/**
   * 生成验证码
   * @param request
   * @param response
   */
  @RequestMapping(value = "login/getVerifyCode")
  public void getVerifyCode(HttpServletRequest request,HttpServletResponse response){
    response.setHeader("Pragma","No-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.setDateHeader("Expires", 0);
    response.setContentType("image/jpeg");

    //生成随机字符串
    String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
    //存入Session, 此处可以根据自己的需求
    HttpSession session = request.getSession();
    session.setAttribute("verifyCode",verifyCode);
    //生成图片
    int w = 100, h = 35;
    try {
      //将图片写入到 response 的输出流即可将图片返回到客户端了
      VerifyCodeUtils.outputImage(w, h , response.getOutputStream(), verifyCode);
    } catch (IOException e) {
      logger.error("生成验证码失败, Cause by: {}", e.getMessage(), e);
    }
  }

import javax.imageio.ImageIO;
import java.awt.*;
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;

/**
 * 生成图片流
 * @Description: Created by zcqshine on 2017/5/18.
 */
public class VerifyCodeUtils {
  private static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
  private static Random random = new Random();

  /**
   * 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.trim().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();
  }

  /**
   * 输出随机验证码图片流, 并返回验证码值
   * @param w
   * @param h
   * @param outputFile
   * @param verifySize
   * @return
   */
  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;
  }

  /**
   * 生成指定验证码图像文件
   * @param w
   * @param h
   * @param outputFile
   * @param verifyCode
   * @throws IOException
   */
  public static void outputImage(int w, int h, File outputFile, String verifyCode) 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, verifyCode);
      fos.close();
    } catch (IOException e) {
      throw e;
    }
  }

  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() "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) {
    File dir = new File("/Users/zcqshine/Downloads/test");
    int w = 200, h= 80;
    for (int i = 0; i< 50; i++){
      String verifyCode = generateVerifyCode(4);
      File file = new File(dir, verifyCode + ".jpg");
      try {
        outputImage(w, h, file, verifyCode);
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }
}