Java后端实现随机验证码图片生成

/**
 * 生成随机验证码图片
 */
@RestController
public class CaptchaController {

    /**
     * 生成随机验证码
     */
    @RequestMapping("/captcha")
    public void generateCaptcha(HttpServletRequest request, HttpServletResponse response) throws IOException {
        // 设置响应头信息
        response.setContentType("image/png");
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);

        // 验证码图片的宽度和高度
        int width = 100;
        int height = 36;

        // 创建 BufferedImage 对象，设置图片大小和类型
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // 获取 Graphics2D 对象，绘制图片
        Graphics2D g = image.createGraphics();

        // 生成随机数，作为验证码
        String captcha = generateRandomString();
        request.getSession().setAttribute("captcha", captcha);

        // 设置字体、字号和颜色
        Font font = new Font("Arial", Font.PLAIN, 20);
        g.setFont(font);
        g.setColor(Color.BLACK);

        // 绘制验证码
        g.drawString(captcha, 20, 25);

        // 添加干扰线和噪点
        addInterference(g, width, height);

        // 输出图片
        ImageIO.write(image, "png", response.getOutputStream());
    }

    /**
     * 生成随机字符串
     */
    private String generateRandomString() {
        String base = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
        Random random = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 4; i++) {
            int number = random.nextInt(base.length());
            sb.append(base.charAt(number));
        }
        return sb.toString();
    }

    /**
     * 添加干扰线和噪点
     */
    private void addInterference(Graphics2D g, int width, int height) {
        Random random = new Random();

        // 添加干扰线
        for (int i = 0; i < 3; i++) {
            int x1 = random.nextInt(width);
            int y1 = random.nextInt(height);
            int x2 = random.nextInt(width);
            int y2 = random.nextInt(height);
            g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
            g.drawLine(x1, y1, x2, y2);
        }

        // 添加噪点
        for (int i = 0; i < 30; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
            g.fillRect(x, y, 1, 1);
        }
    }
}