@FXML
void dragDetected(MouseEvent event) {
/* drag was detected, start drag-and-drop gesture*/
/* allow any transfer mode */
Dragboard db = imageView.startDragAndDrop(TransferMode.ANY);
/* put a string on dragboard */
ClipboardContent content = new ClipboardContent();
content.putImage(imageView.getImage());
db.setContent(content);
event.consume();
}