本文例項為大家分享了java將圖片轉為base64返回給前端的具體程式碼，供大家參考，具體內容如下

一、controller端程式碼

@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、生成驗證碼的程式碼

（從某部落格拷過來直接用的）

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;

/**
 * 驗證碼生成器
 * 
 * 
 */
public class CaptchaGenerator {
  
  /**
   * 驗證碼來源
   */
  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'
  };
  /**
   * 字型
   */
  final private String[] fontNames = new String[]{
      "黑體","宋體","Courier","Arial","Verdana","Times","Tahoma","Georgia"};
  /**
   * 字型樣式
   */
  final private int[] fontStyles = new int[]{
      Font.BOLD,Font.ITALIC|Font.BOLD
  };
  
  /**
   * 驗證碼長度
   * 預設4個字元
   */
  private int vcodeLen = 4;
  /**
   * 驗證碼圖片字型大小
   * 預設17
   */
  private int fontsize = 21;
  /**
   * 驗證碼圖片寬度
   */
  private int width = (fontsize+1)*vcodeLen+10;
  /**
   * 驗證碼圖片高度
   */
  private int height = fontsize+12;
  /**
   * 干擾線條數
   * 預設3條
   */
  private int disturbline = 3;
  
  
  public CaptchaGenerator(){}
  
  /**
   * 指定驗證碼長度
   * @param vcodeLen 驗證碼長度
   */
  public CaptchaGenerator(int vcodeLen) {
    this.vcodeLen = vcodeLen;
    this.width = (fontsize+1)*vcodeLen+10;
  }
  
  /**
   * 生成驗證碼圖片
   * @param vcode 要畫的驗證碼
   * @param drawline 是否畫干擾線
   * @return
   */
  public BufferedImage generatorVCodeImage(String vcode,boolean drawline){
    //建立驗證碼圖片
    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,width,height);
    if(drawline){
      drawDisturbLine(g);
    }
    //用於生成偽隨機數
    Random ran = new Random();
    //在圖片上畫驗證碼
    for(int i = 0;i < vcode.length();i++){
      //設定字型
      g.setFont(new Font(fontNames[ran.nextInt(fontNames.length)],fontStyles[ran.nextInt(fontStyles.length)],fontsize));
      //隨機生成顏色
      g.setColor(getRandomColor());
      //畫驗證碼
      g.drawString(vcode.charAt(i)+"",i*fontsize+10,fontsize+5);
    }
    //釋放此圖形的上下文以及它使用的所有系統資源
    g.dispose();
    
    return vcodeImage;
  }
  /**
   * 獲得旋轉字型的驗證碼圖片
   * @param vcode
   * @param drawline 是否畫干擾線
   * @return
   */
  public BufferedImage generatorRotateVCodeImage(String vcode,boolean drawline){
    //建立驗證碼圖片
    BufferedImage rotateVcodeImage = new BufferedImage(width,BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = rotateVcodeImage.createGraphics();
    //填充背景色
    g2d.setColor(new Color(246,250));
    g2d.fillRect(0,height);
    if(drawline){
      drawDisturbLine(g2d);
    }
    //在圖片上畫驗證碼
    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;
  }
  /**
   * 生成驗證碼
   * @return 驗證碼
   */
  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();
  }
  /**
   * 為驗證碼圖片畫一些干擾線
   * @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());
      //畫干擾線
      g.drawLine(x1,y1,x2,y2);
    }
  }
  /**
   * 獲取一張旋轉的圖片
   * @param c 要畫的字元
   * @return
   */
  private BufferedImage getRotateImage(char c){
    BufferedImage rotateImage = new BufferedImage(height,BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2d = rotateImage.createGraphics();
    //設定透明度為0
    g2d.setColor(new Color(255,255,0));
    g2d.fillRect(0,height);
    Random ran = new Random();
    g2d.setFont(new Font(fontNames[ran.nextInt(fontNames.length)],fontsize));
    g2d.setColor(getRandomColor());
    double theta = getTheta();
    //旋轉圖片
    g2d.rotate(theta,height/2,height/2);
    g2d.drawString(Character.toString(c),(height-fontsize)/2,fontsize+5);
    g2d.dispose();
    
    return rotateImage;
  }
  /**
   * @return 返回一個隨機顏色
   */
  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 驗證碼字元個數
   */
  public int getVcodeLen() {
    return vcodeLen;
  }
  /**
   * 設定驗證碼字元個數
   * @param vcodeLen
   */
  public void setVcodeLen(int vcodeLen) {
    this.width = (fontsize+3)*vcodeLen+10;
    this.vcodeLen = vcodeLen;
  }
  /**
   * @return 字型大小
   */
  public int getFontsize() {
    return fontsize;
  }
  /**
   * 設定字型大小
   * @param fontsize
   */
  public void setFontsize(int fontsize) {
    this.width = (fontsize+3)*vcodeLen+10;
    this.height = fontsize+15;
    this.fontsize = fontsize;
  }
  /**
   * @return 圖片寬度
   */
  public int getWidth() {
    return width;
  }
  /**
   * 設定圖片寬度
   * @param width
   */
  public void setWidth(int width) {
    this.width = width;
  }
  /**
   * @return 圖片高度
   */
  public int getHeight() {
    return height;
  }
  /**
   * 設定圖片高度
   * @param height 
   */
  public void setHeight(int height) {
    this.height = height;
  }
  /**
   * @return 干擾線條數
   */
  public int getDisturbline() {
    return disturbline;
  }
  /**
   * 設定干擾線條數
   * @param disturbline
   */
  public void setDisturbline(int disturbline) {
    this.disturbline = disturbline;
  }
  
}

三、前端顯示

<%@ 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內容，希望對大家的學習有所幫助，也希望大家多多支援我們。