Artists/The arts; Viva Picasso: A Centennial Celebraton, by David Douglas Duncan. New York: The Viking Press. $16.95.

David Duncan's career as a photographer has centered on war and Picasso. This, his fourth book on the latter, vividly portrays the irrepressible fecundity of the artist's creative life at his studio home. There, is the baroque formality of Picasso's villa, we find dedicated informality -- children, goats, ceramic clutter, canvases, canvases. And somewhere in almost every scene the brown-eyed faun whom Duncan calls "the freest spirit -- and the most disciplined -- I have ever known." The most celebrated sequence in this intensely alive photobiography shows Picasso mouthing the vertebra of a fish he has just eaten, next eyeing the shape, them making a print mold from it, and finally applying the result to a large plate in a dramatic pattern. The photos, color and black-and-white, are rich in atmosphere.