Draw a line after zoom in

Question

Hi All,
I want to draw a line after zooming in/out the image. If the image is not scaled, then ever thing is fine. But once I scaled the image and draw the line, the position is not coming correctly. Can you correct me, what's my mistake?
package imagetest;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
public class ZoomAndDraw extends JPanel
    private java.awt.image.BufferedImage image = null;
    private Line2D.Double line = null;
    private double scale = 1.0;
    private int value = 16;
    private double translateX = 0.0;
    private double translateY = 0.0;
    private MouseManager manager = null;
    public ZoomAndDraw()
        line = new Line2D.Double();
        readImage();
        manager = new MouseManager(this);
        addMouseListener(manager);
        addMouseMotionListener(manager);
    private void readImage()
        try
            image = javax.imageio.ImageIO.read(new java.io.File("D:/IMG.JPG"));
        catch (Exception ex)
    @Override
    public Dimension getPreferredSize()
        if (image != null)
            int w = (int) (scale * image.getWidth());
            int h = (int) (scale * image.getHeight());
            return new Dimension(w, h);
        return new Dimension(640, 480);
    @Override
    protected void paintComponent(Graphics g)
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        if (image == null)
            return;
        double x = (getWidth() - scale * image.getWidth()) / 2;
        double y = (getHeight() - scale * image.getHeight()) / 2;
        g2.translate(x, y); // move to center of image
        g2.scale(scale, scale); // scale
        translateX = 0 - x * (1 / scale);
        translateY = 0 - y * (1 / scale);
        g2.translate(translateX, translateY); // move back
        g2.drawImage(image, 0, 0, this);
        g2.setColor(Color.RED);
        g2.draw(line);
        g.dispose();
    public void setLine(Point start, Point end)
        line.setLine(start, end);
        repaint();
    public void addLine(Point start, Point end)
        line.setLine(start, end);
        repaint();
    public void ZoomIn()
        value++;
        scale = (value + 4) / 20.0;
        revalidate();
        repaint();
    public void ZoomOut()
        if (value <= -3)
            return;
        value--;
        scale = (value + 4) / 20.0;
        revalidate();
        repaint();
    class MouseManager extends MouseAdapter
        ZoomAndDraw component;
        Point start;
        boolean dragging = false;
        public MouseManager(ZoomAndDraw displayPanel)
            component = displayPanel;
        @Override
        public void mousePressed(MouseEvent e)
            start = e.getPoint();
            dragging = true;
        @Override
        public void mouseReleased(MouseEvent e)
            if (dragging)
                component.addLine(start, e.getPoint());
                component.repaint();
            dragging = false;
        @Override
        public void mouseDragged(MouseEvent e)
            Point end = e.getPoint();
            if (dragging)
                component.setLine(start, end);
                component.repaint();
            else
                start = end;
    public static void main(String[] args)
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        ZoomAndDraw zoomAndDraw = new ZoomAndDraw();
        //Zoom in call
        zoomAndDraw.ZoomIn();
        zoomAndDraw.ZoomIn();
        zoomAndDraw.ZoomIn();
        frame.add(zoomAndDraw);
        frame.setPreferredSize(new Dimension(640, 480));
        frame.setSize(new Dimension(640, 480));
        frame.setVisible(true);
}Thanks and Regards
Raja.

Answer 1

Hi,
I'm having one more doubt. Just assume, after calling the ZoomIn(), I am drawing a line.
Subsequent ZoomIn() calls (let's say 5 times), changed the actual line position. How do I synchronize the zoom in call with the line coordinates?
public void FireZoomIn()
        new Thread(new Runnable()
            public void run()
                try
                    Thread.sleep(3000);
                catch (InterruptedException iex)
                int count = 0;
                while (count++ < 5)
                    ZoomIn();
        }).start();
public void mouseReleased(MouseEvent e)
            if (dragging)
                component.addLine(start, e.getPoint());
                component.repaint();
                component.FireZoomIn();
            dragging = false;
        }Thanks and Regards
Raja.