Objet

import java.awt.Component;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

public class DraggableMouseAdapter extends MouseAdapter {

    private final Component component;
    private int dx, dy;

    public DraggableMouseAdapter(Component component) {
        this.component = component;
    }

    @Override
    public void mousePressed(MouseEvent e) {
        dx = component.getX() - e.getXOnScreen();
        dy = component.getY() - e.getYOnScreen();
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        component.setLocation(dx + e.getXOnScreen(), dy + e.getYOnScreen());
    }

    public static void init(Component component) {
        DraggableMouseAdapter adapter = new DraggableMouseAdapter(component);
        component.addMouseListener(adapter);
        component.addMouseMotionListener(adapter);
    }
}

import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;

public class ImageComponent extends Component {
    private static final long serialVersionUID = 1;

    private final Image img;

    public ImageComponent(Image img) {
        this.img = img;
        setSize(getSize());
    }

    @Override
    public void paint(Graphics g) {
        g.drawImage(img, 0, 0, null);
    }

    @Override
    public Dimension getSize() {
        return new Dimension(img.getWidth(null), img.getHeight(null));
    }
}

import java.awt.Image;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JFrame;

public class Test {

    public static void main(String[] args) throws IOException {
        Image img = ImageIO.read(new File("C:/image.png"));
        ImageComponent imgComp = new ImageComponent(img);
        DraggableMouseAdapter.init(imgComp);

        JFrame frame = new JFrame();
        frame.setLayout(null);
        frame.setSize(800, 600);
        frame.add(imgComp);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}