From the splendor of Versailles Palace to the intimacy of the Windsors' castle and the sorrows of Omaha Beach these past 10 days, Nancy Reagan's image has been on the line.

How well she did may be the subject of some debate, but at least one American watching--her husband--has already signaled his rave reviews. The most recent came Wednesday as he was leaving the Bundestag chamber after his historic appearance there. He blew her a kiss as she watched adoringly from the balcony.

Sensitive to stories critical of his wife, President Reagan obviously is pleased that she has been well-received officially. The day before, in London's Palace of Westminster, when the speaker of the House of Parliament took notice of the first lady's presence, Reagan broke into enthusiastic applause along with others in the audience.

Giving Europeans a glimpse of the Reagans' close relationship probably hasn't hurt Ronald Reagan's image. Part of the purpose of his visit abroad, from which he returns today, was to portray him to Europeans as a peace-loving president rather than as a trigger-happy cowboy actor. While they were at it, White House aides also sought to portray Nancy Reagan as a serious, caring woman.

But early in the planning stages there were some who said the trip was a no-win proposition for her and that she shouldn't go. Soon after, her schedule was adjusted to balance the exclusive social events with those suggesting more social awareness. At least one fancy party was cut out altogether.

Mrs. Reagan's determination to go created one problem of protocol, according to a highly placed French official, who said that spouses had not been invited. The official said that when it became clear that Mrs. Reagan was coming, it was necessary to invite the spouses of other summit leaders. In Paris, however, Mrs. Reagan's press secretary said that President Mitterrand had personally invited Mrs. Reagan to France when they met last summer at the royal wedding in Britain.

Last year's trip was under completely different circumstances, since the first lady's visit was strictly social. She went to the wedding with an entourage that included some of her close friends. The president, said Nancy Reagan's press secretary Sheila Tate, "even said, 'I want you to have a wonderful time. You really deserve to have a good time.' Remember, this was four months after the assassination attempt."

But on this trip, said Tate, "Even though there has been a great deal of entertaining and all the grandeur of places like Versailles, there have been some great differences. The president is here for important meetings. And she's here to support what he's doing. The whole character of the trip is different, and I think it's unfair to compare this trip with the one she made last year."

Cynical first-lady watchers say that her preference for the privileged life hasn't changed despite efforts of White House aides to play up her more serious interests in combatting drug abuse among youth and her concerns for the elderly.

Her clothes, as usual, attracted attention. The British press reported 18 suitcases went with the Reagans into Windsor Castle. On this trip Mrs. Reagan hasn't worn the same outfit twice, and while there have been some that looked familiar, such as the gown she wore to Mitterrand's dinner at Versailles, there have also been a number of new ones. The black satin knickers with their rhinestone buttons had what some detractors saw as the effect she desired--everybody talked about them.

She had some other surprises as well. At Windsor Castle, where others were awash in diamonds, she wore an imitation necklace that seemed to fool everybody. On her ears, however, were the controversial genuine diamond earrings Harry Winston Inc. lent her more than a year ago and which Tate has said would be returned after this trip.

There was also an ironic touch to the revelation that the queen did not have enough china to serve all her guests from the same service, and the memory of Mrs. Reagan's 220-place-setting service for the White House was raised anew.

Still, she has kept a rigorous schedule in what her staff planned as a "good blend" of her activities with those of the president.

"When she's not with him, she's making very good use of her time in pursuing the same interests she has at home," says an aide.

The White House wanted her to drop the visit to the drug center in Rome because the Reagans were spending only six hours there last Monday, but she wouldn't hear of it.

"It was a mess, but she insisted upon going through with it because she feels so strongly about it," said an aide.

Today, she visited Phoenix House, another drug rehabilitation center, patterned after one in New York. Later in the day, with other wives of NATO country leaders, she took a boat ride on the Rhine.

The view Ronald Reagan offers the world of his wife is sometimes that of a homebody.

"I think we've got everything packed," he said at the White House the morning they left for Europe. "Nancy is upstairs unplugging the toaster."

Then there is the view the world gets through carefully allotted interviews, such as those printed in three European women's magazines to coincide with Mrs. Reagan's visits to Paris, Rome and Bonn.

She told Germany's Bunte that "Nobody can stay married for 30 years without influencing each other." Her interest in politics, she continued, was "sometimes as a 'kite' for my husband."

France's Elle, commenting on her stiffness and lack of knowledge "about the outside world," wondered if she purposely behaves like a "mindless Barbie doll" as a smokescreen for her important role in White House decision-making.

But among her triumphs these past 10 days were her pilgrimage to Normandy to remember America's dead on the 38th anniversary of D-Day and her quiet, unorchestrated talk with the widow of Col. Charles Ray, who was murdered by terrorists in Paris last January.

Both occasions left her visibly moved.

What the image-makers were trying to do became apparent a few weeks before the trip when the very social Countess de Ribes disclosed that she would not be giving a party for Mrs. Reagan in Paris as had been planned. But that wasn't the tumbrel for Mrs. Reagan's titled friends. They were included on guest lists at such events as the performance of "Romeo and Juliet" at the Paris Opera and a private buffet during intermission from which reporters were banned. They were also included at the American Embassy dinner for Mitterrand, and the luncheon for Mrs. Reagan given by the Gerald Van Der Kemps at Claude Monet's home in Giverny.

Mrs. Reagan has worked hard to give the impression to Europeans that her interests in children are universal. In Paris, at a center for the blind, state-run French television showed her gently patting children's hands, stroking their heads and attentively listening to one child playing the piano.

In Rome, she tried to make up for being late by staying longer than the 20 minutes scheduled for her visit to a drug rehabilitation program for youths.

Here in Bonn, she came to the rescue of a 7-year-old girl stopped by security guards when trying to present a bouquet to the Reagans.

Even so, media reaction in France, England and Italy to Nancy Reagan has been either negative or nonexistent.

The left-wing Paris paper Liberation called her visit to Normandy "a telecommanded perfection," adding that "she had a set smile from beginning to end as she stood before the memorial." Liberation's query: "What is Nancy thinking of right at this moment?" Answer: "She carefully remembers to look at the photographers."

Public reaction, too, has seemed indifferent and undemonstrative. When she arrived at the Paris Opera, no one seemed to recognize her or even know she was there. Bring her up in a one-on-one conversation, though, and there has been polite, even occasionally enthusiastic, approval of her.

"We love the President Reagan and Mrs. Reagan," said the proprietor of Giovanni's, a restaurant not far from the U.S. Embassy in Rome, frequented by Reagan's good friend and emissary to the Vatican, William Wilson.

But Nancy Reagan made what some here see as two gaffes that aren't apt to be forgotten soon. One was in Paris involving clothes, the other in London involving children.

"Maybe she thought she had to one-up Jackie Kennedy by wearing those knickers," said an American who lives in Paris, long associated with the fashion industry, which still remembers the then-first-lady's triumphant visit to Paris in 1961. "It's so silly, particularly with the kind of government the French have now."

Mrs. Reagan later expressed surprise to those close to her that there had been such interest in the Galanos evening knickers.

With typical disdain, the French press ignored Mrs. Reagan's clothes, at least while she was in Paris. The English press, on the other hand, resumed attacks upon her begun last summer when she attended the royal wedding. They compared her taste in clothing to Queen Elizabeth's, who is considered dowdy, and grudgingly judged Mrs. Reagan the winner. There was a qualifier by the Daily Express, however, that there was only "one thoroughbred and not just because of the years of royal breeding."

The White House never really expected to win that one.

"They were sitting there waiting to pounce on Mrs. Reagan last year after Lee Annenberg's curtsy to Prince Charles," said a member of the White House staff. "I even remember the headline, 'Ron Orders Nancy Not to Bow.' "

This trip, the Brits were still at it: "What gall she had to carry out her primlipped promise not to curtsy to the queen," said a gossip columnist in the Daily Express. Surprisingly, the tabloids didn't pick up on Mrs. Reagan's second major gaffe, at least while she was still in town. Without explanation, according to hospital administrator Tony Mowan, she canceled a scheduled visit to the cancer ward of St. Bartholomew's Hospital for children the afternoon of Queen Elizabeth's Windsor Castle banquet for the Reagans. At first, the White House said it was a matter "of logistics" in arranging for Mrs. Reagan's return to the castle by helicopter with the president.

"No one likes these things to happen, but it was simply too ambitious a schedule," said an aide. "I think it was necessary to get ready for the dinner."

Later, "security" was given as the reason. The day after Mowan's statement was released to the press, Mrs. Reagan personally telephoned Eleanor Richards, 15, of Kent, a cancer victim who lost a leg and was to have been the first lady's escort at the hospital. She invited Eleanor out to visit her at Windsor the following morning. And when she arrived she had a set of official White House books and a Nancy Reagan signature pen to give her.

Throughout the trip every move Mrs. Reagan made was closely scrutinized. At the arrival ceremony in Bonn for the Reagans, three women focused their cameras on them. When the president saw them, he broke into a grin and told Mrs. Reagan, "Look, they're just like tourists." In fact, they were three of the first lady's top staffers, watching just as closely as the rest of the world.