if (img == null) return;
    void setImage(BufferedImage img)    {         int w = img.getWidth()+3*ViewerUIF.START;        int h = img.getHeight()+2*ViewerUIF.START;        setContainerSize(new Dimension(w, h));        w += 2*ViewerUIF.START;        h += 2*ViewerUIF.START;        setWindowSize(w, h);        canvas.paintImage(img);     }