Java Graphics - 如何屏幕截图(捕获)并选择要用鼠标剪切的区域

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.image.BufferedImage;

import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;

public class Main {
  public static void main(String[] args) throws Exception {
    Robot robot = new Robot();
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    BufferedImage screen = robot.createScreenCapture(new Rectangle(screenSize));

    new ScreenCaptureRectangle(screen);
  }
}

class ScreenCaptureRectangle {
  Rectangle captureRect;

  ScreenCaptureRectangle(final BufferedImage screen) {
    BufferedImage screenCopy = new BufferedImage(screen.getWidth(),
        screen.getHeight(), screen.getType());
    JLabel screenLabel = new JLabel(new ImageIcon(screenCopy));
    JScrollPane screenScroll = new JScrollPane(screenLabel);

    screenScroll.setPreferredSize(new Dimension(300, 300));

    repaint(screen, screenCopy);
    screenLabel.repaint();

    screenLabel.addMouseMotionListener(new MouseMotionAdapter() {
      Point start = new Point();
      @Override
      public void mouseMoved(MouseEvent me) {
        start = me.getPoint();
        repaint(screen, screenCopy);
        screenLabel.repaint();
      }
      @Override
      public void mouseDragged(MouseEvent me) {
        Point end = me.getPoint();
        captureRect = new Rectangle(start, new Dimension(end.x - start.x, end.y
            - start.y));
        repaint(screen, screenCopy);
        screenLabel.repaint();
      }
    });
    JOptionPane.showMessageDialog(null, screenScroll);
  }

  public void repaint(BufferedImage orig, BufferedImage copy) {
    Graphics2D g = copy.createGraphics();
    g.drawImage(orig, 0, 0, null);
    g.setColor(Color.RED);
    if (captureRect == null) {
      return;
    }
    g.draw(captureRect);
    g.setColor(new Color(25, 25, 23, 10));
    g.fill(captureRect);
    g.dispose();
  }
}