java实现后台返回base64图形编码

package com.liginfo.app.util;
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.ByteArrayOutputStream;
import java.io.IOException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Random;
import javax.imageio.ImageIO;
import org.apache.tomcat.util.codec.binary.Base64;
import sun.misc.BASE64Encoder;
/*
 * 返回base64验证码的工具类
 */
public class RandomGraphic {
  // 默认验证码6位
  private static int DEFAULT_CODE_NUMBERS = 6;
  private static Random random = new SecureRandom();
  public static String generateCode(){
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i< DEFAULT_CODE_NUMBERS; i++){
      sb.append(random.nextInt(10));
    }
    return sb.toString();
  }
  public static String generateCode(int numbers){
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i< numbers; i++){
      sb.append(random.nextInt(10));
    }
    return sb.toString();
  }
  /**
   * 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 final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
  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();
  }
  /**
   * 输出指定验证码图片流
   *
   * @param w
   * @param h
   * @param code
   * @throws IOException
   */
  public static String outputImage(int w, int h, 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();
    String result = null;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    boolean flag = ImageIO.write(image, "GIF", out);
    byte[] b = out.toByteArray();
    BASE64Encoder base64Encoder = new BASE64Encoder();
//    result = base64Encoder.encode(b);
    result = Base64.encodeBase64String(b);
    return result;
  }
  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 arg[]){
    for (int i =0;i<2000;i++){
      String s = RandomGraphic.generateCode();
      System.out.println(s);
    }
  }
}

		String code = RandomGraphic.generateVerifyCode(4);
		  String data = "";
		  try {
		  		data = RandomGraphic.outputImage(100,30,code);
		  		j.setAttributes(map);
		  } catch (IOException e) {
			  j.setSuccess(false);
			  j.setMsg("获取验证码失败");
		  		// TODO Auto-generated catch block
			  e.printStackTrace();
		  }