图片验证码工具类（struts中的运用）

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
@SuppressWarnings("restriction")
public class ImageUtil2 {
	//设置画布宽度
	private static int width=60;
	private static int height=20;
	
	public static Map<String ,BufferedImage> createImage(){
			//画布
			BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
			
			//设置画笔
			Graphics g=image.getGraphics();
			//为画布涂色，给画笔上个颜色(随机验证码的背景颜色是随机的)
			Random r=new Random();
			g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
			
			//给画布涂色，给背景添加颜色
			g.fillRect(0,0,width,height);
			
			//添加几条干扰线看看(用黑色的线）
			g.setColor(new Color(0,0,0));
			
			for(int i=0;i<4;i++){
				g.drawLine(r.nextInt(width),r.nextInt(height),r.nextInt(width),r.nextInt(height));
			}
			String imageCode=getNumber(4);
			//画字符串,画验证码
			g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
			g.setFont(new Font(null,Font.BOLD,18));
			int k=5;
			for (int i=0;i<4;i++){
				g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));
				g.drawString(String.valueOf(imageCode.charAt(i)),k,19);
				k=k+12;
			}
			Map<String,BufferedImage> map=new HashMap<String,BufferedImage>();
			map.put(imageCode,image);
			
		return map;
	}
	//应该是StringBuffer或者StringBuilder 不应该用这个String  提高效率啊效率
	public static String getNumber(int num){
		String str="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
		Random r=new Random();
		String check="";
		for(int i=0;i<num;i++){
			check+=str.charAt(r.nextInt(36));
		}
		return check;
		}
	//将图片转换成流？
	public static InputStream getInputStream(BufferedImage image)
			throws IOException {
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
		encoder.encode(image);
		byte[] imageBts = bos.toByteArray();
		InputStream in = new ByteArrayInputStream(imageBts);
		return in;
	}
}