Object[] cells = graph.getRoots();
if (cells.length > 0) {
graph.setSize(graph.getPreferredSize());
Rectangle bounds = graph.getCellBounds(cells).getBounds();// HM, JGraph3.4.1
graph.toScreen(bounds);
// Create a Buffered Image
Dimension d = bounds.getSize();
img = new BufferedImage(d.width, d.height, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics = img.createGraphics();