JFrameの背景図のサイズはウィンドウサイズによって自動的に変更されます

package com.ui;
 
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
 
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
 
public class MainTopPanel extends JPanel {
	private static final long serialVersionUID = -2783727170881461229L;
	private int width;
	private int height;
	private Image image = new ImageIcon(getClass().getClassLoader().getResource("com/resource/ZHU.jpg")).getImage();
	private JButton btnLogon = new JButton("    ");
	private JButton btnCancel = new JButton("      ");
	private JLabel labId = new JLabel("  ：");
	private JLabel labPass = new JLabel("  ：");
	private JTextField fieldId = new JTextField();
	private JPasswordField fieldPass = new JPasswordField();
	private int btnLogon_x = 535, btnLogon_y = 399;
	private int btnCancel_x = 655, btnCancel_y = 399;
	private int labId_x = 495, labId_y = 339;
	private int labPass_x = 495, labPass_y = 369;
	private int fieldId_x = 545, fieldId_y = 339;
	private int fieldPass_x = 545, fieldPass_y = 369;
 
	public MainTopPanel(int width, int height) {
		this.width = width;
		this.height = height;
		this.setLayout(null);
		this.init();
	}
 
	public void setScreenSize(int width, int height) { //          
		this.width = width;
		this.height = height;
	}
 
	public void setLocationComponent(int width, int height) { //           ，        
		int m = this.width - width;
		int n = this.height - height;
		this.btnLogon_x -= m;
		this.btnLogon_y -= n;
		this.btnCancel_x -= m;
		this.btnCancel_y -= n;
		this.labId_x -= m;
		this.labId_y -= n;
		this.labPass_x -= m;
		this.labPass_y -= n;
		this.fieldId_x -= m;
		this.fieldId_y -= n;
		this.fieldPass_x -= m;
		this.fieldPass_y -= n;
		btnLogon.setBounds(this.btnLogon_x, this.btnLogon_y, 102, 22);
		btnCancel.setBounds(this.btnCancel_x, this.btnCancel_y, 102, 22);
		labId.setBounds(this.labId_x, this.labId_y, 57, 17);
		labPass.setBounds(this.labPass_x, this.labPass_y, 57, 17);
		fieldId.setBounds(this.fieldId_x, this.fieldId_y, 191, 22);
		fieldPass.setBounds(this.fieldPass_x, this.fieldPass_y, 191, 22);
	}
 
	private void init() {
		labId.setFont(new Font("    ", Font.PLAIN, 16));
		labId.setForeground(new Color(255, 255, 255));
		labId.setBounds(495, 339, 57, 17);
		labPass.setFont(new Font("    ", Font.PLAIN, 16));
		labPass.setForeground(new Color(255, 255, 255));
		labPass.setBounds(495, 369, 57, 17);
 
		btnLogon.setBounds(535, 399, 102, 22);
		btnLogon.setBackground(new Color(57, 149, 136));
		btnCancel.setBackground(new Color(57, 149, 136));
		btnCancel.setBounds(655, 399, 102, 22);
 
		fieldId.setBounds(545, 339, 191, 22);
		fieldId.setBackground(new Color(57, 149, 136));
		fieldId.setForeground(new Color(255, 255, 255));
		fieldPass.setBounds(545, 369, 191, 22);
		fieldPass.setBackground(new Color(57, 149, 136));
		fieldPass.setForeground(new Color(255, 255, 255));
 
		this.add(labId);
		this.add(labPass);
		this.add(btnLogon);
		this.add(btnCancel);
		this.add(fieldId);
		this.add(fieldPass);
	}
 
	@Override
	protected void paintComponent(Graphics g) {
		super.paintComponent(g);
		g.drawImage(image, 0, 0, width, height ,this);
	}
 
}