java生成验证码

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;

public class RandImgCreater {
    //默认字符列表
    private static final String CODE_LIST = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
    //验证码图片高度
    private static final int HEIGHT = 20;
    //默认字符数
    private static final int FONT_NUM = 4;
    //生成验证码图片存放位置
    private HttpServletResponse response;
    //宽度
    private int width = 0;
    //实际字符个数
    private int iNum = 0;
    //实际字符列表
    private String codeList = "";
    //绘制背景
    private boolean drawBgFlag = false;
    //R
    private int rBg = 0;
    //G
    private int gBg = 0;
    //B
    private int bBg = 0;

    //构造函数（自定义存放位置）
    public RandImgCreater(HttpServletResponse response) {
        this.response = response;
        this.width = 13 * FONT_NUM + 12;
        this.iNum = FONT_NUM;
        this.codeList = CODE_LIST;
    }
    //构造函数（自定义存放位置，字符数）
    public RandImgCreater(HttpServletResponse response,int iNum) {
        this.response = response;
        this.width = 13 * iNum + 12;
        this.iNum = iNum;
        this.codeList = CODE_LIST;
    }
    
    //构造函数(自定义存放位置，字符数，字符列表)
    public RandImgCreater(HttpServletResponse response, int iNum,
            String codeList) {
        this.response = response;
        this.width = 13 * iNum + 12;
        this.iNum = iNum;
        this.codeList = codeList;
    }

    //绘制验证码
    public String createRandImage() {
        //1.生成BufferedImage对象，存放图片
        BufferedImage image = new BufferedImage(width, HEIGHT,
                BufferedImage.TYPE_INT_RGB);

        //2.获得BufferedImage对象的画笔
        Graphics g = image.getGraphics();
        
        //生成随机数生成器
        Random random = new Random();

        //开始绘制背景
        if (drawBgFlag) { 
            //设置画笔颜色
            g.setColor(new Color(rBg, gBg, bBg));
            //绘制矩形
            g.fillRect(0, 0, width, HEIGHT);
        } else {
            //设置画笔颜色(随机)
            g.setColor(getRandColor(200, 250));
            //绘制矩形
            g.fillRect(0, 0, width, HEIGHT);
            //循环155次生成随机干扰线条
            for (int i = 0; i < 155; i++) {
//                设置颜色
                g.setColor(getRandColor(140, 200));
                //起始位置x
                int x = random.nextInt(width);
                //起始位置y
                int y = random.nextInt(HEIGHT);
                //结束位置x1
                int xl = random.nextInt(12);
                //结束位置y1
                int yl = random.nextInt(12);
                //绘制线条
                g.drawLine(x, y, x + xl, y + yl);
            }
        }
        //设置画笔字体、样式、大小
        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
        
        //要返回的字符串
        String sRand = "";
        //循环内随机生成字符
        for (int i = 0; i < iNum; i++) {
            //随机生成字符起始位置
            int rand = random.nextInt(codeList.length());
            //从字符起始位置截取1位字符
            String strRand = codeList.substring(rand, rand + 1);
            //把新生成的字符与旧字符连接(返回用)
            sRand += strRand;
            //设置前景色(字体颜色)
            g.setColor(new Color(20 + random.nextInt(110), 20 + random
                    .nextInt(110), 20 + random.nextInt(110)));
            //绘制字符，第一个字符从0位置开始，每个字符相隔13像素
            g.drawString(strRand, 13 * i + 6, 16);
        }
        //释放资源
        g.dispose();
        try {
            //把图片输出到相应位置
            ImageIO.write(image, "JPEG", response.getOutputStream());
        } catch (IOException e) {

        }
        //返回验证码的字符
        return sRand;
    }

    //设置背景色(R,G,B颜色)
    public void setBgColor(int r, int g, int b) {
        drawBgFlag = true;
        this.rBg = r;
        this.gBg = g;
        this.bBg = b;
    }

    //随机生成颜色
    private Color getRandColor(int fc, int bc) {
        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);
    }
}

效果：

http://yuncode.net/code/c_5222e29542bff63