图片验证码的生成

1   package util;
2
3   import javax.imageio.ImageIO;
4   import javax.servlet.ServletException;
5   import javax.servlet.http.HttpServlet;
6   import javax.servlet.http.HttpServletRequest;
7   import javax.servlet.http.HttpServletResponse;
8   import java.awt.*;
9   import java.awt.image.BufferedImage;
10  import java.io.IOException;
11  import java.util.Random;
12
13
14  /**
15   * 描述：
16   *
17   * @author $author$
18   * @version $Revision$
19   */
20  public class PicCheckCode extends HttpServlet {
21
22      private Font mFont     = new Font("Arial Black", Font.PLAIN, 15); //设置字体
23      private int  lineWidth = 2; //干扰线的长度=1.414*lineWidth
24      private int  width     = 60; //定义图形大小
25      private int  height    = 20; //定义图形大小
26      private int  count     = 200;
27
28      /**
29       * 描述：
30       *
31       * @param fc 描述：
32       * @param bc 描述：
33       *
34       * @return 描述：
35       */
36      private Color getRandColor(int fc, int bc) { //取得给定范围随机颜色
37
38          Random random = new Random();
39
40          if (fc > 255) {
41
42              fc = 255;
43          }
44
45          if (bc > 255) {
46
47              bc = 255;
48          }
49
50          int r = fc + random.nextInt (bc - fc);
51          int g = fc + random.nextInt (bc - fc);
52          int b = fc + random.nextInt (bc - fc);
53
54          return new Color(r, g, b);
55      }
56
57      //处理post
58      public void doPost(HttpServletRequest request, HttpServletResponse response)
59          throws ServletException, IOException {
60
61          doGet (request, response);
62      }
63
64      /**
65       * 描述：
66       *
67       * @param request 描述：
68       * @param response 描述：
69       *
70       * @throws ServletException 描述：
71       * @throws IOException 描述：
72       */
73      public void doGet(HttpServletRequest request, HttpServletResponse response)
74          throws ServletException, IOException {
75
76          //response.reset();
77          //设置页面不缓存
78          response.setHeader ("Pragma", "No-cache");
79          response.setHeader ("Cache-Control", "no-cache");
80          response.setDateHeader ("Expires", 0);
81          response.setContentType ("image/gif");
82
83          // 在内存中创建图象
84          BufferedImage image = new BufferedImage(width, height,
85                  BufferedImage.TYPE_INT_RGB);
86
87          // 获取图形上下文
88          Graphics2D g = (Graphics2D) image.getGraphics ();
89
90          //生成随机类
91          Random random = new Random();
92
93          // 设定背景色
94          g.setColor (getRandColor (200, 250)); //---1
95
96          g.fillRect (0, 0, width, height);
97
98          //设定字体
99          g.setFont (mFont);
100
101         //画边框
102         g.setColor (getRandColor (0, 20)); //---2
103         g.drawRect (0, 0, width - 1, height - 1);
104
105         //随机产生干扰线，使图象中的认证码不易被其它程序探测到
106         for (int i = 0; i < count; i++) {
107
108             g.setColor (getRandColor (150, 200)); //---3
109
110             int x  = random.nextInt (width - lineWidth - 1) + 1; //保证画在边框之内
111             int y  = random.nextInt (height - lineWidth - 1) + 1;
112             int xl = random.nextInt (lineWidth);
113             int yl = random.nextInt (lineWidth);
114             g.drawLine (x, y, x + xl, y + yl);
115         }
116
117         //取随机产生的认证码(4位数字)
118         String sRand = "";
119
120         for (int i = 0; i < 4; i++) {
121
122             String rand = String.valueOf (random.nextInt (10));
123             sRand += rand;
124
125             // 将认证码显示到图象中,调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
126             g.setColor (new Color(20 + random.nextInt (130),
127                     20 + random.nextInt (130), 20 + random.nextInt (130))); //--4--50-100
128
129             g.drawString (rand, (13 * i) + 6, 16);
130
131
132         }
133
134         // 将认证码存入SESSION
135         request.getSession ().setAttribute ("getImg", sRand);
136
137         // 图象生效
138         g.dispose ();
139
140         // 输出图象到页面
141         ImageIO.write (image, "PNG", response.getOutputStream ());
142     }
143 }
144