveils his official White House portrait during a ceremony in the East Room of the White House in Washington May 31, 2012. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS SOCIETY)

Former U.S. President Bill Clinton motions for members of his family to join him onstage after he and former first lady Sen. Hillary Clinton (D-NY) unveiled portraits of themselves in Washington, April 24, 2006. The portraits will hang in the newly-restored National Portrait Gallery, which is scheduled to reopen July 1. The gallery holds the only complete portrait collection of U.S. presidents outside the White House's own. REUTERS/Jonathan Ernst