java将图片转为base64返回给前端

本文实例为大家分享了java将图片转为base64返回给前端的具体代码，供大家参考，具体内容如下

一、controller端代码

@RequestMapping(value = "/captcha")
 public void imagecode(HttpServletRequest request, HttpServletResponse response) throws Exception {
 JSONObject object = new JSONObject();
 CaptchaGenerator vcg = new CaptchaGenerator();
 String vcode = vcg.generatorVCode();
 BufferedImage vcodeImage = vcg.generatorVCodeImage(vcode, true);
 response.setDateHeader("Expires", 0);
 response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
 response.addHeader("Cache-Control", "post-check=0, pre-check=0");
 response.setHeader("Pragma", "no-cache");
 ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
 response.addHeader("code", vcode.toLowerCase());
 try {
  ImageIO.write(vcodeImage, "png", outputStream);
  BASE64Encoder encoder = new BASE64Encoder();
  String base64 = encoder.encodeBuffer(outputStream.toByteArray()).trim();
  base64 = base64.replaceAll("\n", "").replaceAll("\r", "");
  object.put("code", "data:image/jpg;base64," + base64);
  response.getWriter().write(object.toString());
 } catch (IOException e) {
  response.getWriter().write("");
 } finally {
  if (outputStream != null) {
  outputStream.flush();
  outputStream.close();
  response.getWriter().close();
  }
 }

 }

二、生成验证码的代码

（从某博客拷过来直接用的）

package com.kinth.security.web.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.util.Random;

/**
 * 验证码生成器
 *
 *
 */
public class CaptchaGenerator {

  /**
   * 验证码来源
   */
  final private char[] code = {
    '2', '3', '4', '5', '6', '7', '8', '9',
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
    'k', 'm', 'n', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F',
    'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R',
    'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
  };
  /**
   * 字体
   */
  final private String[] fontNames = new String[]{
      "黑体", "宋体", "Courier", "Arial",
      "Verdana", "Times", "Tahoma", "Georgia"};
  /**
   * 字体样式
   */
  final private int[] fontStyles = new int[]{
      Font.BOLD, Font.ITALIC|Font.BOLD
  };

  /**
   * 验证码长度
   * 默认4个字符
   */
  private int vcodeLen = 4;
  /**
   * 验证码图片字体大小
   * 默认17
   */
  private int fontsize = 21;
  /**
   * 验证码图片宽度
   */
  private int width = (fontsize+1)*vcodeLen+10;
  /**
   * 验证码图片高度
   */
  private int height = fontsize+12;
  /**
   * 干扰线条数
   * 默认3条
   */
  private int disturbline = 3;

  public CaptchaGenerator(){}

  /**
   * 指定验证码长度
   * @param vcodeLen 验证码长度
   */
  public CaptchaGenerator(int vcodeLen) {
    this.vcodeLen = vcodeLen;
    this.width = (fontsize+1)*vcodeLen+10;
  }

  /**
   * 生成验证码图片
   * @param vcode 要画的验证码
   * @param drawline 是否画干扰线
   * @return
   */
  public BufferedImage generatorVCodeImage(String vcode, boolean drawline){
    //创建验证码图片
    BufferedImage vcodeImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics g = vcodeImage.getGraphics();
    //填充背景色
    g.setColor(new Color(246, 240, 250));
    g.fillRect(0, 0, width, height);
    if(drawline){
      drawDisturbLine(g);
    }
    //用于生成伪随机数
    Random ran = new Random();
    //在图片上画验证码
    for(int i = 0;i < vcode.length();i++){
      //设置字体
      g.setFont(new Font(fontNames[ran.nextInt(fontNames.length)], fontStyles[ran.nextInt(fontStyles.length)], fontsize));
      //随机生成颜色
      g.setColor(getRandomColor());
      //画验证码
      g.drawString(vcode.charAt(i)+"", i*fontsize+10, fontsize+5);
    }
    //释放此图形的上下文以及它使用的所有系统资源
    g.dispose();

    return vcodeImage;
  }
  /**
   * 获得旋转字体的验证码图片
   * @param vcode
   * @param drawline 是否画干扰线
   * @return
   */
  public BufferedImage generatorRotateVCodeImage(String vcode, boolean drawline){
    //创建验证码图片
    BufferedImage rotateVcodeImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = rotateVcodeImage.createGraphics();
    //填充背景色
    g2d.setColor(new Color(246, 240, 250));
    g2d.fillRect(0, 0, width, height);
    if(drawline){
      drawDisturbLine(g2d);
    }
    //在图片上画验证码
    for(int i = 0;i < vcode.length();i++){
      BufferedImage rotateImage = getRotateImage(vcode.charAt(i));
      g2d.drawImage(rotateImage, null, (int) (this.height * 0.7) * i, 0);
    }
    g2d.dispose();
    return rotateVcodeImage;
  }
  /**
   * 生成验证码
   * @return 验证码
   */
  public String generatorVCode(){
    int len = code.length;
    Random ran = new Random();
    StringBuffer sb = new StringBuffer();
    for(int i = 0;i < vcodeLen;i++){
      int index = ran.nextInt(len);
      sb.append(code[index]);
    }
    return sb.toString();
  }
  /**
   * 为验证码图片画一些干扰线
   * @param g
   */
  private void drawDisturbLine(Graphics g){
    Random ran = new Random();
    for(int i = 0;i < disturbline;i++){
      int x1 = ran.nextInt(width);
      int y1 = ran.nextInt(height);
      int x2 = ran.nextInt(width);
      int y2 = ran.nextInt(height);
      g.setColor(getRandomColor());
      //画干扰线
      g.drawLine(x1, y1, x2, y2);
    }
  }
  /**
   * 获取一张旋转的图片
   * @param c 要画的字符
   * @return
   */
  private BufferedImage getRotateImage(char c){
    BufferedImage rotateImage = new BufferedImage(height, height, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2d = rotateImage.createGraphics();
    //设置透明度为0
    g2d.setColor(new Color(255, 255, 255, 0));
    g2d.fillRect(0, 0, height, height);
    Random ran = new Random();
    g2d.setFont(new Font(fontNames[ran.nextInt(fontNames.length)], fontStyles[ran.nextInt(fontStyles.length)], fontsize));
    g2d.setColor(getRandomColor());
    double theta = getTheta();
    //旋转图片
    g2d.rotate(theta, height/2, height/2);
    g2d.drawString(Character.toString(c), (height-fontsize)/2, fontsize+5);
    g2d.dispose();

    return rotateImage;
  }
  /**
   * @return 返回一个随机颜色
   */
  private Color getRandomColor(){
    Random ran = new Random();
    return new Color(ran.nextInt(220), ran.nextInt(220), ran.nextInt(220));
  }
  /**
   * @return 角度
   */
  private double getTheta(){
    return ((int) (Math.random()*1000) % 2 == 0 ? -1 : 1)*Math.random();
  }

  /**
   * @return 验证码字符个数
   */
  public int getVcodeLen() {
    return vcodeLen;
  }
  /**
   * 设置验证码字符个数
   * @param vcodeLen
   */
  public void setVcodeLen(int vcodeLen) {
    this.width = (fontsize+3)*vcodeLen+10;
    this.vcodeLen = vcodeLen;
  }
  /**
   * @return 字体大小
   */
  public int getFontsize() {
    return fontsize;
  }
  /**
   * 设置字体大小
   * @param fontsize
   */
  public void setFontsize(int fontsize) {
    this.width = (fontsize+3)*vcodeLen+10;
    this.height = fontsize+15;
    this.fontsize = fontsize;
  }
  /**
   * @return 图片宽度
   */
  public int getWidth() {
    return width;
  }
  /**
   * 设置图片宽度
   * @param width
   */
  public void setWidth(int width) {
    this.width = width;
  }
  /**
   * @return 图片高度
   */
  public int getHeight() {
    return height;
  }
  /**
   * 设置图片高度
   * @param height
   */
  public void setHeight(int height) {
    this.height = height;
  }
  /**
   * @return 干扰线条数
   */
  public int getDisturbline() {
    return disturbline;
  }
  /**
   * 设置干扰线条数
   * @param disturbline
   */
  public void setDisturbline(int disturbline) {
    this.disturbline = disturbline;
  }

}

三、前端显示

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
<script src="../static/model/js/jquery-1.11.2.min.js"></script>
</head>
<body>

 <img id="randomImage" src="" />
 <script type="text/javascript">
 $(function() {
  refreshimg();
 })
 function refreshimg() {
  $.ajax({
  type : "POST",
  dataType : "json",
  url : "../article/captcha",
  success : function(data) {
   console.log('base64=' + data.codePic);
   $('#randomImage').attr('src', data.code);
  },
  error : function() {
  }
  });

  $("#randomImage").click(refreshimg)

 }
 </script>

</body>
</html>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。