js把通过图片路径生成base64

主要思想：

　　使用canvas.toDataURL()方法将图片的绝对路径转换为base64编码.

 

一、图片在本地服务器：

var imgSrc = "img/1.jpg";//本地项目文件夹下的图片
      function getBase64(img){//传入图片路径，返回base64
        function getBase64Image(img,width,height) {
          var canvas = document.createElement("canvas");
          canvas.width = width ? width : img.width;
          canvas.height = height ? height : img.height;
          var ctx = canvas.getContext("2d");
          ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
          var dataURL = canvas.toDataURL();
          return dataURL;
        }
        var image = new Image();
        image.src = img;
        var deferred=$.Deferred();
        if(img){
          image.onload =function (){
            deferred.resolve(getBase64Image(image));//将base64传给done上传处理
          }
          return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']
        }
      }
      getBase64(imgSrc)
        .then(function(base64){
          console.log(base64);
        },function(err){
          console.log(err);
        });

二、跨域

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>nick getBase64</title>
</head>
<body>
<div><img id="test" src="" alt=""/></div>
<script src="http://apps.bdimg.com/libs/jquery/2.1.1/jquery.min.js"></script>
<script>
    var imgSrc = "https://img.alicdn.com/bao/uploaded/TB1qimQIpXXXXXbXFXXSutbFXXX.jpg";
//    var imgSrc = "img/1.jpg";
      function getBase64(img){//传入图片路径，返回base64
        function getBase64Image(img,width,height) {//width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小
          var canvas = document.createElement("canvas");
          canvas.width = width ? width : img.width;
          canvas.height = height ? height : img.height;
 
          var ctx = canvas.getContext("2d");
          ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
          var dataURL = canvas.toDataURL();
          return dataURL;
        }
        var image = new Image();
        image.crossOrigin = '';
        image.src = img;
        var deferred=$.Deferred();
        if(img){
          image.onload =function (){
            deferred.resolve(getBase64Image(image));//将base64传给done上传处理
          }
          return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']
        }
      }
      getBase64(imgSrc)
        .then(function(base64){
          console.log(base64);
        },function(err){
          console.log(err);
        });
</script>
</body>
</html>

最近做了一个项目用到了这个，

html代码生成canvas然后生成图片。但是html里面的图片路径必须用base64.所以就找了这个东西。

这个测试分享给大家：链接：http://pan.baidu.com/s/1gfGPhkf 密码：8e34

-------------------------------------------------自己项目---------------------------------------------------------------------------

// 转base64
    getBase64(img) {
      //传入图片路径，返回base64
      function getBase64Image(img, width, height) {
        //width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小
        var canvas = document.createElement("canvas");
        canvas.width = width ? width : img.width;
        canvas.height = height ? height : img.height;
 
        var ctx = canvas.getContext("2d");
        ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
        var dataURL = canvas.toDataURL();
        return dataURL;
      }
      var image = new Image();
      image.crossOrigin = "";
      image.src = img;
      var deferred = $.Deferred();
      if (img) {
        image.onload = function() {
          deferred.resolve(getBase64Image(image)); //将base64传给done上传处理
        };
        return deferred.promise(); //问题要让onload完成后再return sessionStorage['imgTest']
      }
    },

　　------------------------------------------------------自己项目--------------------------------------------------------------------------

//营业执照 picture_license
        var picture_license_a = '';
        if("{$shopsInfo.picture_license}"){
            var url3="https://image.qiniu.chuxiaocheng.cn/{$shopsInfo.picture_license}";
            getBase64(url3)
                    .then(function(base64){
                        picture_license_a = base64;
                        console.log(base64);//处理成功打印在控制台
                    },function(err){
                        //console.log(err);//打印异常信息
                    });
        }

 

  //传入图片路径，返回base64
        function getBase64(img){
            function getBase64Image(img,width,height) { //width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小
                var canvas = document.createElement("canvas");
                canvas.width = width ? width : img.width;
                canvas.height = height ? height : img.height;
                var ctx = canvas.getContext("2d");
                ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
                var dataURL = canvas.toDataURL('image/jpeg', 0.3);
                return dataURL;
            }
            var image = new Image();
            image.crossOrigin = '';
            image.src = img;
            var deferred=$.Deferred();
            if(img){
                image.onload =function (){
                    deferred.resolve(getBase64Image(image));//将base64传给done上传处理
                }
                return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']
            }
        }

 

posted @ 2019-08-17 14:12  搬砖小伙子  阅读(13879)  评论(0)    收藏  举报