myframe/application/src/main/java/com/ctsi/utils/CaptchaUtil.java

package com.ctsi.utils;


import javax.imageio.ImageIO;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Random;

public class CaptchaUtil {
    private static final int WIDTH = 140;
    private static final int HEIGHT = 35;
    private static final int LENGTH = 4;

    public static byte[] generateCaptcha(HttpSession session) throws IOException {
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();

        g.setColor(Color.WHITE);
        g.fillRect(0, 0, WIDTH, HEIGHT);

        g.setColor(Color.BLACK);
        g.drawRect(0, 0, WIDTH - 1, HEIGHT - 1);

        String captcha = generateRandomString();
        g.setFont(new Font("Arial", Font.PLAIN, 20));
        for (int i = 0; i < LENGTH; i++) {
            g.setColor(new Color(new Random().nextInt(255), new Random().nextInt(255), new Random().nextInt(255)));
            g.drawString(String.valueOf(captcha.charAt(i)), 20 * i + 10, 30);
        }

        for (int i = 0; i < 5; i++) {
            g.setColor(new Color(new Random().nextInt(255), new Random().nextInt(255), new Random().nextInt(255)));
            int x1 = new Random().nextInt(WIDTH);
            int y1 = new Random().nextInt(HEIGHT);
            int x2 = new Random().nextInt(WIDTH);
            int y2 = new Random().nextInt(HEIGHT);
            g.drawLine(x1, y1, x2, y2);
        }

        g.dispose();

        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        ImageIO.write(image, "png", outputStream);
        session.setAttribute("captcha", captcha);
        return outputStream.toByteArray();
    }

    private static String generateRandomString() {
        String characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        StringBuilder stringBuilder = new StringBuilder();
        Random random = new Random();
        for (int i = 0; i < LENGTH; i++) {
            int index = random.nextInt(characters.length());
            stringBuilder.append(characters.charAt(index));
        }
        return stringBuilder.toString();
    }
}