javafx setclip渐变蒙版

Question

如何将javafx中的setClip用作渐变Mask？

Pane pane = new Pane();
ImageView iView = new ImageView(new Image("images/img.jpeg"));
pane.getChildren().add(iView);

rMask = new Rectangle(200,250);
rMask.setLayoutX(100);
rMask.setLayoutY(100);

pane.setClip(rMask);