Patchca是Piotr Piastucki写的一个java验证码开源库，打包成jar文件发布，patchca使用简单但功能强大。

本例实现了自定义背景，由于生成图片较小，波动太大时会导致部分文字显示不全，所以更改了滤镜属性。

效果图：

代码如下：

     package com.ninemax.cul.servlet;                    import java.awt.Color;          import java.awt.Graphics;          import java.awt.image.BufferedImage;          import java.awt.image.BufferedImageOp;          import java.io.IOException;          import java.io.OutputStream;          import java.util.ArrayList;          import java.util.List;          import java.util.Random;                    import javax.imageio.ImageIO;          import javax.servlet.ServletException;          import javax.servlet.http.HttpServlet;          import javax.servlet.http.HttpServletRequest;          import javax.servlet.http.HttpServletResponse;          import javax.servlet.http.HttpSession;                    import org.patchca.background.BackgroundFactory;          import org.patchca.color.ColorFactory;          import org.patchca.color.RandomColorFactory;          import org.patchca.filter.ConfigurableFilterFactory;          import org.patchca.filter.library.AbstractImageOp;          import org.patchca.filter.library.WobbleImageOp;          import org.patchca.font.RandomFontFactory;          import org.patchca.service.Captcha;          import org.patchca.service.ConfigurableCaptchaService;          import org.patchca.text.renderer.BestFitTextRenderer;          import org.patchca.text.renderer.TextRenderer;          import org.patchca.word.RandomWordFactory;                    /**           * 验证码生成类           *           * 使用开源验证码项目patchca生成           * 依赖jar包：patchca-0.5.0.jar           * 项目网址：https://code.google.com/p/patchca/           *           * @author zyh          * @version 1.00  2012-7-12 New           */          public class ValidationCodeServlet extends HttpServlet {              private static final long serialVersionUID = 5126616339795936447L;                            private ConfigurableCaptchaService configurableCaptchaService = null;              private ColorFactory colorFactory = null;              private RandomFontFactory fontFactory = null;              private RandomWordFactory wordFactory = null;              private TextRenderer textRenderer = null;                            public ValidationCodeServlet() {                  super();              }                        /**              * Servlet销毁方法,负责销毁所使用资源. <br>              */              public void destroy() {                  wordFactory = null;                  colorFactory = null;                  fontFactory = null;                  textRenderer = null;                  configurableCaptchaService = null;                  super.destroy(); // Just puts "destroy" string in log              }                        public void doGet(HttpServletRequest request, HttpServletResponse response)                      throws ServletException, IOException {                  doPost(request, response);              }                        public void doPost(HttpServletRequest request, HttpServletResponse response)                      throws ServletException, IOException {                  response.setContentType("image/png");                  response.setHeader("cache", "no-cache");                                    HttpSession session = request.getSession(true);                  OutputStream outputStream = response.getOutputStream();                                    // 得到验证码对象,有验证码图片和验证码字符串                  Captcha captcha = configurableCaptchaService.getCaptcha();                  // 取得验证码字符串放入Session                  String validationCode = captcha.getChallenge();                  session.setAttribute("validationCode", validationCode);                  // 取得验证码图片并输出                  BufferedImage bufferedImage = captcha.getImage();                  ImageIO.write(bufferedImage, "png", outputStream);                                    outputStream.flush();                  outputStream.close();              }                        /**              * Servlet初始化方法              */              public void init() throws ServletException {                  configurableCaptchaService = new ConfigurableCaptchaService();                                    // 颜色创建工厂,使用一定范围内的随机色                  colorFactory = new RandomColorFactory();                  configurableCaptchaService.setColorFactory(colorFactory);                                    // 随机字体生成器                  fontFactory = new RandomFontFactory();                  fontFactory.setMaxSize(32);                  fontFactory.setMinSize(28);                  configurableCaptchaService.setFontFactory(fontFactory);                                    // 随机字符生成器,去除掉容易混淆的字母和数字,如o和0等                  wordFactory = new RandomWordFactory();                  wordFactory.setCharacters("abcdefghkmnpqstwxyz23456789");                  wordFactory.setMaxLength(5);                  wordFactory.setMinLength(4);                  configurableCaptchaService.setWordFactory(wordFactory);                                    // 自定义验证码图片背景                  MyCustomBackgroundFactory backgroundFactory = new MyCustomBackgroundFactory();                  configurableCaptchaService.setBackgroundFactory(backgroundFactory);                                    // 图片滤镜设置                  ConfigurableFilterFactory filterFactory = new ConfigurableFilterFactory();                                    List<BufferedImageOp> filters = new ArrayList<BufferedImageOp>();                  WobbleImageOp wobbleImageOp = new WobbleImageOp();                  wobbleImageOp.setEdgeMode(AbstractImageOp.EDGE_MIRROR);                  wobbleImageOp.setxAmplitude(2.0);                  wobbleImageOp.setyAmplitude(1.0);                  filters.add(wobbleImageOp);                  filterFactory.setFilters(filters);                                    configurableCaptchaService.setFilterFactory(filterFactory);                                    // 文字渲染器设置                  textRenderer = new BestFitTextRenderer();                  textRenderer.setBottomMargin(3);                  textRenderer.setTopMargin(3);                  configurableCaptchaService.setTextRenderer(textRenderer);                                    // 验证码图片的大小                  configurableCaptchaService.setWidth(82);                  configurableCaptchaService.setHeight(32);              }                            /**              * 自定义验证码图片背景,主要画一些噪点和干扰线              */              private class MyCustomBackgroundFactory implements BackgroundFactory {                  private Random random = new Random();                            public void fillBackground(BufferedImage image) {                      Graphics graphics = image.getGraphics();                                            // 验证码图片的宽高                      int imgWidth = image.getWidth();                      int imgHeight = image.getHeight();                                            // 填充为白色背景                      graphics.setColor(Color.WHITE);                      graphics.fillRect(0, 0, imgWidth, imgHeight);                                            // 画100个噪点(颜色及位置随机)                      for(int i = 0; i < 100; i++) {                          // 随机颜色                          int rInt = random.nextInt(255);                          int gInt = random.nextInt(255);                          int bInt = random.nextInt(255);                                                    graphics.setColor(new Color(rInt, gInt, bInt));                                                    // 随机位置                          int xInt = random.nextInt(imgWidth - 3);                          int yInt = random.nextInt(imgHeight - 2);                                                    // 随机旋转角度                          int sAngleInt = random.nextInt(360);                          int eAngleInt = random.nextInt(360);                                                    // 随机大小                          int wInt = random.nextInt(6);                          int hInt = random.nextInt(6);                                                    graphics.fillArc(xInt, yInt, wInt, hInt, sAngleInt, eAngleInt);                                                    // 画5条干扰线                          if (i % 20 == 0) {                              int xInt2 = random.nextInt(imgWidth);                              int yInt2 = random.nextInt(imgHeight);                              graphics.drawLine(xInt, yInt, xInt2, yInt2);                          }                      }                  }              }          }  

由于是个Servlet所以web.xml配置如下：

     <servlet>              <servlet-name>validationCode</servlet-name>              <servlet-class>com.ninemax.cul.servlet.ValidationCodeServlet</servlet-class>            </servlet>                      <servlet-mapping>              <servlet-name>validationCode</servlet-name>              <url-pattern>/validationCodeServlet.png</url-pattern>            </servlet-mapping>  

     <img id="validationCode" alt="验证码图片" title="验证码图片" src="<%=path %>/validationCodeServlet.png" onclick="refreshCode(this)" />          <a id="aRecode" href="javascript:void(0);" onclick="refreshCode()">换一张</a>  

     /**          * 刷新验证码          * @param imgObj 验证码Img元素          */          function refreshCode(imgObj) {              if (!imgObj) {                  imgObj = document.getElementById("validationCode");              }              var index = imgObj.src.indexOf("?");              if(index != -1) {                  var url = imgObj.src.substring(0,index + 1);                  imgObj.src = url + Math.random();              } else {                  imgObj.src = imgObj.src + "?" + Math.random();              }          }