CUPERTINO -- Katie Cotton, the guardian of Apple's tightly controlled image under the legendary Steve Jobs and now under CEO Tim Cook, is resigning after more than 18 years helping to shape Apple's neatly manicured public persona.

Cotton, Apple's vice president for worldwide communications and considered one of Silicon Valley's most powerful women, was rarely heard from and usually seen in public only near Jobs and later Cook.

Apple said in a statement to this newspaper that "Katie has given her all to this company for over 18 years. She has wanted to spend time with her children for some time now. We are really going to miss her."

Cotton oversaw the tightly controlled release of company information, a strategy that continues to help build excitement and expectations whenever Apple is on the verge of a big announcement and speculation grows wild in the subsequent information vacuum.

Tim Bajarin, president of Creative Strategies, said Cotton's gracious and warmhearted personality belied the requirements of her job that often put her at odds with journalists covering Apple.

"Their communications strategy added an element of mystery and aura to Apple Computer itself," Bajarin said. "Steve (Jobs) was very much behind the concept of the element of surprise. They just thrived on that kind of marketing communications. And she was the keeper of the gate. As a result, their requests from the media are the highest I've seen of any company outside of Hollywood."

Bajarin says Cotton now deserves time to spend with her children.

"I know she came off to the media as way too strict and probably too rigid and she upset a lot of the media," Bajarin said. "But you can't fault her for following orders. She's the best in the business."

Lynn Fox twice worked in Apple's communications department for a combined six years, beginning in 2000 and ending in 2008.

In an email to this newspaper, Fox called Cotton "absolutely one of the most dynamic, persuasive and 'all in' communications executives I've ever encountered in my 20+ years in PR. A very large group of strong PR people owe their best work experiences to her. I sincerely hope we haven't seen the last of her in these tech parts."

Contact Dan Nakaso at 408-271-3648. Follow him at Twitter.com/dannakaso.