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80 lines
2.0 KiB
Plaintext
80 lines
2.0 KiB
Plaintext
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
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<%!
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// 给定范围获得随机颜色
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Color getRandColor(int fc,int bc) {
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Random random = new Random();
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if(fc > 255) {
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fc = 255;
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}
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if(bc > 255) {
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bc = 255;
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}
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int r = fc + random.nextInt(bc - fc);
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int g = fc + random.nextInt(bc - fc);
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int b = fc + random.nextInt(bc - fc);
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return new Color(r, g, b);
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}
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%>
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<%
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//设置页面不缓存
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response.setHeader("Pragma", "No-cache");
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response.setHeader("Cache-Control", "no-cache");
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response.setDateHeader("Expires", 0);
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// 在内存中创建图象
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int width = 60, height = 20;
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BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
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// 获取图形上下文
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Graphics g = image.getGraphics();
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//生成随机类
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Random random = new Random();
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// 设定背景色
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g.setColor(getRandColor(200,250));
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g.fillRect(0, 0, width, height);
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//设定字体
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g.setFont(new Font(Font.DIALOG, Font.PLAIN, 18));
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//画边框
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//g.setColor(new Color());
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//g.drawRect(0,0,width-1,height-1);
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// 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
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g.setColor(getRandColor(160, 200));
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for (int i = 0; i < 155; i++) {
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int x = random.nextInt(width);
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int y = random.nextInt(height);
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int xl = random.nextInt(12);
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int yl = random.nextInt(12);
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g.drawLine(x,y,x+xl,y+yl);
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}
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// 取随机产生的认证码(4位数字)
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String sRand = "";
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for (int i = 0;i < 4; i++) {
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String rand = String.valueOf(random.nextInt(10));
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sRand += rand;
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// 将认证码显示到图象中
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// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
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g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
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g.drawString(rand, 13 * i + 6, 16);
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}
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// 将认证码存入SESSION
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session.setAttribute("captcha", sRand);
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// 图象生效
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g.dispose();
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// 输出图象到页面
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ImageIO.write(image, "JPEG", response.getOutputStream());
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out.clear();
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out = pageContext.pushBody();
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%>
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