src/org/bs/servlet/backend/CheckCodeServlet.java

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package org.bs.servlet.backend;


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.servlet.ServletException;
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;

public class CheckCodeServlet extends HttpServlet {

	@Override
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("image/jpeg");
		final int width=40;
		final int height=20;
		//创建一张图片
		BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
		Graphics2D g = image.createGraphics();
		//背景
		g.setColor(Color.white);
		g.fillRect(0, 0, width, height);
		//画1000个点
		Random r = new Random();
		for(int i=0;i<250*(width/75);i++){
			g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
			g.fillOval(r.nextInt(width), r.nextInt(height), 2, 2);
		}
		//画随机旋转，随机选取的字符串
		String charSet="abcdefghijklmnopqrstuvwxyz0123456789";
		String code="";
		g.setFont(new Font("Courier",Font.BOLD,width/3));
		double theta =0;//旋转角度
		for(int i=0;i<4;i++){
			//选取字符串
			String c=""+charSet.charAt(r.nextInt(charSet.length()));
			code+=c;
			g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
			//字符旋转
			g.rotate(theta, width/2+(i-3)*width/4+width/8,height/2);
			theta= r.nextInt((int) (Math.PI*25))/100.0-Math.PI/8.0;
			g.rotate(theta, width/2+(i-2)*width/4+width/8,height/2);
			theta=-theta;
			
			g.drawString(c,width/2+(i-2)*width/4, height/2+height/4);
		}
		
		request.getSession().setAttribute("check_code", code);