Java生成随机图片验证码

Java生成随机图片验证码

验证码主要是数字和字母，并且剔除了不容易识别的那些字符，这里通过Servlet将图片对象展示在浏览器。

package servlet;

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.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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

/**
 * 自定生成验证码图片
 */
public class VerificationCodeServlet extends HttpServlet {

    // 排除0、1、I、O这些不易识别的字符
    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' };

    private int imgWidth=100;

    private int imgHeight=30;

    private static final long serialVersionUID = 1L;

    private static Random random = new Random();

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("image/jpeg");//设置输出类型为图片

        String verificationCode = getRandomCode();
        request.getSession(true).setAttribute("code", verificationCode);//放置到session中

        Color color = getRandomColor();
        Color reverseColor = getReverseColor(color);


        BufferedImage bi=new BufferedImage(imgWidth, imgHeight, BufferedImage.TYPE_INT_RGB);//创建一张彩色的图片
        Graphics2D graphics = bi.createGraphics();
        graphics.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
        graphics.setColor(color);
        graphics.fillRect(0, 0, imgWidth, imgHeight);//绘制背景
        graphics.setColor(reverseColor);
        graphics.drawString(verificationCode, 18, 20);//绘制字符

        int n=random.nextInt(50);
        //绘制最多50个随机噪点
        for (int i = 0; i < n; i++) {
            graphics.drawRect(imgWidth, imgHeight,1,1);
        }

        //输出到客户端
        ServletOutputStream sos = response.getOutputStream();
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(sos);
        encoder.encode(bi);
        sos.flush();


    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

    /**
     * 生成4位随机的验证码字符串
     *
     * @return
     */
    private String getRandomCode() {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 4; i++) {
            sb.append(CHARS[random.nextInt(CHARS.length)]);
        }
        return sb.toString();
    }

    /**
     * 生成随机的颜色
     *
     * @return
     */
    private Color getRandomColor() {
        return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));
    }

    /**
     * 获取某颜色的反色
     * @param color
     * @return
     */
    private Color getReverseColor(Color color) {
        return new Color(255 - color.getRed(), 255 - color.getGreen(), 255 - color.getBlue());
    }

}