java生成字母验证码的方法

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 {
  //图片宽高
  private int w=70;
  private int h=35;
  private Random r=new Random();
  private String[] fontNames={"宋体","华文楷体","黑体","微软雅黑","楷体_GB2312"};
  private String codes="234567890qwertyuipasdfghjkzxcvbnmQWERTYUIPASDFGHJKZXCVBNM";
  private Color bgColor=new Color(255,255,255);
  private String text;
  //生成随机颜色
  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];
    int style=r.nextInt(4);//0 无 1 粗体 2 斜体 3 粗+斜
    int size=r.nextInt(5)+24; //生成随机字号 24~28
    return new Font(fontName, style, size);
  }
  //干扰线
  private void drowLine(BufferedImage image){
    //生成4条干扰线
    int num=4;
    Graphics2D bi=(Graphics2D) image.getGraphics();
    for (int i = 0; i < num; i++) {
      int x1=r.nextInt(w);
      int x2=r.nextInt(w);
      int y1=r.nextInt(h);
      int y2=r.nextInt(h);
      bi.setStroke(new BasicStroke(1.5F));
      bi.setColor(Color.BLUE);//干扰线色
      bi.drawLine(x1,y1,x2,y2);
    }
  }
  //随机生成一个字符
  private char randomChar(){
    int index=r.nextInt(codes.length());
    return codes.charAt(index);
  }
  //图片缓冲区
  private BufferedImage createImage(){
    BufferedImage image=new BufferedImage(w, h, BufferedImage.TYPE_INT_BGR);
    Graphics2D bi=(Graphics2D) image.getGraphics();
    bi.setColor(this.bgColor);
    bi.fillRect(0, 0, w, h);
    return image;
  }
  //生成图片
  public BufferedImage getImage(){
    BufferedImage image=createImage();
    Graphics2D bi=(Graphics2D) image.getGraphics();
    StringBuilder sb=new StringBuilder();
    for (int i = 0; i <4; i++) {
      String string=randomChar()+"";
      sb.append(string);
      //每个字符占图片1/4宽
      float x=i*1.0F*w/4;
      //随机字体格式
      bi.setFont(randomFont());
      bi.setColor(randomColor());
      //把字写在图片适当处（h-6指图片距底部6个高度）
      bi.drawString(string, x, h-6);
    }
    this.text=sb.toString();
    drowLine(image);
    return image;
  }
  //返回得到的字体
  public String getText(){
    return text;
  }
  //把图片写入指定位置
  public static void output(BufferedImage image,OutputStream out){
    try {
      ImageIO.write(image, "JPG", out);
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}