JSP效验码图片生成方法

生成方法（一）
// 在内存中创建图象
int width=55, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics g = image.getGraphics();

// 设定背景色
g.setColor(new Color(0xECECEC));
g.fillRect(0, 0, width, height);

//画边框
g.setColor(Color.black);
g.drawRect(0,0,width-1,height-1);
Random random = new Random();
// 取随机产生的认证码(4位数字)
String rand = "";
rand += random.nextInt(9);
rand += random.nextInt(9);
rand += random.nextInt(9);
rand += random.nextInt(9);

// 将认证码存入SESSION
session.setAttribute("rand",rand);

//将认证码显示到图象中,并在12到18象素之间随机设定字体的大小
g.setColor(Color.black);
random.setSeed(new Date().getTime());
g.setFont(new Font("Atlantic Inline",Font.PLAIN,(12 + random.nextInt(6))));
String Str = rand.substring(0,1);
g.drawString(Str,8,17);

g.setFont(new Font("Atlantic Inline",Font.PLAIN,(12 + random.nextInt(6))));
Str = rand.substring(1,2);
g.drawString(Str,20,15);

g.setFont(new Font("Atlantic Inline",Font.PLAIN,(12 + random.nextInt(6))));
Str = rand.substring(2,3);
g.drawString(Str,35,18);

g.setFont(new Font("Atlantic Inline",Font.PLAIN,(12 + random.nextInt(6))));
Str = rand.substring(3,4);
g.drawString(Str,45,15);

// 随机产生88个干扰点，使图象中的认证码不易被其它程序探测到
for (int i=0;i<30;i++)
{
    int x = random.nextInt(width);
    int y = random.nextInt(height);
    g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
    g.drawOval(x,y,0,1);
}

// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());

生成方法（二）
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
Color getRandColor(int fc,int bc){//给定范围获得随机颜色
Random random = new Random();
if(fc>255) fc=255;
if(bc>255) bc=255;
int r=fc+random.nextInt(bc-fc);
int g=fc+random.nextInt(bc-fc);
int b=fc+random.nextInt(bc-fc);
return new Color(r,g,b);
}
%>
<%

int randomLen=4;
try{
randomLen=Integer.parseInt(request.getParameter("param"));
}
catch(Exception e){
  e.printStackTrace();
}

//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

// 在内存中创建图象
int width=13*randomLen+8, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics g = image.getGraphics();

//生成随机类
Random random = new Random();

// 设定背景色
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);

//设定字体
g.setFont(new Font("Times New Roman",Font.PLAIN,18));

//画边框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);

// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor(160,200));
for (int i=0;i<30*randomLen;i++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x,y,x+xl,y+yl);
}

// 取随机产生的认证码(4位数字)
String sRand="";
for (int i=0;i<randomLen;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
// 将认证码显示到图象中
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
//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
g.drawString(rand,13*i+6,16);
}

// 将认证码存入SESSION
session.setAttribute("validcode",sRand);

// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
%>