It has been said that it takes a new President a year or more to learn about his new job, its powers and limitations.

That may be true, but in his first month in office Jimmy Carter has already demonstrated that he knows one thing instinctively about the presidency: that the White House is a stage and he is its director and starring actor.

With the full force of the White House image-making apparatus and his own politically adroit mind guiding the effort, Carter already has gone far in shaping his public image as the nation's 39th President.

It is the image of a President who:

Is determined to reorganize the federal government but cares deeply about federal civil servants and considers himself to be just one of them.

Will be a stern master of the budget process, slashing spending to the minimum, but not at the expense of the social welfare programs that are dear to his heart.

Can do without the trappings of the imperial presidency and remain the sole master of foreign policy, at least a match for any other world leader.

The President has begun to shape these and other aspects of his image in ways that go beyond the much-discussed "symbolism" of the administration and his own deft performance at his first presidential press conference Feb. 8.

Perhaps the best example of this has been the White House's handling of the first Cabinet meetings of the administration, which have been turned into a weekly gold mine of favorable news for Carter.

There have been five Cabinet meetings and after each one a deputy to White House press secretary Jody Powell has appeared in the press briefing room to provide extraordinarily detailed accounts of what transpired. Exact, lengthy quotations from the President have been provided to reporters who dutifully write them down and report them.

The trouble with this is that when a White House press aide quotes the President, the President only says what an ideal President would and should say.

So it was that after one Cabinet meeting, deputy press secretary Rex Granum went on at length quoting Carter telling the Cabinet to cut out the frills, the limousines and such, and to become closer to the people.

It turned out that only about 10 minutes of the more than two-hour Cabinet meeting was devoted to a discussion of frills. Granum spent roughly twice that amount of time quoting the President on the subject while reporting little else of what went on in the meeting.

Last week it was deputy press secretary Walt Wurfel's turn to project the presidential image. His portrayal was of the fiscally responsible Jimmy Carter sternly warning his Cabinet secretaries to hold down spending.

Yes, Wurfel acknowledged, a new budget deficit figure was discussed at the meeting and it would certainly be larger than the $47 billion deficit in the Ford administration's last budget proposal. But no, Wurfel added, he could not talk about that.

The President at one point said he was going to open the Cabinet meetings to reporters, not just deputy press secretaries. But he abandoned that idea last week, conceding the difficulties involved in allowing neutral observers who are more interested in budget deficits than limousines into the inner sanctum of administration conversations.

Carter's own image-building efforts have included his widely publicized visits to government agencies where, speaking like a gentle father, he has reminded the bureaucrats that they are all, himself included, servants of the people.

It is doubtful that these presidential sermons will have much, if any, impact on the performance of the bureaucracy and they certainly will not reduce the difficulties and perils involved in the President's determination to reorganize the government. But as vehicles projecting the image of a President who cares about the people who work for him, they were masterful.

There is nothing evil or sinister in any of this. Image building is part of presidential leadership and Carter's aides argue convincingly it is a necessary first step toward mobilizing the political support to achieve the President's goals.

And there will be more, much more, of it in the months ahead, all under the general direction of press secretary Powell. Because of his long and close personal relationship with Carter, Powell is viewed as more than just the presidential press secretary.

He has also given his office more than a press secretary's functions, consolidating in it White House speech writing, photography, television assistance and media liaison. In effect, Powell controls the entire White House image-making apparatus.

On March 5, Carter, with Walter Cronkite by his side, will host his own live, radio call-in show, answering questions for two hours in the White House. It will be listened to.

Shortly thereafter, he will make a trip, perhaps to attend a series of town meetings in cities around the country. It will be a well-publicized trip.

There is a whole committee at work in the White House, grinding at ideas on how to keep the President close to the people. And while he is staying close, he will be staying in the news, building the kind of image he wants against the day when the problems he faces and the hard choices he will have to make begin to take their inevitable toll.