How to draw a simple little line.

Question

I have a JApplet that loads images from a jar file. This applet can scale the images, and move them left right, up and down.
I just want to be able to draw a line on top of the images and then erase it if needed. How do I do this?
Currently, I have a the jpg images loaded into an Image, which is then converted to an ImageIcon, which is then used to create a JLabel, which is used to create a JScrollPane which finally gets added as a tab on a JTabbedPane.
I was told to use BufferedImage but that didn't help me. Here is what I have currently:
private void draw()
//Get the current image to draw on
JScrollPane jsp = (JScrollPane)m_tabbedPane.getSelectedComponent();
JViewport port = jsp.getViewport();
GrabAndScrollLabel gnsLabel = (GrabAndScrollLabel) port.getView();
ImageIcon ii = (ImageIcon) gnsLabel.getIcon();
BufferedImage bi = new BufferedImage (ii.getIconWidth(),
ii.getIconHeight(),
BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = bi.createGraphics();
g2.setPaint(Color.blue);
g2.drawLineRect(100, 200, 300, 500);
g2.drawImage(ii.getImage(),null,null);
ImageIcon newIcon = new ImageIcon(ii.getImage());
gnsLabel.setIcon(newIcon);
port.setView(gnsLabel);
jsp.setViewport(port);
getRootPane().revalidate();
getRootPane().repaint();
Please help. I can't believe it has to be this difficult to draw a little line.
Thanks.

Answer 1

I have a little more insight into my problem.
I built a sample form Sun (the Map_Line sample). It looks like this:
public class Map_Line extends Applet
private BufferedImage bi;
public Map_Line()
setBackground(Color.white);
Image img = getToolkit().getImage("bld.jpg");
try
MediaTracker tracker = new MediaTracker(this);
tracker.addImage(img, 0);
tracker.waitForID(0);
catch (Exception e)
int iw = img.getWidth(this);
int ih = img.getHeight(this);
bi = new BufferedImage(iw, ih, BufferedImage.TYPE_INT_RGB);
Graphics2D big = bi.createGraphics();
big.drawImage(img, 0, 0, this);
public void paint(Graphics g)
Graphics2D g2 = (Graphics2D) g;
int w = getSize().width;
int h = getSize().height;
int bw = bi.getWidth(this);
int bh = bi.getHeight(this);
g2.drawImage(bi, null, 0, 0);
g2.setColor(Color.white);
g2.setStroke(new BasicStroke(5.0f));
g2.drawLine(10, 10, bw - 10, bh - 10);
public static void main(String[] s)
WindowListener l = new WindowAdapter()
public void windowClosing(WindowEvent e)
System.exit(0);
Frame f = new Frame("Map_Line");
f.addWindowListener(l);
f.add("Center", new Map_Line());
f.pack();
f.setSize(new Dimension(350, 250));
f.show();
Note how the drawing is done in paint. This applet works just fine for me.
The difference is that I'm trying to use the BufferedImage to get my Graphics2D object where as this one gets it from paint (casts Graphics to Graphics2D).
This applet works just fine, but if you try to use the Graphics2D that comes back from the BufferedImage, it doesn't work!.
For example, if I create a member variable:
Graphics2D big;
And then in paint do this:
//Graphics2D g2 = (Graphics2D) g;
Grahics2D g2 = big;
It no longer works!
So, it looks like I need to use something other than the
BufferedImage.createGraphics() to get the Graphics2D object I need.
Does this seem right?
Thanks!