jsp图片验证码de实现

verifycode.jsp <%@ page language="java" contentType="image/jpeg; charset=GBK" pageEncoding="GBK"%><%@ page import="java.awt.*,java.awt.image.*,java.util.*,com.sun.image.codec.jpeg.*,javax.imageio.*"%>

<%!Color getRandColor(int fc, int bc) {//给定范围获得随机颜色 Random random = new Random(); if (fc > 255) fc = 255; if (bc > 255) bc = 255; int r = fc + random.nextInt(bc - fc); int g = fc + random.nextInt(bc - fc); int b = fc + random.nextInt(bc - fc); return new Color(r, g, b); }%><% //设置页面不缓存 response.setHeader("Pragma", "No-cache"); response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expires", 0); // 在内存中创建图象 int width = 60, height = 20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 获取图形上下文 Graphics g = image.getGraphics(); //生成随机类 Random random = new Random(); // 设定背景色 g.setColor(getRandColor(200, 250)); g.fillRect(0, 0, width, height); //设定字体 g.setFont(new Font("Times New Roman", Font.PLAIN, 18)); //画边框 g.setColor(new Color(0, 0, 0)); g.drawRect(0, 0, width - 1, height - 1); // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到 g.setColor(getRandColor(160, 200)); for (int i = 0; i < 155; i++) { int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x, y, x + xl, y + yl); } // 取随机产生的认证码(4位数字) String sRand = ""; for (int i = 0; i < 4; i++) { String rand = String.valueOf(random.nextInt(10)); sRand += rand; // 将认证码显示到图象中 g.setColor(getRandColor(110, 130));//调用函数产生颜色 g.drawString(rand, 13 * i + 6, 16); } //Create a new Session session = request.getSession(true); // 将认证码存入SESSION session.setAttribute("verify", sRand); // 图象生效 g.dispose(); // 输出图象到页面, //有两种方法， //第一种方法：ImageIO.write(); 需要包含javax.imageio.*" ImageIO.write(image, "JPEG", response.getOutputStream()); //第二中方法 ：JPEGImageEncoder,包含com.sun.image.codec.jpeg.* //JPEGImageEncoder encoder = //JPEGCodec.createJPEGEncoder(response.getOutputStream()); //encoder.encode(image); //下面两行一定要有否则会抛出 //getOutputStream() has already been called for this response异常 out.clear(); out = pageContext.pushBody(); %>

使用方法 .... ......