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Java Servlet 實現圖片驗證碼（中文旋轉+干擾線+噪點）完整源碼

編輯：Java 程式設計入門

功能特性

中文驗證碼：從常用字庫隨機抽取 4 個漢字
隨機旋轉：每字符 ±30° 傾斜，抗 OCR 識別
干擾線：5 條隨機顏色/位置曲線
背景/邊框：粉色背景 + 藍色邊框
輸出：image/jpeg 直接寫入 HttpServletResponse

核心實現邏輯

1. 字符庫構建

// 300+ 常用漢字 Unicode 字符串
String base = "\u7684\u4e00\u4e86\u662f\u6211..."; // 省略
char ch = base.charAt(new Random().nextInt(base.length()));

2. 繪製單字符（旋轉+還原）

int degree = new Random().nextInt() % 30;
graphics.rotate(degree * Math.PI / 180, x, 23); // 旋轉
graphics.drawString(String.valueOf(ch), x, 23);
graphics.rotate(-degree * Math.PI / 180, x, 23); // 還原座標系
x += 30; // 下一字符位置

3. 干擾線

graphics.setColor(Color.MAGENTA);
for (int i = 0; i < 5; i++) {
    graphics.drawLine(randomX(), randomY(), randomX(), randomY());
}

完整 Servlet 代碼

package com.sanrong;
import javax.servlet.http.*;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class test4Pic extends HttpServlet {
    private static final int WIDTH = 130, HEIGHT = 30;
    private static final String BASE = "\u7684\u4e00\u4e86..."; // 300+ 常用字

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        BufferedImage img = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = img.createGraphics();

        // 背景
        g.setColor(Color.PINK);
        g.fillRect(0, 0, WIDTH, HEIGHT);
        // 邊框
        g.setColor(Color.BLUE);
        g.drawRect(1, 1, WIDTH-2, HEIGHT-2);
        // 干擾線
        g.setColor(Color.MAGENTA);
        Random r = new Random();
        for (int i = 0; i < 5; i++)
            g.drawLine(r.nextInt(WIDTH), r.nextInt(HEIGHT), r.nextInt(WIDTH), r.nextInt(HEIGHT));
        // 驗證碼文字
        g.setColor(Color.BLUE);
        g.setFont(new Font("宋體", Font.BOLD, 20));
        int x = 10;
        for (int i = 0; i < 4; i++) {
            char ch = BASE.charAt(r.nextInt(BASE.length()));
            int deg = r.nextInt() % 30;
            g.rotate(deg * Math.PI / 180, x, 23);
            g.drawString(String.valueOf(ch), x, 23);
            g.rotate(-deg * Math.PI / 180, x, 23);
            x += 30;
        }

        resp.setContentType("image/jpeg");
        ImageIO.write(img, "jpg", resp.getOutputStream());
    }
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}