The first official portrait of Catherine, Duchess of Cambridge was unveiled Friday at a London gallery where it was hailed by its subject as "amazing" but slammed by some critics.

The National Portrait Gallery commissioned award-winning artist Paul Emsley to produce the painting of Prince William's wife after she became patron of the gallery early last year.

Kate, who attended a private viewing of the painting with her husband Friday ahead of its unveiling to the public, told the artist: "It's just amazing, I thought it was brilliant."

William also appeared thrilled with the work, saying: "It's beautiful, it's absolutely beautiful."

But some critics panned the softly-hued work.

Robin Simon, editor of the British Art Journal, told the Daily Mail: "Fortunately, the Duchess of Cambridge looks nothing like this in real life. I'm really sad to say this is a rotten portrait."

Ben Luke in the London Evening Standard said it was a "gentle, soft-focus image, like a delicately airbrushed photograph or a vaseline-lensed view of a Hollywood star."

"The Duchess explained that she would like to be portrayed naturally -- her natural self -- as opposed to her official self," said Emsley, whose previous commissions have included author V S Naipaul and Nelson Mandela.

"She struck me as enormously open and generous and a very warm person," he added.

The pregnant Duchess, who last month spent several days in hospital with a severe form of morning sickness, met with the artist and his family following the viewing and was looking well.

The head and shoulders portrait, set on Emsley's trademark dark background, was built up using thin layers of oil paint and glazes,with Kate attending two sittings last summer.

National Portrait Gallery Director Sandy Nairne praised Emsley for creating "a captivating contemporary image".