兩種圖片樣式分別是用Graphics類和Graphics2D 類實現(Graphics2D擴展了Graphics類)，可以參考資料，畫出自己想要的圖片

Graphics2D 參考api地址：http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics2D.html

Graphics 參考api地址：http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics.html

代碼實現一 ：

java部分：

import java.awt.Color;
import java.awt.Font;
import
 
 java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
 
import javax.servlet.http.HttpServletResponse;


public class ImageCreate2 extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private int imageWidth = 70;
    private int imageHeight = 20;
    private int codeNumber = 4;
    private int backGround = 30;

    protected
 
 void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        createCode(request, response);
    }

    /**
     * @param request
     * @param response
     * @throws IOException
     */
    private void createCode(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");
        BufferedImage bufferedImage = new BufferedImage(imageWidth,
                imageHeight, BufferedImage.TYPE_INT_BGR);
        Graphics2D g = bufferedImage.createGraphics();
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, imageWidth - 1, imageHeight - 1);
        //g.setStroke(new BasicStroke(3.0f));//幹擾線
        Random random = new Random();
        for (int i = 0; i < backGround; i++) {
            int red = random.nextInt(256);
            int green = random.nextInt(256);
            int blue = random.nextInt(256);
            g.setColor(new Color(red, green, blue));
            int start_X = random.nextInt(imageWidth);
            int start_Y = random.nextInt(imageHeight);
            if (random.nextInt(5) % 3 == 0) {
                int r = random.nextInt(10);
                int startAngle = random.nextInt(360);
                int arcAngle = random.nextInt(360);
                g.drawArc(start_X, start_Y, r, r, startAngle, arcAngle);
            } else {
                int change_X = random.nextInt() % 6;
                int change_Y = random.nextInt() % 6;
                g.drawLine(start_X, start_Y, start_X + change_X, start_Y
                        + change_Y);
            }
        }
        StringBuilder ValidateCode = new StringBuilder();
        g.setFont(new Font("Blackoak Std", Font.BOLD, imageHeight-2));
        g.setFont(new Font("Tahoma", Font.BOLD, imageHeight - 3));
        for (int i = 0; i < codeNumber; i++) {
            int red = random.nextInt(100) + 50;
            int green = random.nextInt(100) + 50;
            int blue = random.nextInt(100) + 50;
            g.setColor(new Color(red, green, blue));
            String code = null;
            int type = random.nextInt(3);
            if (type == 1) {
                code = String.valueOf((char) (random.nextInt(26) + 65));
            } else if (type == 2) {
                code = String.valueOf((char) (random.nextInt(26) + 97));
            } else {
                code = String.valueOf(random.nextInt(10));
            }
            ValidateCode.append(code);
            g.drawString(code, imageWidth / codeNumber * i + 4, 16);
        }
        System.out.println("vcode="+ValidateCode.toString());
//存於session中，以待驗證
        request.getSession().setAttribute("validateCode",
                ValidateCode.toString());
        ServletOutputStream sos = response.getOutputStream();
        ImageIO.write(bufferedImage, "jpeg", sos);
        bufferedImage = null;
        sos.close();
        random = null;
    }

    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    

jsp頁面部分：

<div class="form-group">

            <div class="col-sm-10" style="width:40%;">
                <input style="height: 40px" type="text" class="form-control" id="tpyzm" flag="0" placeholder="請輸入驗證碼">
            </div>
            <div class="col-sm-2 control-label" style="padding:7px; text-align: center;width: 80px;background: #fefefe;border:solid 1px #c9c9c9 ">
               <img src="<%=request.getContextPath()%>/ImageCreate2.do" id="codes2" 
                                        onclick="reloadImg2(‘<%=request.getContextPath()%>‘)" class="vcodeCss"></img>
            </div>
            <div style="height: 40px;padding-top: 10px">
                <span style="color: #333333;font-size: 16px;margin-left: 10px"> 看不清?</span>
                <a style="font-size: 16px;color: #0089d2" onclick="reloadImg2(‘<%=request.getContextPath()%>‘)">換一張</a>
            </div>
            <div class="regist_til col-sm-2">
                 <span class="" aria-hidden="true" id="tpyzmSpan" ></span>
            </div>
        </div>
<script>

//圖片驗證碼
function reloadImg2(url) {
document.getElementById("codes2").src = url+"/ImageCreate2.do?" + "radom="
+ Math.random();
$("#vcode2").focus();
}

</script>

代碼實現二 ：

java部分：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ImageCreate extends HttpServlet{
    private static final long serialVersionUID = 1L;


    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        create(request, response);
    }
    private void create(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
     int []a = null;
     // 大小
     int width = 60;
     int height = 30;
     // 聲明一個圖片類型rgb
     BufferedImage bi = new BufferedImage(width, height,
             BufferedImage.TYPE_INT_BGR);
     // 獲取畫筆
     Graphics g = bi.getGraphics();
     // 背景色
     g.setColor(Color.WHITE);
     // 畫
     g.fillRect(0, 0, width, height);
     // 字體
     g.setFont(new Font("黑體", Font.BOLD, 18));
     // 寫一個字符到bi
     Random r = new Random();
     for (int i = 0; i < 4; i++) {
         // 生成隨機數
         int code = r.nextInt(10);// 0---9之間
         // 畫筆隨機色
         g.setColor(new Color(r.nextInt(256), r.nextInt(256), r.nextInt(256)));
         // 寫出字符
         g.drawString("" + code, i * 15, 10 + r.nextInt(20));   
     }
     //幹擾線
     for(int i=0;i<12;i++){
         g.setColor(new Color(r.nextInt(256), r.nextInt(256), r.nextInt(256)));
     //畫線
         g.drawLine(r.nextInt(60), r.nextInt(30), r.nextInt(60), r.nextInt(30));
     }
     g.dispose();//圖片生成

     //ImageIO.write(bi,"JPEG", new FileOutputStream("e:/a.jpg"));//設置路徑為e：盤下的a.jpg
     ServletOutputStream sos = response.getOutputStream();
     ImageIO.write(bi, "jpeg", sos);
    sos.close();
    bi = null;
     
 }
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

jsp頁面部分：同上，只需改下url則可；

java生成圖片驗證碼實現