package com.util;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics2D;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**

* @ClassName: CaptchaUtil

* @Description: 关于验证码的工具类

* @author 无名

* @date 2016-5-7 上午8:33:08

* @version 1.0

 */

public final class CaptchaUtil

{

    private CaptchaUtil(){}

    /*

     * 随机字符字典

     */

    private static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8',

        '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M',

        'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };

    /*

     * 随机数

     */

    private static Random random = new Random();

    /*

     * 获取6位随机数

     */

    private static String getRandomString()

    {

        StringBuffer buffer = new StringBuffer();

        for(int i = 0; i < 6; i++)

        {

            buffer.append(CHARS[random.nextInt(CHARS.length)]);

        }

        return buffer.toString();

    }

    /*

     * 获取随机数颜色

     */

    private static Color getRandomColor()

    {

        return new Color(random.nextInt(255),random.nextInt(255),

                random.nextInt(255));

    }

    /*

     * 返回某颜色的反色

     */

    private static Color getReverseColor(Color c)

    {

        return new Color(255 - c.getRed(), 255 - c.getGreen(),

- c.getBlue());

    }

    public static void outputCaptcha(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException

    {

        response.setContentType("image/jpeg");

        String randomString = getRandomString();

        request.getSession(true).setAttribute("randomString", randomString);

        int width = 100;

        int height = 30;

        Color color = getRandomColor();

        Color reverse = getReverseColor(color);

        BufferedImage bi = new BufferedImage(width, height,

                BufferedImage.TYPE_INT_RGB);

        Graphics2D g = bi.createGraphics();

        g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));

        g.setColor(color);

        g.fillRect(0, 0, width, height);

        g.setColor(reverse);

        g.drawString(randomString, 18, 20);

        for (int i = 0, n = random.nextInt(100); i < n; i++)

        {

            g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);

        }

        // 转成JPEG格式

        ServletOutputStream out = response.getOutputStream();

        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

        encoder.encode(bi);

        out.flush();

    }

}

-Djava.awt.headless=true \

yum install libXp.so.

yum install dejagnu.noarch :1.4.-.el6

yum install dejavu-sans-mono-fonts.noarch 2.33-.el6

yum install dejavu-serif-fonts.noarch 2.33-.el6

        BufferedImage bi = new BufferedImage(width, height,

                BufferedImage.TYPE_INT_RGB);

       ...........

        // 转成JPEG格式

        ServletOutputStream out = response.getOutputStream();

        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

        encoder.encode(bi);

        // 转成JPEG格式

        ServletOutputStream out = response.getOutputStream();

        ImageIO.write(bi, "JPEG", out);