基于Java实现图形验证码工具类

package com.example.demo.util;

import lombok.extern.slf4j.Slf4j;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.security.SecureRandom;

/**
 * 验证码工具类
 *
 * @author wangbo
 * @since 2024/10/29
 */
@Slf4j
public class CaptchaGeneratorUtil {

    private CaptchaGeneratorUtil() {
        // ...
    }

    public static void main(String[] args) throws IOException {
        // 生成4位随机数字验证码
        String text = generateRandomCode();
        // 创建验证码图片
        BufferedImage image = createImage(text);
        // 保存图片到文件
        ImageIO.write(image, "png", new File("captcha.png"));
    }

    private static final SecureRandom RANDOM = new SecureRandom();

    /**
     * 生成4位随机数字字母验证码
     */
    public static String generateRandomCode() {
        StringBuilder code = new StringBuilder();
        for (int i = 0; i < 4; i++) {
            int i1 = RANDOM.nextInt(3);
            if (i1 == 0) {
                code.append((char) (RANDOM.nextInt(26) + 65));
            } else if (i1 == 1) {
                code.append((char) (RANDOM.nextInt(26) + 97));
            } else {
                code.append(RANDOM.nextInt(10));
            }
        }
        log.info("生成的验证码文本 text = {}", code);
        return code.toString();
    }

    /**
     * 创建验证码图片
     */
    public static BufferedImage createImage(String text) {
        log.info("待生成验证码图片的文本 text = {}", text);
        int width = 75;
        int height = 25;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 使用Graphics2D以获得更好的图形控制
        Graphics2D g2d = image.createGraphics();

        try {
            // 设置背景颜色
            g2d.setColor(new Color(0xDCDCDC));
            g2d.fillRect(0, 0, width, height);

            // 设置字体和颜色
            g2d.setFont(new Font("Arial", Font.BOLD, 20));
            g2d.setColor(new Color(0x004000));

            // 确保文本不会超出图像边界
            FontMetrics fm = g2d.getFontMetrics();
            int textWidth = fm.stringWidth(text);
            // 居中文本
            int x = (width - textWidth) / 2;
            // 居中文本（基线对齐）
            int y = (height - fm.getHeight()) / 2 + fm.getAscent();

            g2d.drawString(text, x, y);

            // 添加噪声线
            for (int i = 0; i < 5; i++) {
                g2d.setColor(new Color(RANDOM.nextInt(255), RANDOM.nextInt(255), RANDOM.nextInt(255)));
                g2d.drawLine(RANDOM.nextInt(width), RANDOM.nextInt(height), RANDOM.nextInt(width), RANDOM.nextInt(height));
            }

            // 设置渲染提示以提高图像质量（可选）
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        } finally {
            // 确保在try块之后释放Graphics2D资源
            g2d.dispose();
        }

        return image;
    }

    private static final String CAPTCHA_PREFIX = "captcha:";

    public static String generateCaptchaRedisKey(String key) {
        return CAPTCHA_PREFIX + key;
    }
}

/**
 * 生成图片验证码
 *
 * @param key UUID字符串
 */
@GetMapping("/captcha/generator/{key}")
public void captchaGenerator(@PathVariable("key") String key, HttpServletResponse response) throws BaseException {
    userService.captchaGenerator(key, response);
}

public void captchaGenerator(String key, HttpServletResponse response) throws BaseException {
    //查看key的验证码是否已存在
    String captchaRedisKey = CaptchaGeneratorUtil.generateCaptchaRedisKey(key);
    boolean hasKey = Boolean.TRUE.equals(redisTemplate.hasKey(captchaRedisKey));
    if (hasKey) {
        throw new BaseException(ErrorCode.USER_KEY_REPETITION);
    }
    String captcha = CaptchaGeneratorUtil.generateRandomCode();
    BufferedImage image = CaptchaGeneratorUtil.createImage(captcha);
    //设置验证码，有效期1分钟
    redisTemplate.opsForValue().set(captchaRedisKey, captcha, 60L, TimeUnit.SECONDS);
    response.setContentType("image/jpeg");
    try (ServletOutputStream out = response.getOutputStream()) {
        ImageIO.write(image, "JPEG", out);
    } catch (IOException e) {
        throw new RuntimeException(e);
    }
}

//校验验证码
String key = loginPage.getKey();
String captcha = loginPage.getCaptcha();
if (StringUtils.isNullOrEmpty(key) || StringUtils.isNullOrEmpty(captcha)) {
    throw new BaseException(ErrorCode.USER_KEY_OR_CAPTCHA_NOT_FOUND);
}
String captchaRedisKey = CaptchaGeneratorUtil.generateCaptchaRedisKey(key);
String redisCaptcha = redisTemplate.opsForValue().get(captchaRedisKey);
if (StringUtils.isNullOrEmpty(redisCaptcha) || !captcha.equalsIgnoreCase(redisCaptcha)) {
    throw new BaseException(ErrorCode.USER_CAPTCHA_ERROR);
} else {
    //删除验证码缓存
    redisTemplate.delete(captchaRedisKey);
}