JSP效驗碼圖片生成方法

生成方法（一）
// 在內存中創建圖象
int width=55, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 獲取圖形上下文
Graphics g = image.getGraphics();

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

//畫邊框
g.setColor(Color.black);
g.drawRect(0,0,width-1,height-1);
Random random = new Random();
// 取隨機產生的認證碼(4位數字)
String rand = "";
rand += random.nextInt(9);
rand += random.nextInt(9);
rand += random.nextInt(9);
rand += random.nextInt(9);

// 將認證碼存入SESSION
session.setAttribute("rand",rand);

//將認證碼顯示到圖象中,並在12到18象素之間隨機設定字體的大小
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);

// 隨機產生88個干擾點，使圖象中的認證碼不易被其它程序探測到
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);
}

// 圖象生效
g.dispose();

// 輸出圖象到頁面
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){//給定範圍獲得隨機顏色
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();
}

//設置頁面不緩存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

// 在內存中創建圖象
int width=13*randomLen+8, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 獲取圖形上下文
Graphics g = image.getGraphics();

//生成隨機類
Random random = new Random();

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

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

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

// 隨機產生155條幹擾線，使圖象中的認證碼不易被其它程序探測到
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);
}

// 取隨機產生的認證碼(4位數字)
String sRand="";
for (int i=0;i<randomLen;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
// 將認證碼顯示到圖象中
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
//調用函數出來的顏色相同，可能是因爲種子太接近，所以只能直接生成
g.drawString(rand,13*i+6,16);
}

// 將認證碼存入SESSION
session.setAttribute("validcode",sRand);

// 圖象生效
g.dispose();

// 輸出圖象到頁面
ImageIO.write(image, "JPEG", response.getOutputStream());
%>