Flemish painter and draughtsman. He was apprenticed to Lancelot Volders (fl 1657-?75) in Brussels from 1668 to 1675. He also studied with the Dutchman Pieter Molyn. He came under the patronage of Herzog Joachim II von Holstein-Plön, who supported his trip to Italy. In Rome he studied the works of Raphael and the ancient monuments and made drawings of the Roman Campagna. His highly popular small paintings were influenced by those of Francesco Albani. Janssens also painted a large altarpiece for the Jesuits of Naples. //