King Charles III on Tuesday unveiled the first official painted portrait of himself since his coronation just over a year ago — a striking oil painting in which he stares head-on against a backdrop of mottled red, pink and fuchsia hues.

The painting, by the renowned portrait artist Jonathan Yeo, was unveiled at Buckingham Palace, the royal family said on social media. Video showed the king tugging at a ribbon attached to fabric covering the towering work, which, as it dropped, appeared to give him a small surprise.

Mr. Yeo, who has painted the likes of David Attenborough, Idris Elba and the activist Malala Yousafzai, began the portrait in June 2021, when the king was still the Prince of Wales. It depicts him wearing the uniform of the Welsh Guards, of which he was a Regimental Colonel, with a butterfly hovering over his shoulder.

Much like that butterfly, the king’s “role in our public life has transformed,” Mr. Yeo said in the statement released on Tuesday by the royal family. “I do my best to capture the life experiences and humanity etched into any individual sitter’s face, and I hope that is what I have achieved in this portrait,” he said, noting that to try to capture the king was “both a tremendous professional challenge, and one which I thoroughly enjoyed and am immensely grateful for.”

The 7.5 foot-by-5.5-foot portrait was commissioned by the Worshipful Company of Drapers, a medieval guild of wool and cloth merchants that is now a philanthropy. It will hang in Drapers’ Hall, the group’s baronial quarters in London’s financial district, which has a gallery of monarchs from King George III to Queen Victoria.

The unveiling came just weeks after the king announced his return to public duties, nearly three months after he disclosed that he had cancer, bringing palpable relief to a country anxious about another wrenching change in the British monarchy.

Mr. Yeo previously told The Times that he had not learned of the king’s illness until after he had completed the painting, which depicts his subject in vivid color with a contemplative yet commanding glare. Mr. Yeo has also painted the king’s wife, Queen Camilla, and his father, Prince Philip. Other subjects have included the former British Prime Minister Tony Blair, the actors Dennis Hopper and Nicole Kidman and the media mogul Rupert Murdoch. He has said that the best portraits capture visual characteristics that remain relevant even as the person ages.

When it came to the king, Mr. Yeo told The Times that he had noticed physical changes in their four sittings together — during which time the king was going through a metamorphosis of stature.

“Age and experience were suiting him,” Mr. Yeo told The Times. “His demeanor definitely changed after he became king.”