Jill Hadley Hooper's sensitive illustrations appear on book covers and in national magazines and newspapers, and her paintings get show time at Goodwin Fine Art. But they were also tailor-made for the pages of Patricia MacLachlan's The Iridescence of Birds, a picture book released last fall about the young Henri Matisse and early influences on his career as a painter. Hooper skillfully meshes the sights and experiences of the artist's boyhood in northern France with the spirit and exuberant color of his later works in her block-print illustrations.