生成java图片验证码

package com.tristan;


import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;

public class Image {

	public static void main(String[] args) throws FileNotFoundException {

		File f = new File("c:/1.jpg");
		OutputStream os = new FileOutputStream(f);
		new Image().getCertPic(0, 0, os);
	}

	//验证码图片中可以出现的字符集，可根据需要修改
	private char mapTable[]={
			'a','b','c','d','e','h',
			'j','k','m','n','p','q',
			'r','s','t','u','v','w',
			'x','y','z','0','2','3',
			'4','5','6','7','8','9'
	};

	public String getCertPic(int width, int height,OutputStream os) {
		if(width<=0) {
			width=60;
		}
		if(height<=0) {
			height=20;
		}

		BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
		//获取图形上下文
		Graphics g = image.getGraphics();
		//设定背景颜色
		g.setColor(new Color(0xDCDCDC));
		g.fillRect(0, 0, width, height);
		//画边框
		g.setColor(Color.black);
		g.drawRect(0, 0, width-1, height-1);
		//随机产生的验证码
		String strEnsure="";
		//4代表4位验证码，如果要生成等多位的验证码 ，则加大数值

		for(int i=0; i<4; i++) {
			strEnsure += mapTable[(int)(mapTable.length*Math.random())];
		}
		//将验证码显示在图像中，如果要生成更多位的验证码，增加drawString语句
		g.setColor(Color.black);
		g.setFont(new Font("Atlantic Inline", Font.PLAIN,18));
		String str = strEnsure.substring(0, 1);
		g.drawString(str, 8, 17);
		 str = strEnsure.substring(1, 2);
		 g.drawString(str, 20, 15);
		 str = strEnsure.substring(2, 3);
		 g.drawString(str, 35, 18);
		 str = strEnsure.substring(3, 4);
		 g.drawString(str, 45, 15);
		 //随机产生10个干扰点

		 Random random = new Random();
		 for(int i=0; i<10; i++ ) {
			 int x = random.nextInt(width);
			 int y = random.nextInt(height);
			 g.drawOval(x, y, 1, 1);
		 }
		//释放图形上下文
		 g.dispose();
		 try{
			 //输出图像到页面
			 ImageIO.write(image, "JPEG", os);
		 }catch(IOException e) {
			 return "";
		 }
		return strEnsure;
	}
}