In 1949, when she was 18, Bridget Riley began formal art study at London’s Goldsmiths’ College. “Bridget Riley Drawings: From the Artist’s Studio” features 24 little-seen figurative and landscape works in pencil, crayon, oil and pastel from the 1940s and ’50s, plus 65 mostly geometric abstractions from 1961 and after, for which she is today well known. Bridget Riley, “New …