How to pan an image using your mouse in Java Swing

Question

I am creating a Java app that will allow users to view images and to pan the image using their mouse. To implement the panning of the image I use a combination of mous

Answer 1

+1 to @Dans answer.

Here is an example I made, basically uses JPanel with added MouseAdapter and overrides mousePressed() and mouseDragged() methods. mouseDragged() method will increment x and y co-ordinates of image accordingly and will be drawn via paintComponent(...) of JPanel and Graphics2D#drawImage(Image img,int x,int y,ImageObserver io).

Before click and drag of mouse:

After click and drag of mouse:

//necessary imports
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.image.BufferedImage;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    /**
     * Default constructor
     */
    public Test() {
        initComponents();
    }

    /**
     * Initialize GUI and components (including ActionListeners etc)
     */
    private void initComponents() {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);

        PanPanel pp = null;
        try {
            pp = new PanPanel(ImageIO.read(new URL("http://www.sellcar.co.za/wp-content/uploads/2011/01/Porsche_911_Turbo.jpg")));
        } catch (Exception ex) {
            ex.printStackTrace();
        }

        frame.add(pp);
        //pack frame (size JFrame to match preferred sizes of added components and set visible
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {

        /**
         * Create GUI and components on Event-Dispatch-Thread
         */
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    //set nimbus look and feel
                    for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                        if ("Nimbus".equals(info.getName())) {
                            UIManager.setLookAndFeel(info.getClassName());
                            break;
                        }
                    }
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException e) {
                    e.printStackTrace();
                }
                //create GUI instance
                Test test = new Test();
            }
        });
    }
}

class PanPanel extends JPanel {

    private int x, y;
    private int width = 400, height = 400;
    BufferedImage img;
    private final static RenderingHints textRenderHints = new RenderingHints(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
    private final static RenderingHints imageRenderHints = new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    private final static RenderingHints renderHints = new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    static int startX, startY;

    public PanPanel(BufferedImage img) {
        x = 0;
        y = 0;
        this.img = img;

        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent me) {
                super.mousePressed(me);
                startX = me.getX();
                startY = me.getY();
            }
        });

        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent me) {
                super.mouseDragged(me);

                if (me.getX() < startX) {//moving image to right
                    x -= 2;
                } else if (me.getX() > startX) {//moving image to left
                    x += 2;
                }

                if (me.getY() < startY) {//moving image up
                    y -= 2;
                } else if (me.getY() > startY) {//moving image to down
                    y += 2;
                }
                repaint();
            }
        });
    }

    @Override
    protected void paintComponent(Graphics grphcs) {
        super.paintComponent(grphcs);
        Graphics2D g2d = (Graphics2D) grphcs;

        //turn on some nice effects
        applyRenderHints(g2d);

        g2d.drawImage(img, x, y, null);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(width, height);
    }

    public static void applyRenderHints(Graphics2D g2d) {
        g2d.setRenderingHints(textRenderHints);
        g2d.setRenderingHints(imageRenderHints);
        g2d.setRenderingHints(renderHints);
    }
}