生成缩略图

package com.dd.web.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.dd.App;

@WebServlet(urlPatterns = { "/image_captcha" })
public class ImageCaptchaServlet  extends HttpServlet{

	/**
	 * 
	 */
	private static final long serialVersionUID = -8214289323044387739L;
	//使用到Algerian字体，系统里没有的话需要安装字体，字体只显示大写，去掉了1,0,i,o几个容易混淆的字符
	public static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
	private static Random random = new Random();
	
	private final static String LOGIN_CAPTCHA = "LOGIN_CAPTCHA";
	
    //imagecaptcha.width=100
    //imagecaptcha.height=40
	private Integer w =  App.getConfigInt("imagecaptcha.width");
	
	private Integer h = App.getConfigInt("imagecaptcha.height");
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
			resp.setHeader("Pragma", "No-cache");  
			resp.setHeader("Cache-Control", "no-cache");  
			resp.setDateHeader("Expires", 0);  
			resp.setContentType("image/jpeg");  
	          
	        //生成随机字串  
	        String verifyCode = generateVerifyCode(4);  
	        //存入会话session  
	        HttpSession session = req.getSession(true);  
	        session.setAttribute(LOGIN_CAPTCHA, verifyCode);  
	        //生成图片  
	        outputImage(w, h, resp.getOutputStream(), verifyCode);  
	}
	/**
	 * 使用系统默认字符源生成验证码
	 * @param verifySize	验证码长度
	 * @return
	 */
	public static String generateVerifyCode(int verifySize){
		return generateVerifyCode(verifySize, VERIFY_CODES);
	}
	/**
	 * 使用指定源生成验证码
	 * @param verifySize	验证码长度
	 * @param sources	验证码字符源
	 * @return
	 */
	public static String generateVerifyCode(int verifySize, String sources){
		if(sources == null || sources.length() == 0){
			sources = VERIFY_CODES;
		}
		int codesLen = sources.length();
		Random rand = new Random(System.currentTimeMillis());
		StringBuilder verifyCode = new StringBuilder(verifySize);
		for(int i = 0; i < verifySize; i++){
			verifyCode.append(sources.charAt(rand.nextInt(codesLen-1)));
		}
		return verifyCode.toString();
	}
	
	/**
	 * 生成随机验证码文件,并返回验证码值
	 * @param w
	 * @param h
	 * @param outputFile
	 * @param verifySize
	 * @return
	 * @throws IOException
	 */
	public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException{
		String verifyCode = generateVerifyCode(verifySize);
		outputImage(w, h, outputFile, verifyCode);
		return verifyCode;
	}
	
	/**
	 * 输出随机验证码图片流,并返回验证码值
	 * @param w
	 * @param h
	 * @param os
	 * @param verifySize
	 * @return
	 * @throws IOException
	 */
	public static String outputVerifyImage(int w, int h, OutputStream os, int verifySize) throws IOException{
		String verifyCode = generateVerifyCode(verifySize);
		outputImage(w, h, os, verifyCode);
		return verifyCode;
	}
	
	/**
	 * 生成指定验证码图像文件
	 * @param w
	 * @param h
	 * @param outputFile
	 * @param code
	 * @throws IOException
	 */
	public static void outputImage(int w, int h, File outputFile, String code) throws IOException{
		if(outputFile == null){
			return;
		}
		File dir = outputFile.getParentFile();
		if(!dir.exists()){
			dir.mkdirs();
		}
		try{
			outputFile.createNewFile();
			FileOutputStream fos = new FileOutputStream(outputFile);
			outputImage(w, h, fos, code);
			fos.close();
		} catch(IOException e){
			throw e;
		}
	}
	
	/**
	 * 输出指定验证码图片流
	 * @param w
	 * @param h
	 * @param os
	 * @param code
	 * @throws IOException
	 */
	public static void outputImage(int w, int h, OutputStream os, String code) throws IOException{
		int verifySize = code.length();
		BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
		Random rand = new Random();
		Graphics2D g2 = image.createGraphics();
		g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
		Color[] colors = new Color[5];
		Color[] colorSpaces = new Color[] { Color.WHITE, Color.CYAN,
				Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
				Color.PINK, Color.YELLOW };
		float[] fractions = new float[colors.length];
		for(int i = 0; i < colors.length; i++){
			colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
			fractions[i] = rand.nextFloat();
		}
		Arrays.sort(fractions);
		
		g2.setColor(Color.GRAY);// 设置边框色
		g2.fillRect(0, 0, w, h);
		
		Color c = getRandColor(200, 250);
		g2.setColor(c);// 设置背景色
		g2.fillRect(0, 2, w, h-4);
		
		//绘制干扰线
		Random random = new Random();
		g2.setColor(getRandColor(160, 200));// 设置线条的颜色
		for (int i = 0; i < 20; i++) {
			int x = random.nextInt(w - 1);
			int y = random.nextInt(h - 1);
			int xl = random.nextInt(6) + 1;
			int yl = random.nextInt(12) + 1;
			g2.drawLine(x, y, x + xl + 40, y + yl + 20);
		}
		
		// 添加噪点
		float yawpRate = 0.05f;// 噪声率
		int area = (int) (yawpRate * w * h);
		for (int i = 0; i < area; i++) {
			int x = random.nextInt(w);
			int y = random.nextInt(h);
			int rgb = getRandomIntColor();
			image.setRGB(x, y, rgb);
		}
		
		shear(g2, w, h, c);// 使图片扭曲

		g2.setColor(getRandColor(100, 160));
		int fontSize = h-4;
		Font font = new Font("Algerian", Font.ITALIC, fontSize);
		g2.setFont(font);
		char[] chars = code.toCharArray();
		for(int i = 0; i < verifySize; i++){
			AffineTransform affine = new AffineTransform();
			affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize/2, h/2);
			g2.setTransform(affine);
			g2.drawChars(chars, i, 1, ((w-10) / verifySize) * i + 5, h/2 + fontSize/2 - 10);
		}
		
		g2.dispose();
		ImageIO.write(image, "jpg", os);
	}
	
	private static Color getRandColor(int fc, int bc) {
		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);
	}
	
	private static int getRandomIntColor() {
		int[] rgb = getRandomRgb();
		int color = 0;
		for (int c : rgb) {
			color = color << 8;
			color = color | c;
		}
		return color;
	}
	
	private static int[] getRandomRgb() {
		int[] rgb = new int[3];
		for (int i = 0; i < 3; i++) {
			rgb[i] = random.nextInt(255);
		}
		return rgb;
	}

	private static void shear(Graphics g, int w1, int h1, Color color) {
		shearX(g, w1, h1, color);
		shearY(g, w1, h1, color);
	}
	
	private static void shearX(Graphics g, int w1, int h1, Color color) {

		int period = random.nextInt(2);

		boolean borderGap = true;
		int frames = 1;
		int phase = random.nextInt(2);

		for (int i = 0; i < h1; i++) {
			double d = (double) (period >> 1)
					* Math.sin((double) i / (double) period
							+ (6.2831853071795862D * (double) phase)
							/ (double) frames);
			g.copyArea(0, i, w1, 1, (int) d, 0);
			if (borderGap) {
				g.setColor(color);
				g.drawLine((int) d, i, 0, i);
				g.drawLine((int) d + w1, i, w1, i);
			}
		}

	}

	private static void shearY(Graphics g, int w1, int h1, Color color) {

		int period = random.nextInt(40) + 10; // 50;

		boolean borderGap = true;
		int frames = 20;
		int phase = 7;
		for (int i = 0; i < w1; i++) {
			double d = (double) (period >> 1)
					* Math.sin((double) i / (double) period
							+ (6.2831853071795862D * (double) phase)
							/ (double) frames);
			g.copyArea(i, 0, 1, h1, 0, (int) d);
			if (borderGap) {
				g.setColor(color);
				g.drawLine(i, (int) d, i, 0);
				g.drawLine(i, (int) d + h1, i, h1);
			}

		}

	}
	
	public static void main(String[] args) throws IOException{
		File dir = new File("E:/verifies");
		int w = 100, h = 40;
		for(int i = 0; i < 50; i++){
			String verifyCode = generateVerifyCode(4);
			File file = new File(dir, verifyCode + ".jpg");
			outputImage(w, h, file, verifyCode);
		}
	}
	
}

<div class="form-row">
							<label for="captchaCode">验证码</label> 
							<input type="text" name="captchaCode" id="captchaCode" maxlength="4" autocomplete="off" />
							<img id="captchaCodeImg" src="${pageContext.request.contextPath }/image_captcha" style="vertical-align:middle;cursor:pointer;margin-top:-20px;" title="看不清，请单击图片" /> 
				</div>
<script>
$('#captchaCodeImg').click(function() {
	var $this = $(this);
	var src = $this.attr('src');
	$this.attr('src', src + (src.indexOf('?') == -1 ? '?' : '') + '' + new Date().getTime());
	$('input[name=captchaCode]').val('');
});
</script>