生成图片验证码（VerifyCode）

package cn.itcast.image;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.junit.Test;

/**
 * 动态生成图片
 * @author HP
 *
 */
public class Demo {
    @Test
    public void fun() throws FileNotFoundException, IOException{
        /**
         * 1.创建图片缓冲区
         * 2.设置其宽高
         * 3.得到这个图片的绘制环境（得到画笔）
         * 4.保存起来
         * 
         */
        BufferedImage bi = new BufferedImage(70,35,BufferedImage.TYPE_INT_RGB);
        Graphics g = bi.getGraphics();//得到绘制环境
        g.setColor(Color.WHITE);//把环境设置为红色
        g.fillRect(0,0,70,35);//填充矩形；从0,0开始，宽70，高35，即整个图片，即为图片设置背景色
        g.setColor(Color.RED);//把环境设置为红色
        g.drawString("Hello", 2, 35-2);//向图片上写入字符串，其中2,2表示x，y轴的坐标
        
        ImageIO.write(bi, "JPEG",new FileOutputStream("F://xxx.jpg"));
    }
    @Test
    public void fun2() throws FileNotFoundException, IOException{
        VerifyCode vc = new VerifyCode();
        BufferedImage bi = vc.getImage();
        VerifyCode.output(bi,new FileOutputStream("F:/xxx.jpg"));
        
        System.out.println(vc.getText());
    }
}

以上是Demo类，下面我们写VerifyCode类

package cn.itcast.image;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;

public class VerifyCode {
    private int w = 70;
    private int h = 35;
    private Random r = new Random();
    //("宋体“，”华文楷体“，”黑体“，”华文新魏“，”华文隶书“，”微软雅黑”，“楷体_GB2312")
    private String[] fontNames = {"宋体","华文楷书","黑体","微软雅黑","楷体_GB2312"};
    //可选的字符
    private String codes = "23456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    //背景色
    private Color bgColor = new Color(255,255,255);
    //验证码上的文本
    private String text;
    //生成随机的颜色
    private Color randomColor(){
        int red = r.nextInt(150);
        int green = r.nextInt(150);
        int blue = r.nextInt(150);
        return new Color(red,green,blue);
    }
    //生成随机字体
    private Font randomFont(){
        int index = r.nextInt(fontNames.length);
        String fontName = fontNames(index); //生成随机的字体名称
        int style = r.nextInt(4);//生成随机的样式，0（无样式），1（粗体），2（斜体），3（粗体+斜体）
        int size = r.nextInt(5)+24;//生成随机字号 24-28
        return new Font(fontName,style,size);
        
    }
    

    private String fontNames(int index) {
        // TODO Auto-generated method stub
        return null;
    }
    //画干扰线
    private void drawLine(BufferedImage image){
        int num = 3;//一共画三条
        Graphics2D g2 = (Graphics2D)image.getGraphics();
        for(int i=0;i<num;i++){//生成两个点的坐标，即4个值
            int x1 = r.nextInt(w);
            int y1 = r.nextInt(h);
            int x2 = r.nextInt(w);
            int y2 = r.nextInt(h);
            g2.setStroke(new BasicStroke(1.5F));
            g2.setColor(Color.BLUE);//干扰线是蓝色
            g2.drawLine(x1,y1,x2,y2); //划线
        }
    }
        //随机生成一个字符
        private char randomChar(){
            int index = r.nextInt(codes.length());
            return codes.charAt(index);
        }
        private BufferedImage createImage(){
            BufferedImage image = new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
            Graphics2D g2 = (Graphics2D)image.getGraphics();
            g2.setColor(this.bgColor);
            g2.fillRect(0, 0, w, h);
            return image;
        }
        //调用这个方法得到验证码
    public BufferedImage getImage(){
        BufferedImage image = createImage();//创建图片缓冲区
        Graphics2D g2 = (Graphics2D) image.getGraphics();//得到绘制环境
        StringBuilder sb = new StringBuilder();//用来装载生成的验证文本
        //向图片中画4个字符
        for(int i= 0;i<4;i++){//循环四次
            String s = randomChar()+"";//随机生成一个字符
            sb.append(s);//把字母添加到sb中
            float x = i*1.0F * w/4;//设置当前字符的x轴坐标
            g2.setFont(randomFont());//设置随机字体
            g2.setColor(randomColor());//设置随机颜色
            g2.drawString(s,x,h-5);//画图
        }
        this.text = sb.toString();//把生成的字符串赋给了this.text
        drawLine(image);//添加干扰线
        return image;
    }
    //返回验证码图片上的文本
    public String getText(){
        return text;
    }
    
    //保存图片到指定的输出流
    public static void output(BufferedImage image,OutputStream out) throws IOException{
        ImageIO.write(image, "JPEG", out);
    }
    

}