ui/src/main/java/ucar/nc2/ui/widget/ScaledPanel.java
public void paintComponent(Graphics g) {
    if (bImage != null)
      g.drawImage(bImage, 0, 0, backColor, imageObs);
  }
public void paintComponent(Graphics g) {
    if (bImage != null)
      g.drawImage(bImage, 0, 0, backColor, imageObs);
  }
System-triggered redraw.